Lebbeus pacmanus, Komai, Tomoyuki, Tsuchida, Shinji & Segonzac, Michel, 2012

Komai, Tomoyuki, Tsuchida, Shinji & Segonzac, Michel, 2012, Records of species of the hippolytid genus Lebbeus White, 1847 (Crustacea: Decapoda: Caridea) from hydrothermal vents in the Pacific Ocean, with descriptions of three new species, Zootaxa 3241, pp. 35-63 : 42-46

Lebbeus pacmanus sp. nov.

( Figs 6–9 )

Material examined. Holotype: RV Natsuhima /DS Shinkai 2000 , NT99-15 cruise, dive #1150, PACMANUS , Manus Basin, Bismarck Sea, 03°43.267’S, 151°40.480’E, 1662 m, 7 November 1999, female (cl 13.9 mm), NSMT-Cr 21983 (ex-JAMSTEC 019523).

Paratype: Same data as holotype, male (cl 11.2 mm), JAMSTEC 0 19524.

Description. Female holotype. Body ( Fig. 6 ) moderately robust for genus; integument moderately firm, surface glabrous.

Rostrum ( Figs. 6 , 7 A, B) straight, directed forward, reaching about distal one-third of first segment of antennular peduncle, 0.4 times carapace length; dorsal margin armed with 6 small teeth, including 4 teeth on rostrum proper and 2 postrostral teeth, ventral margin armed with 4 small teeth in distal 0.2, ventral lamina little developed. Carapace ( Figs. 1 , 7 A, B) with low postrostral median carina extending slightly beyond midlength of carapace; posteriormost postrostral tooth arising at about 0.1 of carapace length; dorsal margin in lateral view gently convex; supraorbital tooth moderately strong, directed forward, gradually tapering distally, arising level of posterior margin of orbit, not reaching tip of antennal tooth; orbital region depressed, orbital margin with convexity, base of eyestalk set between this convexity and suborbital lobe; deep U-shaped notch present inferior to base of supraorbital tooth; suborbital lobe well developed, triangular, reaching tip of antennal tooth; anterolateral margin between antennal and pterygostomial teeth strongly sinuous with deep excavation below antennal tooth.

Abdomen ( Fig. 6 ) dorsally rounded. Second somite with sharply defined, deep transverse groove on tergum. Pleura of anterior three somites broadly rounded; fourth pleuron with tiny posteroventral denticle; fifth pleuron with moderately strong posteroventral tooth. Sixth somite about 1.5 times longer than fifth somite and 1.7 times longer than high, bearing small posteroventral tooth; posterolateral process terminating in small tooth. Telson ( Fig. 7 C) 2.0 times longer than sixth somite, tapering to slighlty convex posterior margin, bearing 5 (right) or 6 (left) dorsolateral spines; posterior margin with 2 pairs of lateral spines (mesial pair longer) and 3 spiniform setulose setae ( Fig. 7 C).

Eye ( Fig. 7 A, B) subcylindrical with stalk slightly narrowing proximally; cornea not dilated, its maximum width about 0.1 of carapace length; ocellus absent.

Antennular peduncle ( Fig. 7 A, B) reaching nearly to distal margin of antennal scale. First segment distinctly longer than distal two segments combined, slightly overreaching midlength of antennal scale, dorsodistal margin armed with 2 or 3 slender teeth; stylocerite far falling short of distolateral margin of first peduncular segment, sharply pointed, mesial margin sinuous. Second segment about 0.4 length of first segment, with l strong dorsolateral distal tooth. Third segment less than half as long as second segment, bearing 1 small dorsodistal tooth. Lateral flagellum with thickened aesthetasc-bearing portion about 0.3 times as long as carapace.

Antenna ( Fig. 7 A, E) with basicerite bearing moderately small ventrolateral tooth; carpocerite reaching about distal 0.2 of antennal scale. Antennal scale 0.5–0.6 times as long as carapace and 2.5 times longer than wide; lateral margin nearly straight; distolateral tooth reaching rounded distal margin of lamella.

Mouthparts similar to those of other species of the genus. Third maxilliped (Fig. 8A) overreaching antennal scale by 0.9 length of ultimate segment; ultimate segment 2.8 times longer than penultimate segment, tapering distally, with short row of darkly pigmented corneous spines distomesially (Fig. 8B); antepenultimate segment subequal in length to two distal segments combined, armed with 1 small tooth and 1 long spiniform seta on distolateral margin and 1 spinule at ventrolateral distal angle (Fig. 8C); lateral surface with row of spiniform setae on blunt ridge adjacent to dorsal margin.

Strap-like, terminally hooked epipods present on third maxilliped to third pereopod, corresponding setobranchs present on first to fourth pereopod ( Fig. 7 F).

First pereopod (Fig. 8D) moderately stout, overreaching antennal scale by half length of dactylus; dactylus (Fig. 8E) about 0.7 times as long as palm, terminating in 2 darkly pigmented corneous claws; fixed finger terminating in single corneous claw. Second pereopod (Fig. 8F) overreaching antennal scale by about 0.7 length of carpus; dactylus terminating in 2 small corneous claws; carpus divided into 7 articles. Third to fifth pereopods moderately long and slender, similar in shape and subequal in length. Third pereopod (Fig. 8G) overreaching antennal scale by full length of propodus; dactylus (Fig. 8H) about 0.2 times as long as propodus, moderately stout (about 3.0 times longer than deep), terminating in acute, darkly pigmented unguis, armed with 6 darkly pigmented accessory spinules on flexor margin, distalmost accessory spinule subterminal, distinctly larger than others, making tip of dactylus appearing biunguiculate; carpus about 0.6 times as long as propodus; merus armed with 6 ventrolateral spines in distal half. Fourth pereopod (Fig. 8I) overreaching antennal scale by 0.7 length of propodus; merus with 4 ventrolateral spines. Fifth pereopod (Fig. 8J) overreaching distal margin of antennal scale by 0.3 length of propodus; merus with 1 spine at ventrolateral distal angle.

8. Lebbeus pacmanus sp. nov., 13.9 mm), DS Shinkai 2000 , Pacmanus , Manus Basin, NSMT-Cr 21983. Left thoracic appendages. A, third maxilliped, lateral view; B, same, distal part of ultimate segment, dorsal (extensor) view; C, same, distal part of antepenultimate segment, lateral view; D, first pereopod, lateral view; E, same, chela, extensor view; F, second pereopod, lateral view; G, third pereopod, lateral view; H, same, dactylus, lateral view; I, fourth pereopod, lateral view; J, fifth pereopod, lateral view. Scale bars: 2 mm for A, D–F, G, I, J; 1 mm for B, C; 0.5 mm for H.

Male paratype. Rostrum ( Fig. 9 A) more slender than in female, not reaching distal margin of first segment of antennular peduncle, 0.4 times as long as carapace; dorsal margin armed with 6 small teeth, including 3 on rostrum and 3 on carapace; ventral margin with 3 tiny teeth in distal 0.2. Carapace ( Fig. 9 A) with postrostral median ridge extending to midlength; dorsal margin in lateral view slightly convex with peak at posteriormost tooth of rostral series. Fourth abdominal pleuron with small but distinct posteroventral tooth. Telson with 6 pairs of dorsolateral spines; posterior margin with 4 spiniform setulose setae flanked by 2 pairs of lateral spines. Corneal width about 0.14 of carapace length ( Fig. 9 A). Antennular flagella ( Fig. 9 A) thicker and more elongate than in female, distinctly longer than carapace; outer flagellum with aestheasc-bearing portion occupying about 0.4 length of total length, about half-length of carapace. Third to fifth pereopods more slender than in female. Endopod of first pleopod ( Fig. 9 B) with poorly defined lobe just lateral to base of terminally located appendix interna. Second pleopod with appendix masculina shorter than appendix interna, bearing about 15 stiff setae ( Fig. 9 C).

Coloration in life. Not known.

Distribution. Known only from the PACMANUS site on the Manus Basin, at a depth of 1662 m.

Etymology. Named after the locality where the type specimens were collected.

Remarks. The three new species described in this paper all belong in a species group characterized by the presence of epipods on the anterior three pereopods. Differentiations of these three new species and close allies are discussed under “Remarks” of Lebbeus thermophilus sp. nov.

Figures

FIGURE 1. Lebbeus laurentae Wicksten, 2010, female (cl 15.9 mm), HOPE 99, dive 1361, EPR 13 ° N, MNHN-IU- 2011 - 5722, entire animal in lateral view. Scale bar: 5 mm.

FIGURE 6. Lebbeus pacmanus sp. nov., holotype, female (cl 13.9 mm), DS Shinkai 2000, dive # 1150, Pacmanus, Manus Basin, NSMT-Cr 21983, entire animal in lateral view. Scale bar: 5 mm.

FIGURE 7. Lebbeus pacmanus sp. nov., holotype, female (cl 13.9 mm), DS Shinkai 2000, dive # 1150, Pacmanus, Manus Basin, NSMT-Cr 21983. A, anterior part of carapace and cephalic appendages, lateral view; B, same, dorsal view; C, telson, dorsal view; D, posterior part of telson, dorsal view; E, left antennal peduncle and scale, ventral view; F, coxae of first to fourth pereopods, showing presence of epipods on first to third pereopod. Scale bars: 5 mm for A; 2 mm for B, C, E, F; 1 mm for D.

FIGURE 9. Lebbeus pacmanus sp. nov., paratype, male (cl 11.2 mm), DS Shinkai 2000, dive # 1150, Pacmanus, Manus Basin, JAMSTEC 0 19524. A, carapace and cephalic appendages, lateral view; B, endopod of left first pleopod, dorsal (anterior) view; C, appendices interna and masculina of left second pleopod, mesial view. Scale bars: 5 mm for A; 1 mm for B; 0.5 mm for C.