Tuesday, 19 April 2022

Freshwater Crabs of Sri Lanka

Sri Lanka is situated in one of the world’s 34 "biodiversity hotspots" (Beenaerts, 2010). Despite the island’s small size (65,600 km2), its freshwater crab diversity is significantly higher than in other tropical Asian countries (Bahir et al., 2005). As of today, the country has recorded 51 species (4% of the global freshwater crab species) of freshwater crabs of the family Gecarcinucidae and 50 of which are endemic (Bahir et al., 2005; Bahir & Gabadage, 2012; Beenaerts, 2010). 

Although, freshwater crabs occur at all elevations throughout the island nearly half the freshwater crabs known to date (23 species) are point endemics (Bahir & Gabadage, 2012; Beenaerts, 2010). The reason why freshwater crabs show such a highly restricted distribution is unclear (Bahir & Gabadage, 2012).  Approximately 80% of crab species (41 out of 51) are restricted to the country’s rainforested south-western ‘wet zone’, which accounts for only a quarter of Sri Lanka’s territory (Bahir et al., 2005). Nearly 90% of the freshwater crabs in Sri  Lanka are globally threatened with 66% being listed under the critically endangered category (Bahir & Gabadage, 2012). 

The American zoologist, J. S. Kingsley (1880) was the one who described the first two crab species in Sri Lanka (Bahir & Gabadage, 2012; Bahir & Ng, 2005; Beenaerts, 2010). He was followed through several studies by Rathbun, (1904) Roux (1915) and Fernando (1960). An extensive review of Sri Lankan freshwater crabs was later done by Bott (1970) who recognized seven species and classified them into four genera and two families (Beenaerts, 2010). Several new genera and species endemic to the island were discovered through further explorations carried out by a number of taxonomists. 

Up to 1994, only eight valid species of freshwater crabs belonging to four genera had been recognized in the country (Bahir & Gabadage, 2012). The extensive exploration work carried out by the National University of Singapore and the Wildlife Heritage Trust of Sri Lanka resulted in the discovery of many new species taking the total number to 51 (Bahir & Gabadage, 2012). Based on a relatively small number of available morphological characters, these 51 species have been presently classified into seven genera [(Oziotelphusa, Spiralothelphusa, Perbrinckia, Ceylonthelphusa, Mahatha, Clinothelphusa and Pastilla) Beenaerts, 2010].

List of freshwater crabs in Sri Lanka
Red List criteria. CR, Critically Endangered; EN, Endangered; VU, Vulnerable; NT, Near Threatened; LC, Least Concern.

1) Ceylonthelphusa alpina (CR)     2) Ceylonthelphusa armata (CR)     3) Ceylonthelphusa callista (CR)     4) Ceylonthelphusa cavatrix (CR)     5) Ceylonthelphusa diva (CR)     6) Ceylonthelphusa durrelli (CR)     7) Ceylonthelphusa kandambyi (EN)     8) Ceylonthelphusa kotagama (CR)     9) Ceylonthelphusa nata (CR)     10) Ceylonthelphusa orthos (CR)

11) Ceylonthelphusa rugosa (NT)     12) Ceylonthelphusa savitriae (CR)     13) Ceylonthelphusa sentosa (EN)     14) Ceylonthelphusa sanguinea (CR)     15) Ceylonthelphusa soror (EN)     16) Ceylonthelphusa venusta (CR)     17) Clinothelphusa kakoota (CR)     18) Mahatha adonis (NT)     19) Mahatha helaya (CR)     20) Mahatha iora (CR)     

21) Mahatha lacuna (CR)     22) Mahatha ornatipes (NT)     23) Mahatha regina (CR)     24) Oziotelphusa ceylonensis (NT)     25) Oziotelphusa dakuna (CR)     26) Oziotelphusa gallicola (CR)     27) Oziotelphusa hippocastanum (EN)     28) Oziotelphusa intuta (CR)     29) Oziotelphusa kodagoda (CR)     30) Oziotelphusa mineriyaensis (EN)     

31) Oziotelphusa populosa (EN)     32) Oziotelphusa ritigala (EN)     33) Oziotelphusa stricta (NT)     34) Pastilla ruhuna (CR)     35) Perbrinckia fenestra (CR)     36) Perbrinckia cracens (CR)     37) Perbrinckia enodis (CR)     38) Perbrinckia fido (CR)     39) Perbrinckia gabadagei (CR)     40) Perbrinckia glabra (CR)     

41) Perbrinckia integra (EN)     42) Perbrinckia morayensis (CR)     43) Perbrinckia punctata (CR)     44) Perbrinckia quadratus (CR)     45) Perbrinckia rosae (CR)     46) Perbrinckia scansor (EN)     47) Perbrinckia scitula (CR)     48) Perbrinckia uva (CR)     49) Spiralothelphusa fernandoi (EN)     50) Spiralothelphusa parvula (EN)     51) Perbrinckia nana (EN)

1) Bahir, M.M., Gabadage, D.E., 2012. Taxonomy and Conservation Status of the Freshwater Crabs  (Crustacea: Decapoda) in Sri Lanka. The National Red List 2012 of Sri Lanka. Conservation Status of the Fauna and Flora. Weerakoon, D.K. & S. Wijesundara Eds., Ministry of Environment, Colombo, Sri Lanka. pp.56-64.
2) Bahir, M.M., Ng, P.K., 2005. Descriptions of ten new species of freshwater crabs (Crustacea: Brachyura: Parathelphusidae: Ceylonthelphusa, Mahatha, Perbrinckia) from Sri Lanka. Contributions to Biodiversity Exploration and Research in Sri Lanka. The Raffles Bulletin of Zoology, Supplement, 12, pp.47-76.
3) Bahir, M.M., Ng, P.K., Crandall, K. and Pethiyagoda, R., 2005. A conservation assessment of the freshwater crabs of Sri Lanka. Raffles Bulletin of Zoology Supplement, 12, pp.121-126.
4) Beenaerts, N., Pethiyagoda, R., Ng, P.K., Yeo, D.C., Bex, G.J., Bahir, M.M. and Artois, T., 2010. Phylogenetic diversity of Sri Lankan freshwater crabs and its implications for conservation. Molecular Ecology, 19(1), pp.183-196.

This page was last updated on 19 April 2022
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