Lebbeus java, Komai & Chang & Chan, 2019

Komai, Tomoyuki, Chang, Su-Ching & Chan, Tin-Yam, 2019, A new deep-sea species of the caridean shrimp genus Lebbeus White, 1847 (Crustacea: Decapoda: Thoridae) from southern Java, Indonesia, Raffles Bulletin of Zoology 67, pp. 150-159 : 151-157

Lebbeus java new species

( Figs. 1–5 )

Material examined. Holotype: ovigerous female (cl 8.7 mm) MZB Cru 4923, south of Java, stn CP 48, 07°51.12′N 107°46.25′E to 07°51.72′N 107°46.38′E, beam trawl, 689– 637 m, mud, coll. KR Baruna Jaya VIII, SJADES 2018, 1 April 2018.

Paratype: 1 ovigerous female (cl 8.5 mm) ZRC 2019.0378 , same data as holotype .

Diagnosis. Body surface glabrous. Rostrum straight, directed forward, reaching midlength of article 2 of antennular peduncle, approximately half length of carapace; dorsal margin armed with 3 or 4 moderately small teeth, including 1 or 2 postrostral; ventral margin armed with 4 small teeth in distal 0.3 on well developed lamina. Carapace with low postrostral ridge extending to at least midlength; supraorbital tooth arising at rostral base; orbital margin with deep notch just inferior to base of postorbital spine; suborbital lobe subtriangular, exceeding beyond antennal spine; anterolateral margin between antennal and small pterygostomial spine strongly sinuous. Pleura of anterior 4 pleomeres rounded, that of pleomere 5 with small posteroventral spine. Telson with 3 pairs of dorsolateral movable spines; convex posterior margin with 4 pairs of unequal spiniform setae. No ocellar spot on eye. Antennular peduncle article 1 with 2 or 3 spines on dorsodistal margin. Antennal carpocerite reaching midlength of scaphocerite; scaphocerite with distolateral spine reaching as far as rounded distal lamella. Strap-like, terminally hooked epipods on maxilliped 3 and pereopods 1–3. Maxilliped 3 overreaching scaphocerite by half length of ultimate article; ultimate article with short row of darkly pigmented spiniform setae on mesial margin distally. Pereopods 3 and 4 with dactyli approximately 0.2 times as long as propodi and bearing 5–7 small accessory spinules over entire length; meri of pereopods 3–5 with 3–5, 3–4 and 1 movable spines on lateral surface, respectively.

Description of holotype. Body ( Fig. 1 ) moderately robust for genus; integument moderately firm, surface glabrous.

Rostrum ( Fig. 2A, B ) straight, directed forward, reaching midlength of article 2 of antennular peduncle, about 0.5 times as long as carapace; dorsal margin armed with 3 moderately small teeth, including 1 on midlength of rostrum and 2 postrostral, distal half unarmed; ventral margin armed with 4 small subdistal teeth, ventral lamina well-developed in distal 0.4; lateral carina obsolescent.

Carapace ( Figs. 1 , 2A, B ) with low postrostral median ridge, extending to posterior 0.2, but becoming obsolete toward posterior; posterior postrostral spine located at about anterior 0.2 of carapace length; dorsal margin in lateral view slightly convex; lateral surface smooth, no trace of ridge on branchial region; supraorbital tooth moderately small, directed forward, located slightly anterior to rostral base, reaching as far as antennal spine; orbital margin with slight convexity posteriorly, base of eyestalk located between this convexity and suborbital lobe; deep notch present below base of supraorbital spine; suborbital lobe prominent, triangular, exceeding beyond antennal spine ( Fig. 2C ); anterolateral margin between antennal and pterygostomial spines strongly sinuous with deep concavity below antennal spine; pterygostomial spine small.

Pleon ( Fig. 1 ) dorsally rounded. Pleomere 2 with distinct anterior transverse groove on tergum. Pleura of anterior three somites broadly rounded; pleuron 4 with rounded, unarmed posterolateral margin; pleuron 5 with small posteroventral spine. Pleomere 6 1.7 times as long as high, bearing small posteroventral spine; posterolateral process terminating in small spine. Telson ( Fig. 2D ) 1.5 times as long as pleomere 6, about 3 times as long as greatest width, tapering to broadly triangular posterior margin, bearing 3 pairs of dorsolateral movable spines; posterior margin with 4 pairs of greatly unequal spiniform setae, second pair strongest ( Fig. 2E ).

Eye ( Figs. 1 , 2B ) subpyriform with eyestalk narrowing proximally; cornea slightly wider than eyestalk, its maximum width approximately 0.2 of carapace length; ocellus absent.

Antennular peduncle ( Figs. 1 , 2B ) reaching distal 0.2 of antennal scaphocerite. Article 1 distinctly longer than distal two articles combined, falling slightly short of midlength of antennal scale, dorsodistal margin armed with 2 (left) or 3 (right) slender spines; stylocerite reaching distolateral margin of article 1, acuminate, mesial margin sinuous. Article 2 about 0.4 length of article 1, with l moderately small dorsolateral distal spine. Article 3 less than half as long as article 2, bearing 1 moderately small dorsodistal spine. Lateral flagellum with thickened aesthetasc-bearing portion about half-length of carapace.

Antenna ( Figs. 1 , 2B ) with basicerite bearing a moderately small ventrolateral spine; carpocerite reaching midlength of scaphocerite. Scaphocerite 0.7 times as long as carapace and 2.8 times as long as wide; lateral margin faintly concave; distolateral spine reaching as far as rounded distal margin of lamella.

Mouthparts not dissected, but without distinctive features on external observation. Maxilliped 3 ( Fig. 3A ) overreaching antennal scaphocerite by half-length of ultimate article. Antepenultimate article with small spiniform seta located at tip of submarginal tubercle adjacent to distolateral margin ( Fig. 2F ); 1 small spiniform seta at ventrodistal angle; lateral surface with longitudinal row of widely spaced stiff setae along bluntly ridged midline. Ultimate article about 3 times as long as penultimate article (= carpus), tapering, with scattered tufts of long stiff setae on lateral surface; distal 0.2 armed with 6 closely spaced movable spines mesially, 1 apical movable spine and 4 widely spaced movable spines laterally ( Fig. 2G ), all darkly pigmented.

Strap-like, terminally hooked epipods present on maxilliped 3 and pereopods 1–3, and corresponding setobranchs on pereopods 1 to 4.

Pereopod 1 ( Fig. 3B ) moderately stout, falling slightly short of distal margin of antennal scaphocerite. Merus with small spine on dorsal margin near articulation with ischium; ventral margin with row of minute spiniform setae proximally. Carpus cup-like, slightly widened distally, shorter than palm; mesial surface subdistally with grooming apparatus consisting of shallow concavity and complex of short stiff setae. Chela ( Fig. 2H ) about 2 times as long as carpus; palm subcylindrical, 2.8 times as long as wide; fixed finger terminating in single, darkly pigmented, basally demarcated claw; dactylus 0.7 times as long as palm, terminating in 2 darkly pigmented, basally demarcated claws.

Pereopod 2 ( Fig. 3C ) overreaching antennal scale by about 0.6 length of carpus. Merus subequal in length to ischium. Carpus divided into 7 articles, article 3 longest. Chela subequal in length to distal 2 carpal articles combined; dactylus shorter than palm.

Pereopods 3–5 relatively long and slender for genus, similar in shape. Pereopod 3 ( Fig. 3D ) overreaching antennal scaphocerite by 0.8 length of propodus; ischium unarmed; merus armed with 5 movable spines on lateral surface adjacent to ventral margin in distal half; carpus about half length of propodus; propodus with single row of well-spaced slender spiniform setae on flexor margin; dactylus ( Fig. 2I ) about 0.2 times as long as propodus, moderately slender (about 4.2 times as long as high), terminating in acute, pigmented unguis, armed with 6 slender accessory spinules over entire length, these spinules increasing in length distally. Pereopod 4 ( Fig. 3E ) overreaching antennal scaphocerite by halflength of propodus; merus with 4 lateral movable spines; dactylus ( Fig. 2J ) about 0.2 times as long as propodus, with 7 accessory spinules. Pereopod 5 ( Fig. 3F ) overreaching antennal scaphocerite by 0.3 length of propodus; merus with 1 lateral movable spine subterminally; propodus with brush-like setal cluster ( Fig. 2K ), consisting of grooming apparatus, distally on flexor margin; dactylus ( Fig. 2K ) 0.2 times as long as propodus, with 7 accessory spinules.

Pleopods 1–5 without distinctive features. Uropod slightly overreaching posterior end of telson; protopod with moderately strong posterolateral spine; exopod subequal to endopod in length, armed with small spiniform setae just mesial to small posterolateral spine.

Note on paratype. Generally very similar to holotype; pleomeres 3–6 and telson missing. Rostrum ( Fig. 4 ) dorsally armed with 4 teeth, including 1 postrostral; ventral margin with 4 small teeth on rather well developed lamina in distal one-third. Meri of pereopods 3–5 with 3, 3 and 1 movable spines on lateral surface distally.

Etymology. The species is named after the island of Java, on whose continental shelf the two specimens of the new species were collected. Used as a noun in apposition.

Colouration in life. See Fig. 5 . Carapace generally reddish, with posteromedian to posterolateral parts paler; rostrum transparent in distal half and reddish in proximal half. Pleon mostly translucent and densely scattered with pink dots except reddish endopods and exopods of pleopods. Telson and uropods mostly reddish; tip of telson white. Antennular peduncle generally reddish, stylocerite whitish; flagella nearly translucent. Antennal peduncle also reddish, basicerite and lateral margin of scaphocerite whitish; flagellum entirely reddish. Maxilliped 3 and pereopods 1–5 generally red; distal half of ultimate article of maxilliped 3 and fingers of pereopod 1 pale yellowish; chela of pereopod 2 mostly pinkish. Eggs yellowish green.

Distribution. Known only from the type locality, south of Java, Indonesia, at depths of 637– 689 m.

Remarks. A division of Lebbeus into four informal species groups on the basis of the presence or absence of strap-like epipods on the maxilliped 3 and pereopods 1–3 has been long adopted because of practical usefulness (e.g., Rathbun, 1904; Butler, 1980; Hayashi, 1992; Fransen, 1997; Komai et al., 2004, 2012), although the phylogenetic significance of such grouping is rather questionable. Lebbeus java , new species, belongs to the species group characterised by the presence of strap-like epipods on maxilliped 3 and pereopods 1–3. It is morphologically most similar to L. formosus , presently known from off Taiwan, among the 39 species referred to this species group. Shared characters are: rostrum reaching midlength of article 2 of antennular peduncle, with three to five dorsal teeth (including two postrostral) and two to four ventral teeth; carapace with deep notch just below base of supraorbital tooth, which arises slightly anterior to the rostral base; anterolateral margin between antennal and pterygostomial spines strongly sinuous with deep concavity just below antennal spine; telson armed with three pairs of dorsolateral spines; article 1 of antennular peduncle with two or three dorsodistal spines, stylocerite reaching distal margin of peduncular article 1; antenna with carpocerite reaching midlength of scaphocerite; dactyli of pereopods 3 and 4 about 0.2 times as long as propodi, armed with slender accessory spiniform setae over entire length of flexor margin. In addition, the colouration in life is also very similar to each other. Nevertheless the following subtle differences may be useful in discriminating the two species (cf. Chang et al., 2010): (1) the ventral blade of the rostrum is better developed in L. java , new species ( Figs. 2A , 4 ) than in L. formosus (cf. Chang et al., 2010: 4 A); (2) the suborbital lobe of the carapace is longer than antennal spine in L. java , new species ( Fig. 2C ) (versus subequal or shorter in L. formosus : cf. Chang et al., 2010: fig. 4A); (3) the posterior margin of the telson is broadly triangular, with four spiniform setae flanked by the longest pair of spiniform setae in L. java , new species ( Fig. 2E ) (versus roundly convex with six spiniform setae flanked by the longest pair of spiniform setae in L. formosus: Chang et al., 2010 : fig. 4E).

Twenty-four COI sequences from six species of the genus Lebbeus were available in the GenBank database ( Table 1). In this study, 657 bp of the barcoding region of the mitochondrial COI gene was sequenced from L. java , new species (holotype) and L. formosus (one of the paratypes). The ML analysis ( Fig. 6 ) suggests that L. java , new species, clustered with a clade including L. laurentae Wicksten, 2010 (registered as L. carinatus Zarenkov, 1976 in GenBank database), L. formosus , L. antarcticus ( Hale, 1941) , and L. virentova Nye, Copley, Plouviez & Van Dover, 2012 . Nevertheless, the present new species has the highest genetic divergence (8.2-9.0%, p -distance) amongst the five species in this clade (the genetic divergence amongst the four other species are 0.6-6.7%; Table 2). The genetic data therefore supports the recognition of the new species, although morphological differences between the new species and L. formosus are quite subtle.

While having higher genetic similarities, the morphological distinctions between the new species and the three other species in the cluster are clear. Lebbeus laurentae is easily distinguished from L. antarcticus , L. java , new species, and L. virentova by the lack of an epipod on the pereopod 3, the small eye, the relatively slender, longer pereopods 3–5, and the usual possession of four to six dorsolateral spines on the telson ( Komai et al., 2012). Lebbeus antarcticus and L. virentova differ from L. java , new species, in the shorter rostrum with a less developed ventral lamina (not reaching the distal margin of the article 1 of the antennular peduncle; Nye et al., 2013: fig. 8A, B; Nye et al., 2012: figs. 1, 2A) and the presence of two or three postrostral teeth on the carapace ( Nye et al., 2012, 2013; one or two postrostral tooth present in L. java , new species). Lebbeus antarcticus differs further from L. java , new species, and L. virentova in having a shorter stylocerite of the antennular peduncle (not reaching the distal margin of the peduncular article 1) and the long carpocerite that overreaches the midlength of the scaphocerite ( Nye et al., 2013: fig. 8A, B). In L. java , new species, and L. virentova , the stylocerite reaches to or slightly beyond the distal margin of the peduncular article 1 ( Fig. 2B ; Nye et al., 2012: fig. 2A); the antennal carpocerite reaches the midlength of the scaphocerite ( Fig. 1 , 4 ; Nye et al., 2012: fig. 2F). Even though the COI genetic divergence between L. antarcticus and L. virentova is low (only 0.6%), these two taxa can be readily separated morphologically. The widely separated geographical distribution between L. antarcticus (Southern Ocean) and L. virentova (Gulf of Mexico) also suggests that the two taxa are distinct.

From Indonesia and its adjacent waters, five species of Lebbeus , L. indicus Holthuis, 1947 (Bali Sea, 1,018 m), L. laevirostris Crosnier, 1999 (Makassar, 779–798 m), L. manus Komai & Collins, 2009 (Manus Basin, 1,575 m), L. pacmanus Komai, Tsuchida & Segonzac, 2012 (Manus Basin, 1,662 m), and L. thermophilus Komai, Tsuchida & Segonzac, 2012 (Manus Basin, 1,323 –1,662 m) are known so far and three of them ( L. indicus , L. laevirostris and L. manus ) are represented only by their respective holotypes. The new species is the first representative from the Indian Ocean part of Indonesia. Lebbeus laevirostris can be readily distinguished from L. java , new species, by the spiniform, unarmed rostrum, four strong postrostral teeth on the anterior half of the carapace and the presence of epipods on the pereopods 1 and 2 (no epipod on pereopod 3). Lebbeus manus differs from the new species in the long rostrum overreaching the distal margin of the scaphocerite and armed only with one dorsal tooth proximally on the dorsal rostral margin (excluding the two postrostral teeth) and the presence of an epipod only on the pereopod 1 ( Komai & Collins, 2009). Lebbeus indicus , L. pacmanus and L. thermophilis all belong to the same species group of L. java , new species, and are characterised by the possession of epipods on the pereopods 1 to 3. Lebbeus indicus is characteristic in having an upturned rostrum, which reaches at least the distal margin of the scaphocerite and the supraorbital tooth arising distinctly anterior to the rostral base ( Holthuis, 1947). Lebbeus pacmanus and L. thermophilus differ from L. java , new species, in having more numerous dorsolateral spines on the telson (five or more). Lebbeus thermophilus is further distinguished from the new species by the shorter rostrum just reaching the distal margin of the article 1 of the antennular peduncle, and the more strongly inflated dorsum of the carapace in ovigerous females ( Komai et al., 2012). Lebbeus pacmanus is distinguished from the new species by the shorter rostrum and stylocerite (both not reaching distal margin of article 1 of antennular peduncle), as well as having smaller eyes ( Komai et al., 2012). With regard to the eastern part of the Indian Ocean, two species, L. clarehannah McCallum & Poore, 2010 , and L. cristagalli McCallum & Poore, 2010 , are known from the continental margin of Western Australia ( McCallum & Poore, 2010) and one species, L. rubrodentatus Bruce, 2010 , is known from the Timor Sea. These Australian species are all “crested species” of Lebbeus ( McCallum & Poore, 2010) .

Figures

Fig. 1. Lebbeus java, new species, holotype, ovigerous female (cl 8.7 mm), MZB Cru 4923, habitus in lateral view.

Fig. 2. Lebbeus java, new species, holotype, ovigerous female (cl 8.7 mm), MZB Cru 4923. A, rostrum and anterior part of carapace, lateral view; B, rostrum, anterior part of carapace and cephalic appendages, dorsal view (outer flagellum of left antennule damaged); C, left suborbital lobe and antennal spine, dorsolateral view; D, telson, dorsal view, partially damaged; E, posterior margin of telson, showing detail of armature, dorsal view; F, distal part of antepenultimate article of right maxilliped 3, lateral view; G, distal part of penultimate article of right maxilliped 3, extensor view; H, chela of right pereopod 1, extensor view; I–K, distal parts of propodi and dactyli of left pereopods 3–5, lateral view.

Fig. 3. Lebbeus java, new species, holotype, ovigerous female (cl 8.7 mm), MZB Cru 4923. A, right maxilliped 3, lateral view; B, right pereopods 1, lateral view; C–F, left pereopod 2–5, lateral view.

Fig. 4. Lebbeus java, new species, paratype, ovigerous female (cl 8.5 mm), ZRC 2019.0378, carapace and cephalic appendages, lateral view.

Fig.5.Lebbeus java, new species, holotype, ovigerous female (cl 8.7 mm), MZB Cru 4923, habitus in lateral view, showing fresh colour.

Fig. 6. Maximum-likelihood (ML) tree from partial sequences of mitochondrial COI gene (504−657 bp) of Lebbeus species available and outgroup based on GTR+G nucleotide substitution model. Numbers at nodes are bootstrap values and only values>50 are shown.