Lebbeus shinkaiae, 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 : 46-51

Lebbeus shinkaiae sp. nov.

( Figs 10–13 , 18 )

Lebbeus washingtonianus: Kikuchi & Ohta 1995: 779 , figs 8–12; Fujikura et al. 1995: 234; Watabe & Miyake 2000: 32; Komai et al. 2004: 121; Martin and Haney 2005: 471 (part); Hashimoto 2007: 198, unnumbered fig. Not Lebbeus washingtonianus (Rathbun, 1902) .

Material examined. Holotype: DS Shinkai 2000 , dive #1182, Hatoma Knoll, Okinawa Trough, 24°51.236’N, 123°50.600’E, 1474 m, 19 May 2000, female (cl 18.2 mm), NSMT-Cr 21982 (ex- JAMSTEC 028214). Paratypes: DS Shinkai 2000 , dive #1187, Hatoma Knoll, 24°51.216’N, 123°50.567’E, 1491 m, 26 May 2000, trap, 1 female (cl 13.0 mm), JAMSTEC 028210; dive #1273, Yonaguni Knoll No. 4, 24°50.912’N, 122°42.043’E, 1339 m, 24 May 2001, slurp gun, 1 male (cl 7.0 mm), 1 female (cl ca. 9.5 mm), JAMSTEC 043589–043594; ROV Hyper-Dolphin, dive #697, 28°23.498’N, 127°38°370’E, 691 m, 20 June 2007, 2 males (cl 7.0, 9.0 mm), 3 females (cl 6.3–13.3 mm), JAMSTEC 072424 – 072432; dive #700, Minami-Ensei Knoll, 28°23.347’N, 127°38.407’E, 712 m, 22 June 2007, 1 male (cl 8.0 mm), 2 females (cl 10.0, 11.6 mm), JAMSTEC 072571 – 072575.

Description. Females. Body ( Fig. 10 ) moderately robust for genus; integument moderately firm, surface glabrous.

Rostrum ( Figs. 10 , 11 A, B) straight, directed forward or slightly descending, falling short of or reaching distal margin of first segment of antennular peduncle, 0.3–0.4 times carapace length; dorsal margin armed with 6–10 teeth, including 3–5 teeth on rostrum proper and 3–5 postrostral teeth; ventral margin armed with 1–3 small teeth clustered subterminally, ventral lamina slightly developed. Carapace ( Figs. 10 , 11 A, B) with low but distinct postrostral median carina extending to at least midlength of carapace, sloping toward rostral base; postrostral teeth relatively small, posteriormost one arising at 0.1–0.2 of carapace length; dorsal margin in lateral view gently convex; supraorbital tooth moderately strong, slightly upturned, arising anterior to level of rostral base, reaching or slightly overreaching tip of antennal tooth; orbital region depressed, orbital margin with convexity, base of eyestalk located between this convexity and suborbital lobe; deep U- or V-shaped notch present below base of supraorbital tooth; suborbital lobe well developed, triangular, reaching distal margin of antennal tooth; anterolateral margin between antennal and pterygostomial teeth strongly sinuous with shallow excavation below antennal tooth.

Abdomen ( Fig. 10 ) dorsally rounded. Second somite with deep transverse groove, posteriorly forming low but distinct ridge. Pleura of anterior three somites broadly rounded; fourth pleuron unarmed or armed with small posteroventral tooth; fifth pleuron with moderately strong posteroventral tooth. Sixth somite about 1.6 times longer than fifth somite and 1.6 times longer than deep, bearing small posteroventral tooth; posterolateral process terminating in small tooth. Telson ( Fig. 11 C) 1.6–1.7 times longer than sixth somite, tapering to slighlty convex posterior margin, bearing 5–7 (rarely 4) dorsolateral spines on each side; posterior margin with 2 pairs of lateral spines (mesial pair longer), 5–6 spiniform setulose setae and several longer thin plumose setae ( Fig. 11 D).

Eye ( Fig. 11 A, B) subpyriform with stalk slightly narrowing proximally; cornea not dilated, its maximum width about 0.15 of carapace length; ocellus absent.

Antennular peduncle ( Fig. 11 A, B) reaching distal 0.2–0.3 of antennal scale. First segment distinctly longer than distal two segments combined, slightly overreaching midlength of antennal scale, dorsodistal margin armed with 1–3 small teeth; stylocerite reaching or slightly overreaching distolateral angle of first peduncular segment, sharply pointed, mesial margin sinuous. Second segment 0.4 length of first segment, with l large 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. 11 A, B, E) with basicerite bearing moderately small ventrolateral tooth; carpocerite reaching midlength of antennal scale. Antennal scale about 0.5 times as long as carapace and 2.4 times longer than wide; lateral margin nearly straight; distolateral tooth not reaching rounded distal margin of lamella.

Mouthparts similar to those of other species of the genus. Third maxilliped ( Fig. 12 A) overreaching antennal scale by 0.6–0.7 length of ultimate segment; ultimate segment 3.6–3.7 times longer than penultimate segment, tapering distally, with short row of darkly pigmented corneous spines distomesially ( Fig. 12 B); antepenultimate segment shorter than distal two segments combined, armed with 1 small tooth on distolateral margin and 1 minute spinule at ventrolateral distal angle ( Fig. 12 C); lateral surface bluntly ridged.

Strap-like, terminally hooked epipods present on third maxilliped to third pereopod, corresponding setobranchs present on first to fourth pereopod ( Fig. 11 F).

First pereopod ( Fig. 12 D) moderately stout, reaching distal margin of antennal scale; dactylus ( Fig. 12 E) 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. 12 F) overreaching antennal scale by 0.4 length of carpus; dactylus terminating in 2 small corneous claws; carpus divided into 7 articles. Third to fifth pereopods moderately long and slender, similar and slightly decreasing in length posteriorly. Third pereopod ( Fig. 12 G) overreaching antennal scale by 0.6–0.7 length of propodus; dactylus ( Fig. 12 H) 0.15–0.18 times as long as propodus, moderately stout (3.0–3.2 times longer than deep), terminating in acute, darkly pigmented unguis, armed with 4 or 5 darkly pigmented accessory spinules on flexor margin, distalmost accessory spinule subterminal, distinctly larger than others, making tip of dactylus appearing biunguiculate; carpus about 0.5 times as long as propodus; merus armed with 0–5 lateral spines. Fourth pereopod ( Fig. 12 I) overreaching antennal scale by 0.3 length of propodus; merus with 0–5 ventrolateral spines. Fifth pereopod ( Fig. 12 J) overreaching distal margin of antennal scale by length of dactylus; merus unarmed or armed with 1 lateral spine.

Males. Carapace ( Fig. 13 A) with nearly straight dorsal margin in lateral view; postrostral median carina extending beyond midlength of carapace. Fourth abdominal pleuron bearing small but distinct posteroventral tooth. Antennular peduncle ( Fig. 13 A) reaching nearly to distal margin of antennal scale; outer antennular flagellum with thickened aesthetasc-bearing portion about 0.4 times as long as carapace; inner flagellum thin, subequal in length to carapace. Endopod of first pleopod ( Fig. 13 B) without lobe just lateral to base of terminally located appendix interna. Appendix masculina on second pleopod shorter than appendix interna, bearing about 15 setae in distal 0.4 ( Fig. 13 C).

Coloration in life. Entirely reddish or light yellowish brown or tan. Cornea darkly pigmented.

Distribution. Okinawa Trough, Japan, 691–1491 m.

Ecology. In the vent fields of the Hatoma Knoll, this species was abundant in deep-sea mussel beds, Bathymodiolus platifrons Hashimoto & Okutani, 1994 . Other decapod crustaceans seen in the vent fields include the alvinocaridid shrimps Alvinocaris longirostris Kikuchi & Ohta, 1995 and Shinkaicaris leurokolos (Kikuchi & Hashimoto, 2000) and the galatheoid squat lobster Shinkaia crosnieri Baba & Williams, 1998 . Observation of video recordings showed that individuals of Lebbeus shinkaiae pick some food items (probably bacterial mats) from the substrate by using the chelae of the first pereopods. It was found that they aggregate on the broken mussels for food.

Etymology. From the name of the deep submersible Shinkai 2000 , which contributed substantially to biological studies of chemosynthetic communities.

Figures

FIGURE 10. Lebbeus shinkaiae sp. nov., holotype, female (cl 18.2 mm), DS Shinkai 2000, dive # 1182, Hatoma Knoll, Okinawa Trough, Japan, NSMT-Cr 21982. Body (thoracic appendages and pleopods omitted) in lateral view. Scale bar: 5 mm.

FIGURE 11. Lebbeus shinkaiae sp. nov., holotype, female (cl 18.2 mm), DS Shinkai 2000, dive # 1182, Hatoma Knoll, Okinawa Trough, Japan, NSMT-Cr 21982. 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 second to fourth pereopods, showing presence of epipod on third pereopod. Scale bars: 5 mm for A – C, E, F; 1 mm for D.

FIGURE 12. Lebbeus shinkaiae sp. nov., holotype, female (cl 18.2 mm), DS Shinkai 2000, dive # 1182, Hatoma Knoll, Okinawa Trough, Japan, NSMT-Cr 21982. 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, H.

FIGURE 13. Lebbeus shinkaiae sp. nov., paratype, male (cl 9.0 mm), JAMSTEC 072424 – 072432. 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: 2 mm for A; 1 mm for B, C.

FIGURE 18. Photographs taken in situ. A, Lebbeus laurentae Wicksten, 2010, one individual is seen on a tube of Riftia pachyptila Jones, 1981, EPR 13 ° N, taken during the HOPE 99 cruise (The blue color of the tubes of R. pachyptira is artificial, resulting from a growth experiment); B, Lebbeus shinkaiae sp. nov., photograph taken at Hatoma Knoll, Okinawa Trough, 1493 m deep, two individuals are seen together with individuals of Alvinocaris longirostris Kikuchi and Ohta, 1995 and Shinkaia crosnieri Baba & Williams, 1998.