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April 28, 2014

 

India

Mud Crab Taxonomy

 

Dr. C.P. Balasubramanian, Principal Scientist, Crustacean Culture Division, at India’s Central Institute of Brackishwater Aquaculture, reports:

 

We have a carried out a study to resolve the taxonomic confusion of mud crabs (Scylla spp) in India. In the study abstracted below, we used mitochondrial markers to identify the common mud crabs in India.  This study demonstrated that mud crabs of India are composed of two species: S. serrata and S. olivacea, which have long been misidentified as S. tranquebarica and S. serrata, respectively.

 

From Abstract. For several years, mud crabs of genus Scylla have been misidentified owing to their high morphological plasticity and the absence of distinct morphological diagnostic characters.  The taxonomic confusion of genus Scylla de Haan is considered to be a primary constraint to the development of aquaculture.  Although genus Scylla was revised using morphological and genetic characteristics, taxonomy of Scylla species occurring in India is still not clear.  In this study, partial sequences of two mitochondrial genes, 16S rRNA and CO1 (Cytochrome C oxidase subunit I) in populations of Scylla species obtained from eleven locations along the Indian coast were used to differentiate and resolve taxonomical ambiguity of the mud crab species in India.  The sequences were compared with previously published sequences of Scylla species.  Both trees generated based on 16S rRNA and CO1 indicated that all S. tranquebarica morphotypes obtained during this study and S. tranquebarica sequences submitted previously from Indian waters reciprocally monophyletic with reference sequence of S. serrata.  Both sequence data and morphological characters revealed that the species S. serrata (Forskal) is the most abundant followed by S. olivacea. Further, the 16S rRNA and COI haplotypes of Indian S. tranquebarica obtained in the study significantly differed with the known S. tranquebarica by 6.7% and 10.6% respectively, whereas it differed with known S. serrata by 0.0–0.7% only, a difference that was not statistically significant.  From these studies it is clear that S. tranquebarica commonly reported from India should be S. serrata (Forskal).

 

Information: Dr. C.P. Balasubramanian, Principal Scientist, Crustacean Culture Division, Central Institute of Brackishwater Aquaculture, 75 Santhome High Road, RA Puram, Chennai 600 024, India (phone 044 24895828, mobile +919444935541, office 044 24818817,044 24816948, email cpbalasubramanian@yahoo.com).

 

Sources: 1. Email to Shrimp News International from Dr. C.P. Balasubramanian.  April 26, 2014.  2. InformaHealthCare.com.  DNA Sequence Information Resolves Taxonomic Ambiguity of the Common Mud Crab Species (Genus Scylla) in Indian Waters.  C.P. Balasubramanian (email cpbalasubramanian@yahoo.com, Central Institute of Brackishwater Aquaculture, Chennai 600 028, Tamil Nadu, India, phone 00 91 9444935541).  Posted online on March 24, 2014.

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