Author(s): Sam Peter, B. Manoj Kumar, Fejila Agnes and Devika Pillai

Abstract: Diphyes dispar is a hydroid in the family Diphyidae. Ecologically, they are insatiable predators of zooplankton and can have significant effects on marine ecosystem formation and functioning. Using morphological characters to accurately assign this species based on taxonomy would require comprehensive anatomical studies. Molecular characterization using DNA barcodes are useful to discover new species, reveal cryptic species and assess taxonomically-significant variation within species with broad or disjunct distributions. In this study, a portion of the mitochondrial Cytochrome Oxidase I (mtCOI) gene obtained from D. dispar was used as DNA barcode for molecular taxonomy. Kimura-2-Parameter (K2P) genetic distance between sequence variants within the dispar species ranged from 0 to 0.058 (mean 0.033). K2P genetic distances were significantly lower between individuals of the same species than between individuals of different species within the genus, Diphyes (mean 0.133; S.D.0.011). A phylogenetic tree generated by Neighbor Joining (NJ) using K2P distances reliably clustered all barcodes of the same species with 100% bootstrap support, ensuring accurate identification of species. Intra- and inter-specific variation of the mtCOI gene is appropriate to be used as a DNA barcode for species-level identification and phylogenetic analysis. This is the first study conducted to characterize D.dispar from the Laccadive Sea, off the south-west coast of Arabian Sea in the Indian Ocean using the sequence analysis of mtCOI. This study provides a set of molecular tools that can be used to address questions of speciation, biodiversity, and population boundaries. In light of the crucial position of zooplankton in ocean food webs, their usefulness as rapid responders to environmental alteration, and the increasing scarcity of taxonomists, the use of DNA barcodes is an important and useful approach for rapid analysis of species diversity and distribution.

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