GENETIC SELECTION

Genetic selection

Selection is the stage of a genetic algorithm in which individual genomes are chosen from a population for later breeding (using the crossover operator).

Genetic selection is the process by which certain traits become more prevalent in a species than other traits. The traits seen in an organism are due to the genes found on their chromosomes. The genes code for the traits that we are able to observe.

Genes have more than one version or allele. We inherit one allele for every gene from each of our parents as shown in Figure 1. Some alleles are seen more frequently in a population because there are factors that select these genes.

In natural selection, natural forces determine the traits seen in an organism. A variation or allele of a trait makes some individuals more suited to survive in the environment. Mating behavior that leads to a sexual preference for a trait is also natural selection.

Natural selection also occurs when a species has a preference for certain traits for sexual reasons. Male peafowl (peacocks) have elaborate tail feathers because female peacocks are attracted to really nice tails. This is called sexual selection since traits are being selected for sexual reasons.


















Artificial selection involves human interference. Humans have been selecting various traits in other organisms for thousands of years. It is how we have developed a huge variety in the colors and flavors of apples. It is also the reason we have little tiny dogs and extremely large dogs. We select traits in plants and animals to use them to our advantage. Artificial selection in plants and animals is not seen as being as controversial, as it is with humans. Genetic selection in humans raises ethical questions, such as who gets Syndrome, Sickle Cell Anemia, Cystic Fibrosis, and Tay-Sachs disease, especially in cases where the mother is at risk.


Mass selection
Mass selection is a common plant breeding practice and effective when traits are highly heritable and easily identified.

Genotypic selection
Genotypic selection' is a term that refers to the. DNA-based enrichment of a particular allele.




Family selection
Family selection refers to mating of organisms from the same ancestral stock that are not directly related to each other. Pure-line selectioninvolves selecting and breeding progeny from superior.

Sib selection
Sib selection is a method of sequential fractionation of a heterogeneous sample that can be applied to isolation of a sequence, gene, or gene family from a complete library.

Progeny testing
Progeny testing is a process by which a sire's genetic merit is measured through the performance of his progeny. Progeny testing is relevant in sheep when meat yield and meat quality traits are important selection criteria.

Combined selection
Combined selection is a technique used to identify individuals with better additive genetic value in a population under selection, using information from the individual itself and its relatives. Such procedure should increase the efficiency of the selection process, maximizing the expected genetic gain. This selection procedure was discussed first by Lush (1947a,b) and can be used successfully in both animal and plant breeding (Bueno Filho, 1992 and Morais, 1992). Its main limitation may be a marked reduction in the genetic variability in the population, with one or few selection cycles, because of the great decrease in its effective size resulting from the selection of many related individuals (Morais, 1992). However, this can be overcome by defining a maximum number of individuals to be selected in the same family (Morais, 1992).

Practical Manual B.Voc

Fresh water fishes
Catla catla










1. Catla (Catla catla), also known as the major (Indian) carp.
2. Catla is a fish with large and broad head, a large protruding lower jaw and upturned mouth. It has large, greyish scales on dorsal side and whitish on belly.
3. Body short and deep, somewhat laterally compressed, its depth more than head length;
4. head very large, its depth exceeding half the head length;
5. body with conspicuously large cycloid scales,


Kingdom: Animalia

Phylum: Chordata

Class: Actinopterygii

Order: Cypriniformes

Family: Cyprinidae

Genus: Labeo

Species: L. rohita

Labeo rohita






1. Body bilaterally symmetrical, moderately elongate, its dorsal profile more arched than the ventral profile;
2. Body with cycloid scales, head without scale; snout fairly depressed, projecting beyond mouth, without lateral lobe; eyes dorsolateral in position, not visible from outside of head;
3. Mouth small and inferior; lips thick and fringed with a distinct inner fold to each lip, lobate or entire;
4. A pair of small maxillary barbels concealed in lateral groove; no teeth on jaws; pharyngeal teeth in three rows; upper jaw not extending to front edge of eye;
5. Simple (unbranched) dorsal fin rays three or four, branched dorsal fin rays 12 to 14; dorsal fin inserted midway between snout tip and base of caudal fin;
6. Pectoral and pelvic fins laterally inserted; pectoral fin devoid of an osseous spine; caudal fin deeply forked
7. Colour bluish on back, silvery on flanks and belly.













Kingdom: Animalia

Phylum: Chordata

Class: Actinopterygii

Order: Cypriniformes

Family: Cyprinidae

Subfamily: Labeoninae

Genus: Cirrhinus
Cirrhinus mrigala

1. Body bilaterally symmetrical and streamlined, its depth about equal to length
2. of head; body with cycloid scales,
3. Head without scales; snout blunt, often with pores; mouth broad, transverse; upper lip entire and not continuous with lower lip, lower lip most indistinct;
4. Single pair of short rostral barbels; pharyngeal teeth in three rows, 5.4.2/2.4.5 pattern; lower jaw with a small post-symphysial knob or tubercle;
5. Origin of dorsal fin nearer to end of snout than base of caudal; dorsal fin as high as body with 12 or 13 branched rays;
6. Unbranched ray of dorsal fin non-osseous and non-serrated; pectoral fins shorter than head; caudal fin deeply forked; anal fin not extending to caudal fin; lateral line with 40-45 scales;
7. Lateral transverse scale rows 6-7/5½-6 between lateral line and pelvic fin base; usually dark grey above, silvery beneath; dorsal fin greyish; pectoral, pelvic and anal fins orange-tipped

Chromosomal organisation in Prokaryotes and Eukaryotes

 The chromosomes are the nuclear components of special organisation, individuality and function.
 They are capable of self-reproduction and play a vital role in heredity, mutation, variation and evolutionary development of the species.
 Karl Nagli (1842) observed rod-like chromosomes in the nuclei of plant cells.
 E. Russow (1872) made the first serious attempt to describe chromosomes.
 E. Strasburger (1875) discovered thread-like structures which appeared during cell division.
 Walter Flemming (1878) introduced the term chromatin to describe the thread-like material of the nucleus that became intensely coloured after staining.
 W. Roux (1883) suspected the involvement of the chromosomes in the mechanism of inheritance.
 Benden and Bovery (1887) reported that number of chromosomes for each species was constant.
 The present name chromosome (Gr., chrom=colour, soma=body) was coined by W. Waldeyer (1888) to darkly stained bodies of nucleus.
 W. S. Sutton and T. Boveri in 1902 suggested that chromosomes were the physical structures which acted as messengers of
 In 1914, Robert Feulgen demonstrated a colour test known as Feulgen reaction for the DNA. In 1924, he showed that chromosomes contain DNA.

Prokaryotic genome
Bacterial DNA:
 In bacteria and blue-green algae, the hereditary material is organised into a single large circular chromosome composed of a circular molecule of double stranded DNA. It is known as bacterial chromosome or nucleoid.
 It lies free in the cytoplasm in the nuclear zone and has no protein around the DNA molecule, as is found in eukaryotic chromosome.
 Some RNA is found associated with it and forms backbone or core. DNA molecule is supercoiled.
 The circular chromosome of Escherichia coli has a contour length of about 1,360mµ and is about 20Ao broad.
 Its molecular weight is about 2.8×109. It has about 50 or more highly twisted or supercoiled loops and about four million nucleotide pairs.
 In addition to the single large circular chromosome, each bacterial cell contains from 1 to 20 much smaller circular duplex DNA molecules which are called plasmids.
 Some of the plasmids become incorporated into the bacterial chromosome and are called episomes.
 These are sometimes transferred from one bacterial cell to another during conjugation and give them new characteristics








EUKARYOTIC CHROMOSOMES
MORPHOLOGY:
Size:
 The size of chromosome is normally measured at mitotic metaphase and may be as short as 0.25 μm in fungi and birds, or as long as 30 μm in some plants such as Trillium.
 However, most metaphase chromosomes fall within a range of 3μm in fruitfly (Drosophila), to 5μm in man and 8μm to 12μm in maize.
 The organisms with less number of chromosome contain comparatively large-sized chromosomes than the chromosomes of the organisms having many chromosomes.
Number:
 The number of the chromosomes is constant for a particular species. Therefore, these are of great importance in the determination of the phylogeny and taxonomy of the species.
 The number or set of the chromosomes of the gametic cells such as sperms and ova is known as the gametic, reduced or haploid sets of chromosomes.
 The haploid set of the chromosomes is also known as the genome.
 The somatic or body cells of most organisms contain two haploid set or genomes and are knows as the diploid cells.
 The diploid cells achieve the diploid set of the chromosomes by the union of the haploid male and female gametes in the sexual reproduction.
 The number of chromosomes in each somatic cell is the same for all members of a given species.
 The organism with the lowest number of the chromosomes is the nematode, Ascaris megalocephalus univalens which has only two chromosomes in the somatic cells (i.e., 2n =2).
 In the radiolarian protozoan Aulacantha is found a diploid number of approximately 1600 chromosomes.
Autosomes and Sex chromosomes
 In a diploid cell, there are two of each kind of chromosome (these are termed homologous chromosomes), except for the sex chromosomes.
 One sex has two of the same kind of sex chromosome and the other has one of each kind.
 For example, in human, there are 23 pairs of homologous chromosomes (i.e., 2n = 46 ; a chromosome number which was established by Tijo and Levan in 1956).
 The human female has 44 non-sex chromosomes, termed autosomes and one pair of homomorphic (morphologically similar) sex chromosomes given the designation XX.
 The human male has 44 autosomes and one pair of heteromorphic or morphologically dissimilar sex chromosomes, i.e., one X chromosome and one Y chromosome.

Shape:
 The shape of the chromosomes is changeable from phase to phase in the continuous process of the cell growth and cell division.
 In the resting phase or interphase stage of the cell, the chromosomes occur in the form of thin, coiled, elastic and contractile, thread-like stainable structures, the chromatin threads.
 In the metaphase and the anaphase, the chromosomes become thick and filamentous. Each chromosome contains a clear zone known as centromere or kinetocore, along their length.
 The centromere divides the chromosomes into two parts, each part is called chromosome arm. The position of centromere varies form chromosome to chromosome and it provides different shapes.
 Telocentric. The rod-like chromosomes which have the centromere on the proximal end are known as the telocentric chromosomes.
 2. Acrocentric. The acrocentric chromosomes are also rod-like in shape but these have the centromere at one end and thus giving a very short arm and an exceptionally long arm. The locusts (Acrididae) have the acrocentirc chromosomes
 3. Submetacentric. The submetacentric chromosomes are J- or L-shaped. In these, the centromere occurs near the centre or at medium portion of the chromosome and thus forming two unequal arms.
 4. Metacentric. The metacentric chromosomes are V-shaped and in these chromosomes the centromere occurs in the centre and forming two equal arms. The amphibians have metacentric chromosomes.










Structure:
While describing the structure of the chromosomes during various phases of cell cycle, cell biologists have introduced many terms for their various components.
1. Chromatid. At mitotic metaphase each chromosome consists of two symmetrical structures, called chromatids. Each chromatid contains a single DNA molecule.
 Both chromatids are attached to each other only by the centromere and become separated at the beginning of anaphase, when the sister chromatids of a chromosome migrate to the opposite poles.
2. Chromonema (ta). During mitotic prophase the chromosomal material becomes visible as very thin filaments, called chromonemata (a term coined by Vejdovsky in 1912).
 A chromonema represents a chromatid in the early stages of condensation. Therefore, ‘chromatid’ and ‘chromonema’ are two names for the same structure : a single linear DNA molecule with its associated proteins. The chromonemata form the gene-bearing portions of the chromosomes.
3. Chromomeres. The chromomeres are bead-like accumulations of chromatin material that are sometimes visible along interphase chromosomes.
 The chromomere-bearing chromatin has an appearance of a necklace in which several beads occur on a string.
 Chromomeres become especially clear in the polytene chromosomes, where they become aligned side by side, constituting the chromosome beads.
 At metaphase the chromosomes are tightly coiled and the chromomeres are no longer visible.








4. Centromere and kinetochore. centromere is the region of the chromosome to which are attached the fibres of mitotic spindle.
 The centromere lies within a thinner segment of chromosome, the primary constriction. The regions of chromosome flanking the centromere contain highly repetitive DNA and may stain more intensely with the basic dyes.
 Centromeres are found to contain specific DNA sequences with special proteins bound to them, forming a disc-shaped structure, called kinetochore




 Under the EM, the kinetochore appears as a plate - or cup-like disc, 0.20 to 0.25 nm, in diameter situated upon the primary constriction or centromere.
 In thin electron microscopic sections, the kinetochore shows a trilaminar structure, i.e., a 10 nm thick dense outer proteinaceous layer, a middle layer of low density and a dense inner layer tightly bound to the centromere
 The DNA of centromere does not exist in the form of nucleosome
 During mitosis, 4 to 40 microtubules of mitotic spindle become attached to the kinetochore and provide the force for chromosomal movement during anaphase.
 The main function of the kinetochore is to provide a centre of assembly for microtubules, i.e., it serves as a nucleation centre for the polymerization of tubulin protein into microtubules
 The chromosomes of most organisms contain only one centromere and are known as monocentric chromosomes.
 Some species have diffuse centromeres, with microtubules attached along the length of the chromosome, which are called holocentric chromosomes.
 In some chromosomal abnormality (induced for example by X-rays), chromosomes may break and fuse with other, producing chromosomes without centromere (acentric chromosomes) or with two centromeres (dicentric chromosomes).
 Both types of these chromosomal aberrations are unstable. The acentric chromosomes cannot attach to the mitotic spindle and remain in the cytoplasm. The dicentric chromosomes lead to fragmentation, since, two centromeres tend to migrate to opposite poles.
 5. Telomere. (Gr., telo=for; meros=part). Each extremity of the chromosome has a polarity and therefore, it prevents other chromosomal segments to be fused with it. The chromosomal ends are known as the telomeres. If a chromosome breaks, the broken ends can fuse with each other due to lack of telomeres.
6. Secondary constriction. The chromosomes besides having the primary constriction or the centromere possess secondary constriction at any point of the chromosome.
 Constant in their position and extent, these constrictions are useful in identifying particular chromosomes in a set.
 Secondary constrictions can be distinguished from primary constriction or centromere, because chromosome bends (or exhibits angular deviation) only at the position of centromere during anaphase.
 7. Nucleolar organizers. These areas are certain secondary constrictions that contain the genes coding for 5.8S, 18S and 28S ribosomal RNA and that induce the formation of nucleoli.
 The secondary constriction may arise because the rRNA genes are transcribed very actively and, thus, interfering with chromosomal condensation.
 In human beings, the nucleolar organizers are located in the secondary constrictions of chromosomes 13, 14, 15, 21 and 22, all of which are acrocentric and have satellites.
 8. Satellite. Sometimes the chromosomes bear round elongated or knob-like appendages known as satellites.
 The satellite remains connected with the rest of the chromosome by a thin chromatin filament.
 The chromosomes with the satellite are designated as the sat chromosomes. The shape and size of the satellite remain constant.
KARYOTYPE AND IDIOGRAM
 All the members of a species of a plant or the animal are characterized by a set of chromosomes which have certain constant characteristics.
 These characteristics include the number of chromosomes, their relative size, position of the centromere, length of the arms, secondary constrictions and satellites.
 The term karyotype has been given to the group of characteristics that identifies a particular set of chromosomes.
 A diagrammatic representation of a karyotype (or morphological characteristics of the chromosomes) of a species is called idiogram.
 Generally, in an idiogram, the chromosomes of a haploid set of an organism are ordered in a series of decreasing size.
 Sometimes an idiogram is prepared for the diploid set of chromosomes, in which the pairs of homologues are ordered in a series of decreasing size.







MATERIAL OF THE CHROMOSOMES
 The material of the chromosomes is the chromatin. Depending on their staining properties, the following two types of chromatin may be distinguished in the interphase nucleus :
1. Euchromatin. Portions of chromosomes that stain lightly are only partially condensed; this chromatin is termed euchromatin.
 It represents most of the chromatin that disperse after mitosis has completed. Euchromatin contains structural genes which replicate and transcribe during G1 and Sphase of interphase.
 The euchromatin is considered genetically active chromatin, since it has a role in the phenotype expression of the genes.
2. Heterochromatin. In the dark-staining regions, the chromatin remains in the condensed state and is called heterochromatin.
 In 1928, Heitz defined heterochromatin as those regions of the chromosome that remain condensed during interphase and early prophase and form the so-called chromocentre.
 Heterochromatin is characterized by its especially high content of repetitive DNA sequences and contains very few, if any, structural genes (i.e., genes that encode proteins).
CHEMICAL COMPOSITION
 Chromatin which has been isolated from rat liver contains DNA, RNA and protein. The proteinof chromatin is of two types : the histones and the non-histones. Rat liver chromatin has been used as a model for chromatin.
1. DNA
 DNA is the most important chemical component of chromatin, since it plays the central role of controlling heredity. The most convenient measurement of DNA is picogram (10-12 gm).
2. Histones
 Histones are very basic proteins, basic because they are enriched in the amino acids arginine and lysine to a level of about 24 mole present. There are five types of histones in the eukaryotic chromosomes, namely H1, H2A, H2B, H3 and H4.
 Histones determining the structure of chromatin play a regulatory role in the repression activity of genes.

జరాయువు

జరాయువు అనగానేమి, వివిధ రకాల జరాయువులను వివరింపుము?
జ. జెన్ కిన్ సన్ జరాయువును తల్లికి మరియు అభివృద్ధిచెందుతున్న పిండమునకు మధ్య పదార్ధాల మార్పిడికి ఉపయోగపడే నిర్మాణముగా వర్ణించెను. మాస్ మాన్, జరాయువును తల్లికి మరియు పిండానికి మధ్య పదార్ధాల మార్పిడికొరకు – పిండబాహ్యత్వచాలు మరియు గర్భాశయ మ్యూకోసా పొరతో క
లసి ఏర్పడే అవయవముగా వర్ణించెను.










మాతృ మరియు భ్రూణ కణజాలముల కలయిక వలన ఏర్పడే నిర్మాణమును జరాయువు అంటారు. ఇది తల్లి నుంచి పిండమునకు పోషకపదార్ధములు సరఫరా చేసే అవయవముగా ఉండవలెను.
జరాయువు ఏర్పాటు, నిర్మాణం
జరాయువు నిర్మాణంలో ప్రాధమికంగా ఆరు రకాల కణజాలాలు పాల్గొంటాయి. వీటిలో మూడు పిండ కణజాలాలు కాగా మిగిలిన మూడు మాతృగర్భాశయ కణజాలాలు
పిండకణజాలాలు
ఎ. పరాయు కణజాలం లేదా భ్రూణ ఉపకళా కణజాలం
బి. భ్రూణ సంయోజక కణజాలం
సి. భ్రూణ ఎండోథీలియం
మాతృ గర్భాశయ కణజాలాలు
ఎ. మాతృ గర్భాశయ ఉపకళా కణజాలం
బి. మాతృ గర్భాశయ సంయోజక కణజాలం
సి. మాతృ గర్భాశయ ఎండోథీలియం

జరాయువు లక్షణాలు ఎ. జరాయువు పిండాన్ని మాతృ కణజాలాన్ని కలుపుతూ ఏర్పడిన నిర్మాణం
బి. ఇది ప్రధానంగా పోషకపదార్ధాలు, ఆక్సిజనును తల్లినుంచి పిండానికి అంద చేయటానికి తోడ్పడుతుంది.
సి. తల్లి, పిండం రక్తకణాలు పరస్పరం కలియకుండా జరాయువు ఒక అడ్డు త్వచం వలె పనిచేస్తుంది.
జరాయువు రకాలు
జరాయువును వివిధ అంశాల ప్రాతిపదికన వివిధ రకాలుగా పేర్కొంటారు అవి
1. జరాయువు ఏర్పాటులో పాల్గొనే పిండబాహ్యత్వచాల పరంగా జరాయువు రకాలు
2. గర్భాశయకుడ్యంతో జరాయువు కలయిక ఆధారంగా జరాయువు రకాలు
3. అంకురికలు విస్తరణ ఆధారంగా జరాయువు రకాలు
4. జరాయువు ఏర్పాటులో పాల్గొనే కణజాలాల ఆధారంగా జరాయు రకాలు

1. జరాయువు ఏర్పాటులో పాల్గొనే పిండబాహ్యత్వచాల పరంగా జరాయువు రకాలు
పిండంలో సొనసంచి, ఉల్బం ( ఆమ్నియాన్), అళిందం (అల్లంటాయిస్)
పరాయువు అను నాలుగు పిండ బాహ్య త్వచాలు ఉంటాయి. వీటిలో ఉల్భం
మినహాయించి మిగిలిన మూడు జరాయువు ఏర్పాటులో పాల్గొనటాన్ని గమనించవచ్చును.
1. జరాయువు ఏర్పాటులో పిండబాహ్యత్వచాల పరంగా జరాయువు రెండురకాలు. అవి
ఎ. సొనసంచి జరాయువు: ఈ రకం జరాయువు ఏర్పాటులో పరాయువు, సొనసంచి పాల్గొంటాయి. దీన్ని కొరియో వైటల్లైన్ జరాయువు అని కూడా పిలుస్తారు. ఇది అత్యంత ప్రాధమిక రకానికి చెందిన జరాయువు.
ఉదా: డైడెల్ఫిస్ వర్జీనియానా (అపొజం), మార్సూపియల్ కేట్
బి. అళింద పరాయువులతో ఏర్పడే జరాయువు: ఇందులో జరాయువు ఏర్పడటంలో పరాయువు, అళిందము ప్రధాన పాత్రవహిస్తాయి. ఈ రెండిటి కలయిక వల్ల అళింద-పరాయుత్వచం ఏర్పడును. ఈ త్వచం వెలుపలివైపునుంచి సన్నని వేళ్ళ వంటి అంకురికలు ఏర్పడతాయి. ఇదేసమయంలో గర్భాశయకుడ్యం వెలుపలి గోడలపై చిన్న చిన్న గుంతలవంటి నిర్మాణాలు ఏర్పడతాయి. అంకురికలు ఈ గుంతలలోకి చొచ్చుకొని పోయి మాతృగర్భాశయకుడ్యం నుంచి పోషకపదార్ధాలను పీల్చుకొంటాయి. ఈ రకమైన జరాయువు యూథీరియా క్షీరదాలలో కనిపిస్తుంది.

2. గర్భాశయకుడ్యంతో జరాయువు కలయిక ఆధారంగా జరాయువు రకాలు
పరాయువు నుంచి ఏర్పడిన అంకురికలు గర్భాశయపు కుడ్యంలోకి వదులుగా లేదా బిగుతుగా అతుక్కొని ఉంటాయి. ఈ కలయిక ఆధారంగా అళిందపరాయు రకపు జరాయువును రెండురకాలుగా పేర్కొంటారు. అవి
ఎ. అపాతుకీ జరాయువు పరాయు అంకురికలు గర్భాశయగోడలతో వదులుగా చొచ్చుకొని ఉంటాయి. ప్రసవసమయంలో ఇవి వెనుకకు లాగబడతాయి. ఇందువల్ల గర్భాశయపు గోడలు పెద్దగా గాయపడవు. కాబట్టి రక్తస్రావం ఉండదు.
ఉదా: గిట్టలు కలిగిన అంగ్యులేట్స్
బి. పాతుకీ జరాయువు ఈ రకపు జరాయువులో పరాయువు, మాతృగర్భాశయపు కుడ్య ఉపకళాకణజాలం దృఢంగా కలిసిపోయి ఉంటాయి. అంకురికలు చెట్టువేరులాగ అనేక శాఖలు కలిగిఉండి గర్భాశయ గోడలలోకి చొచ్చుకొని పోయిఉంటాయి. ఇక్కడ జరాయువు నిర్మాణంలో పాల్గొనే గర్బాశయ కుడ్యాన్ని డెసిడ్యువా అంటారు.
జరాయువు యొక్క ఈ రకమైన నిర్మాణం వలన ప్రసవసమయంలో గర్భాసయ గోడలు (డెసిడ్యువా) పెకలించబడతాయి. దానివల్ల గర్భాశయగోడలు గాయపడి అధికంగా రక్తస్రావం జరుగును.
ఉదా; గబ్బిలాలు, రొడెన్షియా (ఎలుకలు), ప్రైమేట్లు (కోతులు)
కుందేలులో పాతుకీ జరాయువు అయినప్పటికీ, నిర్మాణం కొంచెం భిన్నంగా ఉంటుంది. ప్రసవసమయంలో గర్భాసయ గోడలలోని శ్లేష్మ పటలం జారాయువుతో పాటు పడిపోతుంది. ఇక్కడ గర్భాశయగోడలు పెద్దగా గాయపడవు కనుక రక్తస్రావం జరగదు. కాబట్టి కుందేలులోని జరాయువును అర్ధపాతుకీ జరాయువు అంటారు.

3 అంకురికలు విస్తరణ, ఆధారంగా జరాయువు రకాలు
పరాయువుపై ఉండే అంకురికలు విస్తరణ, ఆకృతిల పరంగా కోరియో అల్లంటాయిస్ జరాయువును ఆరు రకాలుగా పేర్కొన వచ్చును. అవి
ఎ. వ్యాపన జరాయువు: ఈ రకమైన జరాయువులో అంకురికలు మొత్తం పరాయువుపై అసంఖ్యాకంగా ఉండి వెజల్లినట్లుగా వ్యాపించిఉండును. ఈ అంకురికలు గర్భాశయకుడ్యంలోకి చొచ్చుకొని పోవు. ఉదా: పంది, గుర్రం
బి. బీజదళ జరాయువు: ఈ రకమైన జరాయువులో అంకురికల గుంపులు మొక్క బీజదళాల మాదిరిగా అక్కడక్కడా అమరి ఉంటాయి. వీటినడుమ మృదువైన పరాయువు ఉంటుంది. ఈ అంకురికలు గర్భాశయకుడ్యంలోనికి చొచ్చుకొని ఉంటాయి. ఉదా: ఆవు, గొర్రె, జింక
సి. ఇంటర్మీడియట్ జరాయువు: ఇది వ్యాపన జరాయువు, బీజదళ జరాయువులకు మధ్యస్థంగా ఉంటుంది. ఇందులో అంకురికలు వెదజల్లబడి మరియు గుంపులు గుంపులుగాను కూడా ఉంటాయి. ఉదా: జిరాఫి, ఒంటె
డి. మాండలిక జరాయువు: ఈ రకమైన జరాయువు లో అంకురికలు, పరాయువు మధ్యభాగాన్ని చుట్టి పట్టీలవంటి నిర్మాణాల్ని ఏర్పరుస్తాయి. ఈ అంకురికలు గర్భాశయ కుడ్యంలోనికి చొచ్చుకొని ఉంటాయి. ఉదా: నక్క లో మాండలిక జరాయువు రెండు పట్టీలను ఏర్పరచును, కుక్క లో ఒకపట్టీ ఉండును
ఇ. చక్రాభ జరాయువు: ఈ రకమైన జరాయువులో అంకురికలన్నీయూ పరాయువు మీద ఒకే చోట ఒక బిళ్ళ మాదిరి కేంద్రీకృతం అవుతాయి. ఇవి కూడా గర్భాశయకుడ్యంలోకి చొచ్చుకొని ఉంటాయి. ఉదా. రొడెన్షియా క్రమపు జీవులు
ఎఫ్. మెటా డిస్కాయిడల్ జరాయువు: ఇది చక్రాభ జరాయువు అయినప్పటికీ ఏర్పాటులో కొంచెం భిన్నంగా ఉంటుంది. ఇందులో అంకురికలు ప్రారంభ దశలో పరాయువు ఉపరితలం మొత్తం మీద సమానంగా విస్తరించి ఉంటాయి. క్రమేణా అవి ఒకటి లేదా అంతకన్నా ఎక్కువ డిస్క్ లేదా చక్రికల మాదిరిగా ఏర్పడి ఉదరతలానికి మాత్రమే పరిమితమై ఉంటాయి. ఉదా: ప్రైమేట్ లు
4. జరాయువు ఏర్పాటులో పాల్గొనే కణజాలాల ఆధారంగా జరాయు రకాలు
జరాయువు ఏర్పాటులో కనిపించే మాతృ-భ్రూణ కణజాలాలు ప్రాధమికంగా ఆరు రకాలు. అవి
• గర్భాశయ ఉపకళా కణజాలం
• గర్భాశయ సంయోజక కణజాలం
• గర్భాశయ ఎండోథీలియం
• భ్రూణ/పరాయువు ఉపకళాకణజాలం
• భ్రూణ సంయోజక కణజాలం
• బ్రూణ ఎండోథీలియం
ఈ కణజాలాలలో అన్నీకానీ కొన్ని కానీ జరాయువు ఏర్పాటులో పాల్గొంటాయి.
జరాయువు ఏర్పాటులో పాల్గొనే కణజాలాల ఆధారంగా జరాయువు అయిదు రకాలుగా ఉంటుంది. అవి
ఎ. ఎపిథీలియో- కొరియల్ జరాయువు: ఈ రకపు జరాయువులో గర్భాశయపు ఉపకళ, పరాయువు యొక్క ఉపకళా కణజాలాలు జరాయువును ఏర్పరచును. పరాయు భ్రూణ అంకురికలు గర్భాశయ కుడ్యంతో పైపైన అమరి ఉంటాయి. ప్రసవసమయంలో గర్బాశయ గోడలు దెబ్బతినవు
బి. సిన్ డెస్మో-కొరియల్ జరాయువు: ఈ రకమైన జరాయువులో పరాయువుయొక్క ఉపకళా కణజాలాలు, గర్భాశయగోడల యొక్క సంయోజక కణజాలాలతో కలసి జరాయువును ఏర్పరచును. గర్భాశయ గోడల ఉపకళ అంతరించును. ఈ పరిస్థితి సాధారణముగా బీజదళ జరాయువులో ఉండును. ఉదా: ఆవు, గొర్రె
సి. ఎండోథీలియో – కొరియల్ జరాయువు: ఈ రకమైన జరాయువులో పరాయువు యొక్క ఉపకళా కణజాలాలు గర్భాశయ గోడలయొక్క ఎండోథీలియల్ కణజాలాలతో కలసి జరాయువును ఏర్పరచును. గర్భాశయ గోడల ఉపకళ, సంయోజక కణజాల పొరలు అదృశ్యమగును. ఇది మాండలిక జరాయుధారులలో కన్పించును
ఉదా; కుక్క, నక్క, పిల్లి
డి. హీమో – కోరియల్ జరాయువు: ఈ రకమైన జరాయువులో పరాయువు యొక్క సంయోజక కణజాలం గర్భాశయ రక్తనాళికలతో కలిసి జరాయువును ఏర్పరచును. గర్భాశయ ఉపకళ, సంయోజక కణజాలం, రక్తనాళికల అంతఃస్తరం చిట్లి నశిస్తాయి. భ్రూణ అంకురికల యొక్క ఉపకళ బహుకేంద్రకయుతమైన సిన్సిషియం
గా మారును. వాటి సంయోజకకణజాలం పగులును. ఫలితంగా అంకురికలు సరాసరి మాతృ రక్తంతో సంబంధాన్ని పెంపొందించుకొంటాయి. ఉదా: మానవుడు, కోతులు
ఇ. హీమో- ఎండోథీలియల్ జరాయువు: ఈ రకమైన పరాయువు యొక్క ఎండోథీలియల్ కణజాలం గర్భాశయ రక్తనాళాలతో నేరుగా సంబంధాన్ని పెట్టుకొంటుంది. అనగా గర్భాశయపు ఉపకళ, సంయోజక మరియు ఎండోథీలియల్ కణజాలాలు అదృశ్యం అవుతాయి. పిండముయొక్క ఉపకళ, సంయోజక కణజాలాలు కూడా అదృశ్యం అవుతాయి. ఫలితంగా బ్రూణ ఎండోథీలియం మాతృరక్తంలో మునిగి ఉంటుంది. ఉదా; ఎలుక

జరాయువు విధులు
1. జరాయువు పిండానికి పోషకాలను అందిస్తుంది
2. జరాయువు పిండ శ్వాస విసర్జక అవయువంగా పనిచేయును
3. జరాయువు ఎండోక్రైన్ గ్రంధిగా పనిచేసి, ప్రొజెస్టిరాజ్, ఎస్ట్రోజెన్ హార్మోనులను స్రవించును.
ప్రసవ సమయంలో జరాయువు నుంచి విడుదలైన రిలాక్సిన్ అనే హార్మోను సుఖప్రసవానికి

Practical Manual B.Voc

Clarias batrachus

Phylum: Chordata

Class: Actinopterygii

Order: Siluriformes

Family: Clariidae

Genus: Clarias

Species: C. batrachus


1. The walking catfish (Clarias batrachus) is a species of freshwater air breathing catfish native to Southeast Asia, but alsointroduced outside its native range where it is considered an invasive species. It is named for its ability to "walk" across dry land, to find food or suitable environments. While it does not truly walk as most bipeds or quadrupeds do, it has the ability to use itspectoral fins to keep it upright as it makes a sort of wiggling motion with snakelike movements.[1] This fish normally lives in slow-moving and often stagnant waters in ponds, swamps, streams and rivers, flooded rice paddies or temporary pools which may dry up. When this happens, its "walking" skill allows the fish to move to other sources of water. Considerable taxonomicconfusion surrounds this species and it has frequently been confused with other close relatives.[2]





Heteropneustes fossilis

Phylum: Chordata

Class: Actinopterygii

Order: Siluriformes

Family: Heteropneustidae

Genus: Heteropneustes

Species: H. fossilis




Inhabits freshwater, rarely brackish waters. This is primarily a fish of ponds, ditches, bheels, swamps and marshes, but it is sometimes found in muddy rivers. It is able to tolerate slightly brackish water. Its air-breathing apparatus enables it to exist in almost any kind of water. Generally, during the dry season singi lives in semiliquid and semi-dry mud, and even when the mud dries up they take their bodies to the bottom of fissures and crevices formed by the cracking mud. Fertilised eggs are adhesive, demersal and spherical in form.


Chanos chanos
Phylum: Chordata

Subphylum: Vertebrata

Order: Gonorynchiformes

Family: Chanidae
Genus: Chanos

Body fusiform, elongated, moderately compressed, smooth and streamlined. Body colour silvery on belly and sides grading to olive-green or blue on back. Dorsal, anal and caudal fins pale or yellowish with dark margins. Single dorsal fin with 2 spines and 13-17 soft rays. Short anal fin with 2 spines and 8-10 soft rays, close to caudal fin. Caudal fin large and deeply forked with large scale flaps at base in adults. Pectoral fins low on body with axillary (inner basal) scales. Pelvic fins abdominal with axillary scales and 11 or 12 rays. Scales cycloid, small and smooth, 75-91 on lateral line. No scutes (modified pointed scales) along belly. Transparent 'adipose' tissue covers eye. Mouth small and terminal without teeth. Lower jaw with small tubercle at tip, fitting into notch in upper jaw. No bony gular plate between arms of lower jaw. Four branchiostegal rays supporting underside of gill covers. Gill rakers fine and numerous. Attains typical length of 1 m but may reach maximum length of 1.8 m (male).

బీజకణోత్పత్తి

1. బీజకణోత్పత్తి గురించి వ్యాసం వ్రాయుము
జ. శుక్ర జననం, అండజననాలను కలిపి బీజకణోత్పత్తి అంటారు. పురుషజీవులలో శుక్రజననం, స్త్రీ జీవులలో అండజననం జరుగుతుంది.
బీజకోశములలో ఉండే జనన కణాలు విభజన చెంది, స్త్రీలలో అండములు పురుషులలో శుక్రకణములను ఏర్పరచును. ద్వయస్థితిక క్రోమోజోముల సంఖ్యను (2X) కలిగిఉన్న జనన కణాలు క్షయకరణ విభజన ద్వారా ఏక స్థితిక (X) క్రోమోజోముల సంఖ్యను కలిగిన బీజకణాలను ఏర్పరచును.

I శుక్ర జననం
పురుషబీజకణాలు లేదా శుక్రకణాలు ఏర్పడే విధానాన్ని శుక్రజననం అంటారు. ఇది ముష్కంలో జరుగును. ముష్కం నిర్మాణంలో పొడవైన శుక్రోత్పాదక నాళికలు మెలికలు తిరిగి ఉంటాయి. వీటిమధ్య కల ఖాళీలలో రక్తకేశనాళికలు, సంయోజకకణజాలము, నాడులు, లీడిగ్ కణములు ఉంటాయి. ఈ లీడిగ్ కణములు పురుష లైంగిక హార్మోనులను (టెస్టోష్టిరాన్) ఉత్పత్తి చేసి, ద్వితీయలైంగిక లక్షణములు ఏర్పడటానికి దోహదపడును. శుక్రోత్పాదక నాళికల గోడలలో కల జనన కణములు విభజనలు జరుపుకొని శుక్రకణములను ఉత్పత్తి చేయును. ఈ జనన కణముల మధ్య కల ప్రత్యేకమైన కణములైన సెర్టోలి కణములు శుక్రకణముల ఉత్పత్తి అవసరమైన పోషకములను అందించును.

శుక్రకణ జననాన్ని రెండు దశలుగా విభజించవచ్చును. అవి. ఎ. శుక్రకణోత్పాదన కణము ఏర్పడుట బి. శుక్రకణోత్పాదక కణము శుక్రకణముగా ఏర్పడుట
ఎ. శుక్రకణోత్పాదన కణము ఏర్పడుట:
శుక్రకణోత్పాదన కణము మూడు దశలుగా జరుగును. అవి ఎ. కణ విభజన దశ బి. పెరుగుదల దశ సి. పరిణిత దశ
విభజన దశ: శుక్రోత్పాదనాళికల బాహ్య ఉపరితలముపై జననకణాలు ఉంటాయి. ఈ కణాలను ప్రాధమిక బీజకణాలు లేదా శుక్రమాతృకణాలు అంటారు. ఇవి అనేక విభజనలు జరుపుకొని శుక్రకణ మాతృకణాలుగా మార్పు చెందుతాయి. ప్రతి శుక్రకణ మాతృ కణాలు ధ్వయస్థితిక క్రోమోజోములను కలిగి ఉంటాయి. ఈ దశ శిశువు పిండదశలో మొదలయి మరల యుక్తవయసు వచ్చే వరకూ సాగుతుంది.

పెరుగుదల దశ: జీవి యుక్తవయసుకు చేరాకా ప్రతి శుక్రకణ మాతృకణములు తన చుట్టూ ఉన్న సెర్టోలి కణములనుండి ఆహార పదార్ధములను గ్రహించి పెద్దవవుతాయి. వీటిలోని క్రోమోజోములు నాలుగు జతల క్రొమాటిడ్ లను ఏర్పరుచుకొని తదుపరి దశ అయిన క్షయకరణ విభజనకు తయారుగా ఉంటాయి.

పరిణిత దశ: ఈ దశలో ఒక్కొక్క కణం క్షయకరణ విభజన జరుపుకొని నాలుగు ఏకస్థితిక చలన రహిత శుక్రకణాలను ఏర్పరుస్తుంది. మొదటి క్షయకరణ విభజన వలన రెండు ఏకస్థితిక ద్వితీయ శుక్రమాతృకణాలు ఏర్పడును. క్షయకరణ విభజన II వలన ఒక్కో ద్వితీయ శుక్రమాతృకణము రెండు ఏకస్థితిక శుక్రకణాలను ఏర్పరచును. ఇవి తదుపరి విభజనలు జరుపుకొనక, విభేధీకరణ చెంది చలించగలిగే స్పెర్మ్ లేదా శుక్రకణముగా మారును
బి. శుక్రకణోత్పాదకము - చలించే శుక్రకణము ఏర్పడుట
చలన రహిత శుక్రకణాలు (స్పెర్మాటిడ్ లు) చలన సహితంగా, క్రియాశీలకంగా మారటాన్ని శుక్రకణోత్పాదకము లేదా స్పెర్మియోజెనిసిస్ అంటారు.
ఫలదీకరణ సమయములో అండమును చేరి దానితో సంయోగము చెందుట శుక్రకణము యొక్క ప్రాధమిక విధి. ఆ విధిని నిర్వర్తించుటకొరకై శుక్రకణము యొక్క నిర్మాణములో ఈ క్రింది మార్పులు జరుగును.
ఎ. కేంద్రకములో జరుగు మార్పులు: ఈ దశలో శుక్రకణోత్పాదక కేంద్రకం ద్రవాన్ని పోగొట్టుకొని చిన్నదవుతుంది. క్రోమోజోములు కూడా సూక్ష్మ రూపంలోకి వస్తాయి.
బి. ఎక్రోసోము ఏర్పడుట: శుక్రకణ పూర్వాంతమున ఒక టోపీ ఆకారపు నిర్మాణము ఏర్పడుతుంది. దీనిని ఎక్రోసోము అంటారు. ఇది గాల్జి దేహమునుండి ఏర్పడుతుంది. గాల్జి పదార్ధము కళికగా మారి, తనలోని ద్రవమును పోగొట్టుకొని కేంద్రకము యొక్క పైభాగాన్ని కప్పుతుంది. దీనినే కేంద్రక పూర్వఛత్రకము లేక ఎక్రోసోము అంటారు. ఎక్రోసోమునందుకల ఎంజైములు, అండము యొక్క పై త్వచ మును కరిగించి, శుక్రకణ కేంద్రకము అండములోకి ప్రవేశించటంలో తోడ్పడును
సి. తారావత్కేంద్రాలు (సెంట్రియోల్స్): సెంట్రోజోములోని రెండు తారావత్కేంద్రాలో మొదటిది శుక్రకణ మెడ మరియు మధ్య తునకలను ఏర్పరచును. దీనిని సమీపాగ్ర తారావత్కేంద్రము అంటారు. రెండవ తారావత్కేంద్రము అక్షీయ తంతువును కలిగ్ ఇది శుక్రకణిం తోకను ఏర్పరచును. ఇది 9+2 అమరికను కలిగి ఉండును.
డి. మధ్యభాగము: శుక్రకణము మధ్య భాగములో మైటోఖాండ్రియాలన్నీ కేంద్రీకృతమై ఫలదీకరణ సమయములో శుక్రకణము చలించటానికి అవసరమైన శక్తిని అందచేస్తాయి.
ఇ. పరిణితి చెందిన శుక్రకణము: పరిణితి చెందిన శుక్రకణము లో శీర్షము (హెడ్) భాగములో అక్రోజోమ్, కేంద్రకము - మధ్యభాగము(మిడిల్ పీస్) లో రెండు సెంట్రియోల్ లు మరియు తోక లేద కశాభము అను భాగములతో ఉండును

II అండజననం
స్త్రీబీజకోశములోని జననస్థరపు కణాలు అండములుగా అభివృద్ధి చెందటాన్ని అండజననము అంటారు.
సకశేరుకములలో ఒక జత స్త్రీ బీజకోశములు ఉంటాయి. స్త్రీబీజకోశపు ఉపరితలం పై ఉపకళా కణజాలంతో ఒక పొర ఏర్పడును దీనిని జననోపకళ అంటారు. ఈ జనన ఉపకళా కణాలు సమవిభజనలు చెంది చిన్న చిన్న గుంపులు గుంపులుగా కణముల సముదాయములను ఏర్పరచును. ఒక్కొక్క గుంపును గ్రాఫియన్ పుటిక అంటారు. ఒక గ్రాఫియన్ పుటికలో బాగా అభివృధ్ది చెందిన ఒక కణము “అండ మాతృకణముగా” ఏర్పడును. మిగిలిన కణాలు ఈ అభివృద్ది చెందే అండానికి పోషకపదార్ధములను అందించును. ఇలా పరిణితిచెందిన గ్రాఫియన్ పుతిక అండాశయం ఉపరితలానికి చేరి పగిలిపోవటం ద్వారా అండం విడుదల జరుగును. ఈ రకంగా అండాశయం నుండి నుండి అండం విడుదల కావటాన్ని అండోత్సర్గము/అండోత్పత్తి అంటారు.
ఈ ప్రక్రియ మూడు దశలలో జరుగును అవి. ఎ. విభజన దశ బి. పెరుగుదల దశ సి. పరిణిత దశ
విభజన దశ; ఇందులో స్త్రీబీజకోశంలోని జననోపకళ కణాలు అనేక సమవిభజనలు జరుపుకొని ఎక్కువ కణాలను ఏర్పరచును. ఈ కణాలను అండమాతృకణాలు అంటారు. ఇవి కూడా అనేక విభజనలు జరుపుకొని ప్రాధమిక అండమాతృకణం ఏర్పడుతుంది. ఈ దశ వరకూ గల కణాలు అన్నీ ద్వయస్థితిలో ఉంటాయి.
వృద్ధి/పెరుగుదల దశ: ప్రతి అండమాతృకణం ప్రొటీన్ క్రొవ్వులను సొనపదార్ధ రూపం లో ఎక్కువగా సేకరించుకొంటుంది. ఈ సొనపదార్ధం అండంలోని క్రిందిభాగంలో ఎక్కువగా కేంద్రీకృతమౌతుంది, కనుక ఈ భాగాన్ని భృహుత్కంఢ దృవం అనీ దానికి వ్యతిరేకంగా దిశలో ఉన్న భాగాన్ని జాంతవ దృవమనీ అంటారు. సొనపదార్ధాన్ని పూర్తిగా ఏర్పరచుకొన్న అండమాతృకణాన్ని, ప్రాధమిక అండమాతృకణం అంటారు.
పరిపక్వ దశ: ప్రాధమిక అండమాతృకణం మొదటి క్షయకరణ విభజన రెండు అసమాన కణాలుగా ఏర్పడుతుంది. పెద్దకణాన్ని ద్వితీయ అండమాతృకణం అనీ, చిన్నకణాన్ని దృవకణం అని అంటారు. ఇవి ఏకస్థితికాలు. ఇది మరల విభజన జరుపుకోగా ఏర్పడే పెద్దకణాన్ని పరిపక్వ అండము లేదా గుడ్డు అంటారు. మొదటి మరియు రెండవ దృవదేహాలు అదృశ్యమవుతాయి.
అలా ఉత్పత్తి అయిన అండాలు అండోత్పత్తి అనే ప్రక్రియ ద్వారా అండాశయము వెలుపలకు విడుదల చేయబడును.

Canal system in Scypha

Canal system in Scypha
Body of Scypha consists of a complex system of pores and canals. This system is generally referred to as canal system or aquiferous system. Bodywall has cellular layers, outer pinacoderm and inner choanoderm. In between these two layers, there is a non-cellular gelatinous mesenchyme in between. But the bodywall is so folded as to form regularly arranged alternating invaginations and evaginations, establishing the sycon type of canal system. The various components of canal system of Scypha are:
1) Ostia or dermal pores
2) Incurrent canals
3) Prosopyles
4) Radial canals
5) Apopyles
6) Spongocoel
7) Osculum
8) Current of water

1) Ostia or dermal pores:
The external grooves of body surface are stretched over by a thin pore membrane. It bears two or more openings for the ingress of outside water into the body of sponge. These pores are known as Ostia (Latin, Ostium=door) or dermal pores. Because of the presence of contractile cells or myocytes around them, the ostia can reduce in diameter and thus regulate the amount of ingressing (incoming) water.
2) Incurrent canals:
These are the invaginated folds of bodywall and are also called inhalent canals. These communicate with outside through ostia but end blindly at their inner ends. Pinacocytes line these canals throughout.
3) Prosopyles:
Incurrent canals communicate with radial canals through intercellular spaces called prosopyles (Greek. Pros=near, pyle=gate)
4) Radial canals:
Evaginations of bodywall form thimble-shaped chambers lined by flagellated choanocytes. These chambers are called flagellated or radial canals.
Incurrent and radial canals are parallel and alternate with each other, both vertically and radially. The arrangement is such that, in a vertical or tangential section through the wall of a cylinder, each radial canal is surrounded on four sides by incurrent canals, and each incurrent canal is surrounded likewise by four radial canals.
Radial canals end blindly at their outer ends but lead at their inner ends into spongocoel.
5) Apopyles:
Openings of radial canals into spongocoel are called apopyles (Greek apo=away from, pyle=gate) or internal ostia. These are surrounded by contractile myocytes serving as a sphincter.
6) Spongocoel:
It is the large central cavity of the body forming the vertical axis of the cylinder (Greek sponges=sponge+koilos=hollow). In Leucosolenia, spongocoel is lined by flagellated collar cells or choanocytes. In Scypha, the choanocytes line the radial canals, whereas the spongocoel is lined with the epidermal pinacocytes.
7) Osculum:
Spongocoel leads to outside through a terminal opening, the osculum. The oscula are provided with sphincters to regulate the rate of water flow in the body. Sphincters are lined by special contractile pinacocytes.
Sphincters are lined by special contractile pinacocytes, called myocytes (Greek. Myos, muscle+kytos=cell)
8) Current of water
Flow of water in canal system is maintained by continuous beating of flagella of collar cells lining the radial canals. Every beat of a flagellum consists of a normal active stroke and a recovery stroke. Electron microscopy revealed that there is no coordination between the beating of flagella of adjacent cells. The course taken by water current into the canal system is as follows.

Water from outside through dermal ostia Incurrent canals through prosopyles


Radial canals

Through apopyles
to outside Spongocoel Radial canals

HERDMANIA TYPE STUDY

Affinities of Urochordates .

The typical tunicate looks like a non-chordate animal. If the life history of such animal is studied, the larval form reveals the chordate chara’4ters of that animal.
In 1816, Lamarck and Cuvier placed these animals in one class ‘Tunicata’. Allis described a compound Ascidian “Botryllus’ in 1756.KowalevskSi. Worked on the development ofthe Ascidian and placd them’in tunicates after observing the chordate features
.
Urochordates-Resemblance. With Chordate. :- .

1. Presence of dorsal tubular nerve cord,
2. Presence of Notochord,
3. Well developed pharynx with gill-slits.
4. Presence of endostyle on the ventral side of the pharynx
.5. Presence of atrium around pharynx.
.6. Presence of post - anal tail, with tail fin.
, Because of these chordate features tunicates are included in chordates group.

Urochordates-Resemblance with Amphioxus:
1. Presence of notochord.
2. Presence of dorsal tubular nerve cord.
3. Presence of large pharynx with gill slits.
4. Presence of atrium and atriopore.
5. Presence of muscle band.
Thus, the Urochordates show close relation with Cephalochordates. But the



Urochordates differ with other Chordates because of the following peculiar characters.
1 .Presence of retrogressive metamorphosis.
2. Absence of segmentation.
Because of these characters zoologists included these animals in a
Separate sub-phylum Urochordates.
During recent years many zoologists regarded the tunicates as primitive and ancestral forms to chordates as a whole.
previous topic urochordata classification
Urochordata Classification
Classification of Urochordata

Subphylum Urochordata is divided into three classes.
CLASS 1. ASCIDIACEA CLASS 2. THALIACEA CLASS : 3 . LARVACEA (APPENDICULARIA)

CLASS 1. ASCIDIACEA:
1. These are sedentary tunicates.
2. The body is covered by a test.
3. Pharynx is large and contains gill-slits.
4. Notochord, nerve-cord and tail are absent
5. These are Bisexual animals.
6. Life-history includes a typicalTadpole larva. The class Ascidiacea is divided into two orders.
Order 1. Enterogona
These ascidians bear one gonad in the intestinal loop. Neural gland is ventral to the ganglion. Tadpole larva is seen:
Ex: Ascidia and Ciona.
Order: 1. Pleurogona:
In these ascidians,gonads are paired and are present in the atrial wall. Neural gland is dorsal to the ganglion:
Ex : Herdmania, Botryllus.

CLASS 2. THALIACEA :-
1. These Urochordates are free-swimming and pelagic forms.
2. They are covered by transparent test.
3. The brachial and atrial apertures are placed at anterior and posterior ends.
4. Pharynx is small.
5. Gill-slits number is less.
6. Notochord, nerve-cord and tail are absent in the adult.
7. Asexual reproduction is by budding.
‘8. These are bisexual animals.
9. Tailed larva may be present or absent.
10. Alternation of generations can be seen in the life history.
The class thaliacea is divided into three orders.
1. Doliolida, 2. Pyrosomida and 3. Salpida.
Order 1. Doliolida (Cyclomyarla)
1. Barrel shaped body is completely covered by Muscle bands,
2. Pharynx is small
3. Number of gill slits will be small.
4. Tailed larva is seen
5. Sexual Blasto-zooid and asexual oozooid stages will alternate in the life cycle.
Ex :Doliolum.
Order 2. Pyrosomlda :
1. This order includes colonial forms.
2. Muscle bands are small and present at the ends.
3. Gill-slits are many.
4. Tailed larval stage is absent.
Ex : Pyrosoma (Luminescent colonial form).
Order 3. Salplda (Hemimyaria) :-
1. This order includes organisms whose body is prism like.
2. Muscle bands are complete dorsally and incomplete ventrally.
3. Only one pair of lateral gill slits are present.
4. Tailed larval stage is absent.
5. Life history includes alternation of generations.
Ex: Salpa.

CLASS : 3 . LARVACEA (APPENDICULARIA)
1. These are free - swimming, pelagic tunicates.
2. True’ test covering is lacking
3. They show loose gelatinous house.
4. This house is useful for filter feeding.
5. Two gill slits re present.
6. Atrium is absent. ..
7. Notochord and nerve cord are Persistent
8. They show tail throughout their life.
9. Neotenic forms are included.
Ex: Oikopleura. ‘













Urochordata Characters
Urochordata General Characters
The tunicates were first regarded as sponges. Lamark in 1816 placed Tunicata in between the Radiata and Vermes in his system of classification. Later, they were included in Mollusca. In 1866 Kowalevsky kept them in chordates.
Their chordate features are clearly seen in the larval stages. All Urochordates are marine and occur in all the seas. Majority of them are sedentary and some are pelagic.
1. Body shows variation in size and form.
2,. The body is un segmented and has no tail
3. The body is covered by a test. It is formed by tunicine which is
rallied to cellulose. Hence the name Tunicata.
4. Body wall shows one-layered epidermis, dermis is made by connective tissue and muscles, and atrial epithehum.
5.Celome is absent.
6. Atrial cavity surrounds the pharynx, into this cavity the gill slits,anus and genital ducts will open. It opens through atrial aperture.
7. Larva has notochord in the tail. It disappears during metamorphosis.
8. Respiratory system contains gills in the pharyngeal wall.
9. Ciliary mode of feeding is common.
10. Open type of Circulatory system is seen.
11. The heart is ventral and it periodically reverses its function.
12. Nervous system is represented by a single dorsal ganglion in the adult.
13. Excretion is carried on by nephrocytes.
14. Asexual reproduction is by budding.
15. Bisexual animal and cross fertilisation is favored.
16. Fertilization is external.
17. Development includes a minute, free swimming tadpole larva with a tail, a dorsal nerve cord, and a notochord in the tail. In some urochordates retrogressive metamorphosis is seen in the life history.
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Herdmania Excretory Organ:
Excretory Organ Of Herdmania:
A neural gland is present above the brain in herdmaina. it Is brown in colour. It is present In the mantle. 1t is 4mm in diameter. It show branching tibuIes. At one end it leads into a short duct which opens by ciliated funnel above the dorsal tubercle. In the blood nephrocytes cell are present. They coiled waste matter. They come to the neural gland from there, they are sent out The neural gland secretes a hormone. It help in metamorphosis. Neural gland is considered homologous to pituitary glands of vertebrates.

Herdmania- Spicules
Herdmania- Spicules in the test:
In the test of Herdmania two types of calcareous spicules are Present. They are:
1) Microscieres : These are 40 to 80 microns in length. They are minute.
2) Megascleres : These are long spicules. They show different shapes. They are 1.5 to 3.5 mm in length. They are two types.
a) Spindle shaped Megascleres. They are 1.5 to 2.5 mm in length.
b) Pipette shaped Megascleres. They are 3.5 mm. in length.
The rnicroscleres are present only in the test. But the megascleres occur in the test, body wall, and viscera.
Herdmania-Spicules Function:
1) They give support to the test
2) They protect the animal from predators.
3) They fix mantle with test.
Herdmania- Nervous System
NERVOUS SYSTEM OF HERDMANIA:
Herdmania shows brain or nerve ganglion. It is 4 mm long. It is present in the mantle in between the two siphons. A neural gland is present above the brain. From the brain three nerves arise, one goes to the bronchial siphon, and two will go to the atrial siphon. The brain represents the degenerated nervous system of the larva.

Receptors:
1. Red pigmented spots on the test are photoreceptors. They are sensitive to light.
2. Sensory cells of the margins of siphons and tentacles are tango receptors. They are sensitive to touch.
3. The cells on the margins of siphons are rheo receptors. They are sensitive to water currents.
4. Cells lining the siphons are thermo receptors. They are sensitive to changes of temperature.
Herdmania Gonads
Gonads of Herdmanla :
Ans: Herdmania is a bisexual animal. It is a protogynous animal. Ovary matures’ first. Hence cross fertilization takes place.
Herdmania contains a pair of gonads. The left gonad lies in the intestinal loop above the heart. Each gonad shows 10 to 25 lobes arranged in two rows. The median lobe is single and large. Other lobes are oval in shape.
Each lobe shows outer large testicular part and inner small ovarian part. The testicular part is brick red in colour and produces sperms. The ovarian part is pink in colour and produce ova. From each testicular part sperm ductule will arise. They open into spermduct. From each ovarian part ovarian ductule will come. They open into the oviduct. Each gonad has an oviduct and spermduct. They run parallelly and open separately into cloaca behind anus.
Herdmania -Retrogressive Metamorphosis
Retrogressive Metmorphosis in herdmania
During metamorphosis the larva will loose all the chordate characters and attains an invertebrate like form. This type of metamorphosis, where highly advanced larval form ends in a lowly organised adult is called retrogressive metamorphosis.
Fixation of the larva: The larva swims for some time without feeding. It is fixed to a sub- stratum with the help of the adhesive papillae. It stands erect with the tail upwards. Then it undergoes retrogressive metamorphosis.
Changes during metamorphosis:
1.Notochord, nerve cord muscles and tail will be reduced. All the above structures will help the larva to swim freely in the water. But they are not useful to the sedentary adult
2.. The alimentary canal becomes complicated. The pharynx en larges ln size. The number of gill slits will increase by divisions. The stomach and intestine will grow.
3. The nervous system is reduced and the anterior part of nervous system is developed into a small neuralganglion attached to it neural gland is present. ;:
4. The atrial cavity enlarges into a sac like structure.
5. The eyespot and statocyst will completely disappear.
6. Gonads develop from mesencyme.

When these changes are taking place, the region between the adhesive papillae and mouth grows very rapidly. At the same time the growth of the dorsal region is stopped. Because of this, the body rotates through 1800 angle and mouth is brought to the top
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HERDMANIA TADPOLE LARVA
ORGANISATION OF HERDMANIA TADPOLE LARVA:
Herdmania is a hermaphrodite animal. The fertilised eggs undergo holoblastic unequal clevage and it develops into blastula. it shows upper micromeres and lower macromeres. By invagination of the macromeres gastrulation takes place and gastrula is formed. This gastrula develops into a tailed larva called Ascidian Tadpole larva. (Herdmanis life history, is not clearly known. Clavilina’s life history is known. It is followed here.

The larva is 3 mm in length. It has short oval body and a long tail.
This larva shows all the chordate features.
1) The body is covered by thin test.
2) The tail is long and shows a tail fin or caudal fin.
3) The tail is supported by notochord. Hence it comes under urochordata.
4) On the dorsal side above the notochord hollow nerve cord is present. This nerve cord is enlarged at the anterior end as a cerebral vesicle. In the cerebral vesicle pigmented eye spot is present. Statocyst is also present. They work as sense organs.
5) On either side of the notochord in the tail region muscles are Present which are helpful in the locomotion.
6) On the trunk region digestive system is present. It shows large pharynx with few gills slits. They open into atrium. On the mid ventral floor of the pharynx an endostyle is present.
7) Atrium opens out through atriopore.
8) Below the pharynx on the ventral side a muscular heart is present.
9) On the anterior end of the trunk three adhesive papillae are present These are very much useful to attach the larva to the substratum
This Herdmania tadpole larva shows all chordate characters. This larvae ‘undergoes retrogressive’ metamorphosis and develops into adult Herdmania.
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Herdmanla -External characters
External characters of Herdmania
Herdmania is a simple ascidian, In Indian ocean this genus Is represented by 4 species. ,
1. Herdmania pallida, 2. H.ennurensis, 3. H.mauritiana 4. H. ceylonica.
Herdmania belongs to,
Phylum: Chordata,
Sub-phylum: Urochordata,
Class: Ascidiacea,
Order: Pleurogona.
Herdmania is a marine and sedentary animal. It is fixed to rocky substratum by a flat base. When it is disturbed, it suddenly contracts its body, and emits inner contents with force through its apertures. Hence it is called Sea squirt.
External Features :-
It is potato like in shape. It is pink in colour. On the free side, body shows two projections, the brançhial and atrial siphons. The branchial siphon is short. The branchial siphon shows a branchial aperture or the mouth. The atrial siphon is longer. It bears the atrial aperture. Both the openings are bounded by four lips.
Herdmania - external characters.

Test of Herdmania:The body of this animal is covered and protected by test. It Ls a thick, leathery covering of the body.It is secreted by the epidermis of the body wall. It has matrix, corpuscles, fibrils, blood vessels and spicules.
The matrix is composed of tunicin, which is cellulose. The cells in the test are of six types, large eosinophilous cells, amoeboid cells, small eosinophilous cells, vacuolated cells, receptor cells and nerve cells.
Fine fibrils present in the matrix. In the test blood vessels are present. In the test the spicules are calcareous spicules. They are microscleres, and megascleres.
The test protects the body. Anchors the animals to substratum. Its spicules form a supporting frame work.

Herdmania Body wall :
The body-wall of Herdmania is called Mantle. It is thick, and muscular in the antero-dorsal region of the body. It is thin, non-muscular and transparent in the postero ventral region. It shows epidermis, mesenchyme, and inner epidermis.
1.Epidermis : It Is single layer of cells. It covers the bronchial and atrial apertures and siphons. The epidermis is interrupted at places where spicules and blood-vessels pass from the mantle into the test.
. 2. Mesènchyme: It develops from the mesoderm. It has connective tissue containing blood-sinuses, muscle-fibers, nerve fibers and cells. The muscle fibers are long and flat. They contain large nuclei.
3. Inner Epidermis: It is single layer of flat cells. It forms the lining of the atrial cavity. .
‘1.The body-wall protects visceral organs.
2. The outer epidermis secretes the test.
3. The musculature brings contraction of the body and the siphons.
Herdmania Atrium:
In Herdmania coelome is not developed. Atrium is a spacious ectoderm lined cavity. it is covered by the mantle A part of the atrium surrounds the pharynx. The stigmata of the pharynx open into this cavity. Part of the atrium is dorsal to the pharynx. It is very wide and is called cloaca. The rectum and gonoducts open into this. The cloaca opens to the exterior through atrial siphon and trial aperture. The atrial siphon shows a ring of processes called atrial tentacles at its base.

Practical Manual B.Voc

Etroplus surantensis

Phylum: Chordata

Class: Actinopterygii

Order: Perciformes

Family: Cichlidae

Genus: Etroplus











Etroplus suratensis is a euryhaline species that inhabits mainly brackish water and river mouths. It is an oval-shaped cichlid with a short snout, small mouth not extending past the front margin of the eye with a greyish-green colouration on the flanks, with 6 to 8 dark bars and a dark spot at base of the pectoral fin. Most scales on the sides are with a pearly spot (Costa 2007). Macrophytic fragments form the most important component of its diet along with molluscs, although detritus, diatoms, and animal matter are also ingested (De Silva et al. 1984). Many aspects of this species was studies in order to assess it's suitability for culture in ponds and tanks by Jayaprakash et al. (1990).Adults engage in altruistic multiple parental care where several adults care for a single brood that presumably were spawned by only two of the adults (Ward and Wyman 1977).

Mugil cephalus
Phylum: Chordata

Class: Actinopterygii

Order: Mugiliformes

Family: Mugilidae

Genus: Mugil



Mugil cephalus is cosmopolitan in the coastal waters of most tropical and subtropical zones. In the western Atlantic Ocean, it is found from Nova Scotia, Canada south to Brazil, including the Gulf of Mexico. It is absent in the Bahamas and the Caribbean Sea. In the eastern Atlantic Ocean, the striped mullet occurs from the Bay of Biscay (France) to South Africa, including the Mediterranean Sea and the Black Sea. The eastern Pacific Ocean range includes southern California south to Chile.

The flathead grey mullet is catadromous, frequently found coastally in estuaries and freshwater environments. Adult mullet have been found in waters ranging from zero salinity to 75‰, while juveniles can only tolerate such wide salinity ranges after they reach lengths of 4–7 cm. Adults form huge schools near the surface over sandy or muddy bottoms and dense vegetation and migrate offshore to spawn in large aggregations. The larvae move inshore to extremely shallow water, which provides cover from predators as well as a rich feeding ground. After reaching 5 cm in length, these young mullet move into slightly deeper waters.

Flathead grey mullet is a diurnal feeder, consuming mainly zooplankton, dead plant matter, and detritus. Mullet have thick-walled gizzard-like segments in their stomach along with a long gastrointestinal tract that enables them to feed on detritus. They are an ecologically important link in the energy flow within estuarine communities. Feeding by sucking up the top layer of sediments, flathead grey mullet remove detritus and microalgae. They also pick up some sediment which functions to grind food in the gizzard-like portion of the stomach. Mullet also graze on epiphytes and epifauna from seagrasses as well as ingest surface scum containing microalgae at the air-water interface. Larval flathead grey mullet feed primarily on microcrustaceans. Copepods, mosquito larvae, and plant debris have been found in the stomach contents of larvae under 35 mm in length. The amount of sand and detritus in the stomach contents increases with length, indicating that more food is ingested from the bottom substrate as the fish matures.

Eleutheronema tetradachylum

Phylum: Chordata

Class: Actinopterygii

Order: Perciformes

Family: Polynemidae

Genus: Eleutheronema


Dorsal spines (total): 9; Dorsal soft rays (total): 13-15; Anal spines: 3; Anal soft rays: 14 - 16. Pectoral filaments 4; fin membranes vivid yellow in life, except in large specimens, > ca 35 cm SL. Vomer with deciduous tooth plates on both sides, except in juveniles. Posterior part of maxilla deep, 3-4% of SL. Short tooth plate extension onto lateral surface of lower jaw. 7-9% SL (Ref. 41639).

Adults occur mainly over shallow muddy bottoms in coastal waters. Also enter rivers (Ref. 3479, 6390, 11230). Juveniles found in estuaries. During winter, adults ascend the rivers. They usually form loose schools, although larger fish are more often observed in pairs or singly (Ref. 6390). Feed on prawns and fish (largely members of Mugilidae, Engraulidae, and Sciaenidae) with occasional polychaetes. Frequency of crustaceans to fish in the diet varies seasonally. Larvae (7-30 mm TL) feed mainly on copepods and mysids but also take shrimps and prawn larvae (Ref. 57343). Juveniles (31-60 TL) feed on prawns shrimps and mysids (Ref. 57343). Protandrous hermaphrodites. Marketed fresh, frozen, and dried or salted.

Gene Cloning

Gene Cloning – Enzymatic cleavage of DNA, Restriction enzymes (Endonucleases) and Ligation.

Gene Cloning

To clone means to make identical copies. Gene cloning means production of a number of similar copies of a required gene. DNA cloning involves separating a specific gene or DNA segment from a larger chromosome, attaching it to a small carrier DNA. The resultant hybrid DNA is called recombinant DNA, which is transferred to a proper host (bacteria, virus or yeast) and replicated to make multiple copies of the selected gene.

This technology has made it possible to isolate, clone and produce DNA for all the genes in appropriate quantity so that they can be sequenced and characterized. Similarly, some of the genes which are expressed at very low level, can be cloned and desired amount of recombinant proteins can be produced.

Gene cloning involves the following steps

1. Cutting the DNA to be cloned from the chromosomal using sequence specific Restriction Endonuclease.

2. Selecting a cloning vector (a small molecule capable of self-replicating inside host cells), and cutting the cloning vector with the same restriction endonuclease to produce sticky ends.

3. Incubating the vector and subject DNA to join together DNA ligase. The resultant DNA is called recombinant DNA.

4. Transferring the reconbinant DNA to an appropriate host such as bacteria, virus or yeast which will provide necessory biomachinary for DNA replication.

5. Identifying the host cells that contain the recombinant DNA.

Enzymatic Cleavage of DNA
To cut the DNA at specific sites Restriction endonucleases are used. (RENs).
Restrictions Endonucleases:
A Restriction Endonuclease is an enzyme that cuts DNA at specific recognition points known as Restriction sites. These are most important groups of enzymes for manipulation of DNA. These enzymes were discovered in Escherichia coli. In bacteriophages these enzymes restrict the replication of viral DNA. Many types of restriction endonucleases were isolated. RENs were named based on the bacterial from which they were isolated.
The first letter of the enzyme indicates the genus name and next two letters the species name, followed by strain name and finally a number indicating the order of discovery. Eg. EcoRI: here E represents Escherichia, co represents coli, R represents the strain and I represents the first endonuclease.

Types of Endonucleases: over 3000 RENs have been studied in detail and more than 600 are available commercially. Naturally occurring Endonucleases are categorized in to four groups namely type I, II, III and IV based on their nature of their restriction sites. All types of enzymes recognize a specific DNA sequence and cleave that DNA at that point. They differ in their recognition sequence and cofactor requirements.

Type I RENs cuts DNA at random location as far as 1000 or more Basepairs from the recognition site. Type II cuts approximately 25 base pairs from the site. Type I and Type III require ATP. They are large enzymes with multiple subunits.
Type II RENs cut the DNA with in the recognized sequence without the need of ATP. They are smaller and simpler. Hence they are predominantly used in biotechnology.
Most of the Type II RENs generate Sticky ends. The open ends of the DNA molecule after the cut are called as Sticky ends.
The Length of restriction recognition sites varies. The Enzyme EcoRI, SacI etc recognize 6 basepair sequence of DNA. Most of the recognition sequences are palindromes – they read the same forward and backward.

Some of the important RENS and their restriction sites.
Enzyme Source Recognition Sequence Cut
EcoRI
Escherichia coli
5'GAATTC
3'CTTAAG 5'---G AATTC---3'
3'---CTTAA G---5'
EcoRII
Escherichia coli
5'CCWGG
3'GGWCC 5'--- CCWGG---3'
3'---GGWCC ---5'
BamHI
Bacillus amyloliquefaciens
5'GGATCC
3'CCTAGG 5'---G GATCC---3'
3'---CCTAG G---5'
HindIII
Haemophilus influenzae
5'AAGCTT
3'TTCGAA 5'---A AGCTT---3'
3'---TTCGA A---5'
TaqI
Thermus aquaticus
5'TCGA
3'AGCT 5'---T CGA---3'
3'---AGC T---5'


For convenience it is usual practice to simplifly the description of recognition sequences by showing only one strand of DNA, which runs in the 5’ to 3’ direction. Thus the EcoRI recognition sequence would be shown as G\AATTC.
Restriction enzymes with same sequence specificity and cut site are known as isochizomers. Enzymes that recognize the same sequences but cleave at different points are known as Neochizomers. Under extreme conditions like rise in pH, Low ionic strength) RENs are capable of cleaving sequences which are similar but not identical to their definied recognition sequences.

Applications of Restriction Endonucleases:
1. RENs formed in different bacteria can be used to break the DNA of any organism and the required DNA segment can be introduced in the DNA of another organism to produce Recombinant DNA
2. Restriction enzymes are highly useful to get desirable DNA segments. This is because these enzymes break the DNA at specific sites.
3. The DNAsegment isolated with the help of restriction enzymes can be used in DNA probe, genomic libraries and cDNA libraries.
4. With the isolated DNA segments, mRNA can be transcribed with which required proteins can be synthesized.
5. In restriction Fragment Length Polymorphism (RFLP) also restriction enzymes are very useful.

Enzymatic ligation of DNA
To hybridize (attach) the DNA fragments formed by the RENs to a plasmid DNA, the ends of both DNA are to be attached by forming hydrogen bonds and diester bonds. This process of attachment of the DNA fragments is known as Ligation. It is done by certain specialized enzymes called Ligases.

Ligase: (ligare = to glue together) is a special type of enzyme that can link together two DNA strands that have double strand break.
Mertz and Davis, 1972 first succeeded in producing rDNA in Escherichia coli by ligation of the sticky ends of DNA with ligase.
The mechanism of DNA ligase is to form two covalent phosphodiester bonds between 3’hydroxyl ends of one nucleotide with the 5’ phosphate end of another. ATP is required for ligation. Ligase will also work with blunt ends, but neets high concentrations of enzymes.
In mammals there are four specific types of ligases.ie. DNA ligases, I, II, III and IV. LIgases can be classified into two groups on their requirement for ATP and NAD+ as co factors. All eukaryotic enzymes are ATP dependent, whereas most prokaryotic enzymes require NAD+ for their activity.
Most experiments use T4 DNA ligase (isolated from bacteriophase T4) which is most active at 25oC. High temperatures disrupts hydrogen bonding. The commonly available DNA ligases were originally discovered in bacteriophase T4, E.coli and other bacteria.

Applications of Ligases
DNA ligases are essential tools in modern molecular biology for generating rDNA sequences such as
1. Joining double stranded DNA with cohesive or blunt ends
2. Joining of oligonucleotide linkers or adaptors to blunt ended DNA
3. Repairing in duplex DNA, RNA or DNA-RNA hybrids
4. DNA ligases are used with restriction enzyes to insert DNA fragments often genes into plasmids.

Transgenesis and Production of transgenic animals (Fish and Goat).

Transgenesis is the process of introducing an exogenous gene – called transgene- into a living organism so that the organism will exhibit a new property and transmit that property to its offspring. A transgene is the name given to the introduced DNA. The term transgenesis was coined by Gordon and Ruddle in 1981.

Animals produced through transgenesis are called Transgenic animals. Transgenic animals are genetically modified organisms with a new hereditary character.
Transgenic animals can be used to produce valuable products. Many proteins produced by transgenic animals are important for medical applications. For example, a transgenic pig has been produced with the ability to synthesize human hemoglobin for use as a blood substitute. Transgenic goat has been developed to produce a protein needed by the patients suffering from cystic fibrosis. Transgenisis is essential for improving the quality and quantity of the eggs, meat, milk etc, in addition to drug resistant animals.
The Mouse is the first animal used for transgenesis. RD Palmiter and RL Brinter (1982) isolated gene for growth hormone in human being. This gene was ligated with plasmid pBR322 to produce rDNA. It was transferred to the zygote of a mouse invitro. The embryo was implanted in the uterus of a foster mouse. Then the new born mouse was found to be transgenic which contained a gene from humans.

Methods of creation of transgenic Animals
There are three methods used for creations of transgenic animals are DNA micro injection, Embryonic stemcell-mediated gene transfer and Retrovirus mediated gene transfer.

DNA micro injection
Introduction of transgene by microinjection involves the following procedure. A young female mouse is given the FSH (follicle stimulating hormone) and HCG (human chorionic gonadotropin). Thus the mouse produces 30-35 ova. It was allowed to mate with a male. Then the fertilized ova are collected from the fallopian tubes. The transgene is introduced into the male pronucleus by using
micro injection needle. After amphimixis the embryo is allowed to devide. Then the embryo was implanted into the uterus of a foster mother. The new borns are called transgenic mice.

Hence DNA micro injection method is a random method. Success rate is very poor. This method has many disadvantages. The introduced DNA may not insert into the genome of the host. The foster mother may not accept the introduced fertilized ovum for further development. The introduced DNA may not express the desired trait. . A major advantage of this method is its applicability to a wide variety of species..

Embryonic stemcell-mediated gene transfer
The Recombinant DNA is transferred into embryo stem cells (ES). The cells are then cultured in the laboratory and those expressing the desired protein are selected. These modified ES cells are incorporated into the cavity of the embryo. This embryo is raised in a foster mother. The resulting transgenic animal will be a mosaic, because only a small proportion of the cells in its body will be expressing the protein.
Through this method transgenic goats and cows can now be designed to produce human proteins like blood clotting factors intheir milk.

Retroviral vector method:
Small fragments of DNA (8kb) can be effectively transferred by retrovirus. This method is not suitable for the transfer of large fragments of DNA. The main drawback in this method is the risk of retroviral contamination in products (such as human food) produced by transgenic animals. Hence this method is not popular in transgenesis.

DISASTER MANAGEMENT MATERIAL

4. Discuss the disaster management in environment.
Geological processes like earthquakes, volcanoes, floods and landslides are normal natural events which have resulted in the formation of the earth that we have today. They are, however, disastrous in their impacts when they affect human settlements. Human societies have witnessed a large number of such natural hazards in different parts of the world and have tried to learn to control these processes, to some extent.

Earthquakes: Earthquakes occur due to sudden movements of earth.s crust. The earth.s crust has several tectonic plates of solid rock which slowly move along their boundaries. When friction prevents these plates from slipping, stress builds up and results in sudden fractures which can occur along the boundaries of the plates or fault lines (planes of weakness) within the plates. This causes earthquakes, the violent, short-term vibrations in the earth. The point on a fault at which the first movement occurs during an earthquake is called the epicenter.

The severity of an earthquake is generally measured by its magnitude on Richter Scale, as shown below:








The largest earthquake ever recorded occurred on May 22, 1960 in Chile with the estimated magnitude of 9.5 on Richter Scale, affecting 90,000 square miles and killing 6,000 people. The devastating earthquake which hit Bhuj Town in Gujarat had caused massive damage, killing 20,000-30,000 people and leaving many injured. It had an energy equivalent to a 5.3 megaton hydrogen bomb.

Earthquake-generated water waves called tsunamis can severely affect coastal areas. These giant sea swells can move at a speed upto 1000 Km/hr or even faster. While approaching the sea shore they may often reach 15 m or sometimes upto 65 m in height and cause massive devastation in coastal areas. In China such waves killed 8,30,000 people in 1556 and 50,000 in 1976. Anthropogenic activities can also cause or enhance the frequency of earthquakes. Three such activities identified are:

(a) Impoundment of huge quantities of water in the lake behind a big dam.
(b) Under ground nuclear testing.
(c) Deep well disposal of liquid waste.

Damage to property and life can be prevented by constructing earthquake-resistant buildings in the earthquake prone zones or seismic areas. For this, the structures are heavily reinforced, weak spots are strategically placed in the building that can absorb vibrations from the rest of the building, pads or floats are placed beneath the building
on which it can shift harmlessly during ground motion. Wooden houses are preferred in earthquake prone areas as in Japan.


Floods

Generally the stream channels accommodate some maximum stream flow. However, due to heavy rains or sudden snow melt the quantity of water in streams exceeds their capacity and water overflows the banks and causes inundation of the surrounding land. This situation is called flood.
A flood generally doesn.t damage property or cause casualities to an extent as done by other natural disasters. However, it causes a great economic loss and health related problems due to widespread contamination. Virtually anything the flood water touches gets contaminated, posing serious threat to health due to outbreak of epidemics.

Human activities have been the main causes for increasing the severity and frequency of floods. Construction of roads, parking space and buildings that cover the earths surface hardly allows infiltration of water into the soil and speeds up the runoff. Clearing of forests for agriculture has also increased the severity of floods. In India, Uttar Pradesh is considered to be amongst the worst flood hit states of the country. It has nearly 20% of the total 40 million hectares of flood prone zone of the country.

Flood plains, the low lying areas which get inundated during floods help to reduce floods. Building up of flood control structures like flood walls or deepening of river channels have only transferred the problems downstream. Building walls prevents spilling out the flood water over flood plains, but it increases the velocity of water to affect the areas downstream with greater force. Table 5.4 shows the occurrence of natural hazards in our country.

On an average, every year one major disaster hits India, causing huge economic losses and loss of human life. There is a need for systematic studies and strategies to evolve a Disaster Management Plan for our country.

To check the floods, efforts need to be made to restore wetlands, replace ground cover on water-courses, build check-dams on small streams, move buildings off the flood plains etc. Instead of raising buildings on flood plains, it is suggested that floodplains should be used for wildlife habitat, parks, recreational areas and other uses, which are not susceptible to flood damage. River-networking in the country is also being proposed to deal with the flood problem.

Landslides
Landslide occurs when coherent rock of soil masses move downslope due to gravitational pull. Slow landslips don.t cause much worry but sudden rockslides and mudslides are dangerous. Water and vegetation influence landslides. Chemical action of water gradually cause chemical weathering of rocks making them prone to landslides. Vegetation consolidates the slope material, provides cohesion by its root system and also retards the flow of water and its erosion capacity.

However, this can be masked by many other exerting factors like:
(i) Earthquakes, vibrations etc.
(ii) Disturbances in resistant rock overlying rock of low resistance. (iii) Saturation of the unconsolidated sediments with water.
(iv) Unconsolidated sediments exposed due to logging, road or house building.
Landslides are governed by the forces which tend to pull the earth material down slope (move in case of slopes with steeper slip plane) and resisting forces which tend to resist such movements.

It is difficult to control landslides. However, these can be minimized by stabilizing the slope by:
(i) Draining the surface and subsurface water.
(ii) Providing slope support like gabions (wired stone blocks)
(iii) Concrete support at the base of a slope.

Cyclones

Cyclones are recurring phenomena in the tropical coastal regions. Tropical cyclones in the warm oceans are formed because of heat and moisture. One of the requirements for formation of tropical cyclones is that the sea surface temperature (SST) should be above 26°C.

Tropical cyclones move like a spinning top at the speed of 10-30 Km per hour. They can last for a week or so and have a diameter varying between 100 to 1500 Km. Since in the western parts of the main ocean no cold currents exist, tropical cyclones originate there.

Tropical cyclones are called hurricanes in the Atlantic, Caribbean and north eastern Pacific,. ‘typhoons’ in the western Pacific; and ‘cyclones’ in the Indian Ocean and ‘willy willies’ in the sea around Australia. More storms occur in the Bay of Bengal than in the Arabian Sea. Of 5-6 storms that form in the year about half of them are severe.

Hurricane winds (74 miles per hour or more), rains and storm surge (often 50-100 miles wide dome of water) often devastate the area where it strikes on land. The devastation is more when storm surge and normal astronomical tide coincide. Sea water with combined force rushes inlands and inundates the low lying areas.

Management: It is difficult to stop the recurrence of cyclones. Some long term defence measures can help to protect us from devastation. Such measures include, planting more trees on the coastal belt, construction of dams, dykes, embankments, storm shelter, wind breaks, proper drainage and wide roads for quick evacuation.

Explain the solid waste management.
Higher standards of living of ever increasing population has resulted in
an increase in the quantity and variety of waste generated. It is now
realized that if waste generation continues indiscriminately then very
soon it would be beyond rectification. Management of solid waste has,
therefore, become very important in order to minimize the adverse
effects of solid wastes. Solid waste (waste other than liquid or gaseous)
can be classified as municipal, industrial, agricultural, medical, mining
waste and sewage sludge.
Sources of Urban and Industrial Wastes
Urban waste consists of medical waste from hospitals; municipal solid
wastes from homes, offices, markets (commercial waste) small cottage
units, and horticulture waste from parks, gardens, orchards etc.
l Waste from homes (Domestic waste) contains a variety of
discarded materials like polyethylene bags, empty metal and
aluminium cans, scrap metals, glass bottles, waste paper,
diapers, cloth/rags, food waste etc.
l Waste from shops mainly consists of waste paper, packaging
material, cans, bottles, polyethylene bags, peanut shells,
eggshells, tea leaves etc.
l Biomedical waste includes anatomical wastes, pathological
wastes, infectious wastes etc.
l Construction/demolition waste includes debris and rubbles,
wood, concrete etc.
l Horticulture waste and waste from slaughter houses include
vegetable parts, residues and remains of slaughtered animals,
respectively.
The urban solid waste materials that can be degraded by microorganisms
are called biodegradable wastes. Examples of this type of
waste are vegetable wastes, stale food, tea leaves, egg shells, peanut
shells, dry leaves etc. Wastes that cannot be degraded by microorganisms
are called non-biodegradable wastes. For example,
polyethylene bags, scrap metal, glass bottles etc.
Industrial waste: Industrial waste consists of a large number
of materials including factory rubbish, packaging material,
organic wastes, acids, alkalis and metals etc. During some
industrial processing large quantities of hazardous and toxic
materials are also produced. The main sources of industrial
wastes are chemical industries, metal and mineral processing
industries. Radioactive wastes are generated by nuclear power
plants. Thermal power plants produce fly ash in large
quantities. Solid wastes from other types of industries include
scrap metal, rubber, plastic, paper, glass, wood, oils, paints,
asphalt, tars, dyes, scrap leather, ceramics, abrasives, slag,
heavy metals, asbestos, batteries. In Europe and North
America the environmental laws and safety laws are becoming
more stringent due to which disposal of hazardous wastes is
becoming a problem. Cost of disposal of such wastes is
increasing. Therefore, these wastes are being exported to
developing countries which do not even have sufficient
knowledge or technique for their disposal.
Effects of Solid Wastes
Municipal solid wastes heap up on the roads due to improper disposal
system. People clean their own houses and litter their immediate
surroundings which affects the community including themselves. This
type of dumping allows biodegradable materials to decompose under
uncontrolled and unhygienic conditions. This produces foul smell and
breeds various types of insects and infectious organisms besides spoiling
the aesthetics of the site.
Industrial solid wastes are sources of toxic metals and hazardous
wastes, which may spread on land and can cause changes in physico-
chemical and biological characteristics thereby affecting productivity
of soils. Toxic substances may leach or percolate to contaminate the
ground water.
In refuse mixing the hazardous wastes are mixed with garbage
and other combustible waste. This makes segregation and disposal all
the more difficult and risky. Various types of wastes like cans, pesticides,
cleaning solvents, batteries (zinc, lead or mercury) radioactive materials,
plastics are mixed up with paper, scraps and other non-toxic materials
which could be recycled. Burning of some of these materials produce
dioxins, furans and polychlorinated biphenyls, which have the potential
to cause various types of ailments including cancer.
Industrial waste: Industrial waste consists of a large number
of materials including factory rubbish, packaging material,
organic wastes, acids, alkalis and metals etc. During some
industrial processing large quantities of hazardous and toxic
materials are also produced. The main sources of industrial
wastes are chemical industries, metal and mineral processing
industries. Radioactive wastes are generated by nuclear power
plants. Thermal power plants produce fly ash in large
quantities. Solid wastes from other types of industries include
scrap metal, rubber, plastic, paper, glass, wood, oils, paints,
asphalt, tars, dyes, scrap leather, ceramics, abrasives, slag,
heavy metals, asbestos, batteries. In Europe and North
America the environmental laws and safety laws are becoming
more stringent due to which disposal of hazardous wastes is
becoming a problem. Cost of disposal of such wastes is
increasing. Therefore, these wastes are being exported to
developing countries which do not even have sufficient
knowledge or technique for their disposal.
Effects of Solid Wastes
Municipal solid wastes heap up on the roads due to improper disposal
system. People clean their own houses and litter their immediate
surroundings which affects the community including themselves. This
type of dumping allows biodegradable materials to decompose under
uncontrolled and unhygienic conditions. This produces foul smell and
breeds various types of insects and infectious organisms besides spoiling
the aesthetics of the site.
Industrial solid wastes are sources of toxic metals and hazardous
wastes, which may spread on land and can cause changes in physico-
chemical and biological characteristics thereby affecting productivity
of soils. Toxic substances may leach or percolate to contaminate the
ground water.
In refuse mixing the hazardous wastes are mixed with garbage
and other combustible waste. This makes segregation and disposal all
the more difficult and risky. Various types of wastes like cans, pesticides,
cleaning solvents, batteries (zinc, lead or mercury) radioactive materials,
plastics are mixed up with paper, scraps and other non-toxic materials
which could be recycled. Burning of some of these materials produce
dioxins, furans and polychlorinated biphenyls, which have the potential
to cause various types of ailments including cancer.

Practical Manual B.Voc

Megalops cyprinoides

Phylum: Chordata

Class: Actinopterygii

Order: Elopiformes

Family: Megalopidae

Genus: Megalops












In appearance, it is like the Atlantic tarpon, Megalops atlanticus: olive-green on top, and silver on the sides. The large mouth is turned upwards; the lower jaw contains an elongated, bony plate. The last ray of the dorsal fin is much longer than the others, reaching nearly to the tail. It is capable of filling its swim bladder with air and absorbing oxygen from it. Species in fresh water tend to be smaller than the saltwater species, growing just over 50 cm (20 in), while saltwater species grow over a 1 m (3.3 ft). They live an upwards of 44 years and mature within two. They complete their metamorphosis from their larvae stage in 10 days.[2]


Lates calcarifer


Phylum: Chordata

Class: Actinopterygii

Order: Perciformes

Family: Latidae

Genus: Lates





This species has an elongated body form with a large, slightly oblique mouth and an upper jaw extending behind the eye. The lower edge of the preoperculum is serrated with a strong spine at its angle; the operculum has a small spine and a serrated flap above the origin of the lateral line. Its scales are ctenoid. In cross section, the fish is compressed and the dorsal head profile clearly concave. The single dorsal and ventral fins have spines and soft rays; the paired pectoral andpelvic fins have soft rays only; and the caudal fin has soft rays and is truncate and rounded. Barramundi are salt and freshwater sportfish, targeted by many. They have large, silver scales, which may become darker or lighter, depending on their environments. Their bodies can reach up to 1.8 m (5.9 ft) long, though evidence of them being caught at this size is scarce. The maximum weight is about 60 kg (130 lb). The average length is about 0.6–1.2 m (2.0–3.9 ft). Its genome size is about 700 Mb, which was sequenced and published in Animal Genetics (2015, in press) by James Cook University.
Barramundi are demersal, inhabiting coastal waters, estuaries, lagoons, and rivers; they are found in clear to turbid water, usually within a temperature range of 26−30 °C. This species does not undertake extensive migrations within or between river systems, which has presumably influenced establishment of genetically distinct stocks in Northern Australia.

ఫలదీకరణం

2. ఫలదీకరణం ను విశదీకరింపుము
జ. స్త్రీ బీజకణం మరియు పురుష బీజకణముల కలయికను ఫలదీకరణం అంటారు. లైంగిక ప్రత్యుత్పత్తి జరిపే జీవులలో ఫలదీకరణ ముఖ్యమైన క్రియ. ఇందులో రెందు ఏకస్థితిక కణాలైన అండము మరియు శుక్రకణములు కలయిక వల్ల ద్వయస్థితిక సంయుక్త బీజము ఏర్పడుతుంది. సంయుక్తబీజం పిండంగా మారి పిల్ల జీవిగా వృద్ధి చెందుతుంది.
ఫలదీకరణ జంతువుల శరీరం వెలుపల జరిగితే బాహ్యఫలదీకరణం (కప్ప) అని, శరీరం లోపల జరిగితే అంతరఫలదీకరణ అని (మానవుడు) అంటారు. బాహ్య ఫలదీకరణంలో శుక్రకణాలు మరియు అండాలను పరిసరాల మాధ్యమం లోకి విడుదల చేయ బడతాయి. శుక్రకణం అండమును చేరి ఫలదీకరణ జరుపుతుంది. అంతర ఫలదీకరణలో పురుష జీవి తన శుక్రకణాలను స్త్రీ ప్రత్యుత్పత్తి వ్యవస్థ లోనికి ప్రవేశపెడుతుంది. తరువాత శుక్రకణము చురుకుగా కదులుతూ అండమును చేరుకొని ఫలదీకరణ జరుపును.
కొన్ని సందర్భములలో శుక్రకణాలు కొన్ని రసాయినిక పదార్ధముల ప్రభావముచేత అండముల వద్దకు చేర్చబడతాయి

ఫెర్టిలైజిన్ మరియు యాంటి ఫెర్టిలైజిన్
శుక్రకణములను ఆకర్షించు పదార్ధమును ఫెర్టిలైజిన్ అంటారు. ఇది పక్వము పొందిన అండములనుండి ఎక్కువమొత్తాలలో విడుదల చేయబడుతుంది. ఇది అండముల పరిసర మాధ్యమము లోకి (నీరు లేదా కణబాహ్య ద్రవాలు) స్రవింపబడి, సమీపములో నున్న శుక్రకణములను తనవైపునకు ఆకర్శించును.
శుక్రకణము ఉపరితలముపై యాంటి ఫెర్టిలైజిన్ అను పదార్ధమును కలిగిఉంటుంది. ఫెర్టిలైజిన్ – యాంటిఫెర్టిలైజిన్ అణువులు ఒకదానితొ ఒకటి బంధనము ఏర్పరచు కొనటం ద్వారా శుక్రకణము అండముల ప్రాధమిక కలయిక జరుగుతుంది.

కెపాసిటేషన్: శుక్రకణం స్త్రీ ప్రత్యుత్పత్తి వ్యవస్థ మార్గములో ప్రవేసించిన తరువాత, దాని ఉపరితల త్వచములో కల ప్రొటీన్ల నిర్మాణంలో మార్పు వస్తుంది. అప్పుడు మాత్రమే ఇది, అండము యొక్క వెలుపలి పొర అయిన జోనా పెల్లుసిడా ను చొచ్చుకు పోగలిగే సామర్ధ్యాన్ని పొందుతుంది. ఈ ప్రక్రియను కెపాసిటేషన్ అంటారు.
శుక్రకణము అండములో ప్రవేశించుట: శుక్రకణం అండాన్ని చేరగానే దాని లోని ఎక్రోసోము లైసిన్ అనే ఎంజైమును స్రవించి అండం యొక్క వెలుపలి పొర అయిన జోనా పెల్లుసిడాను కరిగించును. తరువాత ఎక్రోసోము సాగి సన్నని పొడవైన నాళిక వలె ఏర్పడును. దీనిని ఎక్రోసోమల్ తంతువు అంటారు. ఇది అండములోనికి చొచ్చుకొని పోవును.
అండము ఉత్తేజమును పొంది ప్రతిచర్యను చూపుట: ఎక్రోసోమల్ తంతువు అండమును తాకగానే అండము యొక్క ఉపరితలము ముందుకు సాగి శంకువు వంటి ఫలదీకరణ కొన ను ఏర్పరచును. ఇది హయలిన్ అనబడు పదార్ధముతో ఏర్పడును. ఈ ఫలదీకరణ కొన ముందుకు విస్తరించి శుక్రకణమును తనలోనికి లాక్కొనును. తరువాత నెమ్మది నెమ్మదిగా ఫలదీకరణ కొన లోనికి ముడుచుకు పోవును.
పాలిస్పెర్మీ నిరోధము: సాధారణంగా అండములోనికి ఒక శుక్రకణము మాత్రమే ప్రవేశిస్తుంది. కానీ కొన్ని సందర్భాలలో ఒకటి కంటే ఎక్కువ శుక్రకణాలు ప్రవేసించటాన్ని పాలిస్పెర్మ్య్ అంటారు. అలాంటి పరిస్థితులలో అట్టి అండములోని పిండము అభివృద్ది చెందక నశించిపోవును. కనుక ఒక శుక్రకణము ప్రవేశించిన తరువాత అండత్వచాలలో అనేక బౌతిక రసాయినిక చర్యలు జరిగి, మరొక శుక్రకణము లోనికి ప్రవేశించకుండా నిరోధిస్తాయి.
ప్రాక్కేంద్రకాల కలయిక: అండంలో ప్రవేశించిన వెంటనే శుక్రకణం తల లావెక్కి పురుష ప్రాక్కేంద్రకం గా మారుతుంది. అదే సమయంలో అండంలోని కేంద్రకం చివరి పరిపక్వ విభజన జరుపుకొని ఫలదీకరణకు సిద్దమౌతుంది. అండకేంద్రకాన్ని స్త్రీ ప్రాక్కేంద్రకం అంటారు. ఈ రెండు కేంద్రకాలు క్షయకరణ విభజన ద్వారా ఏర్పడినవి కనుక వీటిలో ఏకస్థితిక క్రోమోజోములు ఉంటాయి. ఈ రెండుక్రోమోజోముల కలయిక వలన ఏర్పడే సంయుక్తబీజం ద్వయస్థితిక స్థితిని పొందుతుంది.
శుక్రకణ కేంద్రకం (పురుషకేంద్రకం) స్త్రీ కేంద్రకాన్ని చేరుకొనే మార్గాన్నిశుక్రకణ మార్గం అంటారు. స్త్రీ ప్రాక్కేంద్రకం కూడా పురుషకేంద్రకాన్ని చేరటానికి కొంతదూరం ప్రయాణిస్తుంది. ఇవి రెండు తమ కేంద్రక త్వచాలను కరిగిపోయి, పిత్రు మరియు మాతృ క్రోమోజోములు రెండు పక్కపక్కకు చేరి సమవిభజనకు (అండం విభజనలు జరుపుకొని పిండాన్ని ఏర్పరచును) సిద్దమవుతాయి. ఫలదీకరణ సమయంలో జరిగే కేంద్రక పదార్ధముల కలయిక వలన పితృ మరియు మాతృ లక్షణాలు కలిసిపోతాయి. స్త్రీ మరియు పురుష ప్రాక్కేంద్రకాల కలయిక అనంతరం అండాన్ని సంయుక్త బీజం అంటారు.
సంయుక్త బీజములో క్రోమోజోముల నిడివి పెరుగుతుంది, మైటోఖాండ్రియాల సంఖ్య పెరుగును, కేంద్రకాంశము పెద్దదగును. ఎండోప్లాస్మిక్ రెటిక్యులం, గాల్జి, సెంట్రోజోములు అదృశ్యం అవుతాయి. ప్రొటీన్లు, కొవ్వులు, గ్లైకోజెన్ వంటి ఆహారపదార్ధలతో తయారయ్యే సొనపదార్ధం అండములో నిక్షిప్తం చేయబడుతుంది. ఫలదీకరణమ్ జరిగిన వెంటనే విదళనం మొదలౌతుంది.

Practical Manual B.Voc

Tilapia mossambica
Phylum: Chordata

Class: Actinopterygii

Order: Perciformes

Family: Cichlidae

Subfamily: Pseudocrenilabrinae

Tribe: Tilapiini

Genus: Oreochromis


The native Mozambique tilapia is laterally compressed, and has a deep body with long dorsal fins, the front part of which have spines. Native coloration is a dull greenish or yellowish, and there may be weak banding. Adults reach approximately 35 centimetres (14 in) in length and up to 1.13 kilograms (2.5 lb). Size and coloration may vary in captive and naturalized populations due to environmental and breeding pressures. It lives for up to 11 years.
It is a remarkably robust and fecund fish, readily adapting to available food sources and breeding under suboptimal conditions. It also tolerates brackish water and survives temperatures below 50 °F (10 °C) and above 100 °F (38 °C). Sustained water temperatures of 55 degrees are lethal to Mozambique tilapia.
Body compressed; caudal peduncle longer than deep. Scales cycloid. A knob-like protuberance present behind upper jaw on dorsal surface of snout. Upper jaw length shows sexual dimorphism, and mouth of male larger than that of female. First gill arch with 20 to 22 gillrakers. Lateral line interrupted. Spinous and soft ray parts of dorsal fin continuous. Dorsal fin with 15 to 18 spines and 10 to 13 soft rays. Anal fin with 3 spines and 9-10 rays. Caudal fin truncated. Colour in spawning season, pectoral, dorsal and caudal fins becoming reddish; colour male shows much brighter orange tail than female.

Hypophthalmichthys molitrix
Phylum: Chordata

Class: Actinopterygii

Order: Cypriniformes

Family: Cyprinidae

Genus: Hypophthalmichthys

Species: H. molitrix
Identification: The silver carp is a deep-bodied fish that is laterally compressed. They are a very silvery in color when young and when they get older they fade from a greenish color on the back to silver on the belly. They have very tiny scales on their body but the head and the opercles are scaleless. They have a large mouth without any teeth in the jaw, but they have pharyngeal teeth. Its eyes are situated far forward on the midline of the body and are slightly turned down.
Silver carp are unlikely to be confused with native cyprinids due to size and unusual position of the eye. They are most similar to bighead carp (H. nobilis) but have a smaller head, and upturned mouth without teeth, a keel that extends forward past pelvic fin base, lack the dark blotches characteristic of bighead carp and have highly branched gill rakers.
Juvenile fish lack spines in fins. Metalarvae and early juvenile are similar to bighead carp (Hypophthalmichthys nobilis) but pectoral fin extends only to base of pelvic fin (as opposed to beyond in the pelvic fin in bighead)
The species is known for leaping out of the water when startled (e.g., by noises such as a boat motor).

DIGESTIVE SYSTEM OF PILA NOTES

DIGESTIVE SYSTEM OF PILA

It consists of

I) Alimentary canal
II) Digestive glands

Alimentary canal of Pila is a coiled tube extending from the mouth and ending at the anus.

Entire canal may be divided into three regions
A) Foregut - buccal cavity and oesophagus
B) Midgut - stomach and intestine
C) Hind gut – rectum

A) Foregut

1) Buccal cavity:
 This is a chamber into which mouth opens

 It is lined by cuticle and surrounded by a large, thick-walled, highly muscular and pear shaped structure, the buccal mass.

 Its wall is provided with several sets of muscles for its movement and the movement of radula

a) Buccal musculature: Out of several sets of muscles, the protractors are well developed. They include

i) a median dorsal-three pairs of anterior dorso-laterals and two pairs of posterior dorso-laterals on the dorsal surface and
ii) three anterior muscles and
iii) a pair of long and strong latero-ventral forward muscles on the ventral surface.

 These muscles are mainly concerned with the protrusion and depression of the buccal mass.

b) Vestibule and jaws: Buccal cavity is regionated into an anterior tubular part called vestibule, and a posterior part.

 The posterior limit of the short vestibule is marked by a pair of thickened jaws, placed dorso-laterally one on each side and connected together by a thin cuticular membrane.

 Anterior cutting edge of each jaw is truncated and serrated, bearing numerous small and two or three large tooth-like processes.

 Wall of the vestibule is beset with longitudinal muscle fibres that form the mouth sphincter.

 Sphincter regulates the opening of the mouth and operates the jaws at the time of feeding.

c) Odontophore: In the posterior part of the buccal cavity the floor is raised into a thick muscular structure called tongue mass or odontophore.

 Structure is supported by two sets of cartilages

i) a pair of more or less triangular superior cartilages lying below the epithelium at the top of the odontophore

ii) a pair of S-shaped lateral cartilages, with thick ventral edges and thin dorsal edges, lying on the sides.

 Anteriorly the odontophore forms a small process, the sub-radular organ, roofing a narrow space called the sub-lingual cavity.

d)Radula: Buccal cavity contains a brownish, chitinous, curved, ribbon-like structure, called the radula or lingual ribbon.

 Its anterior end bearing a pair of wing-like flaps, runs longitudinally over the summit of the odontophore.

 Its posterior end is lodged in a band-like, 2mm wide radular sac flexed behind and below the buccal mass.

 Radula itself is formed by secretion of the epithelial lining of the radular sac.


 Below the radula lies a delicate and elastic, sub-radular membrane.

 Dorsal surface of the radula bears teeth arranged in numerous transverse rows.

 Each row contains seven teeth, one central rachidian, and one lateral and two marginals on its either side, giving the formula 2, 1, 1, 1, 2.

 Radula is moved forward and backward on the odontophore for rasping food particles.

 Movements, called chain-saw movements (Huxley), are brought about by protractor and retractor muscles; the radula can even be protruded from the mouth.

 Regular use causes the radula to wear off at the anterior end, but the loss is made good by regular addition of radular material at the posterior end

2) Oesophagus: This is a narrow and long tube emerging dorsally from the buccal mass.

 Running posteriorly for a short distance, it turns to left and enters the visceral mass to open into the stomach

3) stomach: It lies on the left side of the visceral mass, below the pericardium.

 Its cavity is U-shaped which is regionated into a broad posterior cardiac chamber that receives the oesophagus and a narrow anterior pyloric chamber from which the intestine starts.

 Lining of the stomach is folded; folds of the cardiac stomach are low and run from right to left, while those of the pyloric stomach are somewhat prominent and run transversely.

 A short rounded and blind pouch, the caecum, arises from the lower outer wall of the pyloric chamber.

 At the junction of two chambers of the stomach opens a duct from the digestive gland.

4) Intestine: Pyloric stomach is followed by a long and coiled intestine. It runs backward into the visceral mass where it makes 2.5 or 3 coils, between the gonad in front and the digestive gland behind, before joining the rectum.

5) Rectum: It comprises of a thick-walled tube which extends into the branchial chamber of the mantle cavity between the ctenidium and genital duct.

 Its external opening, the anus, lies about 6 mm away from the edge of the right nuchal lobe.

II) Digestive glands

1. Salivary glands. These are two in number and lie on either side of the posterior part of the buccal mass.

 Each gland looks like a branching white mass.

 A duct from each gland enters the muscles of the buccal mass and then opens into the buccal cavity in the area of the dorsal buccal glands.

 Salivary secretion contains mucin-like substance and a carbohydrase enzyme.

2. Digestive gland. A somewhat triangular plate or cone with a convex outer and more or less flattened inner surface occupies the greater part of the coiled visceral mass.

 This structure is a digestive gland (often referred to as the liver or hepatopancreas), which is also coiled and is brownish to dirty green in colour.

 It has two main lobes, smaller in contact with the stomach and larger extending to the apex of the spiral.

 Two separate ducts arise from two lobes which unite together to form a common duct before opening into the stomach.

 These ducts, open into the digestive gland, branch repeatedly and end blindly in a very large number of small tubes the alveoli.

 Alveoli are lined with a digestive epithelium made up of three types of cells
i) secretory cells- secrete a cellulose digesting enzyme
ii) resorptive cells- digest proteins intracellularly
iii) lime cells- store calcium phosphate.

 Semi-digested food enters into these alveoli, where digestion of cellulose and proteins takes place.

3. Oesophageal pouches: A pair of simple, rounded, cream-coloured oesophageal pouches lies below the salivary glands.

 Each pouch opens by a narrow duct at the junction of the buccal cavity and oesophagus.

 These pouches probably secrete digestive enzymes.

4. Buccal glands: These are a pair of glandular areas in the roof of the buccal cavity, a little in front of its junction with the oesophagus.

 Each glandular area consists of two pads, separated by an oblique longitudinal furrow; each pad bears a row of transverse grooves.

 Exact function of these glands is not known. They are probably of the nature of accessory digestive glands.