Current knowledge of the abyssal Harpacticoida is based on occasional catches made with inadequate equipment. The variability at the species level is mainly expressed in the armature of the thoracic segments and of the first 2 antennular joints. Fifth thorax and 1st and 2nd abdominal segments with the same irregular denticulation of the edges on the dorsal side.
Swimming bones characterized by the rod-like setae on the distal endopodite joints and by the very short and swollen spines of the exopodites. These spines as well as the dorsal spines of the cephalon are of the same type as in our specimen. Maxillary body relatively short and stout; proximal endite with 6 setae; endopodite more reduced and narrower than in other species of the genus.
The differences between the 2 species are particularly noticeable in the dimorphic armor of the male antennules. The posterior edge of the cephalothorax is coarsely serrated, the dorsal spines are straight, reaching the middle of the 2nd thoracic segment; no denticulation between spines.
First joint pubescent with apical corner only slightly produced. Second joint
Posterior sides of these segments bear slightly converging pairs of dorsal spines reaching at least the middle of the next segment and a pair of dorsolateral spines. Fifth thoracic segment and 1st and 2nd abdominal segments have a pair of dorsal and a pair of dorsolateral short spines. Ventral sides of abdominal segments serrated; this serration also extends to the dorsal side of the 4th and 5th abdominal segments.
Lateral extensions of the 2nd, 3rd and 4th thoracic segments broad and wing-like with 3-stepped outer edges. This relatively small species appears to be closely related in these characters to another small species of the genus, Pontostratiotes horrida Brodskaya. Nothing similar is found in the other bones or in any other species of the genus.
Armature of swimming legs, as in most species of the genus, identical to that of P. The specific name refers to the tiny serrations on the posterior edges of the body segments. PIV is relatively well developed compared to the other two species of the genus, with a transversely elongated base.
Cerviniella brodskayae is characterized by the one-articulated condition of the endopodites of PI I and PIII. There appears to be no significant difference in the structure of the mouthparts of the 3 species.
Temperatures at the shallow arctic and deep sea Indian Ocean stations are more or less similar, but the temperatures of the Mediterranean stations are at least 10° higher. I propose that this represents a new sensory organ of the copepod, which I propose to call "Brodskaya's organ" and which is probably similar to a statocyst. Antennula of the plump shape characteristic of the genus, formed of 5 joints; 3rd joint especially short.
The very small size of the second (external) apical seta of the last endopodite joint of PIV should be emphasized. However, the differences are quite numerous: the furca of our species is relatively longer, the rostrum is longer and narrower, the segment margins are toothed, PV is longer and narrower, different limbs bear surface hairs and the basal endite of the maxilla is false. It is far too early to use the limited knowledge of the Abyss Harpacticoids to choose sides.
Cerviniidae is actually a very primitive family of the order, but in our as yet unpublished abyssal material are also many representatives of evolutionarily advanced families. Pontostratiotes Brady with 10 species is, as it currently appears, the characteristic genus for the abyssal dynamic fauna. It should also be mentioned that the deep bottoms off the East African coast also yielded many new species of Pogonophora, of which 5 are of the genus Siboglinum (Ivanov, 1963).
The present material contained for the first time several specimens of one species, in two cases both females and males of the same species. Mention should also be made of the very large size of some Pontostratiotes, which, exceeding 3 mm, are by far the largest harpactioids known. FIGURES 1-5.-Pontostratiotes scotti Brodskaya, female: 1, cephalon and first three thoracic segments 2, abdomen in ventral view and PV; 3, PII; 4, PIV; 5, PV. FIGURES 6-12.-Pontostratiotes scotti Brodskaya, female: 6, antennula; 7, antenna; 8, mandible;.
FIGURES 14—18.—Pontostratiotes abyssicola Brady, female: 14, posterior margin of cephalon and first three thoracic segments; 15, abdomen ventral view and PV; 16, antenna; 17, PI; 18, PHI. FIGURES 99-100.-Pontostratiotes horrida Brodskaya, female: 99, general habitus, dorsal view; 100, third and fourth thoracic segments, side view. FIOURE 178.—PontostratioUs sixtorum, new species, P1V. FIGURE 179.—Pontostratiotes sixtorum, new species, spikes of rod-shaped setae on endopodite of PIV high magnification.
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