Sesarma meridies, Schubart & Koller, 2005

Schubart, Christoph D. & Koller, Peter, 2005, Genetic diversity of freshwater crabs (Brachyura: Sesarmidae) from central Jamaica with description of a new species, Journal of Natural History 39 (6), pp. 469-481 : 473-479

Sesarma meridies sp. n.

( Figures 2–4 )

Material examined. HOLOTYPE: one male ( SMF 29338), Jamaica (Clarendon): Crooked River, tributary to Rio Minho (, 18 ° 089N, 77 ° 209W), 12 March 1995, leg. C. D. Schubart and R. Diesel.

PARATYPES: one male and five females ( SMF 29339), same data as holotype; two males and two females ( RMNH D 50431), Jamaica (Clarendon): Grantham, tributary to Rio Minho (18 ° 09919.30N, 77 ° 23948.10W, 345 m), 14 March 2003, leg. C. D. Schubart , R. Brodie, T. Santl and T. Weil ; two males and two females ( USNM 1020443 ), same data as RMNH D 50431; one male and one female ( NHM 2004 . 74–75), same data as RMNH D 50431; one male and one female ( NHMW 19934 ), same data as RMNH D 50431; one male and one female ( ZRC 2004.0451 ), same data as RMNH D 50431; seven males and three females ( ANSP CA7303 ), Jamaica (Clarendon): Pindars River (5 Bullhead River ) and tributary, between Kellits and Brandon Hill ( JBS 383 ; 18 ° 10.199N, 77 ° 14.859W; 456 m), 11 October 2000, leg. C. D. Schubart and G. Rosenberg ; two males and seven females ( ANSP CA7304 ), Jamaica (St Ann–Clarendon): Pedro River , next to bridge ( JBS 382 ; 18 ° 11.729N, 77 ° 13.089W; 464 m), 11 October 2000, leg. C. D. Schubart and G. Rosenberg.

Other material: one male and one female ( CDS), same data as RMNH D 50431; three males and two females ( CDS), Jamaica (Clarendon): Thomas River between Nine Turns and Smithville, 14 March 2002, leg. C. D. Schubart , R. Brodie, T. Santl and T. Weil ; two males and four females ( ANSP CA7305 ), Jamaica ( St Catherine ): Knollis River (tributary to Rio Magno ) between Rio Magno and Ham Walk ( JBS 398 ; 18 ° 13.069N, 76 ° 57.639W; 323 m), 14 October 2000, leg. C. D. Schubart and I. Muratov.

Etymology. The name ‘ meridies ’ is Latin and means ‘south’. It is used as a noun in apposition and thus is independent of the gender of the genus name (in this case neuter). The name makes reference to the fact that the newly described species is so far the only Jamaican freshwater crab restricted to river systems draining to the south of the island.

Diagnosis. General body form flattened, body height 0.47 times carapace breadth. Carapace comparatively broad and smooth; all regions well defined. Anterolateral borders with one comparatively short and straight exorbital tooth. Row of 10–14 hornytipped tubercles on dactyli of male chelae not very prominent and not reaching distal end. Walking legs comparatively short: merus less than 2.4 times as long as broad in all legs, pereiopod 4 approximately twice as long as carapace length. Male pleon vaulted and with straight lateral margin of segments, telson relatively short. Gonopod slender, terminal horny endpiece slightly deflexed.

Description. Body form flattened (bh/cw50.47¡0.01, n 521). Carapace broader than long (cl/cw50.86¡0.01, n 521) widening posteriorly. Greatest width at posterior angles (cw at tooth/posterior cw50.98¡0.01, n 521). Carapace regions clearly delimited, especially gastric ones. Carapace surface mostly glabrous and smooth, evenly covered with small and coarse granules. Branchial regions with various oblique striae of different lengths and scattered setae ( Figure 2A ). Interorbital region subdivided into four frontal lobes. Median ones more bulged and broader than lateral ones. Lateral lobes often with row of granules; median lobes with short and oblique row of granules (if any). Posterior frontal lobes reduced (in large animals a slight elevation still visible), instead a short row of granules usually present. Front relatively narrow (iw/cb50.48¡0.01, n 521) with ventral border granular, lateral margins subparallel and median emargination ( Figures 2A , 4A ). Exorbital tooth triangular; anterolateral margin anterior to deep notch comparatively short and straight (el/cl50.15¡0.01, n 521). Anterolateral tooth triangular and bent upwards, the tip thus pointing dorsofrontally ( Figures 2A , 4A ). Posterior to tooth, a distinct bulge, where anterior striae of branchial regions meet anterolateral borders, representing a second, now rudimentary anterolateral tooth. Posteriorly carapace slopes ventrally. Lateral carapace border ventrally fringed by a row of long setae on the upper branchiostegite. The setal row is interrupted several times by gaps subdividing it into five to six distinct groups; gaps tend to be at same height as anterolateral teeth and carapace striae. Lateral carapace border and parallel row of setae meet ventral carapace at height of third ambulatory leg without fusing, thus leaving small gap between them. Pterygostomian region and branchiostegite covered with dense and regular reticulation. Anterior triangular area, separated by grooves, with shorter non-reticulated setae. Epistome setose, with endostomial cristae along ventral border. Epistomial wings in close connection with base of the second antennae. Setae delimiting Verwey’s groove mostly reduced. Orbit lined with setae. Cornea of eyes broader than eyestalk ( Figure 2B ). Gap between third maxillipeds clearly exposes mandibles and palps of second maxillipeds.

Chelipeds in adult animals homochelous, but sexually dimorphic, those of females markedly smaller and weaker (prh/cw50.35¡ 0.07 in 10 males, 0.28¡ 0.01 in 11 females, t -test P 50.0025). Merus triangular in cross-section, all three borders with regular row of granules. Upper border with subdistal projection and rounded distal tip. Inner face ventrally bulged, with two longitudinal rows of setae, lower one extending over full length, upper one only extending to proximal half. Dorsal to upper row, presence of an irregular field of short and stout setae. Ventral face triangular, smooth and glabrous. Outer face with several transverse rows of granules of varying length. Carpus with regular longitudinal row of granules on proximal border and tuft of grooming setae in close connection with ventral setal row from inner face of merus. Outer face with mostly granular crests of different length. Palm approximately 0.5 times as high as long (prh/prl50.55¡ 0.04 in 10 males, 052¡ 0.01 in 11 females; t -test P 50.038). Dorsal row of granules semi-continuous; often broken once at half its length, sometimes the granules are of irregular size and distance. Upper inner face often with oblique lines of larger-sized granules ( Figure 3A ). Outer face completely covered with coarse granules. Inner face irregularly granulate, with a patch of larger granules in its centre. Palm about 1.6–1.7 times as long as dactylus (1.63¡ 0.03 in 10 males, 1.68¡ 0.02 in 11 females; t -test P 50.0005). Regular row of 10–14 small hornytipped tubercles on dorsal edge of dactylus from proximal to about three-quarters length ( Figure 3A ). Fingers in large animals slender and curved, resulting in an oval gap between the cutting edges ( Figure 3B ); not so in small animals. Cutting edges with teeth along their whole length. Tips of fingers with horny edges, pointed in dactylus fitting into groove from pollex (immovable finger). Tufts of setae parallel to teeth on inner side of fingers

Pereiopods 2–5 moderately long; fourth longest, ventral length about twice carapace length (4prp/cl52.01¡0.05, n 521). Merus of walking legs less than 2.4 times as long as broad (pereiopod 2: 2.31¡0.09; pereiopod 3: 2.35¡0.1; pereiopod 4: 2.37¡0.08; pereiopod 5: 2.27¡0.1; n 520–21). Upper border crested and with subdistal tooth. Posterior faces with transverse granular striae in pereiopods 2–4. Anterior faces smooth and glabrous ( Figure 3C ). Upper border of carpus with weakly granulated crest; all posterior faces with two and anterior faces of pereiopods 2–4 with one longitudinal granular crest. Propodus with oblique longitudinal crest on proximal half of anterior face of pereiopods 2– 4 ( Figure 3C ), not in pereiopod 5; similarly oblique crest on posterior face of all pereiopods. Ventral face and dorsal border of propodi in males with pubescence gradually decreasing from pereiopod 2 to 5: dorsal border of pereiopod 2 is almost completely covered with setae, while ventral border is only covered to two-thirds its length; dorsal border of pereiopod 5 covered to one-third its length and ventral face only with few distal spines; pereiopods 3 and 4 with an intermediate pubescence. Females with no pubescence on ventral face of propodi except distal end of pereiopod 2. Dactyli slightly curved with six longitudinal rows of setae: dorsal, antero-dorsal, postero-dorsal, ventral, antero-ventral and postero-ventral; distal end horny-tipped and without setation ( Figure 3C )

Sternite III weakly granulated and mostly glabrous ( Figure 4B ). Other sternites smooth and glabrous. In males, pleon conspicuously vaulted from fronto-ventral view, third abdominal segment broadest; lateral borders of fourth and fifth abdominal segment comparatively straight. Sixth abdominal segment with lateral borders convex. Telson relatively short, about as long as wide at base ( Figure 4B ). Female pleon broadly oval; telson invaginated in sixth abdominal segment, about as long as broad. Male gonopods slender, slightly twisted and distally deflexed with horny apex ( Figure 3D ).

Colour in life. Sesarma meridies sp. n. has a more or less homogeneous dark orange to rusty colour.

Measurements. The following measurements refer to the largest male (SMF 29338) and female (Rio Magno) from the material studied, respectively: carapace width 23.44/ 23.05 mm; carapace length 20.22/ 19.94 mm; body height 11.09/ 11.15 mm; frontal breadth 11.20/ 11.41 mm.

Type locality. Holotype from tributary of Rio Minho (Crooked River) next to road between Crooked River and Trout Hall.

Figures

Figure 2. Sesarma meridies sp. n., male holotype (SMF 29338), carapace. (A) Dorsal view; (B) frontal view. Scale bars: 1 cm.

Figure 3. Sesarma meridies sp. n., male holotype (SMF 29338). (A) Left cheliped dorsal view; (B) left chela outer face; (C) anterior and posterior face of second walking leg; (D) gonopods, right one denuded. Scale bars: 1 cm (A–C); 1 mm (D).

Figure 4. Comparison of Sesarma meridies sp. n., male holotype (SMF 29338) and S. aeindsor Türkay and Diesel, 1994 (R-148). (A) Anterior carapace with anterolateral tooth; (B) male pleon and sternum. Upper drawings, Sesarma meridies sp. n.; lower drawings, S. aeindsor. Scale bars: 1 cm.