Lebbeus tenuipes Komai & Matsuzaki 2022, n. sp.
Creators: name: Komai, Tomoyuki
name: Matsuzaki, Koji
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Thoridae
Lebbeus
Lebbeus tenuipes

description: Lebbeus tenuipes n. sp.
[New Japanese name: Pirika-ibara-mo-ebi]
(Figs. 9–12)
Material examined. Holotype. CBM-ZC 16699, ovigerous female (cl 10.9 mm), Nemuro Strait, off Rausu, 200– 300 m, July 2019, commercial baited trap for pandalids, coll. K. Matsuzaki, DNA voucher.
Paratypes. CBM-ZC 16700, 1 ovigerous female (cl 11.0 mm), Nemuro Strait, off Rausu, 200–300 m, 7 September 2015, commercial baited trap for pandalids, coll. K. Matsuzaki; CBM-ZC 16701, 1 female (cl 12.4 mm), same data as holotype, DNA voucher.
Diagnosis. Rostrum (Figs. 10A; 11A) styliform with moderately narrow ventral blade, gently curving dorsally, distinctly overreaching distal margin of antennal scaphocerite, 1.4–1.5 times as long as carapace; dorsal margin armed with 4 small teeth, including 2 on proximal 0.4 of rostrum and 2 postrostral (posteriormost tooth located at 0.3 of carapace length); ventral margin armed with 3–5 teeth. Carapace (Fig. 10A) with low postrostral ridge; supraorbital spine small, arising at level of posterior margin of orbit; no notch below supraorbital spine; pterygostomial spine small; anterolateral margin between antennal and pterygostomial spines gently sinuous. Pleon (Fig. 10B) with pleura of anterior 3 pleomeres rounded, unarmed, that of pleomere 4 with small posteroventral spine, that of pleomere 5 with strongly produced posteroventral spine. Telson (Fig. 11D, E) armed with 5 or 6 dorsolateral spiniform setae on either side; posterior margin convex, with 2 pairs of unequal spiniform setae and 3 medial pairs of minute spiniform setae. Antennular peduncle (Figs. 10A, 11B) slender, reaching distal 0.2 of scaphocerite; article 1 with small spine on dorsolateral distal angle; stylocerite falling short of distal margin of peduncular article 1, proximolateral lobe gently convex. Antenna (Figs. 10A; 11B, F) with scaphocerite 3.6 times as long as wide, distolateral spine far exceeded by distomesially produced, rounded lamella; carpocerite reaching midlength of scaphocerite. Maxilliped 3 (Fig. 12A) overreaching distal margin of antennal scaphocerite by 0.4 length of ultimate article; ultimate article 4.2 times as long as penultimate article, bearing row of 3 or 4 cuspidate setae distomesially. Pereopod 1 (Fig. 12B) relatively slender, reaching distal 0.2 of scaphocerite. Pereopod 3 (Fig. 12D) slender, overreaching antennal scale by 0.8 length of propodus; dactylus (Fig. 11L) 0.15 times as long as propodus, 4 times longer than wide, with 5 or 6 narrowly spaced accessory spiniform setae on entire flexor margin; merus armed with 6 or 7 spiniform setae on lateral surface. Strap-like epipods on maxilliped 3 and pereopods 1 and 2 (Fig. 11O).
Description. Holotype. Body (Figs. 9, 10A, B) moderately stout; integument moderately firm, surface glabrous.
Rostrum (Figs. 10A; 11A) styliform, gently curving dorsally, distinctly overreaching distal margin of antennal scaphocerite, 1.5 times as long as carapace; dorsal margin armed with 4 small teeth including 2 on rostrum proper (anteriormost tooth located at 0.4 of rostral length, and then anterior 0.6 leaving unarmed) and 2 postrostral (posteriormost tooth located at 0.3 of carapace length); ventral blade moderately developed, broadly convex, deepest at midlength length, margin armed with 5 small teeth more widely spaced anteriorly; lateral carina obsolete. Carapace (Fig. 10A) with low postrostral ridge extending beyond midlength of carapace, becoming broader and blunt posteriorly; dorsal profile in lateral view faintly convex; orbital margin faintly sinuous, ventral part limbed marginally (Fig. 11C), postorbital region shallowly depressed; supraorbital spine small, arising at level of posterior margin of orbit; no notch below supraorbital spine; suborbital lobe distinct, rounded (Fig. 11C); antennal spine small, well exceeding beyond suborbital lobe; pterygostomial spine small, directed anteroventrally; anterolateral margin between antennal and pterygostomial spines slightly sinuous; no conspicuous ridges on lateral surface.
Pleon (Fig. 10B) with pleura of anterior three pleomeres rounded, unarmed, that of pleomere 4 with small but conspicuous posteroventral spine, and that of pleomere 5 with strong posteroventral spine. Pleomere 2 tergum with shallow transverse groove. Pleomere 3 rounded dorsally, posterodorsal margin substantially produced posteriorly. Pleomere 6 1.7 times as long as pleomere 5, 2.3 times as long as high, with relatively strong posteroventral spine and posterolateral process terminating in small spine. Telson (Fig. 11D, E) reaching posterior margin of uropodal endopod, 1.4 times as long as pleomere 6, relatively narrow, armed with 6 pairs of dorsolateral spiniform setae; posterior margin triangular, with 2 pairs of unequal spiniform setae laterally (mesial pair longer and stouter than lateral pair) and 3 medial pairs of minute, slender spiniform setae.
Eye (Fig. 10A; 11B) subpyriform; cornea large, darkly pigmented, its maximum width approximately 0.3 of carapace length; ocellus present. Eyestalk short, cup-shaped.
Antennular peduncle (Figs. 10A; 11B) slender, reaching distal 0.25 of antennal scaphocerite. Article 1 longer than distal two articles combined, with small spine on dorsolateral distal angle; stylocerite moderately slender, partially in touch with first article mesially, slightly curving dorsally, terminating in acute spine slightly overreaching distal margin of peduncular article 1, proximolateral lobe showing as obtuse convexity. Article 2 subcylindrical, armed with small spine at dorsolateral distal angle. Article 3 short, with small spine on dorsodistal margin. Upper flagellum (damaged in left side) with thickened aesthetasc-bearing portion about half-length of carapace; lower flagellum longer than upper flagellum.
Antenna (Figs. 10A; 11B, F) with moderately stout basicerite, bearing blunt dorsolateral projection and small ventrolateral spine. Scaphocerite subequal in length to carapace, 3.6 times as long as wide; lateral margin nearly straight; distolateral spine relatively slender, far exceeded by distomesially produced, rounded lamella. Carpocerite reaching midlength of scaphocerite.
Mouthparts not dissected. Maxilliped 3 (Fig. 12A) relatively slender, overreaching distal margin of antennal scaphocerite by 0.4 length of ultimate article; ultimate article 4.2 times as long as penultimate article, bearing 8, including 3 on distomesial margin, darkly pigmented cuspidate setae partially circumscribing terminal margin (Fig. 11G); antepenultimate article shorter than distal two articles combined, with 1 minute spiniform seta at ventrolateral distal angle, dorsodistal margin with 1 minute spine, dorsolateral margin with 1 tiny spine accompanied with 1 long stiff setae (Fig. 11H); exopod absent.
Pereopod 1 (Figs. 11I; 12B) slender, reaching distal 0.2 of antennal scaphocerite. Chela 1.3 times as long as carpus, 6.7 times as long as wide; dactylus 0.6 times as long as palm, terminating in 2 black corneous claws (Fig. 11J); fixed finger terminating in single black claw; palm 4.3 times as long as wide, with short row of grooming setae on flexor-mesial face proximally. Carpus subcylindrical; grooming apparatus consisting of rows of stiff setae fringing proximal side of deep depression on subdistal portion on dorsal face and subdistal cluster of short stiff setae on mesial face. Merus 6.9 times as long as wide, with minute spine on near dorsal margin proximally and short row of minute spiniform setae on ventral margin proximally (Fig. 11K). Ischium with 4 spiniform setae on ventrodistal margin (Fig. 11K).
Pereopod 2 (Fig. 12C) moderately slender, overreaching antennal scale by length of chela and distalmost carpal segment. Chela 0.2 times as long as carpus, with tufts of short setae on fingers and at base of dactylus; dactylus 0.8 times as long as palm. Carpus subdivided into 7 segments, length ratio of segments: 1: 0.7: 2.6: 0.9: 0.6: 0.4: 0.9; distalmost segment with tufts of short setae. Merus subequal in length to ischium.
Pereopod 3–5 (Fig. 12D–F) relatively long and slender. Pereopod 3 (Fig. 12D) overreaching antennal scale by 0.8 length of propodus; dactylus (Fig. 11L) 0.15 times as long as propodus, 4 times longer than wide, terminating in moderately slender, clearly demarcated unguis, with 6 accessory spiniform setae on entire flexor margin, increasing in length distally, distalmost accessory seta curved, wider than unguis; propodus 24 times longer than wide, having evenly spaced minute spiniform setae arranged in 2 rows on flexor margin; carpus 0.6 times as long as propodus, unarmed: merus 13 times longer than wide, armed with 7 spiniform setae on lateral surface; ischium unarmed. Pereopod 4 (Figs. 12E) similar to pereopod 3, overreaching antennal scale by 0.7 length of propodus; dactylus (Fig. 11M) 0.14 times as long as propodus, with 6 accessory spiniform setae; merus with 6 spiniform setae on lateral surface. Pereopod 5 (Fig. 12F) generally similar to pereopods 3 and 4, overreaching antennal scale by half-length of propodus; dactylus (Fig. 11N) with 6 accessory spiniform setae; propodus with cluster of grooming setae on flexor surface in distal 0.2 of flexor margin; merus with 3 spiniform seta on distal half of lateral face.
Strap-like epipods present on maxilliped 3 and pereopods 1 and 2, anterior two epipods terminally hooked, interacting with setobranchs on pereopods 1 and 2, respectively; epipod on pereopod 2 simple, no setobranch on pereopod 3 (Fig. 11O).
Pleopods without distinctive features.
Uropod (Figs. 10B, 11D) reaching posterior margin of telson. Protopod terminating in strong acute spine posterolaterally. Exopod slightly longer than endopod, slightly overreaching tip of telson, with small posterolateral spine exceeded by spiniform seta arising at its mesial base. Endopod reaching tip of telson.
Eggs oval, approximately 1.0× 1.3 mm.
Paratypes. Generally similar to holotype. Rostrum 1.4–1.5 times as long as carapace, armed with 4 teeth on dorsal margin, including 2 postrostral, and 3 or 4 teeth on ventral margin. Telson armed with 5 or 6 dorsolateral spiniform setae on either side. Pereopod 3 dactylus with 5 accessory spiniform setae on flexor margin; merus with 6 or 7 robust spiniform setae on lateral surface. Pereopod 4 dactylus with 5 or 6 accessory spiniform setae on flexor margin; merus with 6 robust spiniform setae. Pereopod 5 dactylus with 5 accessory spiniform setae; merus with 2 or 3 robust spiniform setae in distal half.
Colouration in life. Body generally pale pink, tip of rostrum reddish, red spot on tergum of pleomere 3; scattered red spots also on each pleomere laterally; cornea dark brown; antennular and antennal peduncles generally pale pinkish, antennal carpocerite with red longitudinal stripe laterally; flagella uniformly reddish; maxilliped 3 whitish generally, with tinge of red on carpus and antepenultimate article; pereopod 1–5 generally white; dactyli of pereopods 3–5 reddish, distal parts of propodi also reddish; meri of pereopods 3–5 each with 2 red transverse bands; pleopods 1–5 generally semi-translucent, each with tinge of red on protopod; ventrolateral expansions of protopods of pleopods 2–5 each with white spot on distal part; eggs yellow (Fig. 9).
Distribution. Presently known only from Nemuro Strait, at depths of 200– 300 m.
Remarks. Lebbeus tenuipes n. sp. is referred to the species group characterised by the possession of epipods on the pereopods 1 and 2, as well as L. subtilis n. sp. Morphologically, the present new species is most similar to L. unalaskensis among the 24 species in the group. The rostrum with a moderately developed ventral lamina is common to the two species; the rostral length exceeds the carapace length in these two species. The unarmed part of the rostrum is greatly variable in L. unalaskensis, but some specimens of L. unalaskensis has a unarmed part of the dorsal margin occupying more than the half length of the rostrum, also being similar to L. tenuipes n. sp. in this regard. Lebbeus tenuipes n. sp. differs from L. unalaskensis by the proportionally longer rostrum (1.4–1.5 times as long as the carapace versus 1.1–1.3 times as long), more numerous dorsal (including postrostral teeth) and ventral teeth on the rostrum (four versus five to seven and three or four versus four to seven, respectively), the relatively large cornea (the corneal width 0.30 of the carapace length versus 0.18–0.21; Fig. 10A versus Kim 2012: fig. 45) and the more slender pereopods 3–5 (Fig. 12D–F versus Kim 2012: fig. 45). In addition, L. tenuipes n. sp. is much smaller in the body size than L. unalaskensis (ovigerous females cl 10.9–12.4 mm versus cl 22.0 mm).
Lebbeus tenuipes n. sp. is readily distinguished from L. subtilis n. sp. by the better developed ventral blade of the rostrum (cf. Fig. 11A versus Fig. 6A), the longer antennular stylocerite reaching the distal margin of the peduncular article 1 (versus falling short of it) (Fig. 11B versus Fig. 7A) and the more slender dactyli of the pereopods 3–5 (cf. Fig. 11L–N versus Fig. J–L). The living colouration is also different between the two species: in L. tenuipes n. sp., there are a few reddish spots on the pleon (Fig. 9), while in L. subtilis n. sp., the pleon has red transverse bands on pleomeres 1–5 (Fig. 5).
The status of L. tenuipes n. sp. is well supported by the genetic analyses: COI divergence between L. tenuipes n. sp. and the known congeneric species ranges from 7.0 to 21.9% (Table 3); 16S divergence ranges from 2.1 to 7.6% (Table 4). The intraspecific divergences are 1.0% (COI) and 0.4% (16S). The 16S divergence between L. tenuipes n. sp. and the morphologically close L. unalaskensis is 3.7–3.9%.
Etymology. From the combination of the Latin, tenuis (= slender) and pes (= leg) in reference to the relatively long and slender pereopods 3–5 of this new species.
description: Published as part of Komai, Tomoyuki & Matsuzaki, Koji, 2022, Three new species of the thorid shrimp genus Lebbeus White, 1847 (Decapoda: Caridea) from Nemuro Strait, Hokkaido, Japan, with supplemental note on L. fujimotoi Matsuzaki, Hibino & Komai, 2015, pp. 151-181 in Zootaxa 5133 (2) on pages 168-171, DOI: 10.11646/zootaxa.5133.2.1, http://zenodo.org/record/6521560