Leptomenaeus nhatrangensis, Uriš, Zdenek Ď & Horká, Ivona, 2008

Uriš, Zdenek Ď & Horká, Ivona, 2008, A new shrimp species of the genus Leptomenaeus Bruce, 2007 (Crustacea: Decapoda: Pontoniinae) from Vietnam, Zootaxa 1872, pp. 45-58 : 46-53

publication ID	https://doi.org/ 10.5281/zenodo.183978
DOI	https://doi.org/10.5281/zenodo.6234946
persistent identifier	https://treatment.plazi.org/id/0D388794-FF89-FF8D-EEF5-D476FEA0FDEC
treatment provided by	Plazi
scientific name	Leptomenaeus nhatrangensis
status	sp. nov.

Treatment

Leptomenaeus nhatrangensis View in CoL sp. nov.

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

Material examined. Hon Chong Beach, N of Nhatrang, Nhatrang Bay (South China Sea), Vietnam, 12° 17' 45.8" N; 109°14' 05.7" E, lower side of boulder, 1 m, hand net, 10 Sep. 2007, coll.: I. Horká: 1 Ψ ov., holotype, CMNH-ZC 0 2245.

Diagnosis. Leptomenaeus species with dorsal outline of carapace and rostrum straight; rostrum far overreaching basal antennular segment; rostral formula 2 + 7/3, epigastric spine and three proximal dorsal rostral teeth with distinct basal suture, first ventral tooth distinct, distal ventral teeth vestigial; inferior orbital angle produced, with subacute tip, feebly developed ventral flange, and inner, medial keel; antennule elongate, peduncle subequal to postorbital carapace length, intermediate segment 0.6 of proximal segment length, with lateral lamina width about 0.2 of length; antennal basicerite with small lateral tooth; eyes well developed, subcylindrical, stalk with accessory pigment spot; second to third thoracic sternites elongate, unarmed, fourth and fifth with pair of low oblique ridges separated by median notch; first pereiopods chelae with cutting edges serrate; second pereiopods feebly developed, very slender, subequal and similar, chelae slender, fingers elongate and exceeding palm length, cutting edges finely serrate throughout length; ambulatory pereiopods slender, dactyls slender, biunguiculate; sixth abdominal segment elongate, subequal to postorbital carapace length; telson with two pairs of small dorsal spines, first pair slightly before 0.5 of telson length, with three pairs of posterior telson spines.

Description of holotype female. Small-sized pontoniine shrimp ( Fig. 1 View FIGURE 1 ) with body slender, subcylindrical, posterior abdomen compressed. General dorsal outline of carapace and rostrum straight, not sinuate.

Rostrum ( Fig. 2 View FIGURE 2 B) well developed, 0.75 of CL, reaching to middle of intermediate antennular segment ( Fig. 2 View FIGURE 2 A,B), straight, not arched dorsally, with slightly upturned tip; with 8 small acute dorsal teeth, first three more densely grouped and with basal sutures, remaining teeth diminishing anteriorly, with interdental setae; lateral carinae obsolete, ventral margin with three distal teeth, first tooth larger, distal two vestigial.

Carapace smooth, glabrous; orbit with shallow postorbital groove ( Fig. 2 View FIGURE 2 B). Inferior orbital angle strongly produced, with obtusely angulate apex and feebly developed ventral flange. Supraorbital spines absent, epigastric, hepatic and antennal spines present; antennal spine marginal, placed well below and exceeding inferior orbital angle; hepatic spine fixed, slender, about two spine lengths posterior to anterior carapace margin, slightly lower than antennal spine level and anterior to epigastric spine level. Anterolateral angle of branchiostegite not produced.

Epistome with obsolete median carina. Second to third thoracic sternites elongate, unarmed, with low median carina, fourth and fifth with pair of low oblique ridges separated by median notch, posterior sternites unarmed ( Fig. 3 View FIGURE 3 J). Five pleurobranchs present.

Abdomen ( Fig. 1 View FIGURE 1 ) very well developed, elongate, smooth, glabrous. Third segment posterodorsally produced, non-carinate, pleura rounded; fourth and fifth not acutely produced posteriorly; sixth segment elongate, subequal to postorbital carapace length and 2.4 times longer than fifth abdominal segment.

Telson ( Fig. 2 View FIGURE 2 C) length about 0.8 of CL, 3.5 times greater than maximum width, lateral margins angulate at anterior third, posteriorly convergent, concave. Two pairs of small similar submarginal dorsal spines present, anterior pair slightly before midlength, posterior pair on about 0.75 of telson length. Posterior margin rounded, about 0.4 of anterior width, lateral spines small, subequal to dorsal spines, intermediate spines about 0.2 of telson length, submedian spines about 0.3 of intermediate spine length, plumose.

Eyes ( Fig. 2 View FIGURE 2 A,B) well developed, subcylindrical, overreaching half length of basal antennular segment, cornea globular, well pigmented, diameter 1.2 of eyestalk width; stalk length subequal to corneal diameter, separated from cornea by deep, dorsally shallower, groove. Small accessory pigment spot, feebly faceted, present dorsolaterally on posterior corneal margin. Ophthalmic somite ( Fig. 2 View FIGURE 2 B) without median ophthalmic process.

Antennule ( Fig. 2 View FIGURE 2 A, B) elongate, peduncle subequal to postorbital carapace length; basal segment with stylocerite normal and straight laterally, distolateral margin slightly sinuate terminating in slender tooth not overreaching narrowly triangular lamina medially; upper surface and distal dorsal margin with series of plumose soft-stem setae, ventromedial tooth present on level slightly before distal end of eyes; intermediate segment 0.6 of proximal segment length, flattened, with widened lateral lamina and narrow distomedial lamina; dorsal surface, lateral and anterior margin with plumose setae; flagella well developed. Upper flagellum with 8 segments fused, short free ramus two-segmented, longer free ramus filiform, with about 11 articles; with 9 pairs and a single terminal aesthetascs. Lower flagellum lost in holotype.

Antennal basicerite ( Fig. 2 View FIGURE 2 B) with small ventrolateral tooth and high subtriangular compressed dorsal process rounded apically; scaphocerite ( Fig. 2 View FIGURE 2 A) well developed, length 0.9 of CL, reaching to end of antennular peduncle, length 4 times maximum width, lateral margin concave, with strong distolateral tooth terminating at 0.8 of scaphocerite, lamina strongly angulate distomedially. Carpocerite short, about 0.25 of scaphocerite length.

Mouthparts, right side examined. Mandible ( Fig. 3 View FIGURE 3 A, B) small, slender, without palp; molar process elongate, truncate distally, with acute teeth and setose field; incisor process well developed, distally obliquely rounded with series of about 7 subequal denticles. Maxillula ( Fig. 3 View FIGURE 3 C) with feebly bilobed palp, lower lobe with long styliform and distally slightly swollen seta ( Fig. 3 View FIGURE 3 D); upper lacinia broad, distal margin truncated, with numerous simple spines and simple setae; lower lacinia with about 10 plumose setae along distal and ventral margin. Maxilla ( Fig. 3 View FIGURE 3 E), with slender palp, about 4.5 times longer than basal width, tapering slightly distally, three short plumose setae laterally; basal endite simple, with about 9 slender simple distal setae; coxal endite obsolete, medial margin non-setose; scaphognathite normal, about 4 times longer than central width, anterior lobe about twice longer than basal width, medial margin convex, marginal setae densely plumose. First maxilliped ( Fig. 3 View FIGURE 3 F) with slender palp bearing single terminal and two medial plumose setae, about 15 times longer than basal width; basal endite well developed, broad, distally rounded, medial margin straight, with numerous long serrate marginal and submarginal setae; coxal endite short, with several serrate setae; exopod with well developed flagellum with four plumose terminal setae, caridean lobe large, with densely plumose marginal setae; epipod large, widely triangular, feebly bilobed, lobes subequal. Second maxilliped ( Fig. 3 View FIGURE 3 G) of normal form, endopod with dactylar segment about four times longer than broad, with numerous stout serrate spines medially and some long simple spines distally and proximally; propodal segment with distal margin broadly rounded with long slender marginal setae, several simple setae along dactylo-propodal junction; carpus, merus and ischiomerus without special features; exopod with well developed flagellum with four long plumose terminal setae; coxa with medial margin slightly produced, rough, with ovate epipod laterally, without podobranch. Third maxilliped ( Fig. 3 View FIGURE 3 H) with endopod slender, reaching about to distal end of carpocerite; ischiomerus feebly distinct from basis, about 9 times longer than proximal width, medial and ventral margins with scattered simple setae; penultimate segment about 0.75 of ischiomerus, about 15 times longer than width, with several long serrate ventral setae and one single dorsal, terminal; ultimate segment about half of penultimate segment length, with numerous groups of finely serrate spiniform setae; basis short, about 0.15 of ischiomeral length, exopod with flagellum well developed, reaching to 0.8 of ischiomerus length, with four long terminal plumose setae; coxa with low, widely arched lateral plate, without arthrobranch.

First pereiopod ( Fig. 4 View FIGURE 4 A) slender; not reaching end of scaphocerite and slightly overreaching end of intermediate antennular segment; chela ( Fig. 4 View FIGURE 4 B) about 0.4 of CL, fingers ( Fig. 4 View FIGURE 4 C) simple, tips hooked, distal 0.8 of cutting edges with low sharp lamina bearing serration of about 40 fine recurved denticles, distal portion of lamella simple; palm 1.3 times longer than fingers and about 3 times longer than deep, with about 5 rows of short serrulate brush setae proximomedially; carpus 1.3 times chela length, width subequal to palm depth, twice tapering proximally, with several serrulate setae distoventrally posterior to palmar brush setae; merus 1.2 of carpus length, about 14 times longer than wide, unarmed; ischium half of merus length, slightly wider than merus; basis and coxa ( Fig. 3 View FIGURE 3 J) without special structures.

Second pereiopods ( Fig. 4 View FIGURE 4 D) feebly developed, very slender, subequal and similar, overreaching distal end of scaphocerite by length of fingers; chela ( Fig. 4 View FIGURE 4 E) slender, small, subequal to first pereiopod chela, fingers ( Fig. 4 View FIGURE 4 F) elongate, slightly curved medially, about 1.25 times palm length, tips strongly hooked, depressed, cutting edges straight, finely serrate throughout length, with about 70 fine recurved denticles on low cutting lamina; palm slender, slightly compressed, length about 3.5 times depth; carpus about 1.6 of chela length, distal width subequal to palm depth, tapering proximally; merus about 0.85 of carpus length, without distoventral tooth; ischium 0.9 of merus; merus and ischium uniformly wide, width subequal to palm and distal carpus.

Third pereiopods ( Fig. 4 View FIGURE 4 G) slender, overreaching distal end of scaphocerite by dactylus and propodus; dactylus ( Fig. 4 View FIGURE 4 H) slender, about 7 times longer than basal depth, biunguiculate, without basal ventral process, with small proximal tubercle dorsally; accessory ventral tooth more slender and half length of unguis; propodus about 20 times longer than wide, terminal pair of ventral spines slender, long, almost half of dactylus length, four single spines gradually diminishing from the distal one, 0.8 of terminal pair length, to vestigial proximal spine, simple setae distally; carpus subequal in length and slenderness to propodus; merus 1.15 times longer than carpus, length about 20 times width, unarmed distoventrally; ischium 0.4 of merus length, only slightly wider than later.

Fourth and fifth pereiopods ( Fig. 4 View FIGURE 4 J,K) similar to third, fifth leg slightly longer, with distal setae on dorsal margin plumose, not simple.

Uropod ( Fig. 2 View FIGURE 2 C) with protopodite bluntly produced, with branches well exceeding distal end of telson; exopod with lateral margin straight, unsetose ventrally, lateral margin terminating in small acute tooth and slightly larger mobile spine medially; endopod oval, shorter than exopod.

About 40 eggs present on pleopods, at later eyespots stage of development.

Measurements (mms). Ovigerous female, holotype: CL 2.25; TL approx. 12; RL 1.7; 5-th abdominal segment dorsal length 0.9; 6-th abdominal segment dorsal length 0.9; telson length 1.75; pairs of dorsal telson spines position 0.85 and 1.3; eye length 0.74, cornea diameter 0.4; scaphocerite 2.0 x 0.5; pereiopods 1–5 total lengths: P1 3.7; P2 5.7; P3-5 6.5–7.0; P1 fingers-chela-carpus-merus lengths 0.32-0.76-0.94-1.2 (resp.); P2 fingers-chela-carpus-merus lengths 0.46-0.36-1.4-1.2 (resp.); P3-5 lengths 6.5; P5 dactylus-propodus-carpusmerus-ischium lengths 0.42-1.7-1.65-1.95-0.8 (resp.); eggs diameters 0.48–0.52 x 0.30–0.38.

Habitat. The single specimen was found at dusk on the underside of a larger boulder among other blocks of dead corals, above the sandy bottom at a depth of about one meter. The habitat is similar to those reported for L. dolichosternum ( Okuno & Mitsuhashi 2003: 493) —“the species lives beneath large pieces of coral rubbles (about 20 cm diameter) on a silty bottom at a depth of 1.5 m.” No possible invertebrate host was observed in the close vicinity of the specimen collected.

Color in life ( Fig. 5 View FIGURE 5 ). Agrees, in general, with that reported by Okuno & Mitsuhashi (2003) for L. dolichosternum , and with a color photograph ( Kawamoto & Okuno 2003: 38) of that species, except for coloration of internal organs and eggs. Body and legs generally transparent. Third abdominal sternite with a wide “Vshaped” white figure (rather a “circle” in L. dolichosternum ), anteriorly with interrupted narrow orangebrownish outline. Several irregular patches of white and brown situated on abdomen in front of V-shaped figure. White dots on the blade and wide bands on distal margin of scaphocerite and basal part of its distal marginal setae; longitudinal line of 6–8 orange-red dots irregularly surrounded by white on uropodal exopod, two or three grouped distally to wide patches; similar red dots with white irregularly scattered on internal organs and in a longitudinal line on the bottom of abdomen. Several dots on rostrum and median line of carapace. Eyes with cornea dark, brownish-orange longitudinal path situated inside eyestalks. Antennae, internal organs of cephalothorax and egg-mass densely colored. Brownish-orange marbling symmetrically distributed on flattened antennular eyestalks and scaphocerites, leaving the latter transparent laterally and with longitudinal line of 3–4 dark blue dots. The marbling continues through the cephalic region to more compactly dark coloration of thoracic internal organs, the hepatopancreas is rather greyish and densely covered by mostly oblique cream striae ( Fig. 5 View FIGURE 5 B,C). The egg mass is greenish-grey with red, brown and cream marbling.

Etymology. The name is derived from both the Nhatrang City and Nhatrang Bay, pointing to the type locality.

Distribution. Known only from the type locality in the South China Sea: Nhatrang Bay, southeastern Vietnam.