ABSTRACT
Two colonial ascidians Didemnum granulatum and D. psammathodes were collected from Tuticorin coastal waters. These ascidians were sequenced at 603 and 576 bp region of the mitochondrial cytochrome oxidase subunit I gene (COI) for phylogenetic analysis. Barcode sequences were extracted via FASTA format from NCBI. The genetic distances of submitted DNA sequences were compared with related ascidian species. Didemnum granulatum (JQ013198) sequence shows maximum identical 99% with D. vexillum. Didemnum psammathodes (JN624758) sequence submitted at present shows maximum identical 100% with another D. psammathodes sequence which was already submitted in NCBI. The sequence also shows maximum identical 90-89% with D. vexillum. From the present study it is concluded that precise and accurate identification of ascidians could be performed using the barcode sequences of the mitochondrial DNA (in the COI gene).