Pertsovius heterodentatus Andronov & Kosobokova, 2011, n. gen.

Pertsovius heterodentatus n. gen. et sp. nov.

(Figures 5–6)

Material examined. Holotype: adult female, dissected, body length 0.70 mm. ZIN accession number 91098. Collected during the USCGC “ Healy ” Ocean Exploration-05/2 cruise, station 5, Canada Basin (73° 24’N, 153° 33’W), 5 July 2005, bottom depth 3850 m, depth of collection 3000– 2000 m. Paratype: adult female, dissected, body length 0.70 mm. ZIN accession number 91099. Collected during the USCGC “ Healy ” Ocean Exploration-05/2 cruise, station 5, Canada Basin (73° 24’N, 153° 33’W), 5 July 2005, bottom depth 3850 m, depth of collection 2000– 1000 m.

Species description. Prosome ovoid in dorsal view (Fig. 5: 1), nearly three times as long as urosome and 1.9 times as long as wide. The first pediger partly separate from cephalosome (Fig. 5: 2), while fourth and fifth pedigers fused.

Genital complex slightly asymmetrical (Fig. 5: 3) with lateral borders strongly convex, and large spermathecae obvious. Genital double somite approximately equal in length to subsequent two somites combined: anterior part strongly protruding ventrally forming a thick wide fold covering middle part of double somite (Fig. 5: 5). Anal somite nearly twice as long as preceding somite. Antennule of 24 free segments, reaching about to posterior border of caudal rami (Fig. 5: 2). Mouthparts as in P. tridentatus. No substantial differences from appendages of other species in the genus noted, except for maxilliped syncoxa lobe one having one seta (Fig. 5: 5, 6).

Р1-Р4 (Fig. 6: 1–5) of typical structure for genus: endopods one-segmented, exopods three-segmented. Outer distal spine on first segment of P1 exopod long, almost reaching middle of outer border of third segment.

Outer distal spine of first exopodal segment of Р2 extending beyond distal end of second segment. Outer bor- der edge of third exopodal segment of left Р2 armed with three spines, but right Р2 with only two spines, both in holotype (Fig. 6: 2) and in paratype (Fig. 6: 3).

Differential diagnosis. The presence of three outer spines on the third exopodal segment of the left Р2 and only two spines on the right Р2 is characteristic only for this species. The appearance of the genital field, specifically the protruding thick wide fold that covers the middle part of the double somite (Fig. 5: 3 and 4) serves as an additional diagnostic character for the females of this species.

Etymology. The specific name refers to the number of external spines on the distal segment of left (three spines) and right (two spines) exopods of P2.