Marine Biology (2+1)

Identification of zooplankton

 Introduction

The subclass Copepoda is represented in the marine plankton by free forms belonging to eight out of the nine orders of this group of Crustacea (Boxshall & Halsey, 2004): Platycopioida, Calanoida, Mormonilloida, Misophrioida, Hapacticoida, Cyclopoida, Siphonostomatoida, Monstrilloida. Add Poecilostomatoida which can no longer be considered as a group phylogenetically separated from Cyclopoida, and the controversial Thaumatopsylloida which are rejected by the above mentioned taxonomists. The order of Gelyelloida is defined from species in subterranean karstic systems. The role of the free Copepoda in the pelagic ecosystem is essential from a trophic point of view, as a link between the primary production and the larvae and juveniles of fishes and perhaps cephalopods. They characterize the secondary production of the sea. The specific composition and the biological cycles of the species are essential factors to determine in the course of time. The species form important indicators for the different water masses, being directly related to the characteristics and dynamics of these.

Oithona rigida Phylum : Arthropoda

Class : Maxillipoda (Crustacea)

 Order : Cyclopoida

Family : Oithonidae

Genus : Oithona

Species : rigida Smaller body with 2nd antennae containing 2 joined endopods. The endopod distal segment is as long as the proximal segment. In females, the uniramose, slender and spine like 5th legs are present. The genital segments are little longer than the other urosome segments. The maxillipeds and 2nd maxillae are slender and covered with numerous spiny bristles. The anterior end is bluntly rounded. The first antennae reached upto end of the 3rd metasome only and it is twice geniculated and the sheathing base appears to be present. The body is broader at the centre than at either end and the four segments are found behind head. Body usually with many pigments without prominent eyes. Paired egg sacs may sometimes be seen attached to the anterior end of the upper abdomen. Urosome nearly as long as metasome. Caudal setae coarsely plumose which forming a fan.

Corycaeus danae Phylum : Arthropoda

 Class : Maxillipoda (Crustacea)

 Order : Poecilostomatoida

Family : Corycaeidae

Genus : Corycaeus

Species : danae The body is not depressed but clavate. The head is round anteriorly. Cuticular eye lenses are present on the cephalosome, one at each corner. The 2 free metasomal segments are not usually fused. The last metasomal segments and the penultimate segments are provided with tailward projections or lappets. These lappets, though long, do not reach the end of the genital segment. The urosome is 2 segmented. The 2nd antennae are much larger, stout and subchelate. The coudal rami are styliform. The sac is single and borne dorsally on the genital segment, which overhangs the anal segment. (Length 1.6 1.7 mm Female).

Phylum : Arthropoda

Class : Maxillopoda

Order : Copepoda

Suborder: Calanoida

Family : Acartiidae

Genus : Acartia

Size Male: 0.73-0.80 mm. Female: 1.08-1.27 mm. Distinguishing characteristics Top of head is flat or slightly triangular. Long, slender cigar-shaped body. Long, spaced out setae on antennae. Fresh specimens usually transparent, with prominent eye-spot (red or black). Metasome is pointed anteriorly in dorsal view and bears a pair of sharp points posteriorly. This feature can be used to separate this species from other Acartia spp. Furca rather short. Furcal setae robust with fan-shape. Rostral filaments present (others in the Acartia genus have no rostrum). Male Posterior metasome terminates in symmetrical points. Urosome 5-segmented. Urosome segment 1 with lateral hairs. 1st antenna geniculate on right side only. Female Posterior metasome as in male. Urosome has no spines but has fine dorsal hairs on the posterior border of the first 2 segments. Genital segment is longer than the following segment. Antenna 1 extends to the tip of the caudal rami; 1st segment has strong, thick spine. Acartia erythraea Giesbrecht 1889

 Phylum : Arthropoda

 Class : Maxillipoda (Crustacea)

Order : Calanoida

Family : Acartiidae

Genus : Acartia

Species : erythraea The urosome has 5 segments, of which the 4th one is very short. The 2nd urosomal segments are more wider with 2 pairs of prominent spines. The 1st segment bears the lateral genital aperture. The right 1st antenna is indistinctly geniculate. (Length 1 1.3 mm Male). The posterior margin of the metasome is drawn out into prominent spines. Further, there are 2 smaller spines situated dorsally nearer the midline. The urosome is 3 segmented. The 1st antennae are similar on both sides. The 5th leg is uniramose, slender and spine like. The terminal claw of the base and slightly thickened at the base are slightly curved. (Length 1 1.5mm Female).

Euterpina acutifrons (Dana, 1847) Phylum : Arthropoda

Class : Maxillipoda (Crustacea)

Order : Harpacticoida

Family : Tachidiidae

Genus : Euterpina

Species : acutifrons Euterpina acutifrons (Dana, 1847) It is a monospecific genus as it has only one species. The body is subpyriform or arched and the cephalosome is drawn out in front into a greatly prominent rostral projection, which is acute at the tip. Fifth pair of legs formed by two undivided juxtaposed plates.

Microsetella norvegica (Boeck, 1864) Phylum : Arthropoda

Class : Maxillipoda (Crustacea)

Order : Harpacticoida

Family : Ectinosomidae

Genus : Microsetella

Species : norvegica Microsetella norvegica (Boeck, 1864) Body is fusiform and gently compressed laterally. It can be generally recognized and distinguished from Macrosetella by its smaller size and the greater body width. It has geniculated antennules. The 3rd and 4th segments of the metasome and all the segments of the urosome carry transverse rows of spinules. The caudal rami are as long as broad and are indistinct. The caudal setae are also as long as the body nearly 1 ½ times the length of the body. Metis jousseamei Phylum :

Arthropoda Class : Maxillipoda (Crustacea)

Order : Harpacticoida

Genus : Metis

Species : jousseamei

MALE: Length 0.3-0.4 mm. FEMALE (Fig. 149) The body is very short, compact and onion-shaped. The 5th pair of legs is rudimentary and more or less fused. Length 0.4-0.5 mm.