Abstract

Limited research has been conducted on the biology and life history of the cobia, Rachycentron canadum, and no information on cobia molecular genetics has been published. This migratory, pelagic species is nearly circumglobally distributed. These fish are sought by offshore recreational anglers and are the basis of important commercial fisheries. Our preliminary research consisted of a characterization of the mtDNA control region and flanking tRNA genes. Whole DNA isolates were obtained from muscle tissue samples collected from cobia caught in Mississippi coastal waters. Universal primers were used in PCR amplifications to generate fragments of approximately 2,000 base pairs (bp). Subsequent direct sequencing produced sequences containing portions of cytochrome b and 12S rRNA, the entire tRNAs for proline (pro), threonine (thr), and phenylalanine (phe) and portions of the control region. Using these sequences, species specific primers were constructed in the tRNAs pro and phe flanking the control region and used in subsequent amplifications. The sequence of the entire control region of six cobia was obtained and found to range in size from 1067 to 1068 bp. One termination associated sequence (TAS-I) and four conserved sequence blocks (CSB D, I, II, III) were identified and compared with other fish species. Sequence variability of the control region was loW; only three transversions and seven indels were found between the six cobia. Additional sequence data is needed from geographically isolated regions to determine if sufficient sequence variability exists in the control region for it to serve as a useful molecular marker in population and stock enhancement studies

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