Diversity of Brachyuran Crabs of Kanyakumari Area, South West Coasts of India

Brachyuran crabs are the most diverse group of crustaceans. The infraorder Brachyura contains 6,793 species in 93 families as many as the remainder of the Decapoda. The brachyuran crab diversity was studied from ten stations of Kanyakumari District (8.0780° N, 77.5410°E) of Tamil Nadu; south west coast of India, which recorded 40 species, 16 genera from 7 families during the study. Out of the seven the most diverse families are Portunidae and Leucosiidae. Out of 16 genera, Charybdis has 23 species under the family Portunidae. INTRODUCTION Brachyuran crabs found at even 6000m depths to seas shore and are dominant in many estuarine habitats where salinity and temperatures can fluctuate dramatically daily (Ng et al., 2008). Tropical and subtropical regions have more number of crab species compared to temperate and cold regions (Fransozo and Negreiros-Fransozo, 1996; Boschi, 2000a). Brachyuran crabs, comprise about 700 genera and 5000 to 10,000 species worldwide (Kaestner, 1970; Melo, 1996; Ng, 1998; Martin and Davis, 2001; Sternberg and Cumberlidge, 2001; Ng et al.,2008; Yeo et al., 2008), out of which 2,600 are present in Indo-West Pacific Region (Serene, 1968). Boschi (2000) and Hendrickx (1995, 1999) prepared major species of crab lists for the Americas. Since 1961, there has not been notable progress in the studies of diversity of crabs of west coast of India, except few occasional reports. Within this period, the taxonomic status of several species has also been revised. Hence, there is a need to update the current knowledge of the biodiversity studies of crabs of south west and south east coasts of India. In India 705 brachyuran crab species represented under 28 families, 270 genera have been reported (Venkataraman & Wafar, 2005). Tamil Nadu coast has 404 species of crabs belonging to 26 families and 152 genera (Kathirvel, 2008). Maximum percentages of crab catches are landed from Gulf of Mannar, Palk Bay, Nagapattinam and Puducherry landings of Tamil Nadu coast in India (Rao et al., 1973). Chennai coast has witnessed an annual crab landings were over 1500 t (Thangaraj Subramanian, 1998). There were number of studies reported about the diversity of brachyuran crabs near our study area, Gulf of Mannar areas (Jeyabaskaran and Ajmal Khan, 2007), Pondicherry mangrove areas (Satheeshkumar and Khan, 2011), Pichavaram mangrove areas (Ajmal Khan et al., 2005; Ravichandran and Kannupandi, 2007) and Parangipettai coast (John Samuel et al., 2004; John Samuel and Soundarapandian, 2009). The entire kanyakumari distirct was surveyed and ten identified stations were marked for detailed Brachyuran crab study. Hoping that, this study would bring out more new species and new reports from this region. Also the literature shows there is a lacuna on the diversity of Brachyuran crabs of Kanyakumari coast hence this present study was attempted. MATERIALS AND METHODS Specimens were collected monthly from 10 stations, randomly selected from Kanyakumari (8.0780° N, 77.5410°E) south west coast of India (Fig.1). The selected ten stations are (i) Kanyakumari Market, (ii) Behind Arogyamatha Church, (iii) Rakshakatheruvu, (iv) Arogyamathatheruvu, (v) Antony street, (vi) Chinnamuttom Harbour, (vii) Gandhi Park, (viii) Sunset Point, (ix) Kanyakumari Kovalam and (x) Pallam. Specimens collected by handpicking from coasts, from trawl bycatches, visiting landing centres, for a period of August 2013 to June 2014. The burrowing intertidal crabs collected either by digging or by pouring dilute formalin or weak acid inside the borrow. From each site the collection was made from a 1m x 1m quadrate area during low tide. The collected crabs were then washed in sea water, photographed from the sites itself and kept in ice boxes, packed and transported to laboratory. These were processed appropriately and samples were preserved. Specimens were identified up to the species level as far as possible. The species level identification was done using text books/monographs/ reprints/CD ROMs & standard publications, keys (Sakai, 1976; Sethuramalingam and Ajmal Khan, 1991) and with the help of subject experts. RESULTS AND DISCUSSION The survey during August 2013 to July 2014 revealed the occurrence of 7 families, 16 genera and 40 species (Table 1 and Fig 2)