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Molecular genetic approaches to resolve taxonomical ambiguity of mud crab species (Genus Scylla) in Indian waters - In ET Quinitio, FDP Estepa, YC Thampi Sam Raj & A Mandal (Eds.), Proceedings of the International Seminar-Workshop on Mud Crab Aquaculture and Fisheries Management, 10-12 April 2013, Tamil Nadu, India, 2015 - Rajiv Gandhi Centre for Aquaculture (MPEDA)Mud crab or mangrove crab (Genus Scylla de Haan) is one of the most extensively cultured and economically important brachyuran crabs from the family Portunidae in Indo-Pacific countries, including India. Mud crabs exhibit variations in colour, size, spination, polygonal pattern and habitat. These contribute to the confusion in their identification. Accurate identification of the species is essential in the breeding programmes of domesticated stocks and is a crucial factor in the success of stock enhancement programmes. The taxonomic uncertainty of the genus Scylla in India is still an issue and several papers are being published using misleading identification. This is the first attempt to resolve the taxonomical ambiguity of mud crabs commonly found in Indian waters using multiple molecular genetic approaches. ITS-1, RAPD, PCRRFLP and mt-DNA sequencing along with traditional morphometric methods were used. Furthermore, a PCR method was developed by which mud crab species in India could be identified rapidly and accurately. The results of gene sequencing along with other molecular markers clearly indicated that the ‘green’ morph of Indian mud crab is S. serrata, while the ‘brown’ one is S. olivacea which was validated using the revised classification of mud crabs by Keenan et al. (1998). The S. serrata commonly mentioned in published literatures from India is S. olivacea and the S. tranquebarica, as believed by many Indian researchers, should be classified as S. serrata. Therefore, caution should be taken while interpreting or implementing the biological, molecular and aquaculture data published in those literatures.
Conference paper- In ET Quinitio, FDP Estepa, YC Thampi Sam Raj & A Mandal (Eds.), Proceedings of the International Seminar-Workshop on Mud Crab Aquaculture and Fisheries Management, 10-12 April 2013, Tamil Nadu, India, 2015 - Rajiv Gandhi Centre for Aquaculture (MPEDA)The present study described the Scylla species collected from Cochin backwaters for two years from June 2010 to May 2012. Identification and description of Scylla species were carried out based on the morphological characters focusing on the first and second male gonopods, and third maxillipeds.The first male pleopods of the three species were found to be similar in shape, but variations were observed in the setation pattern. S. serrata and S. tranquebarica showed two patches of setae on the inner margin on its posterior end, which was thin and inconspicuous in the former, while thick and conspicuous in the latter. S. olivacea was found to possess only a single tuft of thick setae on the inner margin of the first male pleopod. The second male pleopods were similar in S. serrata and S. tranquebarica, while found to be varied in S. olivacea. The second male pleopods were found to possess setation on the inner margin on its posterior region in S. olivacea, which was totally absent in S. serrata and S. tranquebarica. There were no significant variations in the third maxillipeds among the three Scylla spp. The third maxillipeds of three Scylla spp. were characterized by broad and flattened merus and ischium, lined with thick hairs on the inner margin.The present study shows the occurrence of three species, Scylla serrata, S. tranquebarica and S. olivacea, in Cochin backwaters. However identification of species needs to be confirmed using molecular techniques.