The freshwater crabs of Danum Valley Conservation Area in Sabah, East Malaysia, with a description of a new species of Thelphusula Bott, 1969 (Crustacea, Brachyura, Gecarcinucidae, Potamidae, Sesarmidae).

Peter K L Ng,Paul Y C Ng

doi:10.3897/zookeys.760.24787

Abstract

Seven species of freshwater crabs from three families are recorded from and around the Danum Valley Conservation Area in Sabah, Malaysian Borneo: Thelphusula capillodigitus sp. n., Thelphusula dicerophilus Ng & Stuebing, 1990, Arachnothelphusa terrapes Ng, 1991, Terrathelphusa secula Ng & Tan, 2015, Parathelphusa valida Ng & Goh, 1987 (new record) (Gecarcinucidae); Isolapotamon ingeri Ng & Tan, 1998 (Potamidae); and Geosesarma danumense Ng, 2002 (Sesarmidae). The new species of Thelphusula Bott, 1979, can be distinguished from all congeners by a unique combination of morphological features, most notably the presence of dense patches of short setae on the fingers of the adult male chelipeds, as well as the structure of the male first gonopod. Arachnothelphusa terrapes is confirmed to be a phytotelm species. A key to all species in the conservation area is provided.

Highlights

Danum Valley Conservation Area, northeastern Borneo, in the Malaysian state of Sabah contains over 400 square kilometres of pristine rainforest and is a key conservation area on the island (Hazebroek et al 2011)
The first author has been involved in studies of the freshwater decapod crustacean fauna in the area since the late 1980s, and five species of freshwater and semiterrestrial crabs have been reported far: Thelphusula dicerophilus Ng & Stuebing, 1990, Arachnothelphusa terrapes Ng, 1991, Terrathelphusa secula Ng & Tan, 2015 (Gecarcinucidae Rathbun, 1904); Isolapotamon ingeri Ng & Tan, 1998 (Potamidae Ortmann, 1896); and Geosesarma danumense Ng, 2002 (Sesarmidae Dana, 1851) (Ng 1991, 2002; Ng and Stuebing 1990; Ng and Tan 1998, 2015)
While superficially resembling T. hulu Tan & Ng, 1997, from the Maliau Basin in Sabah in morphology and habits, it can be distinguished from this and all congeners by its setose male cheliped dactyli, as well as a number of other carapace features. It is here described as T. capillodigitus sp. n

Summary

Introduction

Danum Valley Conservation Area, northeastern Borneo, in the Malaysian state of Sabah contains over 400 square kilometres of pristine rainforest and is a key conservation area on the island (Hazebroek et al 2011). C. Colón, 17 October 1996; 1 male (22.0 × 17.6 mm) (ZRC 1997.0142), in pitfall trap, Danum Valley Field Centre, Lahad Datu, Sabah, coll. R. Stuebing, 23 July 1989; 1 male, 2 females (ZRC 1008.1346), Sungei Palun Tambun, tributary of Sungei Segama, upstream of Danum Valley Field Centre, Lahad Datu, Sabah, coll.

Results

Conclusion