Sericosura curva, Arango, Claudia P. & Linse, Katrin, 2015

Arango, Claudia P. & Linse, Katrin, 2015, New Sericosura (Pycnogonida: Ammotheidae) from deep-sea hydrothermal vents in the Southern Ocean, Zootaxa 3995 (1), pp. 37-50 : 45

Sericosura curva sp. nov.

( Figs 6–7 )

Material examined. Holotype— female ( NHMUK 2015. 104), ex JC42-F-477A, from Expedition JC42 RRS James Cook, Station JC 42-4-10 ISIS 142, 0 1 February 2010, East Scotia Ridge, Site E9, Marshland, 60°2'49.56"S, 29°58'41.88"W, 2396 m.

Paratypes — ( NHMUK 2015. 105), ex JC42-F-477A, from Expedition JC42 RRS James Cook, Station JC 42-4- 10 ISIS 142, 0 1 February 2010, East Scotia Ridge, Site E9, Marshland, 60°2'49.56"S, 29°58'41.88"W, 2396 m, one female, DNA voucher. ( NHMUK 2015. 106–115), ex JC42-F-477A, from Expedition JC42 RRS James Cook, Station JC 42-4-10 ISIS 142, 0 1 February 2010, East Scotia Ridge, Site E9, Marshland, 60°2'49.56"S, 29°58'41.88"W, 2396 m, eleven specimens; (QM-S98778), ex JC42-F-477A, one specimen; (QM-S98779), ex JC42-F-477B, one specimen.

Other material — (QM-S98777), ex JC42-F-728A, from Expedition JC42 RRS James Cook, Station JC 42-4- 10 ISIS 150, 0 9 February 2010, East Scotia Ridge, Site E9, Marshland, 59°41'72.2''S, 28°21'108''W, 1436 m, one specimen.

Diagnosis. Ocular tubercle as wide as tall, with dorsal papillae; proboscis slender, sharply bent downwards.

Description. Female holotype. Trunk fully segmented, somites with dorsal spine-covered ridges, thick setae on lateral processes margins ( Fig. 6 A, D). Cephalon widest at its anterior margin, triangular, narrowing distally; ocular tubercle prominent, as wide as tall, blunt, dorsal papillae present, eyes not visible. Abdomen long, thick, horizontal, reaching to midpoint of coxa 2 of fourth pair of legs, with short, thick scattered setae. Proboscis long, cylindrical, wider at base, tapering, sharply curved downward beneath the cephalon, dorsal projection at tip ( Fig. 6 F). Chelifore ( Fig. 6 C) seen in frontal and lateral views, scape one-segmented, chelae vestigial, palm about 0.8 length of scape, no fingers. Palp seven-segmented ( Fig. 6 F, 7B), P1 short, wide, P3 shortest, with few setae, P4 longest segment, P5–7 with lateral long, thick setae, P5 longer than P7, P5 more robust. Oviger ten-segmented ( Fig. 6 B, 7C, D), O4 and O5 subequal, longest; O1–O5 almost glabrous except for a few short scattered setae; O6 triangle-shaped, densely setose, long setae; O7–9 also with very long setae, O10 small, glabrous; oviger spines simple. Legs ( Fig. 6 E, 7A) with setae of various lengths, coxa 3 with brush of long ventral setae, shorter, margin with thicker dorso-distal setae, as in coxae 1 and 2; femur and tibiae with dorsal, lateral and ventral row of thick setae. Coxa 2 length twice coxae 1 or 3 ( Fig. 7 A); femur and tibiae subequal in length; tarsus very short. Propodus slender ( Fig. 7 E), no heel, seven sole spines; main claw half propodal length; auxiliaries half the main claw length.

Male oviger spine formula 0:2:0:2, spines simple, not denticulate ( Fig 7 D); O10 about 0.3 of O9. Femur slender, cement gland dorsal, near proximal margin with low surface bulge and a short tube pointing anteriorly on each leg ( Fig. 7 F).

Measurements male holotype (in mm).Trunk length: 3.11; trunk width: 2.14; abdomen: 1.13; proboscis: 2.2 if extended; third leg coxa 1: 0.75; coxa 2: 1.22; coxa 3: 0.80; femur: 2.45; tibia1: 2.46; tibia 2: 2.43; tarsus: 0.23; propodus:1.22; main claw: 0.53; auxiliaries: 0.25.

Etymology. Latin adjective curvus, ‘bent’, referring to the sharp bend of the proboscis.

Remarks. Leg span about 18 mm. Smaller in size than other two cohabiting species. No other Sericosura species has such sharply curved proboscis. The propodus is of uniform shape on all legs. The seven-segmented palps resemble those of S. cyrtoma Child & Segonzac, 1996 from the East Pacific Rise, but the fifth segment is not as wide, the two distal segments are subequal. The main claw and auxiliary claws are not as long as in the new species. The proboscis is also carried ventrally in S. cyrtoma but it is not curved to the same extent.

Figures

FIGURE 6. Sericosura curva sp. nov., holotype, female (NHMUK 2015. 104). A, body, dorsal view; B, trunk, anteroventral view; C, lateral view of cephalon with ocular tubercle (oc), arrows pointing to the chelifores; D, dorsolateral view of cephalon, trunk, lateral processes and abdomen; E, third leg (coxae 1 and 2 missing); F, lateral view of the proboscis (pr), palp (pa) and chelifore (ch).

FIGURE 7. SEM images. Sericosura curva sp. nov., paratype male (NHMUK 2015.106 - 115). A, third leg, coxae (C 1 - 3) and femur (F); B, palp, P 2 - 7, first segment missing; C, oviger, O 2 - 10, first segment missing; D, detail of oviger segments O 7 - 10; E, third leg tarsus (ta), propodus (pd), main claw (mc) and auxiliaries (au); F, proximal half of femur with cement gland (cg) ending in a narrow tube pointing anteriorly.