Uca (Austruca) cryptica, Naderloo, Reza, Türkay, Michael & Chen, Hui-Lian, 2010

Naderloo, Reza, Türkay, Michael & Chen, Hui-Lian, 2010, Taxonomic revision of the wide-front fiddler crabs of the Uca lactea group (Crustacea: Decapoda: Brachyura: Ocypodidae) in the Indo-West Pacific, Zootaxa 2500, pp. 1-38 : 12-14

Uca (Austruca) cryptica sp. nov.

( Figs. 5 , a–k, 7b, 8b)

Holotype. 1 male ( ZSM), Indonesia, West Flores, mangroves, coll. date and collector unknown.

Paratypes. 1 male [( SMF 17167) CL 8.5, CB 15.9 mm], Phillipines, Naawan, ded. K. Sakai; 2 males ( NHMW), Indonesia, Celebes, 0 1.1894, leg. Wolf.

Diagnosis. Front broad. Anterolateral margin moderately convergent ( Fig. 5 a). Major male chela palm with supramarginal groove, partly beset with setae ( Fig. 5 e). G1 with palp, relatively short, hardly reaching to base of horny endpiece ( Fig. 5 i). This last one flat, with flanges not inclined, about as broad as long, strongly bent in lateral direction, forming much smaller angle with the stem. Inclination of endpiece is much stronger than in any other species of the lactea -group, Position and displacement of suture as in U. annulipes ( Figs. 5 ij). Median plate of the gastric mill with 6 teeth ( Fig. 7 b).

Description. Carapace smooth. Front broad (about 1/7 times as broad as carapace). Venterolateral margin of carapace moderately convergent ( Fig. 5 a), distinctly crested; posterolateral margin distinctly crested, extending curvedly backwards, ending in level of central cardiac region; posterolateral striae short. External orbital angle acute, long triangular, directed antero-externally, tip very slightly incurbed frontally. Upper orbital border sinuous, with two crests bordering eyebrow, in its broadest part about 1/3 breadth of eyestalk. Lower orbital border ( Fig. 5 b) regularly granulate, with granules increasing in size from inner to outer part. Pterygostomian regions beset regularly with feathered bristles, becoming scarce towards lower orbital border ( Fig. 5 b).

Third maxillipeds with merus 1/3 length of ischium. longitudinal broad groove on ischium and merus, close to inner margin, bordered with short setae; long setae along inner margin of ischium, merus.

Major chela merus ( Fig. 5 c) with scarce granules on anterior upper portion of outer surface; inner dorsal margin with large granules; lower margin denticulate, denticles becoming large dorsally ( Fig. 5 d). Carpus definitively longer than broad, outer surface smooth, anterior upper margin with a row of granules, alternating in size; inner surface with scattered granules. Palm ( Fig. 5 e) with outer surface minutely granular; lower margin with row of large granules; supramarginal groove adjacent to lower margin, beset with short setae; inner surface ( Fig. 5 f) with oblique tuberculate ridge, high, with large granules; proximal ridge at dactylus base parallel to distal one, both strongly tuberculate. Dactylus high in proximal part, higher than fixed finger; both fingers with enlarged proximal tooth; subdistal tooth on fixed finger. Small chela ( Fig. 5 g) with smooth ridge on outer surface, extending from lower distal end of palm to proximal two thirds of fixed finger; without teeth on cutting edge of fingers, gap large, broader than adjacent dactylus.

Second to fifth pereiopods with merus having convex borders, granular crests on anterior margin ( Fig. 5 h); remaining joints smooth. Dactylus moderately curved.

Sternum smooth, transverse lines not reaching midline, longitudinal line present in thoracic segments 6-8. Episternites not completely separated from respective sternites.

Male abdomen tapering from segments 2 to 5, segment 6 with subparallel margin; length of all segments between 3 and 6 subequal.

G1 with stem ( Fig. 5 i) slightly bent in dorso-lateral direction; palp rather short, hardly reaching to base of horny endpiece. This last one about as long as broad, flat, with flanges not inclined, distal border oblique ( Fig. 5 j), with terminal opening of sperm channel in midline; dorsal lobe reaching slightly beyond ventral one; whole endpiece bent in lateral direction, thus forming rather small angle with stem, its inclination is much larger than in any other species of the lactea -group. Suture of sperm channel displaced ventrally from base to tip ( Fig. 5 k).

Median tooth plate of the gastric mill ( Fig. 7 b) with 6 teeth; two first ones massive, different in shape; 3-5 decreasing in size distally; third one clearly narrow, large gap between it and second and third teeth; 4 and 5 nearly in the same size, small gap between them; last one shorter, attached to plate dorsally. Lateral tooth plate ( Fig. 8 b) with 17 comb-shaped teeth.

Distribution. Up to now only known from Indonesia and the Philippines.

Remarks. The new species is distinct from any other lactea -group members by the peculiar shape of its G1, particularly the strongly inclined endpiece. There are other characters that allow its identification. The presence of a supramarginal groove on the major male chela palm leads to the exclusion of all similar species except U. annulipes and U. perplexa . It is distinguishable from these two species by the fact that the new species lacks a tuft of setae on the lower anterior corner of the merus of the large chela, which is present in U. perplexa and U. annulipes . As only the holotype and two paratypes (NHMW) can be compared in this respect, the Philippines paratype lacking the large chela, the identification has always to be determined by examining the G1. Regarding the median tooth of the gastric mill ( Figs. 7 a, b), this species is closely related to U. iranica by having 6 teeth on the median plate, but readily distinguishable from all other members of the group. Considering the general features of the apical part of the G1 and median tooth plate of the gastric mill, Uca cryptica sp. nov. can be properly attributed to Clade W (this clade already includes U. albimaba , U. annulipes and U. iranica ) proposed by Shih et al. (2009).

Nothing is known about the biology and ecology of the new species, and very few specimens are known. Etymology. We name it cryptica to point out the fact that it was hidden among numerous museum specimens and still remained undiscovered.

Figures

FIGURE 5. Uca cryptica sp. nov. Holotype male (ZSM): a, lateral margin of carapace; b, infraorbital region; c, merus of major chela, outer surface; d, merus of major chela, inner surface; e, major chela, outer surface; f, major chela, inner surface; g, minor chela, outer surface; h, last walking leg (right); i, G 1, lateral surface; j, apical part of G 1, lateral surface; k, apical part of G 1, mesial surface.

FIGURE 7. Median tooth plate of the gastric mill, ventral face: a, Uca iranica Pretzmann, 1971, male (SMF 34650); b, Uca cryptica sp. nov., paratype (SMF 17167).

FIGURE 8. Lateral tooth plate of the gastric mill, mesial face: a, Uca iranica Pretzmann, 1971, male (SMF 34650); b, Uca cryptica sp. nov., paraptype (SMF 17167).