Naushonia kiiensis, Komai & Hirabayashi, 2020

Komai, Tomoyuki & Hirabayashi, Isao, 2020, A new species of the laomediid mud shrimp genus Naushonia Kingsley, 1897 (Decapoda: Gebiidea) from Japan, Zootaxa 4816 (1), pp. 92-100 : 93-100

Naushonia kiiensis n. sp.

[New Japanese name: Kii-kagite-shako-ebi]

Figs 1–5

Material examined. Holotype: CBM-ZC 15914, male (cl 3.5 mm), Sabiura , Kushimoto, Kii Peninsula, Japan, un- der dead coral rubble on sand bottom at 14 m depth, 22 May 2018, SCUBA diving, coll. I. Hirabayashi.

Diagnosis. Rostrum subtriangular, with spinose lateral margins. Carapace anterior dorsum with 5 longitudinal carinae, all spinulose, middorsal carina extending nearly to posterodorsal margin, interrupted by W-shaped cervical groove; posterior dorsum rugose. Pleomeres 1 and 2 each with low but clearly delimited middorsal carina, pleomeres 3–5 without clearly discernible middorsal carina; pleura 2–5 all smooth on margins. Telson lateral margins with 3 pairs of spinules. Antennal scaphocerite lateral margin serrated with 7 or 8 spines, including straight terminal spine. Maxilliped 3 merus with spinose distolateral margin. Pereopod 1 ischium with spinulose lateral margin; merus lateral margin also spinulose, dorsomesial distal lobe with 3 strong spines, dorsal surface with submarginal ridge adjacent to mesial margin; palm lateral margin serrated with 14–22 small spines, mesial margin also serrated proximal to pollex, occlusal margin serrated along entire length, middle tooth prominent, stronger than pollex. Pereopods 3 and 4 dactyli bearing few minute spiniform setae on lateral surfaces. Uropodal protopod smooth on posterior margin.

Description. Holotype male. Body ( Figs 1A, B , 2 A–C) moderately robust.

Rostrum ( Figs 1A , 2A ) strongly flattened dorsoventrally, subtriangular in dorsal view, slightly overreaching distal margin of article 2 of antennular peduncle, terminating in small spine overreaching subterminal spines; lateral margins slightly convex, each serrated with 6 small spines; dorsal surface with shallow median depression extending posteriorly to rostral base.

Carapace ( Fig. 1A , 2A ) subcylindrical, with distinct linea thalassinica extending over entire length; surface with few very short setae. External orbital spine simple, acuminate, directed forward. Anterolateral margin spinulose, deeply notched just inferior to small branchiostegal spine; pterygostomial angle acuminate with 4small spines. Gastric region convex, sloping down to rostrum, with five longitudinal carinae, including mid-dorsal carina interrupted by cervical groove, all carinae spinulose; mid-dorsal carina low, anterior section starting from level of post-antennal notch, posterior section not reaching to posterodorsal margin of carapace; submedian carinae slightly diverging posteriorly, extending from posterior to orbital margin to about half length of carapace; lateral carinae diverging posteriorly, extending from level of orbital margin to 0.4 of carapace length. Cervical groove conspicuous, across slightly posterior to mid-length of carapace, W-shaped in dorsal view. Posterior dorsum rugose with sparse granules and faint elevations. Branchiostegite largely smooth, but with few granules dorsally.

Pleon ( Figs 1B , 2B, C ) slightly depressed dorsoventrally; pleura 1–5 all rounded marginally. Pleomere 1 unarmed on anterolateral margin; posterior tergum with distinct median carina and weakly delimited transverse carina on either side, anteromesial part forming distinct shoulder; anterior tergum depressed below; pleuron concealed by anterior pleuron of pleomere 2. Pleomere 2 with obsolescent mid-dorsal carina on tergum; lateral surface with distinct longitudinal carina (= lateral carina) dividing tergum and pleura; pleuron slightly asymmetrical. Pleomere 3 tergum with trace of middorsal carina anteriorly; lateral carina distinct. Pleomere 4 tergum without even trace of mid-dorsal carina; lateral carina distinct. Pleomere 5 tergum with trace of mid-dorsal carina and transverse carina on either side; lateral carina short, but distinct. Pleomere 6 widened posteriorly, smooth; posterolateral process blunt. Telson ( Fig. 2D ) 1.3 times longer than wide, slightly narrowing posteriorly; dorsal surface shallowly sulcate medially, with longitudinal row of 4 minute denticles on either side; lateral margins with 3 pairs of minute spines in posterior half; posterior margin rounded, unarmed.

Ocular peduncles ( Figs 1A , 2A ) short, without tubercle or spine on distomesial margin; cornea darkly pigmented, as wide as eyestalk, partially visible in dorsal view.

Antennular peduncle ( Figs 1A , 2A ) short, nearly reaching distal margin of article 5 of antennal peduncle. Article 1 not visible in dorsal view, nearly as long as distal two articles combined, armed with minute distolateral and small ventromesial distal spines; dorsal surface with statolith opening closed by stiff setae. Article 2 with minute distolateral spine. Article 3 unarmed. Lateral flagellum slightly longer than peduncle, composed of about 10 articles; mesial flagellum about 0.7 length of lateral flagellum.

Antennal peduncle ( Figs 1A , 2A ) stout. Article 1 with spinulose ventrodistal margin. Article 2 with row of 4 small spines on distolateral margin and 1 small spine on ventrodistal margin. Article 3 with small subdistal spine on ventromesial margin. Articles 4 and 5 each with distolateral spine; article 5 wider than long. Scaphocerite moderately broad, short, overreaching base of peduncular article 5; lateral margin slightly convex, serrated with 7 or 8 spines (including straight terminal spine); mesial margin strongly convex, with row of stiff setae; dorsal surface with low longitudinal carina. Antennal flagellum stout, longer than body; articles with several short setae on distal margins.

Epistomial horn relatively slender, almost reaching distal margin of article 1 of antennular peduncle.

Mouthparts not dissected. Maxilliped 3 ( Fig. 4A ) with moderately stout endopod composed of 5 articles. Coxa unarmed. Basis short, with 2 spinules on mesial surface. Ischium slightly widened distally, distodorsal angle only slightly produced; crista dentata well developed, with row of unequal, sharp teeth, distomesial angle produced ( Fig. 4B ). Merus shorter than ischium; distolateral to distoventral margin with 5 spines; dorsolateral margin also with 1 small spine subdistally. Carpus short, cup-shaped; extensor surface unarmed. Propodus subcylindrical. Dactylus subequal in length to carpus, tapering into blunt tip, with thick cluster of setae on flexor surface. Exopod proximal article overreaching distal margin of ischium; flagellum consisting of 5 articles. Epipod large, margins with sharp denticles; mastigobranch well developed; podobranch consisting of numerous, slender lamella.

First pereopods (= chelipeds) ( Fig. 3 ) large, subchelate, equal in size, symmetrical in shape, strongly flattened dorsoventrally. Ischium widened distally; mesial surface flanked by clearly delimited dorsomesial and ventromesial margins, both with row of microscopic spinules; distomesial distal angle produced into small blunt spine; lateral margin carinate, also with row of microscopic spinules. Merus widened distally, cross section nearly triangular; ventromesial margin clearly delimited only in distal half, almost smooth; dorsomesial margin distinct over entire length, microscopically spinulose, distal angle produced into 3-spined lobe; mesial surface excavate distally; dorsal surface with some small spines distally and with longitudinal ridge adjacent to ventromesial margin, merging proximally to ventromesial margin; lateral margin bluntly carinate, serrated with row of spinules increasing in size distally. Carpus short, slightly widened distally, surface microscopically granular; lateral margin sharply carinate; dorsodistal margin spinulose. Palm elongate subovate in general outline, rhomboidal in cross-section, about twice as long as wide (including pollex), longer than ischium and merus combined; lateral margin carinate, serrated with row of spinules increasing in size distally (14 in right, 22 in left); mesial margin sharply carinate, serrated with row of 7 small spines, and with row of sparse setae; dorsal surface also weakly elevated along midline, weakly granular along midline, with few spines adjacent to occlusal margin; ventral surface weakly elevated along midline, with scattered granules lateral to midline, nearly smooth mesial to midline; pollex directed forward, acuminate, arising at about mid-length of palm; occlusal margin strongly oblique, with prominent tooth located at about midlength of occlusal margin, distal part serrated with row of sharp teeth, proximal part also serrated with smaller spines of similar size and sparse setae. Dactylus moderately slender, gently curved, closing completely against occlusal margin, tip overlapping dorsal surface of palm when closed; extensor margin with row of thin, numerous setae, proximal part not particularly expanded; flexor margin sharply carinate.

Pereopod 2 ( Fig. 4C ) stout, simple. Ischium with produced ventrodistal angle. Merus with sparse row of elongate setae on ventral margin. Carpus about 0.3 times as long as merus. Propodus slightly longer than wide, slightly shorter than carpus. Dactylus lanceolate, terminating in acute unguis; extensor margin gently arcuate in mesial view; extensor surface with dense, more or less elongate serrate setae; flexor margin minutely pectinate in distal half of its length; mesial face glabrous ( Fig. 4D ).

Pereopods 3–5 generally similar, but decreasing in length posteriorly. Pereopod 3 ( Fig. 4E ) with sparse short setae on merus to dactylus; ischium about 0.6 length of merus; merus slightly narrowed distally, 4.8 times longer than wide, unarmed; carpus about 0.4 times as long as merus; dactylus ( Fig. 4F ) about 0.5 times as long propodus, about 6.3 times longer than wide, ending in slender, basally demarcated unguis, nearly straight except for slightly curved distal part, lateral surface with 3 minute spiniform setae adjacent to extensor margin, slightly sinuous flexor margin with row of minute setae followed by comb-like, toothed lamella on proximal half of its length.

Pereopod 4 ( Fig. 4G, H ) dactylus with 2 minute spiniform setae on lateral surface. Pereopod 5 ( Fig. 4I, J ) dactylus flexor margin with comb-like toothed lamella on proximal 0.6, no spiniform setae on outer surface; gonopore located at tip of papilla-like projection.

Branchial formula identical with other congeneric species (cf. Komai & Anker 2015: table 1). Epipod on pereopod 4 small, without marginal denticles.

Pleopod 1 absent. Pleopods 2–5 biramous, rami slender, lanceolate, subequal, without appendix interna; no appendix masculina of pleopod 2.

Uropod ( Fig. 4K ) with spinulose transverse suture on both exopod and endopod. Exopod with 5 small spines on distal half of lateral margin, with spiniform seta at posterolateral angle; dorsal surface with 2 longitudinal ridges, lateral ridge with few spinules, middorsal ridge unarmed. Endopod lateral margin with 3 small spines (including posterolateral spine), no spiniform seta at posterolateral angle; dorsal surface with spinose middorsal ridge. Protopod with smooth posterodorsal margin.

Colour in life. Body and appendages generally semi-translucent white, hepatopancrea inside of cephalothorax pale yellow; cornea darkly pigmented ( Fig. 5 ).

Distribution. Known only from the type locality in Japan; 14 m deep.

Remarks. Naushonia kiiensis n. sp. most closely resembles N. serratipalma in the anterior carapace ornamentation and the shape and general armature of the pereopod 1. Nevertheless, the new species is distinguished from N. serratipalma by the following particulars: (1) the gastric median and submedian carinae are spinulose in N. kiiensis n. sp. ( Fig. 1A ), while generally granular in N. serratipalma (cf. Komai & Anker 2010: fig. 5B, C; Komai & Anker 2015: fig. 7A); (2) the cervical groove is W-shaped in the dorsal view in N. kiiensis n. sp. ( Fig. 2A ), rather than broadly U-shaped or transverse in N. serratipalma (cf. Komai & Anker 2010: fig. 5A; Komai & Anker 2015: fig. 7A); (3) the posterior carapace dorsum is rugose in N. kiiensis n. sp. ( Figs 1A , 2A ), whereas smooth in N. serratipalma (cf. Komai & Anker 2010: fig. 5A, B); (4) the pleomere 1 is provided with a sharply delimited middorsal carina in N. kiiensis n. sp. ( Fig. 2B ), but only a trace is discernible in N. serratipalma (cf. Komai & Anker 2010: fig. 5E); (5) the pereopod 1 merus is provided with a longitudinal carina on the dorsal surface adjacent to the mesial margin in N. kiiensis n. sp. ( Fig. 3B ), whereas such a carina is absent in N. serratipalma (cf. Komai & Anker 2010: fig. 6A; Komai & Anker 2015: fig. 7B); (6) the distomesial lobe of the pereopod 1 merus is armed with three teeth in N. kiiensis n. sp. ( Fig. 3B ), rather than armed with more than four smaller teeth in N. serratipalma ; (7) the lateral margin of the pereopod 1 palm bears fewer spinules in N. kiiensis n. sp. than in N. serratipalma (cf. Fig. 3A, B versus Komai & Anker 2010: fig. 6C, D; Komai & Anker 2015: fig. 7B, C).

Prior to this study, three species of Naushonia have been recorded from Japanese waters, viz., N. carinata , N. japonica and N. lactoalbida (cf. Komai & Anker 2015). Of the three, N. carinata and N. lactoalbida are known from the Ryukyu Islands, and in fact, the two species are wide spread in the tropical West Pacific or Indo-West Pacific ( Berggren 1992; Komai 2004; Dworschak et al. 2006; Anker et al. 2015; Komai & Anker 2015). On the other hand, N. japonica is so far restricted to the warm temperate Japanese mainland (Honshu) ( Komai & Anker 2015). Thus the present new species is the second occurring in the Japanese mainland, although its actual distribution remains unknown.

Komai (2004) suggested that plankotonic zoeas collected in Gokasho Bay, Mie Prefecture, central Japan, and attributed to an unidentified Naushonia sp. by Konishi (2001), might actually represent N. japonica , but the discovery of the present new species from closer locality may obscure the identity of the larvae of Konishi (2001). DNA barcoding identification will be useful to determine the real specific identity of larvae, when sequence data based on adult specimens of certain specific identity will be accumulated.

Etymology. The specific epithet “ kiiensis ” is derived from Kii District, where the type locality is embraced.

Figures

FIGURE 1. Naushonia kiiensis n. sp., holotype, male (cl 3.5 mm), CBM-ZC 15914. A, carapace and cephalic appendages, left lateral view; B. pleon, telson and uropod, left lateral view.

FIGURE 2. Naushonia kiiensis n. sp., holotype, male (cl 3.5 mm), CBM-ZC 15914. A, carapace and cephalic appendages, dorsal view (setae on left antennae omitted); B, pleomeres 1–4, dorsal view; C, pleomere 5, dorsal view; D, telson, dorsal view; E, right antennal peduncle, ventral view.

FIGURE 3. Naushonia kiiensis n. sp., holotype, male (cl 3.5 mm), CBM-ZC 15914, right pereopod 1. A, chela and carpus, dorsal view; B, same, ventral view (setae omitted); C, merus and ischium, dorsal view; D, same, ventral view (setae omitted).

FIGURE 4. Naushonia kiiensis n. sp., holotype, male (cl 3.5 mm), CBM-ZC 15914. A, right maxilliped 3, lateral view; B, ischium of left maxilliped 3, ventral view; C, left pereopod 2, lateral view; D, same, dactylus, mesial view; E, left pereopod 3, lateral view; F, same, dactylus, lateral view; G, left pereopod 4, lateral view; H, same, dactylus, lateral view; I, right pereopod 5, lateral view; J, same, dactylus, lateral view; K, left uropod, dorsal view (perpendicular; setae omitted).

FIGURE 5. Naushonia kiiensis n. sp., holotype, male (cl 3.5 mm), CBM-ZC 15914. Habitus, showing coloration in life. A, dorsal view; B, right lateral view.