Leptalpheus pierrenoeli Anker 2008, n. sp.

Leptalpheus pierrenoeli n. sp.

(Figs 1; 2; 3A, B)

Leptalpheus sp. 4 aff. forceps – Anker et al. 2006b: 686.

TYPE MATERIAL. — Holotype: Panama, Caribbean coast, Isla Grande, southern shore, village, near Cabañas Super Jackson, from burrow, bait suction pump, depth 0.5-1 m, coll. A. Anker and C. Hurt, 6.X.2005, fcn 05-105, 1 ♂, CL 4.5, TL 14.6 (MNHN-Na 17067).

ETYMOLOGY. — Th is new species is named after Dr Pierre Y. Noël (MNHN), who directed the author’s Ph.D. thesis on the taxonomy and phylogeny of the

Alpheidae (Anker 2001), and also in recognition of his numerous contributions to the biology and taxonomy of caridean shrimps.

TYPE LOCALITY. — Isla Grande, Caribbean coast of Panama.

DISTRIBUTION. — Tropical western Atlantic: presently known only from the type locality: Isla Grande, Caribbean coast of Panama.

DESCRIPTION

Body moderately slender (Fig. 3A, B), carapace and abdomen slightly compressed laterally, glabrous. Carapace with hardly visible anterolateral suture proximal to base of antenna (Fig. 1B). Frontal margin with broad, subtriangular, bluntly ending rostral projection, without orbital teeth or crests (Fig. 1B). Pterygostomial angle bluntly protruding anteriorly; branchiostegial region with pronounced lip anteriorly (Fig. 1B); cardiac notch deep. Eyes not visible in dorsal view, anterior portion visible in lateral view (Fig. 1A, B); anteromesial process bluntly subtriangular, feebly protruding (Fig. 1B); cornea small, lateral, pigmented (Fig. 1B). Ocellar beak not conspicuous.

Antennular peduncle relatively stout (Fig. 1A), second segment about 1.5 times as long as broad, longer than dorsally visible portion of first segment; stylocerite slightly exceeding distal margin of first segment, acute distally (Fig. 1A); ventromesial carina of first segment with very strong, anteriorly acute tooth; lateral flagellum biramous, with shorter ramus distinct, inserted at fourth segment (Fig. 1B). Antenna with basicerite bearing strong ventrolateral tooth (Fig. 1B); scaphocerite broadly ovate, anterior margin of blade slightly convex, not protruding beyond distolateral tooth (Fig. 1A); carpocerite long, stout, reaching far beyond scaphocerite (Fig. 1A, B).

Mouthparts not dissected, appearing typical for genus in external view. Th ird maxilleped moderately slender, elongate; lateral plate acutely produced (Fig. 1C); ultimate segment with rows of long, distally thickened setae, tip unarmed; arthrobranch well developed (Fig. 1C).

Chelipeds strongly asymmetrical in shape, unequal in size (Fig.2),carried folded (Fig.3A).Major cheliped moderately enlarged; ischium without subtriangular tooth on ventromesial margin (Fig. 2A); merus moderately slender, elongate, ventrally depressed, with rugose ventromesial margin (Fig. 2A, B), blunt distally; carpus short, cup-shaped, with large blunt distomesial tooth (Fig. 2A); chela subcylindrical, palm ventromesially excavated (Fig.2A), about three times as long as high (Fig. 2C), smooth except for a somewhat rugose ventral margin (Fig. 2A); adhesive discs absent (Fig. 2B); fingers about half as long as palm, moderately curved (Fig. 2B), finger tips crossing when chela closed (Fig. 2C); pollex with two smaller proximal teeth and one larger distal tooth separated by large hiatus (Fig. 2C, D); dactylus with two smaller proximal teeth, one larger median tooth opposed to hiatus of pollex, and two smaller distal teeth (Fig. 2C, D). Minor cheliped (Fig. 2E) with unarmed ischium; merus slender, ventrally slightly depressed; carpus very short, cup-shaped, with subacute distolateral tooth (Fig. 2E, G); chela smooth, flattened on mesial side (Fig. 2E, F), fingers slightly longer than palm, tips crossing when chela closed; cutting edge of pollex with small irregularly subtriangular teeth on proximal half, most distal tooth largest, situated slightly beyond mid-length of pollex; dentition of dactylus nearly identical to that of pollex (Fig. 2G).

Second pereiopod small, slender; ischium slightly shorter than merus; carpus five-segmented, segment ratio approximately: 2.5/1/1/1/2 (Fig. 1D); chela simple, slender, much longer than first carpal segment; fingers longer than palm (Fig. 1D). Third pereiopod with unarmed ischium; merus flattened mesially, more than twice as long as ischium, about five times as long as wide (Fig. 1E), ventral margin convex; carpus less than half length of merus, with distoventral spine; propodus longer than carpus, with two ventral spines and one distoventral spine proximal to dactylus; dactylus simple, slender, about 3/5 length of propodus, curved (Fig. 1E). Fourth pereiopod similar to third. Fifth pereiopod much more slender than third and fourth pereiopods (Fig. 1F), not flattened mesially; ischium, merus and carpus unarmed; merus not convex ventrally; propodus as long as merus, without spines, distolaterally with three rows of setae; dactylus similar to that of third and fourth pereiopods (Fig. 1F).

First to fifth abdominal somites with minute pits; posteroventral angles rounded; sixth somite with articulated plate posteroventrally. Male second pleopod (Fig. 1I) with appendix interna and appendix masculina, latter slightly longer than former and with three slender spine-like setae on apex (Fig. 1I). Uropod with lateral lobe of protopod (sympodite) bearing two small acute teeth distally (Fig. 1J); endopod longer than exopod, without specific features; exopod with truncate posterior margin, with distolateral tooth adjacent to distolateral spine (Fig. 1J); lateral half of diaeresis shallowly concave, mesial half deeply incised forming large triangular tooth proximal to mesial margin (Fig. 1J). Telson moderately large, more than twice as long as wide proximally (Fig. 1K); dorsal surface covered with minute pits and bearing two pairs of spines inserted at some distance from lateral margin, at about 2/5 and 2/3 length of telson, respectively (Fig. 1K); posterior margin feebly rounded, with two pairs of spines at posterolateral angles: long mesial and very short lateral spines (Fig. 1K); anal tubercles not distinct. Gill/exopod formula typical for genus: 5 pleurobranchs (above P1-5); 1 arthrobranch (above Mxp3); 0 podobranch; 2 lobe-shaped epipods (Mxp1-2); 5 mastigobranchs or strap-like epipods (Mxp3, P1-4); 5 sets of setobranchs (P1-5); 3 exopods (Mxp1-3).

Size

Th e holotype is 4.5 mm CL and 14.6 mm TL.

Colour pattern

Semitransparent with patches of red chromatophores over most of the body and particularly dense (and therefore more intense red) on dorsal and dorsolateral areas of the carapace, tail fan, antennular peduncles, orbital area and along posterior margin of abdominal somites thus forming diffuse transverse bands on the abdomen; walking legs, second pereiopod and antennular/antennal flagella semitransparent, colourless; major cheliped hyaline-white (chromatophore pattern visible in Figure 3A, B).

ECOLOGY

The single specimen was collected from a burrow of unknown host in about knee-deep water. The substrate was fine sand with some shell debris and patches of seagrass (more extensive seagrass beds nearby). Although the host was not collected several specimens of the callianassid ghostshrimps, Neocallichirus grandimana (Gibbes, 1850) (Fig. 3C) and N. rathbunae (Schmitt, 1935) (Callianassidae), collected at the same site (including some on the same day and a few meters away from the collection site of L. pierrenoeli n. sp.) suggest that one of them may be the host of this species. Neocallichirus species were previously reported as hosts of Leptalpheus (see Anker et al. 2006b: table 1).

REMARKS

Leptalpheus pierrenoeli n. sp. appears to be morphologically closest to the heterogeneous L. forceps species group, which also includes L. forceps and L. felderi from the western Atlantic, and L. mexicanus Ríos & Carvacho, 1983 from the eastern Pacific, as well as at least three undescribed taxa in the western Atlantic and eastern Pacific (see Anker et al. 2006b: table 1). However, the new species is not closely related to any of the aforementioned described species, being separated from all of them by the unique dentition on the cutting edges of the fingers of the major chela; the absence of a mesial tooth on the ischium of the major cheliped; and the distinctly longer stylocerite (overreaching the distal margin of the first antennular peduncle vs. not reaching this margin in the other three species).

The new species differs more specifically from L. forceps (cf. Williams 1965, see also Figs 4; 5) by the much shorter antennular peduncles; the stouter major chela, with comparatively longer fingers; the anterior margin of the carapace with a blunt rostral projection (vs. rounded in L. forceps); and in life, also by the more intense red colour (compare Figs 3A, B and 6A, B). It can be distinguished from L. felderi (cf. Anker et al. 2006b) by the absence of orbital crests (present in L. felderi); the unarmed ischium of the third pereiopod (vs. with spine in L. felderi); the absence of a brush of long flexible setae on the dactylus of the major chela (present in L. felderi); the different arrangement of teeth on the cutting edges of the fingers of the major and minor cheliped; the five-segmented carpus of the second pereiopod (vs. four-segmented in L. felderi); and the colour pattern (cf. Fig. 3A, B [black-andwhite photographs] and Anker et al. 2006b: fig.6A, B). Finally, L. pierrenoeli n. sp. differs in several respects from L. mexicanus (cf. Ríos & Carvacho 1983), including the much less produced rostral projection; the major cheliped with shorter, less twisted, less gaping and differently armed fingers; the much shorter antennular peduncles; and the colour pattern (A. Anker pers. obs.).