Naushonia karashimai, Sato & Komai, 2023

Sato, Taigi & Komai, Tomoyuki, 2023, A new species of the mud shrimp genus Naushonia Kingsley, 1897 (Decapoda: Gebiidea: Laomediidae) from the Ryukyu Islands, southwestern Japan, inhabiting burrows of an axiidean shrimp, Zootaxa 5270 (3), pp. 561-572 : 563-571

publication ID	https://doi.org/ 10.11646/zootaxa.5270.3.7
publication LSID	lsid:zoobank.org:pub:F2415908-A3DA-4A57-9B3E-41DB9BB0F1E7
DOI	https://doi.org/10.5281/zenodo.7863493
persistent identifier	https://treatment.plazi.org/id/22362392-A2BA-4859-8E4E-F2E298EDBAB4
taxon LSID	lsid:zoobank.org:act:22362392-A2BA-4859-8E4E-F2E298EDBAB4
treatment provided by	Plazi
scientific name	Naushonia karashimai
status	sp. nov.

Treatment

Naushonia karashimai View in CoL n. sp.

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

( Figs. 1–5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 )

Type material. Holotype: RUMF-ZC-7521, female (cl 6.6 mm), Yakata, Onna, Okinawa Island , collected by T. Sato, R. Ueda & H. Nakajima, 28 February 2022.

Paratypes: RUMF-ZC-7522, 1 male (cl 4.9 mm), 1 female (cl 6.9 mm), same data as holotype (collected from different burrows of N. acanthus ); CBM-ZC 17091, 1 female (cl 6.5 mm), Yakata, Onna, Okinawa Island , collected by T. Sato, 16 December 2021 ; CBM-ZC 17092, 1 female (cl 7.6 mm), Kujuzaki, Urasoe, Okinawa Island , collected by T. Sato, 18 November 2021 , DNA voucher; RUMF-ZC-7523, female (cl 6.9 mm), Sunabe, Chatan, Okinawa Island , 21 December 2021 , collected by T. Sato; RUMF-ZC-7524, 1 female (3.7 mm), mouth of Okukubi River, Kin, Okinawa Island , collected by T. Sato, 2 January 2022 .

Description. Body ( Figs. 1 View FIGURE 1 , 2A–D View FIGURE 2 ) relatively robust, substantially depressed dorsoventrally.

Rostrum ( Figs. 2A, C View FIGURE 2 , 5A–D View FIGURE 5 ) strongly flattened dorsoventrally, falling slightly short of distal margin of article 2 of antennular peduncle, with acute tip and pair of conspicuous lateral teeth located at distal 0.2–0.25, making rostrum appear distally tridentate, lateral margins (posterior to lateral teeth) each with few spinules in addition to main tooth; dorsal surface shallowly depressed medially, with several spinules adjacent to lateral margins.

Carapace ( Fig. 2A, C View FIGURE 2 ) subcylindrical, with distinct linea thalassinica extending over entire length; surface covered with relatively dense, short setae. Postorbital spine with smooth mesial margin and spinulose lateral margin. Anterolateral margin deeply notched just inferior to small branchiostegal spine, margin superior to branchiostegal spine with several spinules increasing in size toward inferior; pterygostomial angle rounded, with 2–4 spinules. Gastric region convex, sloping down to rostrum, with 5 low, minutely granulate carinae; anterior part of mid-dorsal carina distinct, extending anteriorly to level of postorbital notches, while post-cervical part rudimentary; submedian carinae slightly diverging posteriorly, extending from level of orbital margins to slightly anterior to mid-length of carapace; lateral carinae diverging posteriorly, extending from posterior to orbital margin to 0.3 of carapace length. Cervical groove shallow, across about midlength of carapace, transversely straight.

Pleon ( Fig. 2B, D View FIGURE 2 ) surface sparsely pitted and covered with relatively dense short setae; pleura 1–5 all rounded marginally. Pleomere 1 unarmed on anterolateral margin; tergum divided by shallow transverse groove, anterior part smooth; posterior part with vestigial mid-dorsal carina. Pleomere 2 with low mid-dorsal carina; lateral surface with vestigial longitudinal carina (=lateral carina) dividing tergum and pleura; pleuron broad, anteroventral angle subacute, posteroventral angle obtusely angular. Pleomeres 3–5 each with vestigial mid-dorsal carina; lateral carinae also vestigial. Pleomere 6 not particularly widened posteriorly, with vestigial mid-dorsal carina; posteroventral angle rounded; posterolateral process low, blunt. Telson ( Fig. 2B, E View FIGURE 2 ) 1.1 times longer than wide, slightly narrowing posteriorly; dorsal surface with scattered spinules, particularly numerous on posterior half; slightly elevated medially in anterior part; shallow groove on midline in posterior part; lateral margins with 3 pairs of minute denticles in posterior half; posterior margin rounded, unarmed.

Eyestalk ( Fig. 2A, C View FIGURE 2 ) short, with spinule at distomesial angle; cornea darkly pigmented, as wide as eyestalk, partially visible in dorsal view.

Antennular peduncle ( Figs. 2A, C View FIGURE 2 , 3E View FIGURE 3 ) slightly falling short of mid-length of article 5 of antennal peduncle. Article 1 not visible in dorsal view, slightly longer than distal two articles combined, armed with minute distolateral and small ventromesial distal spines; dorsal surface with statolith aperture closed by stiff setae. Article 2 with minute distolateral and distomesial spine. Lateral flagellum slightly longer than peduncle, composed of about 15 segments; mesial flagellum about 0.7 length of lateral flagellum.

Antennal peduncle ( Figs. 2A, C View FIGURE 2 , 3E View FIGURE 3 ) stout. Article 1 with spinulose ventrodistal margin. Article 2 (= basicerite) with row of 3 small spines on distolateral margin and 1 small spine on ventrodistal margin. Article 3 with subdistal spine on ventromesial margin. Articles 4 and 5 each with distolateral spine; article 5 (= carpocerite) almost as long as wide. Scaphocerite moderately broad, short, overreaching base of peduncular article 5; lateral margin convex, serrated with 5–7 spines (including terminal spine); mesial margin strongly convex, unarmed or armed with small spine just proximal to base of terminal spine, and with row of stiff setae; dorsal surface with low submedian carina. Flagellum slightly shorter than body; segments with several short setae on distal margins.

Epistomial horn ( Fig. 3E View FIGURE 3 ) short, almost reaching level of proximal one-third of article 1 of antennular peduncle.

Mouthparts not dissected. Maxilliped 3 ( Fig. 4A View FIGURE 4 ) coxa with setobranch composed of several long setae arising from small tubercle located near base of epipod. Basis short, with 2 spinules on mesial surface. Endopod moderately stout, composed of 5 articles. Ischium slightly widened distally, distodorsal angle produced, acuminate; crista dentata well developed, with row of sharp teeth, distomesial angle produced ( Fig. 4B View FIGURE 4 ). Merus shorter than ischium; distolateral to distoventral margin with several spinules; lateral surface with few spinules adjacent to dorsal margin. Carpus short, cup-shaped; extensor surface unarmed. Propodus subcylindrical, with oblique rows of short setae on mesial face, composing grooming apparatus. Dactylus subequal in length to propodus, tapering into blunt tip, with thick cluster of setae on flexor surface. Exopod slender, proximal article overreaching distal margin of ischium; flagellum multi-articulated. Epipod large, tapering distally, margins spinulose (spinules on dorsal margin much larger than those on ventral margin); mastigobranch well developed, subrectangular with truncate distal margin, narrowing basally; podobranch consisting of numerous, slender lamella.

Pereopods 1 (= chelipeds) ( Fig. 3A–D View FIGURE 3 ) large, subchelate, equal in size, symmetrical in shape, strongly flattened dorsoventrally. Ischium widened distally; narrow mesial surface flanked by clearly delimited dorsomesial and ventromesial margins,former with row of microscopic spinules,latter smooth; lateral margin carinate,microscopically spinulose.Merus widened distally,cross-section subtriangular;ventromesial margin not clearly delimited;dorsomesial margin distinctly delimited over entire length, spinulose, distal angle produced into 5–7-spined lobe; mesial surface smooth, excavate distally; dorsal surface with row of small spinules adjacent to dorsomesial margin; lateral margin carinate, microscopically serrated. Carpus short, slightly widened distally, surface microscopically granular; lateral margin carinate, microscopically spinulose; dorsodistal margin spinulose. Palm elongate subrectangular in general outline, nearly elliptical in cross-section, about twice as long as wide (including pollex), longer than ischium and merus combined; lateral margin carinate, microscopically spinulose; margin proximal to pollex sharply carinate, microscopically spinulose; dorsal surface slightly elevated along midline, with numerous, scattered, short setae; ventral surface also weakly elevated along midline, with scattered, short setae adjacent to lateral and mesial margins; pollex directed mesially, acuminate, arising proximally on mesial margin of palm; occlusal margin sharply carinate, occupying most of palm mesial margin, only slightly converging distally against lateral margin, armed with 5 or 6 sharp teeth on distal 0.3, proximal 0.7 straight, with row of spinules. Dactylus elongate, as long as palm, moderately slender, gently curved, closing completely against palm occlusal margin, tip overlapping dorsal surface of palm and reaching near base of propodus when closed; extensor margin with row of thin, numerous setae, proximal part not particularly expanded; flexor margin sharply carinate.

Pereopod 2 ( Fig. 4C View FIGURE 4 ) stout, simple. Ischium with produced ventrodistal angle. Merus with sparse row of elongate setae on ventral margin. Carpus about 0.4 times as long as merus. Propodus slightly longer than wide, slightly shorter than carpus. Dactylus ( Fig. 4D View FIGURE 4 ) lanceolate, terminating in acute unguis; extensor surface with dense, serrulate setae; flexor margin minutely pectinate in distal half of its length; mesial face glabrous.

Pereopods 3–5 ( Fig. 4E, G, I View FIGURE 4 ) generally similar in structure and armature, decreasing in length posteriorly. Pereopod 3 ( Fig. 4E View FIGURE 4 ) with sparse short stiff setae on ischium to dactylus. Ischium about half length of merus. Merus slightly narrowed distally, 3.8 times longer than wide, unarmed. Carpus about 0.4 times as long as merus. Propodus slender, subequal in length to merus, with 5 closely set spiniform setae on subterminal portion of flexor margin. Dactylus ( Fig. 4F View FIGURE 4 ) about 0.5 times as long as propodus, about 5.7 times longer than wide, ending in slender, basally demarcated unguis, nearly straight except for slightly curved distal part; lateral surface with 9–14 spiniform setae arranged in irregular 2 rows and 3–5 spiniform setae on extensor margin; flexor margin very slightly sinuous, bordered with thin lamellae consisting of comb-like row of microscopical spiniform setae and cluster of 3–8 longer spiniform setae proximal to midlength.

Pereopod 4 dactylus ( Fig. 4H View FIGURE 4 ) with 9–11 spiniform setae on lateral surface and 4–5 spiniform setae on extensor margin. Pereopod 5 dactylus ( Fig. 4J View FIGURE 4 ) without spiniform setae on lateral surface and extensor margin.

Branchial formula as for other congeneric species (cf. Komai & Anker 2015: table 1); pereopod 4 coxa with setobranch and without podobranch.

Pleopod 1 absent in male. Female pleopod 1 uniramous; articulation between protopod and ramus obsolete. Pleopods 2–5 each with slender, lanceolate rami; exopods longer than endopods, latter without appendices internae in both sexes.

Uropod ( Fig. 2E View FIGURE 2 ) with spinulose transverse suture on both exopod and endopod. Exopod with 4 small spines on distal half of lateral margin, with spiniform seta at posterolateral angle; dorsal surface with 2 low longitudinal ridges, without spinules. Endopod lateral margin only with a posterolateral spine, no spiniform seta at posterolateral angle; dorsal surface with spinules on middorsal ridge. Protopod posterodorsal margin with 4 tiny tubercles.

Variation. The armature on the rostral lateral margins is somewhat variable among the specimens examined. In the two paratypes, there is a minute spine just mesial to the base of the principal lateral tooth on either side (RUMF-ZC-7523, 7524; Fig. 5B, D View FIGURE 5 ); in the holotype and the other paratypes (RUMF-ZC-7521, 7522, CBM-ZC 17091, 17092), there is no such an additional spine ( Fig. 5A, C View FIGURE 5 ).

The eyes are more exposed in the two small paratypes (RUMF-ZC-7524, cl 3.7 mm; RUMF-ZC-7522, cl 4.9 mm) than in the other larger specimens (cl 6.5–7.6 mm). Furthermore, spiniform setae on the pereopods 3 and 4 dactyli are fewer in those two small specimens (5–7 on lateral face and 0–1 on extensor margin in pereopod 3; 5–6 on lateral face and 0–2 on extensor margin in pereopod 4) than in the other specimens (9–14 on lateral face and 3–5 on extensor margin in pereopod 3; 9–11 on lateral face and 4–5 on extensor margin in pereopod 4) ( Fig. 5E View FIGURE 5 versus Fig. 4F, G View FIGURE 4 ). These differences seem to reflect ontogenetic change.

Distribution. So far known only from Okinawa Island, Ryukyu Islands, southwestern Japan.

Ecology. All the type specimens of Naushonia karashimai n. sp. were collected from burrows of the strahlaxiid shrimp Neaxius acanthus (Axiidea) ( Fig.6B View FIGURE 6 ),by using a manual suction pump.Burrows of N.acanthus were constructed on sand and small coral rubble substrates with seagrasses, e.g., Cymodocea rotundata and Thalassia hemprichii , in the intertidal zone of inner reef ( Fig. 6A View FIGURE 6 ). During the collection, five other animal species, associated with burrows of N. acanthus , were also encountered ( Fig. 6C–F View FIGURE 6 ): Austrolethops wardi Whitley, 1935 (Teleostei: Gobiidae ), Salmoneus sp. ( Decapoda : Alpheidae ), unidentified phenacolepadid limpets ( Gastropoda: Phenacolepadidae ), Barrimysia cumingii (A. Adams, 1856) ( Bivalvia: Galeommatida : Lasaeidae ) and an unidentified galeommatid clam ( Bivalvia: Galeommatida ). The present new species was the most uncommon among those associates.

Etymology. The new species is named after Natsu Karashima (Graduate School of Agriculture, University of the Ryukyus), who kindly supports the first author’s (TS) research, especially in taking photographs of fresh specimens (e.g., Sato & Ueda 2020; Sato 2022; this study).

Remarks. Naushonia karashimai n. sp. is readily distinguished from all the other species in Naushonia by the rostrum having a pair of conspicuous teeth on the lateral margins of the rostrum, which makes the rostrum, in dorsal view, appear distally tridentate, and in having the pollex of the cheliped palm located proximally on the mesial margin. In the other congeneric species, the rostrum is rounded or acutely triangular, but not tridentate distally; the fixed finger of the cheliped propodus is located at or adjacent to the midlength of the mesial margin ( Goy & Provenzano 1979; Martin & Abele 1982; Berggren 1992; Ngoc-Ho 1996; Juarrero et al. 1997; Alvarez et al. 2000, 2010, 2017; Komai 2004; Dworschak et al. 2006; Alvarez et al. 2010; Komai & Anker 2010, 2015; Anker 2014; Komai & Hirabayashi 2020).

During this study, five 16S sequences (five species) and two COI sequences (two species) have been generated for Naushonia ( Table 1 View TABLE 1 ). In the GenBank database, no sequence data of definitely identified species of Naushonia is available. Using the 16S rRNA sequences, preliminary phylogenetic analysis by ML method has been performed ( Fig. 7 View FIGURE 7 ). The new species is placed in the sister position of N. carinata in the best tree, although bootstrap support is not high. K2P genetic divergence values between species range from 5.7% to 29.3%; the value between N. karashimai n. sp. and the most closely related N. carinata is 28.3% ( Table 2 View TABLE 2 ).

All the specimens of Naushonia karashimai n. sp. were collected by extraction from openings of burrows constructed by Neaxius acanthus with a suction pump, often together with the lasaeid bivalve Barrimysia cumingii , which is known as an obligatory symbiotic associate of N. acanthus (cf. Kneer et al. 2008; Goto 2022). Although direct evidence of symbiosis (e.g., evidence from observation of burrow insides using a fiber scope) is not available yet, the situation suggests that the present new species is closely associated with N. acanthus .