Hipótesis específica

Genus Clausocalanus

Small to medium sized copepods which may initially be confused with Paracalanus, but differ in that the females have a longer urosome in relation to the length of the body and the P5 is more robust and simple, bifurcated distally with only tiny spikes on the end rather than a long spine. P5 uniramous on both sides, symmetrical, 3-segmented. The anterior cephalosome and posterior metasome segments are rounded. Cephalosome fused to first pedigerous segment. Rostrum bifurcated. Urosome 4-segmented. Male rostrum reduced to a knob. P5 uniramous, legs of unequal length, longer leg nearly always on the left, 5-segmented with segment 5 short and attached sub-apically to the previous segment; shorter leg, 3-segmented, less than half the length of segment 1 of the other leg.

Clausocalanus arcuicornis (Dana, 1849)

Length: females: 1.08-1.62 mm; males: 0.97-1.20 mm.

Female: Rostrum in lateral view short, bifurcated, thick at its base, usually straight or slightly curved and directed ventrally. Genital segment in lateral view straight or, more often slightly concave in the region of the seminal receptacle; 1.5 times as long as urosome segment 3. The third segment of the simple P5 as long as the two preceding segments together. Terminal points of segment 3 of leg 5 bifurcated, sometimes with tiny spinules on inner and outer margins.

Male: Second urosome segment as long as the two following segments together. Rostrum in lateral view knoblike and protruding ventrally. P5 uniramous and asymmetrical, right leg short, usually 3-segmented; left leg robust, longer than urosome, armed distally with long slender straight setae.

Recorded: Rodrigues, Madagascar.

Clausocalanus arcuicornis: Female. A, dorsal; B, lateral; C, rostrum lateral and dorsal; D. basipod 2 of P2 (upper), basipod 2 of P3 (lower); E, P5; F genital segment lateral. Male. G, dorsal; H, lateral; I, urosome lateral; J, urosome dorsal; K, P5; L, basipod 2 of P2 (upper), basipod 2 of P3 (lower). Figures from Frost and Fleminger (1968).

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Clausocalanus furcatus (Brady, 1883)

Length: females: 0.94-1.31 mm; males: 0.70-0.92 mm.

Female: Rostrum in lateral view usually thick, short, and slightly curved, bifurcated at tip. Genital segment profile in lateral view rather uneve n, generally shorter in length than the second or third segments. The 2 distal segments of the P5 are of similar length, the coxa very short; terminal points of bifurcated segment 3 never with tiny spinules.

Male: Rostrum in lateral view not well developed and not protruding ventrally. Longer P5 usually on the right side, occasionally on the left, longer than the urosome; shorter leg usually 2- segmented, tiny distal segment spine- like. Recorded: Madagascar.

Clausocalanus furcatus: Female. A, lateral; B, genital segment lateral; C, P5. Male. D, lateral; E, dorsal; F, metasome dorsal; G, urosome; H, P5. Figures A-C from Bradford-Grieve (1994); D-H from Frost and Fleminger (1968).

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Clausocalanus paululus Farran, 1926

Length: females: 0.66-0.80 mm; males: 0.47-0.56 mm.

Female: Rostrum slender and curved posteriorly. In lateral view genital segment with a depression in mid segment, longer than either of the following 2 segments. Points on distal P5 not divergent and may have tiny spines on inner and outer margins.

Male: Short squat body. In lateral view rostrum knob-like and projecting ventrally. P5 left longer than urosome; right P5 2-segmented with tiny spine- like distal segment.

Recorded: Madagascar.

Clausocalanus paululus: Female. A, lateral; B, rostrum lateral; C, genital segment lateral; D, P5. Male. E, lateral; F, head lateral; G, urosome dorsal; H, P5. Figures from Frost and Fleminger (1968).

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Family Euchaetidae

Most of this group are large copepods. Both the male and female have very large maxillipedes, associated with their carnivorous diet, and also long urosomes. The innermost (appendicular) seta on each furca is very well developed and usually much longer than the other caudal setae. The anterior of the cephalosome in both sexes, in most species, comes to a point when viewed dorsally. In lateral view a single strong rostrum is obvious and just behind this is a frontal eminence that varies from a slightly raised ledge with a small sensory bristle to a strong curved point. The A1 have characteristic very long setae. The female genital segment is very prominent when viewed laterally and different species have characteristic shapes that are used in identification. The female often has a single egg sac still attached. The P5 is absent in females. The male P5 is very large and characteristic, with rudimentary endopodites; left leg with a complex distal joint.

Genus Euchaeta

The innermost seta on each furca is greatly developed, straight and much thicker and longer than the other caudal setae. The P5 terminal exopodite segments in both right and left legs of the male taper into long spines.

Of the three Euchaeta species so far recorded for the area, E. indica and E. rimana belong to the

marina species group while E. longicornis belongs to the concinna species group. These two groups can be distinguished by the following features.

In both groups the basis of the female maxilliped has both long and short spines along the proximal half of the medial margin (Fig. A). The serrated lamella of the male left P5 exopodite reaches or extends beyond a tuft of stiff hairs (Fig. C). In the marina group the two endopodal setae of the female maxillule 2 are armed with both long and short spines (Fig. B), while in the

concinna group only one seta is armed this way (Fig. D). Males in the marina group have on the exopod of the left P5, 3 lobes, one which is next to the tuft of hairs (Fig C), not present in the

concinna group (Fig E).

Identification features of limbs mentioned in the text. From Park (1994).

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Euchaeta indica Wolfenden, 1905

Length: females: 2.4-2.68 mm; male: 2.32-2.56 mm. Belongs to the marina species group.

Female: Frontal eminence on forehead well developed. In lateral view, the genital segment is about twice as long as the broadest part. Genital segment is as long as the combined length of the next three segments and is irregular in outline when viewed from the dorsal and ventral sides. Urosome segment 2 is about half the length of the genital segment and is equal to the combined length of segments 3 and 4. The appendicular seta is much longer than any of the others. The last metasome segment and the urosome segments are densely covered with short fine hair s. A1 extend to the end of urosome segment 2.

Male: P5 like E. marina in general appearance, distinguished by the structure of the serrated lamella, which is bilobed distally, with double rows of teeth bordering the lobes.

Recorded: Rodrigues, Zuza, Aldabra, CPR.

Euchaeta indica: Female. A, dorsal; B, head lateral; C, urosome left lateral; D, urosome left lateral; E, urosome right lateral; F, urosome ventral; G, urosome dorsal; H, maxilla, fifth lobe and endopod omitted.. Male. I, lateral; J, head lateral; K, exopod of left P5. Figures A, I from Mori (1937; as E. wolfendeni); B-H, J, K From Park (1994).

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Euchaeta rimana Bradford, 1974

Length: females: 2.80-4.30 mm; males: 3.11-4.10 mm.

Also belongs to the marina species group and was originally recorded as E. marina which is now recognised to be restricted to the Atlantic and Mediterranean.

Female: Can only be separated from E. marina by the structure of the genital segment. In both dorsal and ventral view, the left side of the genital segment is smoothly curved, without any prominent projection; the right side with a moderate projection. Posterior metasome segments are slightly asymmetrical in dorsal view, slightly more extended on right.

Male: The serrated structure of the lamella of the left P5 exopod segment 2 is the only morphological feature of the appendages found to be different between this species and E. marina. The distal margin has an unserrated gap in E. marina but not in E. rimana. The thick spine originating at the base of the lamella is less than half the length of the lamella.

Recorded: Rodrigues, Zuza, Madagascar, CPR.

Euchaeta rimana: Female. A, head lateral; B, urosome lateral left; C, urosome lateral le ft; D, urosome left right; E, urosome dorsal; F, urosome ventral. Male. G, head lateral; H, exopod of left P5; I, distal end of serrated lamella. Figures from Park (1994).

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