Phricotelphusa Sirindhorn N. Sp., a New Freshwater Crab from Thailand (Decapoda, Brachyura, Gecarcinucidae)

PHRICOTELPHUSA SIRINDHORN N. SP., A NEW FRESHWATER CRAB FROM THAILAND (DECAPODA, BRACHYURA, GECARCINUCIDAE)

PHAIBUL NAIYANETR Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok, Thailand

ZUSAMMENFASSUNG Beschreibung einer neuen Art der Gattung Phricothelphusaaus dem Süsswasser Thailands. Diese Krabbenart wird besonders von ihrer auffallend schönen Schwarzweiss-Farbe charakterisiert.

INTRODUCTION

In 1986 on a field trip of the Carcinology course of Chulalongkorn Univer- sity to the southern part of Thailand, the author collected two specimens of a new species of freshwater crab of the genus Phricotelphusa Alcock, 1909, belong- ing to the family Gecarcinucidae Rathbun, 1904. The species was found in mountain streams of the Ngao Waterfall Forest Park in Amphoe Muang ( = Muang district), Ranong Province. Thirty living specimens of the same species were collected from the same place in 1987. The description of the new species is provided in this paper. The holotype and pairs of paratypes of the new species are deposited in the collection of Rijksmusum van Natuurlijke Historie (RMNH), Leiden, The Netherlands and paratypes are deposited in the collection of Chulalongkorn University, Museum of Zoology, Bangkok, Thailand (CUMZ) and in Naturmuseum Senckenberg, Frankfurt am Main, the Federal Republic of Germany (SMF).

Phricotelphusa sirindhorn new species (figs. 1, 2; pl. 1) - Material. The Ngao Waterfall Forest Park, Amphoe Muang, Ranong Province, S. Thailand, under small stones in mountain streams of Ngao Mountain at 300 feet above sea level, 6 December 1986, leg P. Naiyanetr, 1 O' holotype, 1 0' paratype; same locality, 20 November 1987, 13 0", 17 9, paratypes collected by the author and graduate students of Chulalongkorn University. Measurements. - Holotype: 1 0", cl. 16 mm, cb. 20 mm; paratypes: 14 0", cl. 13-17 mm, cb. 16-21 mm, 17 cl. 9-20 mm, cb. 17-25 mm. 226

Etymology. - The specific name is given in honour of Her Royal Highness Princess MAHA CHAKRI SIRINDHORN, as a token of respect and in recognition of Her great interest in the study of the natural history of Thailand. Her Royal Highness graciously permitted the use of Her name for this most beautiful and interesting species. The Thai name for this species is Pu Chao Fa and the proposed English name Panda Crab. - Diagnosis. Carapace quadrate, convex, wider than long, surface smooth. Epigastric and post orbital crests distinct. A short but prominent crest is visible in the anterior part of the carapace just mediad of the orbit, it is separated from the orbital margin by a narrow groove and from the rest of the frontal part of the carapace by a wider groove. Mandibular palps with two terminal segments. The dorsal surface of the body and the chelipeds are of a purely white colour. There is a dark violet mask-like area below the lateral and anterior margins of the carapace, this dark area includes the orbital chambers and a narrow area below the orbits extending from one epibranchial tooth to the other and including the distal part of the third maxillipeds. Also the ambulatory legs are of this dark violet colour. - Description. Carapace quadrate, convex and smooth. Regions distinct. Frontal margin granulated, directed slightly downward; its distal margin is concave in the middle and convex at the sides; when measured at the base it is less than 1/3 as wide as the carapace. The anterior surface of the front is granulated. Post orbital crests distinct, slightly oblique, not reaching to the cervical regions. Epigastric crests distinct, oblique, not reaching the post orbital crests; epigastric lobes not prominent, separated by a deep median groove which is single between the crests, but double more posteriorly. Cervical groove rather shallow, but the H-shaped part distinct. Supra- and infra-orbital margins granular. Orbit oval, fully occupied by the eyes. Antero-lateral margin rounded, slightly granulated, crested, with a prominent, forward poin- ting, epibranchial tooth. External orbital angle well developed, tooth-shaped, outer margin longer than inner. Postero-lateral margins straight, slightly con- verging, covered with fine, oblique rows of minute granules. Sub-orbital, sub- branchial and pterygostomial regions smooth. Third maxillipeds smooth, ischium squarish, without median sulcus. Exopod without any flagellum. Mandibular palps with two terminal segments. Anterior margin of epistome straight. Posterior margin with sharp, triangular median lobe, lateral sides with a low, blunt, obtuse median angle, outer portions (surrounding efferent openings) strongly concave. Chelipeds unequal, the left being larger and stronger with the segments higher. Fingers of both chelipeds slender, shorter than palm, tips strongly curved, horn-coloured. Cuttings edges of major chelipcd with 16 to 19 tooth- like denticles, 1 to 3 of which distinctly larger than the rest. Cutting edges of minor cheliped lined with 18 or 19 tooth-like denticles, 1 or 2 slightly larger