Sensiava cf. secunda sp. nov.

(Figs 5–8)

Material examined. Three adult males, body length 2.80–3.00 mm. Collected by the DIVA –II expedition above the sea bed in the South Atlantic: 1 male, 15 March 2005, 00º09’S 02º30’W, at a depth of 5054 m; 1 male, 20 March 2005, 00º45’S 05º35’W, at a depth of 5142 m; and 1 male, 20 March 2005, 00º43’S 05º31’W, at a depth of 5142 m.

Description. Male. Body length 2.80–3.00 mm. Prosome 2.2–2.6 times as long as urosome (Fig. 5 A–B). Rostrum as 2 filaments (Fig. 5 C). Cephalosome and pedigerous somite 1 incompletely separate, and pedigerous somites 4 and 5 completely separate; posterior corners in dorsal view obtuse-triangular; as short rounded lobes in lateral view (Fig. 5 A–B). Urosome of 5 somites (Fig. 5 A–B). Caudal rami with 1 dorsal seta, 1 ventral seta, and 4 terminal setae (Fig. 5 D).

Antennule (Fig. 6 A–D, 7A–B) nearly as long as body, right (Fig. 6 A–D), of 23 articulating segments, segments XIX to XXIII transformed, compared to left; armature as follows: I–1 s + 1ae, II– IV–6 s + 2ae + 2, V–2 s + 2?, VI–2 s + 1?, VII–2 s +2ae, VIII–2 s + 1ae, IX–2 s + 2ae, X– XI–3 s + 3ae, XII–1 ae, XIII–1ae, XIV–2s + 1ae, XV–1s + 1ae, XVI–2s (1 seta curved), XVII–2s+1ae, XVIII–2s + 1ae, XIX–1s + 1ae + 1spine, XX–1s + 1ae + 1spine, XXI–1s + 1ae, XXII–XXIII–1s + 1spine, XXIV–2s, XXV–2s, XXVI–2s, XXVII–XXVIII–5s + 1ae. Left (7A–B) antennule of 24 articulating segments, armature as follows: I–1 s + 1ae, II– IV–6 s + 4ae, V–2 s + 2ae, VI–2 s + 1ae, VII–2 s +2ae, VIII–2 s + 1ae, IX–2 s + 2ae, X– XI–3 s + 3ae, XII–1 ae, XIII–1ae, XIV–2s + 1ae, XV–1s + 1ae, XVI–2s + 1ae, 1 seta curved, XVII–1s + 1ae, XVIII–2s + 1ae, segments XIX to XXIII not transformed, their armature as follows: XIX– 1s + 1ae, XX–1s + 1ae, XXI–1s + 1ae, XXII–1s, XXIII–1s.

Oral parts and swimming legs as in females, except for: i) in antenna endopod segment 2 with only 5 + 5 setae saved, other setae broken, precise setae number not observed; ii) mandible basis with 2 setae (endopod damaged); iii) maxillule with one of 4 coxal setae small; iv) maxilla praecoxal endite (previously considered as proximal praecoxal endite) with 4 setae and a small attenuation (vs 5 setae in female) and maxilla endopod with 3 worm-like and 5 brush-like sensory setae (vs additional 1 small slerotized seta in female); v) maxilliped endopod segment 5 with 2 very long setae (Fig. 7 D vs Fig. 3 E), and vi) P4 posterior surface of coxa, basis, exopod and endopod with sparse spinulation compared to females.

P5 (Fig. 8 A–E), asymmetrical, with uniramous right leg (small rudiment of endopod present), and biramous left leg; coxae fused, of similar size, left basis slightly longer than right. Right leg exopod 3-segmented; segment 2 with small spine distally, segment 3 spine-like and tapering distally. Left leg with 2-segmented exopod, segment 1 with moderate medial projection and small lateral spine, segment 2 of complex structure (Fig. 8 D–E), with cavity opening terminally surrounded by rows of spinules anteriorly and posteriorly. Left endopod 1-segmented, curved, longer than 2-segmented exopod, with terminal spine-like attenuation.

Remarks. Sensiava secunda sp. nov. female is distinguished from its congeners by the following combination of characters: i) shape and moderate size of spermatheca, which is only slightly upturned anteriorly (vs. large, or elongate, strongly directed anteriorly spermatheca in other congeners, Figs 9 F,G; 13A, 14A); ii) one seta at the antenna basis is very short (shared with S. peculiaris sp. nov., vs. this seta is much longer in S. cf. longiseta and Sensiava sp., Figs 13 B and 14 B); iii) maxilla endopod with 1 small sclerotized seta plus 3 worm-like and 5 brushlike sensory setae (vs. 3 worm-like and 5 brush-like sensory setae in other congeners); iv) maxilliped syncoxa with 1 sclerotized seta on proximal praecoxal endite, 2 sclerotized setae on middle praecoxal endite and 3 sclerotized setae, 1 with poorly developed brush, on distal praecoxal endite; (vs. different setal arrangements in other congeners, e.g. Figs 11 C, 13F); v) lateral spines of P1 exopod segments 1 to 3 with distal half attenuated into a thread-like apex (vs. tapering to stiff point or slightly attenuated, Fig. 13); vi) P1 endopod lateral lobe without spinules (shared with all congeners, except for S. peculiaris, which has a lobe ornamented with spinules); vii) female P5 coxa slightly more elongate than basis; exopod with 4 distal spines partly or completely separate from the segment, medial is the longest (vs. coxa slightly less elongated than basis and exopod with 1 subterminal attenuation and 3 spines completely separate in S. peculiaris; data for the other congeners absent due to poor condition of this limb).

Sensiava cf. secunda males are much smaller (2.80–3.00 mm) than the described males of S. longiseta (4.60- 4.80 mm). They differ from the males of S. longiseta also in: i) the shape of the geniculated antennule transformed segments XIX–XXIII (see Markhaseva & Schulz 2006, Fig. 2 C); ii) presence of 4 setae on the coxal endite of maxillule (vs. 3 setae in S. longiseta); iii) presence of a small brush at the seta of the distal praecoxal setal group of maxilliped (brush absent in S. longiseta); and a different shape of left P5 exo- and endopods (see Markhaseva & Schulz 2006, Fig. G–L).

These male specimens are similar to females of S. secunda in size and share with those females a general shape of oral limbs and the swimming leg setation. However, they differ in some details and thus are currently tentatively attributed to this species, as Sensiava cf. secunda .