Lebbeus fujimotoi, Matsuzaki, Koji, Hibino, Mai & Komai, Tomoyuki, 2015

Matsuzaki, Koji, Hibino, Mai & Komai, Tomoyuki, 2015, A new species of the caridean shrimp genus Lebbeus White, 1847 (Crustacea: Decapoda: Thoridae) from the southwestern Sea of Okhotsk, Hokkaido, Japan, Zootaxa 4032 (3), pp. 309-318 : 311-317

Lebbeus fujimotoi n. sp.

[New Japanese name: Rausu-tsunonaga-mo-ebi] Figs. 2–5

Material examined. Holotype: Off Rausu, Shiretoko Peninsula, eastern Hokkaido, in Nemuro Strait, 500–800 m, 8 September 2014, commercial shrimp trap, ovigerous female (cl 21.1 mm), CBM-ZC 13124.

Paratypes: Same data as holotype, 2 ovigerous females (cl 27.4, 27.5 mm), AMF-ZC0001; off Rausu, 44°01.53’N, 145°23.07’E, 800 m, 16 July 2015, 1 female (cl 19.8 mm), AMF-ZC0002; off Rausu, 44°02.32’N, 145°22.47’E, 700 m, 28 July 2015, 1 male (cl 17.6 mm), CBM-ZC 13125.

Description. Females. Body ( Fig. 2 ) moderately slender; integument thin, surface glabrous.

Rostrum ( Figs. 2 , 3 A) strongly upturned, distinctly overreaching distal margin of antennal scale, 1.4–1.7 times as long as carapace, deepest at about proximal one-third of its length; dorsal margin armed with 4 small teeth including 2 on rostrum proper (anterior tooth arising at about proximal 0.3, and 2 postrostral (posteriormost tooth located at 0.24 of carapace length); ventral margin armed with 7 or 8 teeth, becoming more widely spaced anteriorly; lateral carina obsolete.

Carapace ( Figs. 2 , 3 A, B) with postrostral ridge extending to 0.8 of carapace length, becoming blunt posteriorly. Orbital margin evenly concave, ventral part rimed marginally; postorbital region shallowly depressed; supraorbital tooth small, arising at level of posterior margin of orbit; no conspicuous notch below supraorbital tooth; suborbital lobe distinct, rounded, but hardly visible in lateral aspect. Antennal tooth well developed, slender; pterygostomial tooth small; anterolateral margin between antennal and pterygostomial teeth faintly sinuous.

Pleon ( Fig. 2 ) with pleura of anterior three pleomeres rounded, those of fourth and fifth pleomeres each with sharp posteroventral tooth. Third pleomere rounded dorsally, posterodorsal margin moderately produced posteriorly. Sixth pleomere about 1.7 times as long as fifth pleomere, 2.1 times as long as high, with small posteroventral tooth and sharply pointed posterolateral process. Telson ( Figs. 3 C) moderately narrow, tapered in posterior 0.6, armed with 6 or 7 pairs of dorsolateral spines; posterior margin terminating in blunt, setose triangular projection, flanked by 2 pairs of unequal spines (mesial pair longer and stouter than lateral pair) ( Fig. 3 D).

Eye ( Fig. 3 A, B) subpyriform. Cornea large, darkly pigmented, its maximum diameter about 0.20 of carapace length; ocellus absent. Eyestalk short, cup-shaped.

Antennular peduncle ( Figs. 3 A, B) relatively slender. First segment longer than distal two segments combined, with slender spine at dorsolateral distal angle; stylocerite moderately slender, partially in touch with first segment mesially, terminating in sharp tooth slightly overreaching distal margin of first segment. Second segment about 0.6 times as long as first segment, slightly broadened distally, armed with slender tooth at dorsolateral distal angle. Third segment short, with small tooth on dorsodistal margin. Lateral flagellum elongate; aesthetasc-bearing portion thickened, about 1.5 times as long as carapace, bearing dense aesthetascs; mesial flagellum elongate, about 1.9 times as long as carapace.

Antenna ( Figs. 3 A, B, E) with moderately stout basicerite, bearing blunt dorsolateral projection and sharp ventrolateral tooth. Antennal scale 0.8 times as long as carapace, 3.5 times as long as wide; lateral margin nearly straight; distolateral tooth relatively slender, slightly overreaching rounded distal margin of lamella. Carpocerite reaching midlength of antennal scale.

Mouthparts not dissected. Third maxilliped ( Fig. 4 A) relatively slender, overreaching distal margin of antennal scale by half length of ultimate segment. Ultimate segment about 3.3 times as long as penultimate segment; distal portion bearing several corneous spines ( Fig. 4 C). Antepenultimate segment slightly shorter than distal two segments combined, with 1 minute dorsal tooth and 1 lateral spinules on distal margin, and with 1 small spinule at ventrodistal angle ( Fig. 4 B). Exopod absent. Coxa with strap-like epipod ( Fig. 3 F).

First pereopod ( Fig. 4 D) relatively slender. Chela ( Fig. 4 E) 1.4 times longer than carpus; distal part of fingers with few tufts of stiff setae; dactylus about 0.8 times as long as palm, terminating in 2 corneous claws; fixed finger terminating in single corneous claw. Carpus slightly widened distally, slightly longer than palm. Merus about 6.8 times as long as wide, with short row of spiniform setae on ventral margin proximally. Ischium unarmed.

Second pereopod ( Fig. 4 F) moderately slender, overreaching antennal scale by length of chela. Chela about 0.2 times as long as carpus. Carpus subdivided into 7 articles, third article longest, occupying 0.3 times whole carpal length. Merus about 1.4 times as long as ischium.

Third to fifth pereopods relatively long and slender for genus, generally similar in structure and ornamentation. Third pereopod ( Fig. 4 G) overreaching antennal scale by about half length of propodus. Dactylus ( Fig. 4 H) no more than 0.2 times as long as propodus, 3.1 times longer than wide, terminating in slender, clearly demarcated unguis, bearing 6 or 7 accessory spinules on flexor margin; these accessory spinules noticeably increasing in length distally. Propodus about 16.0 times as long as wide, with 2 rows of slender spinules on flexor surface. Carpus 0.6 times as long as propodus, unarmed on lateral surface. Merus about 13.0 times as long as wide, armed with 7–10 lateral spines. Ischium unarmed,

Fourth pereopod ( Fig. 4 I) overreaching antennal scale by about 0.3 length of propodus; dactylus no more than 0.2 times as long as propodus, with 6 or 7 accessory spinules; carpus 0.5 times as long as propodus; merus with 4– 9 lateral spines. Fifth pereopod ( Fig. 4 J) reaching antennal scale by tip of propodus; dactylus ( Fig. 4 K) slightly more than 0.10 times as long as propodus, with 6 accessory spinules; propodus with cluster of grooming setae on flexor surface distally; carpus 0.6 times as long as propodus; merus with 1–4 lateral spines.

Branchial formula summarized in Table 1. First to third pereopods lacking epipods. Coxa of first pereopod with setobranch corresponding to epipod on third maxilliped.

Uropod ( Fig. 3 C) with protopod terminating in acute tooth posterolaterally; exopod subequal in length to endopod.

Eggs oval, large, 1.6–1.9 mm x 2.0– 2.6 mm.

Male. Generally similar to females. Rostrum ( Fig. 5 A) 1.35 times as long as carapace; dorsal margin with 4 teeth including 2 postrostral, distal 0.7 unarmed; ventral margin with 8 teeth. Inner antennular flagellum ( Fig. 5 A) slightly stouter than in females, about 1.5 times as long as carapace. Meral spines on third to fifth pereopods 7, 6, 2, respectively. Endopod of first pleopod ( Fig. 5 B) tapered, lateral margin sinuous; appendix interna terminal, with obtuse angle at lateral base of appendix interna. Appendix masculina of second pleopod ( Fig. 5 C) slightly shorter than appendix interna, non-tapered rod-like, bearing numerous long stiff setae on terminus to distal 0.7 of mesial face.

Size. Male cl 17.6 mm; largest female cl 27.5 mm, ovigerous females cl 21.1–27.5 mm.

Coloration in life. Rostrum red. Carapace mottled with red and white. Pleon banded with red and white (first pleomere entirely red, second with white medial band, third to sixth pleomeres whitish anteriorly). Telson generally red, with white dorsolateral spines. Antennular and antennal flagella uniformly red. Third maxilliped and pereopods whitish on lateral side and red on mesial side. Protopods of pleopods generally red, with white spots distally and laterally. Posterior margin of uropods whitish. See Fig. 6 .

Distribution. So far known only from the type locality, Nemuro Strait, southwestern part of the Sea of Okhotsk, at depths of 500– 800 m.

Remarks. As mentioned above, four informal species groups based on the development of epipods on the third maxilliped and first to third pereopods are recognized in Lebbeus . Although such grouping may be stereotyped (cf. Bruce 2010; Schiaparelli et al. 2015), it is still useful in comparison of species based on morphology. The present new species belongs to the informal species group characterized by the possession of epipod only on the third maxilliped, containing only L. elegans presently known only from the Sea of Japan (Komai et al. 2004). Lebbeus fujimotoi n. sp. is easily distinguished from L. elegans by the elongate (far overreaching the distal margin of the antennal scale), strongly upturned rostrum with more numerous ventral teeth (seven or eight versus one to four). In L. elegans , the rostrum is short (far falling short of the distal margin of the antennal scale), nearly straight or very slightly up-curved. Furthermore, the anterolateral margin of the carapace is only slightly sinuous in L. fujimotoi n. sp., whereas strongly sinuous with a deep concavity just inferior to the antennal tooth in L. elegans : the fourth pleuron is armed with a sharp posteroventral tooth in L. fujimotoi n. sp., rather than unarmed in L. elegans ; the dorsolateral spines of the telson are more numerous in L. fujimotoi n. sp. than in L. elegans (seven or eight pairs versus three or four pairs).

In the general structure of the rostrum (noticeably upturned and reaching or overreaching the distal margin of the antennal scale, and the distal 0.7–0.8 of the dorsal margin leaving unarmed) and a small supraorbital tooth without a ventral notch, the following seven congeneric species are similar to L. fujimotoi n. sp.: L. curvirostris Zarenkov, 1976 (East Pacific, off Peru), L. kiae Schiaparelli, Ahyong & Bowden, 2015 ( Antarctica, Ross Sea), L. longipes ( Kobjakova, 1936) (Sea of Japan and Sea of Okhotsk), L. manus Komai & Collins, 2009 (Southwest Pacific, Bismarck Sea), L. polaris ( Sabine, 1824) (Arctic and adjacent areas), L. splendidus Wicksten & Méndez, 1982 (East Pacific, off Peru) and L. unalaskensis ( Rathbun, 1902) (North Pacific), but all differ from the new species in the possession of epipods at least on the first pereopod and the proportionally shorter rostrum (subequal to or at most 1.3 times as long as the carapace). The unarmed fourth pleuron distinguishes L. curvirostris , L. kiae , L. manus , L. polaris and L. splendidus from L. fujimotoi n. sp.

From the Sea of Okhotsk, 15 species of Lebbeus have been reported: L. armatus ( Owen, 1839) , L. brandti ( Brashnikov, 1907) , L. fasciatus ( Kobjakova, 1936) , L. grandimana ( Brashnikov, 1907) , L. heterochaelus ( Kobjakova, 1936) , L. longidactylus ( Kobjakova, 1936) , L. longipes ( Kobjakova, 1936) , L. magnificus Komai, 2015 , L. polaris ( Sabine, 1824) , L. schrencki ( Brashnikov, 1907) , L. speciosa (Urita, 1942) , L. spinirostris ( Kobjakova, 1936) , L. unalaskensis ( Rathbun, 1902) (= L. brevipes Kobjakova, 1936 ; see Hayashi 1992), L.

uschakovi ( Kobjakova, 1936) , and L. vinogradowi ( Zarenkov, 1960) ( Brashnikov 1907; Kobjakova 1936, 1937; Urita 1942; Vinogradov 1950; Zarenkov 1960; Hayashi 1992; Komai 2015). Of them, L. heterochaelus , L. longidactylus , L. magnificus , L. spinirostris , L. uschakovi , and L. vinogradowi have not been recorded outside the Sea of Okhotsk, all being represented only by the type descriptions. The occurrence of the present new species is also limited to the southwestern part of the Sea of Okhotsk at present. It can be said that the species level diversity and potential endemism of the genus in this marginal sea in the northwestern Pacific is high for the high latitudinal location.

Etymology. The new species is dedicated to Mr. Shigemi Fujimoto, the captain of the fishing boat “Hoyumaru”, who has much helped the first and second authors to collect deep-water animals from the Nemuro Strait for exhibition in AMF and faunal and reproductive studies.

Figures

FIGURE 2. Lebbeus fujimotoi n. sp., holotype, female (cl 21.1 mm), CBM-ZC 13124, habitus in lateral view.

FIGURE 3. Lebbeus fujimotoi n. sp., holotype, female (cl 21.1 mm), CBM-ZC 13124. A, carapace and cephalic appendages, lateral view; B, fourth to sixth pleomeres, lateral view; C, coxae of third maxilliped to second pereopods, showing presence of epipod only on third maxilliped; D, anterior part of carapace and cephalic appendages, dorsal view; E, telson, dorsal view; F, posterior part of telson, dorsal view; G, left antennal peduncle and scale, ventral view. Scale bars: 10 mm for A – E, G; 1 mm for F, H. Abbreviations: M 3, third maxilliped; P 1, P 2, first and second pereopod, respectively.

FIGURE 4. Lebbeus fujimotoi n. sp., holotype, female (cl 21.1 mm), CBM-ZC 13124, thoracic appendages. A, right third maxilliped, lateral view; B, same, distal part of antepenultimate segment, mesial view; C, same, distal part of ultimate segment, dorsal view; D, left first pereopod, lateral view; E, same, chela, lateral view; F, left second pereopod, lateral view; G, left third pereopod, lateral view; H, same, dactylus, lateral view; I, left fourth pereopod, lateral view; J, left fifth pereopod, lateral view; K, same, dactylus, lateral view. Scale bars: 10 mm for A, D, F, G, I, J; 2 mm for B, C, E, H, K.

FIGURE 5. Lebbeus fujimotoi n. sp., male (cl 17.6 mm), CBM-ZC 13125. A, carapace and cephalic appendages, lateral view; B, endopod of first pleopod, dorsal view; C, appendices interna and masculina of left second pleopod, dorsal view. Scale bars: 5 mm for A; 1 mm for B, C.

FIGURE 6. Lebbeus fujimotoi n. sp., female (ca. cl 27 mm), living specimen in aquarium in AMF (not preserved), color image showing the colouration in life.