Leslibetaeus caribbaeus Anker, 2011, n. sp.
Creators: name: Anker, Arthur
Publisher: name: Zenodo
Year: 2011
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Alpheidae
Leslibetaeus
Leslibetaeus caribbaeus

description: Leslibetaeus caribbaeus n. sp.
(Figs 1, 2)
Type material. Holotype: ovigerous female (CL 3.35 mm), USNM 401035, Trinidad & Tobago, Tobago Island, Sandy Bay, sta. 5, sand, depth 1 m, coll. R. Heard, 7 April 1992.
Description. Body moderately elongate, not particularly compressed. Carapace glabrous except for minute scarce setae. Frontal margin of carapace evenly rounded, without rostrum or orbital teeth (Fig. 1 A). Pterygostomial angle rounded (Fig. 1 B); posterior margin with well-developed cardiac notch.
Abdominal somites with pleura rounded posteroventrally; sixth somite without articulated flap. Telson broad, tapering distally, at least 1.7 times as long as greatest width, with convex lateral margins; proximal width at least four times width of posterior margin; dorsal surface with two pairs of very small submarginal spiniform setae, situated at about 0.5 and 0.7 telson length, respectively; posterior margin short, straight, with two pairs of spiniform setae at each posterolateral angle, lateral spinoform setae being less than 0.3 length of mesial spiniform setae, and two long, non-plumose median setae between mesial spiniform setae (Fig. 1 H); anal tubercles not distinct.
Eyestalks completely concealed in dorsal view; anterior portion visible in lateral view (Fig. 1 A, B), anteromesial margin rounded, without tubercle; cornea moderately well developed, in lateral position. Epistomial sclerite with small acute projection.
Antennular peduncle somewhat flattened dorso-ventrally, not particularly elongate; first article with stylocerite somewhat apressed, almost reaching distal margin of first article, tip acute, slightly curved mesially (Fig. 1 A), ventromesial carina without distinct tooth; second article longer than visible portion of first article and longer than third article, about 1.3 times as long as wide; lateral flagellum with secondary ramus represented by a small knob furnished with long aesthetascs (Fig. 1 B), proximal fused portion composed of at least five articles. Antenna with basicerite relatively stout, distoventral margin bearing subacute tooth (Fig. 1 B); scaphocerite ovate-subrectangular, short, reaching beyond half-length of carpocerite and to distal margin of second article of antennular peduncle; lateral margin somewhat convex, with small setae; blade broad, with convex anterior margin, latter overreached by strong, sharp distolateral tooth (Fig. 1 C).
Mouthparts not dissected, typical for family in external observation. Third maxilliped elongate, slender; coxa with rounded lateral plate; antepenultimate article slightly flattened, subtriangular in cross section; penultimate article about twice as long as wide, with stout spiniform seta on distodorsal margin; ultimate article tapering distally, with rows of serrulate setae and two spiniform setae on dorsal margin (including strong subdistal one), ending in corneous, subacute tip (Fig. 1 D); exopod reaching to 0.75 length of antepenultimate article; arthrobranch well developed.
Chelipeds equal in size, symmetrical in shape, carried extended, robust (Fig. 1 E); ischium stout, dorsal margin produced distodorsally, with two robust, curved spiniform setae; merus stout, smooth, flattened ventrally, more than three times as long as wide, with blunt distomesial and distolateral margins; carpus cup-shaped, somewhat constricted dorsally, distal margin broadly rounded, without deep emargination laterally (Fig. 1 E); mesial face with comb-like setae, their disposition as illustrated (Fig. 1 F); chela short, moderately swollen; palm smooth, somewhat compressed, flattened mesially; linea impressa and adhesive discs absent; fingers about 0.6 length of palm, almost not gaping when closed; cutting edges straight except for small shift at about mid-length of fingers (Fig. 1 G), tips simple, crossing when chela closed.
Both second pereiopods missing in the holotype. Third pereiopod with ischium, merus, carpus and propodus compressed; ischium about three times as long as wide, with short spiniform seta on ventrolateral surface, near ventral margin; merus somewhat broadened, with slightly convex dorsal and ventral margins, about four times as long as wide; carpus much shorter and narrower than merus, with stiff seta on distoventral surface; propodus longer than carpus, with at least five slender spiniform setae on ventral margin in addition to a pair of stouter distoventral spiniform setae adjacent to dactylus (Fig. 2 A); dactylus simple, conical, slightly curved, about 0.3 propodus length, slightly emarginate proximally, furnished with a tuft of setae at about 0.7 dactylar length (Fig. 2 B). Fourth pereiopod very similar to third; propodus with six spiniform setae in addition to a pair of stouter distoventral spiniform setae adjacent to dactylus (Fig. 2 C). Fifth pereiopod distinctly more slender than third and fourth, less compressed; ischium without spiniform seta on ventrolateral surface, with slender spiniform seta on distodorsal margin; merus almost five times as long as wide, smooth; carpus much shorter than merus, without distoventral seta; propodus with at least four slender spiniform setae along ventral margin in addition to pair of stouter spiniform setae adjacent to dactylus, distolateral surface with rows of elongate setae forming a dense brush (propodal brush); dactylus similar to that of third or fourth pereiopods, except for being longer and more slender (Fig. 2 D, E).
Uropods slightly exceeding telson; lateral lobe of protopod distally acute; endopod and exopod subequal in length, without specific features; exopod with diaeresis somewhat sinuous, with broad, feebly projecting tooth in its lateral half, ending in small acute distolateral tooth adjacent to robust distolateral spiniform seta (Fig. 1 I).
Gill/exopod formula typical for genus (Anker et al. 2006). Colour in life not recorded.
Etymology. The name refers to the Caribbean Sea, which embraces the island of Tobago, the type locality of the new species.
Habitat. Field notes indicated only that the specimen was found in sand at a depth of 1 m; it was most probably extracted with a suction pump or by sieving sediments (R. Heard, pers. comm.).
Type locality. Sandy Bay, Tobago.
Distribution. Presently known only from the type locality.
Remarks. Leslibetaeus caribbaeus n. sp. is closely related to the Eastern Pacific L. coibita (see below), differing from it only in the proportions of the third and fourth pereiopods and in two features on the chelipeds. In L. caribbaeus n. sp., the ischium is almost three times as long as wide and the merus about four times as long as wide (Fig. 2 A), whereas in L. coibita, both ischium and merus are stouter (= broader), the ischium being only twice as long as wide and the merus 3.5 times as long as wide (Fig. 3 C). In L. caribbaeus n. sp., the cheliped carpus is evenly cup-shaped, with distal margin being broadly rounded in lateral view (Fig. 1 E), whereas in L. coibita, the distal margon of the cheliped carpus is deeply emarginated in lateral view (Anker et al. 2006, fig. 4a). The disposition of comb-like rows of setae on the mesial face of the cheliped carpus is somewhat different between the two species (compare Fig. 1 F and Anker et al. 2006: fig. 4d). Finally, in L. caribbaeus n. sp., the cutting edges of the cheliped fingers are only mildly “lane-shifted” at about mid-length of finger length (Fig. 1 G), whereas in L. coibita, this shift is much more distinct (Anker et al. 2006: fig. 4j). The chelipeds of L. coibita appear to be generally slightly stouter than in the Caribbean species. In addition, in L. caribbaeus n. sp., the antennal scaphocerite reaches to the distal margin of the second article of antennular peduncle (Fig. 1 A); in L. coibita, the scaphocerite clearly falls short of this margin (Anker et al. 2006: fig. 2a). Another possible difference between the two transisthmian species may lie in the relative size and number of eggs (embryos), and therefore, in their larval development. The holotype of L. caribbaeus n. sp. carries a dozen or so relatively small eggs, with diameter ~ 0.2–0.3 mm. In contrast, only one large egg, with a diameter of almost 0.5 mm, was attached to the posterior pleopods in the specimen of L. coibita from Taboga (Fig. 3 B), suggesting a more advanced larval development in the Pacific species [although some eggs were probably lost before the specimen has been photographed].
description: Published as part of Anker, Arthur, 2011, The alpheid shrimp genus Leslibetaeus Anker, Poddoubtchenko & Wehrtmann, 2006 in the Western Atlantic, with description of a new species from Tobago (Crustacea, Decapoda), pp. 63-68 in Zootaxa 2734 on pages 64-66, DOI: 10.5281/zenodo.276572