Biological identification of ascidians from Vizhinjam Bay, southwest Coast of India using CO1 gene sequences.

Ascidians are ecologically important components of marine ecosystems, yet the taxonomy and diversity of ascidians remain largely unexplored. Only <60% of reported ascidian species in India have been taxonomically described and identified and the rest of the species remain unidentified due to uncertainty in the morphology-based identification. We explored the usefulness of CO1 gene sequences for molecular level identification and mtDNA data in assessing phylogenetic relationships of 15 ascidian species. The mean sequence divergences within and among the species fell into the mean divergence ranges found in ascidian group. Species that are most similar grouped together formed a cluster. Clusters of species in a clade indicate that the species are closely related. Species that are highly divergent formed a separate branch. This study has concluded that the CO1 gene sequence is an effective tool to ascertain the molecular taxonomical studies on ascidians.

Comparative study on bioremediation of heavy metals by solitary ascidian, Phallusia nigra, between Thoothukudi and Vizhinjam ports of India.

Ascidians belonging to the sub-phylum Uro-chordata are used as potential model organisms in various parts of the world for biosorption of metals. The sedentary nature, filter feeding habits, presence of vanadocytes and the absence of kidneys cause them to accumulate metals. The present study was aimed to compare biosorption of metals such as cadmium, copper, lead, mercury and vanadium in test and mantle body of solitary ascidian Phallusia nigra between two ecologically significant stations such as Thoothukudi (Station 1) and Vizhinjam (Station 2) ports of India. Monthly samplings of water and P. nigra were done for a period of one year from September 2010 to August 2011 and subjected to analysis of metal accumulation. The average metal concentrations except mercury in the Thoothukudi water were found to be higher of comparable magnitudes than the Vizhinjam water. One-way ANOVA showed significant differences between the stations. A comparison of average metal concentrations in the test and mantle body of P. nigra between two stations showed that the enrichment of V, Cd, Pb, Cu and Hg in the Thoothukudi samples may be due to high bioaccumulation factors of these elements as compared to other species of ascidians. The bioaccumulation factors were in the order of V>Pb>Cd>Cu> Hg for the test and mantle body in stations 1 and 2. Application of one-way ANOVA for the concentration of these metals between test and mantle body showed significant differences in both stations. Similarly, ANOVA for biosorption of these trace metals by P. nigra showed significant difference between stations. Metal concentrations recorded in this ascidian could effectively be used as good reference material for monitoring metal contamination in Indian sea waters.