Molecular identification and genetic variation studies in fifteen polychaete species of the Vellar estuary by COI gene sequence

Abstract

Identification of polychaetes from the Vellar estuary mangroves is very essential to assess their diversity status. In this study, we have used sequences of the Cytochrome Oxidase I (COI) from 15 species belongs to eight families to barcode and investigate the molecular variation among the Vellar estuary polychaetes. Based on the sequence data, it was observed that the maximum A+T content (62.00%) was recorded in Diopatra neapolitana and minimum (55.00%) in Laonice cirrata. Similarly, the maximum C+G value of 45.00% was observed in Laonice cirrata and least content of 38.00% was estimated in Capitella capitata and Diopatra neapolitana. The maximum K2P distance (1.459) was found between Lubrineridae and Capitellidae family. Whereas, the minimum K2P distance of 0.270 was observed between Nereididae and Spionidae. However, the maximum K2P distance within family was observed in Lubrineridae (0.197) and the minimum value of 0.005 was recorded in Spionidae.The maximum K2P distance (1.459) was found between the genus Capitella and Lumbrineris whereas the minimum distance (0.230) was observed between Platynereis and Perinereis. However, the maximum K2P distance within genus was observed in Perinereis (0.211) whereas the minimum distance of 0.005 was perceived in Laonice. The intra genus K2P genetic distance in Marphysa, Naineris, Platynereis, Capitella, Diopatra was zero. The maximum likelihood tree clearly demonstrates the efficacy of COI gene in discriminating polychaete individuals both at conspecific and congeneric levels. Further molecular tools such as microsattelite, RAPD is needed to assess the population structure of the above identified species.