Naushonia latimana, Komai, Tomoyuki & Anker, Arthur, 2010

Komai, Tomoyuki & Anker, Arthur, 2010, Two new species of the laomediid genus Naushonia Kingsley, 1897 (Crustacea: Decapoda: Gebiidea) from the Indo-West Pacific, Zootaxa 2504, pp. 31-46 : 32-38

Naushonia latimana n. sp.

( Figs. 1 A, B; 2–4)

Material examined. Holotype: male (CL 3.4 mm), FLMNH UF Arthropoda 13630, Mayotte, off Mahoré (Grande Terre), 12°85.93’S, 45°26.86’E, scuba diving, exposed reef flat, under algae-covered rocks in coarse sand, depth 2–3 m, leg. A. Anker, 2.VI.2008. Paratype: 1 female (CL 3.3 mm), FLMNH UF Arthropoda 13609, same collection data as for holotype.

Description of holotype. Body ( Fig. 1 A) moderately robust. Rostrum ( Fig. 2 A–D) strongly flattened dorsoventrally, generally rounded in dorsal view, reaching distal margin of second segment of antennular peduncle; lateral margins with row of numerous small spines increasing in size distally, terminal spine distinctly larger than other spines; dorsal surface with shallow median depression.

Carapace ( Fig. 2 A–D) somewhat compressed laterally, with distinct linea thalassinica extending over entire length; surface generally smooth, with some scattered setae; anterodorsal surface posterior to rostral base with scattered minute granules on either side of carapace midline. Postorbital spine small, simple, acuminate, with minutely spinulose mesial margin. Anterolateral margin spinulose, deeply notched, ventral to minute branchiostegal spine. Gastric region convex, with five longitudinal carinae, including mid-dorsal carina interrupted by cervical groove, all carinae granulate; mid-dorsal carina low, anterior section starting from level of postantennal notch, posterior section extending to posterodorsal margin of carapace; submedian carinae slightly diverging posteriorly, extending from level of postantennal notch to 0.4 carapace length; lateral carinae slightly diverging posteriorly, extending from level of posterior orbital margin to anterior 0.2 carapace length. Cervical groove conspicuous, short, not extending onto lateral surface.

Abdomen ( Fig. 2 E, F) with faint sculpture; ventral margins of pleura rounded. First somite unarmed on anterolateral margin; dorsal surface with obliquely transverse ridge and trace of mid-dorsal ridge on posterior half of tergum; pleuron small, with shallow depression forming separation from tergum. Second somite with trace of mid-dorsal ridge, with two obliquely transverse and single longitudinal lateral ridges; pleuron nearly symmetrical. Third somite with trace of mid-dorsal ridge and well-marked lateral ridges. Fourth somite with trace of mid-dorsal and lateral ridges and with shallow rounded depression on either side of midline in posterior half of tergum. Fifth somite with trace of rounded depression on either side of midline and rather distinct lateral ridge. Sixth somite widened posteriorly, with flared posteroventral margins, nearly smooth on dorsal surface; posterolateral process blunt.

Telson ( Fig. 2 E) 1.4 times longer than wide, rounded posteriorly, with pair of minute lateral spines arising posterior to telson mid-length; lateral margins anterior to lateral spine slightly convex, nearly parallel; dorsal surface with trace of dorsolateral ridges and with scattered tiny spinulose tubercles; posterior margin fringed with stiff setae increasing in length posteriorly.

Eyes ( Fig. 2 C, D) short, slightly longer than wide; cornea darkly pigmented, as wide as eyestalk, clearly visible in dorsal view; eyestalk with minute tubercle on distomesial margin, hardly visible in lateral view.

Antennular peduncle ( Fig. 2 C, D) short, nearly reaching distal margin of fifth segment of antennal peduncle. First segment not visible in dorsal view, almost as long as distal two segments combined, with small spine on ventrodistal margin, ventromesial margin apparently unarmed; dorsal surface with statolith opening closed by stiff setae. Second segment with minute distolateral spine. Third segment unarmed on distolateral margin. Lateral flagellum slightly longer than peduncle, composed of 12 articles; mesial flagellum about 0.7 length of lateral flagellum, composed of eight articles.

Antennal peduncle ( Figs. 2 C, D, 4A) stout. First segment with faintly denticulate ventrodistal margin. Second segment with row of three small spines on distolateral margin. Third segment with small subdistal spine on ventromesial margin. Fourth and fifth segments each with one distolateral and one distomesial spines; fifth segment slightly wider than long. Antennal scale moderately broad, short, reaching distal margin of fourth peduncular segment; lateral margin gently convex, armed with five or six sharp spines (including terminal spine) in distal 0.7 of its length, spines increasing slightly in size distally; mesial margin strongly convex, with row of stiff setae; dorsal surface with low longitudinal carina. Antennal flagellum longer than body; articles with several short to moderately long setae on distal margins.

Epistomial horn ( Fig. 4 A) relatively slender, falling slightly short of distal margin of first segment of antennular peduncle.

Mouthparts not dissected. Third maxilliped ( Fig. 4 B) with moderately slender endopod composed of five segments. Coxa with setobranch composed of numerous stiff long setae. Basis short, with one prominent spine on mesial surface ( Fig. 4 C). Ischium slightly broadened distally, distodorsal angle ending in blunt spine; ventral margin with several minute denticles; crista dentata well developed, with row of sharp spines generally decreasing in size proximally ( Fig. 4 C). Merus shorter than ischium, with small distodorsal spine. Carpus short, distodorsal margin not projecting. Propodus subequal in length to dactylus. Dactylus tapering into blunt tip, with thick cluster of setae on flexor surface. Exopod slender, triarticulated, proximal article slightly overreaching distal margin of ischium, distal article very short, flexed against proximal article; flagellum short, but well developed. Epipod large, margins with sharp denticles; mastigobranch well developed; podobranch distinctly lamellate.

First pereopods (= chelipeds) ( Figs. 1 A, 3A–D) strong, subchelate, equal in size, symmetrical in shape, strongly flattened dorsoventrally. Ischium widened distally; mesial surface flanked by clearly delimited dorsomesial and ventromesial margins, former with row of spinules, latter smooth; lateral margin carinate, smooth. Merus widened distally, nearly triangular in cross-section; distodorsal margin with row of spinules laterally; distomesial angle produced in relatively narrow, rounded lobe, bearing marginal spinules; lateral margin bluntly carinate, with row of spinules dorsally; mesial face narrow, with some sharp granules, dorsomesial margin delimited with row of spinules, ventromesial margin also delimited with row of spinules, continuing to distomesial lobe; ventral surface bluntly elevated along midline, ventromesial face with some granules. Carpus short, slightly widened distally; dorsal surface minutely granular, distodorsal margin minutely denticulate, dorsolateral margin sharply delimited; lateral surface almost smooth; ventral surface weakly elevated along midline, distoventral margin smooth; mesial margin with a few denticles. Palm widened distally to tip of fixed finger, nearly elliptical in cross-section, 1.3 times as long as wide (including fixed finger), subequal in length to ischium and merus combined; dorsal surface nearly smooth, lateral margin carinate, granulated, with row of sparse setae; mesial margin sharply carinate, weakly denticulate, with row of sparse setae; ventral surface weakly elevated along midline, with scattered short setae; fixed finger arising at 0.3 length of palm; cutting edge (= margin opposed to dactylus) oblique, with two prominent and three small sharp teeth distally, proximal margin serrated with small teeth clearly visible in dorsal view. Dactylus moderately slender, strongly curved, closing completely against cutting edge of fixed finger, not overreaching base of fixed finger when closed; dorsal (extensor) margin with row of stiff setae, proximal part not particularly expanded; ventral (flexor) margin sharply carinate.

Second pereopod ( Fig. 4 D) moderately stout, simple. Merus with sparse row of long setae on ventral margin. Carpus about 0.4 times as long as merus. Propodus slightly longer than wide, slightly shorter than carpus. Dactylus ( Fig. 4 E) lanceolate, weakly curved, terminating in acute unguis; dorsal surface with dense, more or less elongate serrate setae; ventral margin minutely pectinate in distal half.

Third to fifth pereopods similar, decreasing in length posteriorly. Third pereopod ( Fig. 4 F) with ischium having smooth dorsal and ventral margins, both with row of sparse short setae; merus slightly narrowed distally, 5.6 times longer than wide, unarmed; carpus about 0.4 times as long as merus; propodus with ventral margin bearing row of stiff setae decreasing in length distally; dactylus ( Fig. 4 I) 0.6 times as long propodus, about 6.6 times longer than wide, terminating in slender unguis, lateral surface unarmed, ventral margin with comb-like, toothed lamella on proximal 0.7 of its length. Fourth and fifth pereopods as illustrated ( Fig. 4 G, H, J, K). Male gonopores ( Fig. 4 L) papilla-like.

Branchial formula shown in Table 1 . Epipod on fourth pereopod small, without marginal denticles.

First pleopods absent. Second to fifth pleopods biramous, rami slender, lanceolate, subequal, lacking appendix interna; appendix masculina absent on second pleopod.

Uropod ( Fig. 4 M) with spinulose transverse suture on both exopod and endopod. Exopod with serrate lateral margin, with long movable spine at posterolateral angle; dorsal surface with low median ridge. Endopod with lateral margin serrated in posterior half; dorsal surface with low median ridge. Protopod with smooth posterodorsal margin.

Remarks on female paratype. Generally similar to male holotype ( Fig. 1 B), except for some minor details. Rostrum proportionally narrower, subtriangular in shape. Lateral flagellum of antennule with 10 articles. Chelipeds slightly smaller than in male; lateral margin of palm nearly smooth. First pleopods present; left pleopod normally developed, biarticulated; right pleopod very small, appearing as rudimentary bud, consisting of single article.

Colour in life. Body and appendages pale yellowish to whitish, semitransparent ( Fig. 1 A, B).

Distribution. Presently known only from the type locality in Mayotte, Comoro Archipelago, southwestern Indian Ocean.

Habitat. Relatively exposed back reef, coarse sand with algae-covered rubble and rocks, depth: 2– 3 m. Etymology. Name referring to the relatively broad palm of the cheliped ( latimana = broad-handed in Latin).

Remarks. Although the two type specimens are relatively small at CL 3.3–3.4 mm, both have clearly discernible gonopores on the fifth (holotype, male) or on the third (paratype, female) pereopod and are therefore not juveniles. Naushonia latimana n. sp. is morphologically similar to N. japonica , N. perrieri and the below described N. serratipalma n. sp. Characters distinguishing these four species are summarised in Table 2.

Figures

FIGURE 1. Habitus in dorsal view. A, Naushonia latimana n. sp., holotype, male (CL 3.4 mm), FLMNH UF Arthropoda 13630, Mayotte, Comoro Archipelago; B, same species, paratype, female (CL 3.3 mm), FLMNH UF Arthropoda 13609, same locality as holotype; C, Naushonia serratipalma n. sp., holotype (CL 4.5 mm), FLMNH UF Arthropoda 16437, Moorea, Society Archipelago, French Polynesia.

FIGURE 2. Naushonia latimana n. sp., holotype, male (CL 3.4 mm), FLMNH UF Arthropoda 13630. A, carapace and cephalic appendages, dorsal view; B, carapace, lateral view; C, anterior part of carapace and cephalic appendages, dorsal view (antennal flagella partially omitted); D, same, lateral view; E, abdomen and telson, dorsal view; F, abdomen, telson and uropod, lateral view. Scale bars: 0.5 mm.

FIGURE 4. Naushonia latimana n. sp., holotype, male (CL 3.4 mm), FLMNH UF Arthropoda 13630. A, left antenna and epistomal horn, ventral view; B, left third maxilliped, lateral view; C, basis and ischium of left third maxilliped, dorsal view; D, left second pereopod, lateral view; E, propodus and dactylus of left second pereopod, mesial view; F, left third pereopod, lateral view; G, left fourth pereopod, lateral view; H, left fifth pereopod, lateral view; I – K, dactyli of left third to fifth pereopods, lateral view; L, coxa and basis of left fifth pereopod, ventromesial view. Scale bars: 0.5 mm; M, left uropod, dorsal view.