PLANKTON PRACTICAL MATERIAL

1. Coscinodiscus
Classification:
Empire Eukaryota
Kingdom Chromista
Phylum Bacillariophyta
Subphylum Coscinodiscophytina
Class Coscinodiscophyceae
Subclass Coscinodiscophycidae
Order Coscinodiscales
Family Coscinodiscaceae
Genus Coscinodiscus
1. This is centric diatom
2. Cells are discoid and wedge-shaped, visible in girdle view with one side
higher than the other (may not be visible in all orientations).
3. Valves are most convex at the tallest part of the cell, near one end of the cell. Cells have a rosette of larger areolae at the centre of the valve.
4. Chloroplasts are smooth and disc-shaped.
5. Cells are yellow-brown in colour."About 8 areolae in 10 μm near centre, 10 midway to margin, and 11 near margin; on edge of valve mantle 13 in 10 μm.
6. Chamber openings small, dotlike. Outer closing membrane of areolae very
delicately poroid. Radial rows and secondary spiral rows distinct. Marginal spinulae and the hyaline lines radiating from the spinulae toward the center distinct, 5 - 7 μm apart. Two small processes or apiculi on margin at distance of about 120° from each other. Girdle formed from the two similar. No intercalary bands".

2. Chaetoceros
Empire Eukaryota
Kingdom Chromista
Subkingdom Harosa
Infrakingdom Heterokonta
Phylum Ochrophyta
Subphylum Khakista
Class Bacillariophyceae
Subclass Coscinodiscophycidae
Order Chaetocerotales
Family Chaetocerotaceae
Genus Chaetoceros
1. Cells are usually connected in chains, and are roughly rectangular in
girdle view and elliptical in valve view (elliptic cylinder),
2.Two spines arising from each valve.
3.Adjacent cells are linked by the crossing or touching of the spines near the base.
4.Cells are yellow-brown in colour.


3. Biddulphia
Classification:
Empire Eukaryota
Kingdom Chromista
Phylum Bacillariophyta
Subphylum Bacillariophytina
Class Mediophyceae
Subclass Biddulphiophycidae
Order Biddulphiales
Family Biddulphiaceae
1. Cells robust, rectangular in girdle view, elliptical in valve view, with prominent elevations at the poles.
2. Normally seen in girdle view, often growing in zig-zag chains attached to filamentous seaweeds, etc. Often found also in inshore plankton samples. Plastids numerous, discoidal.
3. A very common marine genus but taxonomically extremely confused (see below). Valves bipolar/lanceolate to almost circular, often with waxy margins. Valves surface often furrowed with various thickenings, spines (often conspicuous in the central region) or ridges.
4. Apices bearing rounded pseudocelli on low or extended elevations. Valve mantle not well-defined but extreme edge of valve often recurved and variously moulded. Areolae large with perforate vela of the cribrum type. Simple pores also occur occasionally in the valve framework.
5. Internally with conspicuous plain ridge (pseudosepta) beneath the external indentations of the valve.
6. One to several rimoportulae present, sessile, clustered in centre; external tubes often stout and surmounted by two spines. Cingula with a complete, close valvocopula and 3-4 split copulae; areolae large, in rows; fluting of girdle corresponding to that of valve edge.

4. Skeletonema

Phylum Bacillariophyta
Subphylum
Class Coscinodiscophyceae
Subclass Thalassiosirophycidae
Order Thalassiosirales
Family Skeletonemaceae
Genus Skeletonema

1.Cells are short and cylindrical, usually connected in long, straight or slightly undulate chains by a marginal ring of spines (strutted processes).
2.The valve face is convex to flat. Spines interlock midway between adjacent cells, visible as a dotted ring; spine lengths are variable (Horner.
3.There are two chloroplasts per cell and the nucleus is located centrally. Strutted processes are tubular but semicircular in cross section.

4.One labiate process is present near the center of the valve inside the ring of processes.
5.Molecular data has recently separated S. costatum into several species. These distinctions cannot be made without detailed examination of their morphology.

5. Leptocylindrus


Phylum Ochrophyta
Subphylum Khakista
Class Coscinodiscophyceae
Subclass Chaetocerotophycidae
Order Leptocylindrales
Family Leptocylindraceae
Genus Leptocylindrus
1.Cells are cylindrical and form long, straight chains. Cells are connected by the whole valve surface.
2.The central parts of the valve face may be slightly convex/concave, fitting into the concavity/convexity of an adjacent valve.
3.Cells are thin-walled and do not have any obvious spines or processes. Using SEM, short flap-like spines are visible on the border between the valve face and mantle (Hasle and Syvertsen 1997).
4.Chloroplasts are numerous small ovoid plates, distributed throughout the cell (Cupp 1943). Intercalary bands are not visible with LM.
5. Resting spores form as a result of sexual reproduction, they consist of two unequal valves and are found in an auxospore.
6.Resting spores are covered with spicules.

6. Pleurosigma
Phylum Bacillariophyta
Subphylum Bacillariophytina
Class Bacillariophyceae
Subclass Bacillariophycidae
Order Naviculales
Suborder Naviculineae
Family Pleurosigmataceae
Genus Pleurosigma
1. Valves are elongate and sigmoid. Striae are composed of evenly spaced decussate rows.
2. The rows are arranged in 3 patterns: a trans-apical row and two opposing oblique rows.
3. Internally, the areolae are occluded by hymenes. The raphe is strongly sigmoid, with a narrow axial area.
4. The sternum is thickened equally on both sides. The raphe terminates proximally in a small oval, expanded central area defined by two curved ridges.
5. Proximal raphe ends are slightly inflated and straight, or unilaterally bent. The distal raphe ends are hooked and deflected to opposite sides on the mantle.
6. The valve mantle is relatively shallow and the valve / mantle interface is broad and curved. Two to four ribbon-like plastids extend from apex to apex.



7. Asterionella

Phylum Ochrophyta
Subphylum Khakista
Class Bacillariophyceae
Subclass Fragilariophycidae
Order Fragilariales
Family Fragilariaceae
Genus Asterionellopsis

1.Cells are needle-shaped and arranged in star-like and helical chains. In girdle view, cells have a narrow and elongated neck with a broad triangular base.
2. The end of the neck is not lobed. Adjacent cells are attached by the valve face of the base; therefore cells are usually seen in girdle view.
3. In valve view, the base is lobed. One or two plate-like chloroplasts are located in the base (Cupp 1943). Cells are yellow-brown in colour.
4. Characteristics observable under SEM: "Slit fields or apical pores at both ends of valve.
5. A single labiate process present at the narrow end of the valve. Transapical striae are very delicate.


8. Thalassionema
Classification:
Empire Eukaryota
Kingdom Chromista
Phylum Bacillariophyta
Subphylum Bacillariophytina
Class Bacillariophyceae
Subclass Fragilariophycidae
Order Thalassionematales
Family Thalassionemataceae
Genus Thalassionema
1.Cells are usually in star-shaped or zigzagged chains connected by mucilage pads on the ends of valves. Cells are rectangular in girdle view, with valve ends that are similar in shape and width, and are narrowly elliptical in valve view.
2.Chloroplasts are small and numerous.
3.Cells are yellow-brown in colour (Guiry 2011).Each valve has two labiate processes, one on each end; a small apical spine is sometimes also present.
3."Marginal areolae are visible as ribs with LM.
4.The sternum is broad and without areolae.
5.Internally, each valve pole has a simple, slit-like labiate process, which appears externally as a small, round hole.

9. Thalassiothrix


Classification:
Empire Eukaryota
Kingdom Chromista
Phylum Bacillariophyta
Subphylum Bacillariophytina
Class Bacillariophyceae
Subclass Fragilariophycidae
Order Thalassionematales
Family Thalassionemataceae
Genus Thalassiothrix

1. Cells needle-like, straight, slightly curved or sigmoidal in girdle view, forming radiating colonies, joined by bent foot poles (one end of frustule); head poles separated.
2. Apical axis 420–5680 µm; transapical axis 1.5–6 µm; foot pole apexrounded; head pole apex rounded but with 2 protruding spines.
3. Areolae in a single marginal row, 12–17 in 10 µm, with complex vela. Row of fine spines, marginal on the vela, pointed towards the head pole, 1–2 in 10 µm, occurring along the frustule but more abundant towards the head pole. Small foramina on valve surface.
4. Labiate process at each apex.
5. Chloroplasts numerous, spherical.


10. Amphora

Phylum Bacillariophyta
Subphylum Bacillariophytina
Class Bacillariophyceae
Subclass Bacillariophycidae
Order Thalassiophysales
Family Catenulaceae
Genus Amphora

Solitary cells that can be motile and almost always occur in girdle view. The cells appear elliptical with flat truncate ends. The cell appears as a large slice of orange. The valves are asymmetrical and are sometimes smaller or constricted at each end of the cell. Both rapheslie on the same side of the valve. There are generally two or more plastids that occur in different positions throughout the cell.

Epiphytic on plants, stones and mud. A large mainly marine genus with relatively few species in freshwater.



11. CERATIUM
Phylum Dinoflagellata
Subphylum
Class Dinophyceae
Subclass
Order Gonyaulacales
Family Ceritiaceae
Genus Ceratium

1.Ceratium furca has a wide girdle and a prominent straight apical horn.
2.C. furca also has two unequal posterior horns.
3.The right horn is shorter than the left.
4.There is a thin bar that connects the two horns.
5.C. furca is yellow-brown and has thick thecal plates.


12. Protoperidinium

Phylum Myzozoa
Subphylum Dinoflagellata
Class Dinophyceae
Subclass
Order Peridiniales
Family Protoperidiniaceae
Genus Protoperidinium

1.Protoperidinium oceanicum cell is star-shaped with one long apical
horn and two long antapical horns.
2.The centre of the cell theca is round with a protrusion on each side.
3.The cell cingulum is narrow and has wide lists.
4.The two antapical horns are long, tubular, pointed and divergent.
5. The left antapical horn is a bit shorter and thinner than the right. Cells have a deep sulcus that forms a strong indentation between the horns.
6.The theca is reticulated with spiny junctions, making it look very ornate under SEM.


13. Dinophysis

Phylum Dinoflagellata
Subphylum
Class Dinophyceae
Subclass
Order Dinophysiales
Family Dinophyciaceae
Genus Dinophysis

1.Cells are broadly subovoid and widest posteriorly.
2.Cells have a curved dorsal margin and an almost straight ventral margin. The cell surface has deep poroids.
3.Cells also have two well-developed sulcal lists.
4.The left sulcal list is about ⅘ of the cell length.
5.The right sulcal list is also long and can extend beyond the second rib.
6.Dinophysis fortii has a wide rounded posterior and reticulation on the sulcal lists. D. fortii cells have many large centrally placed chloroplasts.



Trichodesmium
Kingdom: Bacteria

Phylum: Cyanobacteria

Order: Oscillatoriales

Genus: Trichodesmium

Trichodesmium, also called sea sawdust, is a genus of filamentous cyanobacteria. They are found in nutrient poor tropicaland subtropical ocean waters (particularly around Australia and in the Red Sea, where they were first described by Captain Cook). Trichodesmium is a diazotroph; that is, it fixes atmospheric nitrogen into ammonium, a nutrient used by other organisms.Trichodesmium is the only known diazotroph able to fix nitrogen in daylight under aerobic conditions without the use ofheterocysts.[1]
Trichodesmium can live in solitude or in colonies. These colonies are visible to the naked eye and sometimes form blooms, which can be extensive on surface waters. These large blooms led to widespread recognition as "sea sawdust/straw"; in fact, the Red Sea gets most of its eponymous colouration from the corresponding pigment in Trichodesmium erythraeum. Colonies of Trichodesmium provide a pseudobenthic substrate for many small oceanic organisms including bacteria, diatoms,dinoflagellates, protozoa, and copepods (which are its primary predator); in this way, the genus can support complex microenvironments.
Like most cyanobacteria, Trichodesmium has a gram negative cell wall. However, unlike other aerobic diazotrophs, heterocysts (structures found in cyanobacteria which protect nitrogenase from oxygenation) are lacking in Trichodesmium. This is a unique characteristic among aerobic diazotrophs which fix nitrogen in daylight. Photosynthesis occurs using phycoerythrinlight harvesting phycobiliprotein which is normally found within heterocysts in other diazotrophs.
Instead of having localized stacks of thylakoids, Trichodesmium has unstacked thylakoids found throughout the cell. Trichodesmium is highly vacuolated and the content and size of the vacuoles shows diurnal variation. Large gas vesicles (either along the periphery as seen in T. erythaeum or found distributed throughout the cell as seen in T. thiebautii) allow Trichodesmium to regulate buoyancy in the water column. These gas vesicles can withstand high pressure, presumably those up to 100 – 200 m in the water column, allowing Trichodesmium to move vertically through the water column harvesting nutrients.

Spirulina
Domain: Bacteria

Kingdom: Eubacteria

Phylum: Cyanobacteria

Order: Spirulinales

Family: Spirulinaceae

Genus: Spirulina






Spirulina is a genus of blue-green algae used as a nutritional supplement. Blue-green algae, which are microscopic fresh-water organisms, are also known as cyanobacteria. Their color is derived from the green pigment of chlorophyll, and the blue from a protein called phycocyanin. The species most commonly recommended for use as a nutritional supplement are Spirulina maxima and Spirulina platensis. These occur naturally in warm, alkaline, salty, brackish lakes, but are also commonly grown by aquaculture and harvested for commercial use. Spirulina contains many nutrients, including B vitamins, beta-carotene, gamma-linolenic acid, iron, calcium, magnesium, manganese, potassium, selenium, zinc, bioflavonoids , and protein.
Spirulina is about 65% protein by composition. These proteins are complete, in that they contain all essential amino acids , plus some nonessential ones. In that regard, it is similar to animal protein, but does not contain saturated fats, or residues of hormones or antibiotics that are in some meats. Since spirulina is normally taken in small amounts, the quantity of dietary protein supplied for the average reasonably well-nourished person would not be significant. However, it is a good source of trace minerals, some vitamins, bioflavonoids, and other phytochemicals. It also has high digestibility and bioavailability of nutrients.


Nostoc sp
Kingdom: Bacteria

Phylum: Cyanobacteria

Class: see taxonomic note

Order: Nostocales

Family: Nostocaceae

Genus: Nostoc


Nostoc is a genus of cyanobacteria found in a variety of environmental niches that forms colonies composed of filaments of moniliform cells in a gelatinous sheath.
The name Nostoc was coined by Paracelsus.[1]
Nostoc can be found in soil, on moist rocks, at the bottom of lakes and springs (both fresh- and saltwater), and rarely in marine habitats. It may also grow symbiotically within the tissues of plants, such as the evolutionarily ancient angiospermGunnera and the hornworts (a group of bryophytes), providing nitrogen to its host through the action of terminally differentiated cells known as heterocysts. These bacteria contain photosynthetic pigments in their cytoplasm to perform

Anabaena
Kingdom: Bacteria

Phylum: Cyanobacteria

Order: Nostocales

Family: Nostocaceae

Genus: Anabaena
Anabaena is a genus of filamentous cyanobacteria that exists as plankton. It is known for its nitrogen fixing abilities, and they form symbiotic relationships with certain plants, such as the mosquito fern. They are one of four genera of cyanobacteria that produce neurotoxins, which are harmful to local wildlife, as well as farm animals and pets. Production of these neurotoxins is assumed to be an input into its symbiotic relationships, protecting the plant from grazing pressure.
A DNA sequencing project was undertaken in 1999, which mapped the complete genome of Anabaena, which is 7.2 million base pairs long. The study focused on heterocysts, which convert nitrogen into ammonia. Certain species of Anabaena have been used on rice paddy fields, proving to be an effective natural fertilizer.


Copepoda
Kingdom: Animalia

Phylum: Arthropoda

Subphylum: Crustacea

Class: Maxillopoda

Subclass: Copepoda

Copepods vary considerably, but can typically be 1 to 2 mm (0.04 to 0.08 in) long, with a teardrop-shaped body and large antennae. Although like other crustaceans, they have an armoured exoskeleton, they are so small that in most species, this thin armour, and the entire body, is almost totally transparent. Some polar copepods reach 1 cm (0.39 in). Most copepods have a single median compound eye, usually bright red and in the centre of the transparent head; subterranean species may be eyeless. Like other crustaceans, copepods possess two pairs of antennae; the first pair is often long and conspicuous.
Copepods typically have a short, cylindrical body, with a rounded or beaked head. The head is fused with the first one or two thoracic segments, while the remainder of the thorax has three to five segments, each with limbs. The first pair of thoracic appendages is modified to form maxillipeds, which assist in feeding. The abdomenis typically narrower than the thorax, and contains five segments without any appendages, except for some tail-like "rami" at the tip.[4]
Because of their small size, copepods have no need of any heart or circulatory system (the members of the order Calanoida have a heart, but no blood vessels), and most also lack gills. Instead, they absorb oxygen directly into their bodies. Their excretory system consists of maxillary glands.


Amphipods
Kingdom: Animalia

Phylum: Arthropoda

Subphylum: Crustacea

Class: Malacostraca

Superorder: Peracarida

Order: Amphipoda



The body of an amphipod is divided into 13 segments, which can be grouped into a head, a thorax and an abdomen.[4]
The head is fused to the thorax, and bears two pairs of antennae and one pair of sessilecompound eyes.[6] It also carries the mouthparts, but these are mostly concealed.[7]
The thorax and abdomen are usually quite distinct and bear different kinds of legs; they are typically laterally compressed, and there is no carapace.[6] The thorax bears eight pairs of uniramous appendages, the first of which are used as accessorymouthparts; the next four pairs are directed forwards, and the last three pairs are directed backwards.[6] Gills are present on the thoracic segments, and there is an open circulatory system with a heart, using haemocyanin to carry oxygen in the haemolymphto the tissues. The uptake and excretion of salts is controlled by special glands on the antennae.[4]
The abdomen is divided into two parts: the pleosome which bears swimming legs; and the urosome, which comprises a telsonand three pairs of uropods which do not form a tail fan as they do in animals such as true shrimp.





Lucifer
Phylum Arthropoda
Subphylum Crustacea
Class Malacostraca
Superorder Eucarida
Order Decapoda
Suborder Dendrobranchiata
Superfamily Sergestoidea
Family Luciferidae
Genus Lucifer














 Sometimes called the ghost shrimp.
 Appearance of an elongated shrimp; it almost seems to have been stretched.
 Carapace is extremely laterally compressed.
 Head section is longer and narrower than the thorax, resulting in the eyes and antennae being widely distant from the mouthparts.
 Rostrum is short and pointed.
 3 pairs of pereiopods instead of the usual 5; the 3rd pair is partially chelate .
 Telson in males has 2 distinct projections on the ventral surface.
 Almost transparent.
Distribution
 South-eastern Australian waters (Dakin and Colefax 1940). Melbourne Harbour (Borradaille 1916). South-eastern Tasmanian waters and Derwent Estuary (Ong 1967, Nyan Taw 1978). Indian Ocean and South China Sea (Hansen 1919).
 Particularly abundant in the coastal waters of south-eastern Australia where it can often make sorting of other plankton difficult because of the large numbers.
 Nyan Taw (1978) reported that it is a dominant species in the inshore coastal waters of south-eastern Tasmania during winter months.

Euphasiid

Kingdom: Animalia

Phylum: Arthropoda

Subphylum: Crustacea

Class: Malacostraca

Superorder: Eucarida

Order: Euphausiace
. The profuse exposed gills of euphausiids arise from the coxae of the thoracic legs (feathery entirely exposed). They are conspicuous and are progressively larger toward the posterior of the thorax. In mysids and in the penaeid and caridean decapods the gills, when present, arise beneath the carapace, are relatively compact, and only partly exposed (mostly hidden beneath carapace).

2. In euphausiids and decapods, the carapace is firmly attached to all eight thoracic segments. In mysids, the carapace is attached only to the three anterior segments of the thorax.

3. The rostrum and frontal plate in euphausiids and mysids are parts of a basically horizontal projection of the carapace. In the decapods (penaeids and carideans) the frontal plate supports an elevated, laterally compressed rostrum, often acute and anteriorly or dorsally notched.

4. The antennae. The 3-segmented peduncle of the 1st antenna in euphausiids, particularly the lappet on segment 1, provides important taxonomic characters. In pelagic decapoods and mysids the peduncles are usually relatively simple and uniform. In the larger nektonic species of sergestid decapods, the flagella of the 1st antenna can be extremely elongate and thread-like, and the flagellum of the 2nd antenna can be uniquely coiled like a spring.

5. The abdominal pleura. These are lateral coverings of abdominal segments 1-5 in euphausiids and pelagic decapods. They consist of plates, with free ventral edges (pleuron seg. 2 overlaps seg. 3). In most mysids the abdominal segments are nearly cylindrical, without lateral plates. Caridean decapods are unique in that the pleura of the 2nd abdominal segment overlap pleura of both the 1st and 3rd segments (pleuron seg 2 overlaps seg 1&3).

6. Statocysts. The broad proximal ends of the endopods of the uropods in mysids (except the predominantly deep living Lophogastridae and one small family of Mysida) have conspicuous circular statocysts (uropods with statocyst). Sergestid decapods have statocysts, but they are at the bases of the peduncles of the 1st antennae . Statocysts are not known in euphausiids (uropods without statocyst).

7. The telson of adult euphausiids is about as long as the exopod of the uropod, and has an acute distal point which is flanked by a pair of very strong posterior lateral spines which extend beyond the telson tip. In mysids the telson is shorter than the uropods, paddle-like and spinose in some species, rarely with an acute tip, and in many genera it is cleft distally, appearing as a two-pronged, sometimes spinose or setose fork. In sergestid decapods the tip of the telson is bluntly rounded, shorter than the uropod, and marginally setose.


Mysid

Kingdom: Animalia

Phylum: Arthropoda

Subphylum: Crustacea

Class: Malacostraca

Subclass: Eumalacostraca

Superorder: Peracarida



The head of a mysid bears two pairs of antennae and a pair of large, stalked eyes. The head and first segment (or sometimes the first three segments) of the thorax are fused to form the cephalothorax. The eight thoracic segments are covered by the carapace which is attached only to the first three. The first two thoracic segments bearmaxillipeds which are used to filter plankton and organic particulate from the water. The other six pairs of thoracic appendages are biramous (branching) limbs known aspereopods, and are used for swimming, as well as for wafting water towards the maxillipeds for feeding. Unlike true shrimps (Caridea), females have a marsupiumbeneath the thorax. This brood pouch is enclosed by the large, flexible oostegites, bristly flaps which extend from the basal segments of the pereopods and which form the floor of a chamber roofed by the animal's sternum. This chamber is where the eggs are brooded, development being direct in most cases.[2]
The abdomen has six segments, the first five of which bear pleopods, although these may be absent or vestigial in females. The fourth pleopod is longer than the others in males and has a specialized reproductory function.[2]
The majority of species are 5–25 mm (0.2–1.0 in) long, and vary in colour from pale and transparent, through to bright orange or brown. They differ from other species within the superorder Peracarida by featuring statocysts on their uropods (located on the last abdominal segment). These help the animal orient itself in the water and are clearly seen as circular vesicles: together with the pouch the statocysts are often used as features that distinguish mysids from other shrimp-like organisms.[3]


Pteropod

Kingdom: Animalia

Phylum: Mollusca

Class: Gastropoda

Clade: Heterobranchia

Informal group: Opisthobranchia

Informal group: Pteropoda
Pteropoda (common name pteropods, from the Greek meaning "wing-foot") are specialized free-swimming pelagic sea snails and sea slugs, marine opisthobranch gastropods. The monophyly of Pteropoda is the subject of a lengthy debate; they have even been considered as paraphyletic with respect to cephalopods.[1] Current consensus, guided by molecular studies, leans towards interpreting the group as monophyletic.[2]
Pteropoda encompasses the two clades Thecosomata, the sea butterflies, and Gymnosomata, the sea angels. The Thecosomata (lit."case-body"[3]) have a shell, while the Gymnosomata ("naked body") do not. The two clades may or may not be sister taxa; if not, their similarity (in that they are both pelagic, small, and transparent, and both groups swim using wing-like flaps (parapodia) which protrude from their bodies) may reflect adaptation to their particular lifestyle.


Ostracoda

Kingdom: Animalia

Phylum: Arthropoda

Subphylum: Crustacea

Class: Ostracoda










The body of an ostracod is encased by two valves, superficially resembling the shell of a clam. A distinction is made between the valve (hard parts) and the body with its appendages (soft parts).
Soft parts[edit]
The body consists of a head and thorax, separated by a slight constriction. Unlike many other crustaceans, the body is not clearly divided into segments. The abdomen is regressed or absent, whereas the adult gonads are relatively large.
The head is the largest part of the body, and bears most of the appendages. Two pairs of well-developed antennae are used to swim through the water. In addition, there is a pair of mandibles and two pairs of maxillae. The thorax typically has two pairs of appendages, but these are reduced to a single pair, or entirely absent, in many species. The two "rami", or projections, from the tip of the tail, point downwards and slightly forward from the rear of the shell.[14]
Ostracods typically have no gills, instead taking in oxygen through branchial plates on the body surface. Most ostracods have no heartor circulatory system, and blood simply circulates between the valves of the shell. Nitrogenous waste is excreted through glands on the maxillae, antennae, or both.[14]
The primary sense of ostracods is likely touch, as they have several sensitive hairs on their bodies and appendages. However, they do possess a single naupliar eye, and, in some cases, a pair of compound eyes, as well.[14]


Cladocera
Kingdom: Animalia

Phylum: Arthropoda

Subphylum: Crustacea

Class: Branchiopoda

Subclass: Phyllopoda

Order: Cladocera














They are mostly 0.2–6.0 mm (0.01–0.24 in) long, with the exception of Leptodora, which can be up to 18 mm (0.71 in) long.[1] The body is not obviously segmented and bears a folded carapace which covers the thorax and abdomen.[2]
The head is angled downwards, and may be separated from the rest of the body by a "cervical sinus" or notch.[2] It bears a single black compound eye, located on the animal's midline, in all but two genera, and often, a single ocellus is present.[3] The head also bears two pairs of antennae – the first antennae are small, unsegmented appendages, while the second antennae are large, segmented, and branched, with powerful muscles.[2] The first antennae bear olfactory setae, while the second are used for swimming by most species.[3] The pattern of setae on the second antennae is useful for identification.[2] The part of the head which projects in front of the first antennae is known as the rostrum or "beak".[2]
The mouthparts are small, and consist of an unpaired labrum, a pair of mandibles, a pair of maxillae, and an unpaired labium.[2]They are used to eat "organic detritus of all kinds" and bacteria.[2]
The thorax bears five or six pairs of lobed, leaf-like appendages, each with numerous hairs or setae.[2] Carbon dioxide is lost, and oxygen taken up, through the body surface.[2]