Belongs within: Gecarcinucidae.
The Parathelphusidae are a family of freshwater crabs found from southern Asia to New Guinea.
A crab out of water
Published 23 October 2015
Crabs are, of course, one of the most instantly recognisable groups of crustaceans. We all know what they look like, and we all know where can find them: under rocks at the beach, among seaweed,… climbing trees?
Though most of us probably think of crabs as animals of the seaside, there are several crab lineages that are found further inland, either in bodies of fresh water or among damp forests. One such group is the Parathelphusinae, an assemblage of freshwater crabs found in south-east Asia and the Indian subcontinent. A single genus, Somanniathelphusa, is found in southern China as far north as Taiwan and the adjacent mainland. Another, Austrothelphusa, is found in Australia. The group is diverse and new species continue to be described at a fair rate of knots. Most are found in swamps or on the banks of water bodies, in which they dig burrows up to a metre in depth (Davie 2002). They often emerge from the water to forage terrestrially, and at least one species, the Sri Lankan Ceylonthelphusa scansor, has been found in association with phytotelmata (water-filled hollows) in trees (Ng 2005). Parathelphusines are distinguished from the other subfamily of the Asian freshwater crab family Gecarcinucidae, the Gecarcinucinae, by the presence of a strong lateral groove on the male’s second gonopods (Klaus et al. 2006). Until recently, most sources have treated these two groups as distinct families, but phylogenetic studies have suggested the Gecarcinucidae in the restricted sense to be non-monophyletic. The situation is further complicated by the diagnostic gonopod groove becoming reduced in some genera, so their gonopods look superficially more like gecarcinucines’.
The Gecarcinucidae differ from the grapsoid terrestrial crabs in that they do not need to return to the sea to release their eggs to hatch into larvae. Instead, gecarcinucids produce relatively large eggs that hatch directly into miniature crabs, that are brooded for a short period by the females before being released to face the world. Because of the lack of a planktonic stage, some parathelphusines have quite restricted ranges, and many are threatened by human developments.
Systematics of Parathelphusidae
Characters (from Brandis & Sharma 2005): Second gonopod with spoon-like projection embracing the stem funnel-like, ending in groove formed by lateral invagination and projecting ventro- and dorsolateral margins; male abdomen very narrow, lateral margins sinuous. Eyes with small cornea.
<==Parathelphusidae |--+--Ceylonthelphusa rugosaDC06 | `--Oziothelphusa senexDC06 `--+--Parathelphusa Milne Edwards 1853DC06, BS05 | |--P. convexa De Man 1879H86 | |--P. hydrodromous (Herbst 1794)OM03 | |--P. maculataDC06 | `--P. (Barythelpusa) wolterecki Balss 1937B50 `--+--Sayamia sexpunctataDC06 `--Rouxana Bott 1969DC06, H86 |--R. ingramiDC06 |--R. minimaDC06 `--R. phreatica Holthuis 1982DC06, H86
*Type species of generic name indicated
References
[BS05] Brandis, D., & S. Sharma. 2005. Taxonomic revision of the freshwater crab fauna of Nepal with description of a new species (Crustacea, Decapoda, Brachyura, Potamoidea and Gecarcinucoidea). Senckenbergiana Biologica 85: 1–30.
[B50] Brooks, J. L. 1950. Speciation in ancient lakes (concluded). Quarterly Review of Biology 25: 131–176.
[DC06] Daniels, S. R., N. Cumberlidge, M. Pérez-Losada, S. A. E. Marijnissen & K. A. Crandall. 2006. Evolution of Afrotropical freshwater crab lineages obscured by morphological convergence. Molecular Phylogenetics and Evolution 40 (1): 227–235.
Davie, P. J. F. 2002. Zoological Catalogue of Australia vol. 19.3B. Crustacea: Malacostraca: Eucarida (part 2): Decapoda—Anomura, Brachyura. CSIRO Publishing: Collingwood (Australia).
[H86] Holthuis, L. B. 1986. Decapoda. In: Botosaneanu, L. (ed.) Stygofauna Mundi: A Faunistic, Distributional, and Ecological Synthesis of the World Fauna inhabiting Subterranean Waters (including the Marine Interstitial) pp. 589–615. E. J. Brill/Dr W. Backhuys: Leiden.
Klaus, S., C. D. Schubart & D. Brandis. 2006. Phylogeny, biogeography and a new taxonomy for the Gecarcinucoidea Rathbun, 1904 (Decapoda: Brachyura). Organisms, Diversity and Evolution 6: 199–217.
Ng, P. K. L. 1995. Ceylonthelphusa scansor, a new species of tree-climbing crab from Sinharaja Forest in Sri Lanka (Crustacea: Decapoda: Brachyura: Parathelphusidae). J. South Asian nat. Hist. 1 (2): 175–184.
[OM03] Oh, C.-W., C.-W. Ma, R. G. Hartnoll & H.-L. Suh. 2003. Reproduction and population dynamics of the temperate freshwater shrimp, Neocaridina denticulata denticulata (de Haan, 1844), in a Korean stream. Crustaceana 76 (8): 993–1015.