First barcodes of Bathynomus kensleyi (Lowry & Dempsey, 2006) and Bathynomus decemspinosus (Shih, 1972) from the Southeast coast of India

Abstract

Due to their large size, bathynomids (Crustacea, Isopoda, Cirolanidae), belonging to the “supergiant group” of isopods, have long been prominent. The distribution of giant isopods from inshore to deep-sea environments has been reported. There was a shortage of molecular taxonomic data for these species. While DNA barcoding has proven to accelerate species identification, due to lack of reference sequences in the database, the results of environmental DNA barcoding remain mysterious. The present is therefore aimed at identifying giant isopods and generating barcode sequences for the four species that occur on India’s southeast coast. The trawl by-catches have been used for DNA extraction, amplification of COI genes and sequencing. Basic Local Alignment Search Tool (BLAST) and neighbor joining tree analysis showed that the sequences of Bathynomus kensleyi and B. decemspinosus were barcoded for the first time. DNA barcodes of B. giganteus and B. doederleinii has <3% variation compared to DNA barcodes of the same species sequenced elsewhere and made available through Genbank, whereas B. kensleyi and B. decemspinosus exhibited >7% variation to other species of the genus Bathynomus. Analysis of Kimura-2 parametric genetic distance includes 6 species of Bathynomus genera barcoded to date and an average distance of 2.1% has been found. We recommend a minimum of 3% variation based on genetic distances as a barcoding gap to differentiate and identify species in Bathynomus genera or until a new barcoding gap has been suggested after sequencing more species.