Morphological and molecular identification of the freshwater crab, Barytelphusa cunicularis from Kanniyakumari, India

Abstract

Aim: The present study aims to assess the taxonomical identification of commercially important freshwater crab, Barytelphusa cunicularis from Kumba River, Kanniyakumari using morphological and molecular tools. Methodology: Samples of B. cunicularis were collected from Kumba River flowing in Kilamalai, Kanniyakumari district. The species identification was carried out through morphological keys constructed out of a coding matrix and phylogenetic tree (Maximum Parsimony) using Mesquite and PAUP4 software. 18S rRNA sequence was subjected to BLAST analysis, and the phylogenetic tree was constructed through Maximum Likelihood method using MEGA 11 software. Pairwise genetic distance of the species (p-distance,p = nd/n) was also assessed by comparing the K2P values involving phylogenetically close and distant relatives. Results: Coding matrix prepared using the morphological keys, raised out of 28 distinctive characteristics of B. cunicularis and comparison with its phylogenetic relatives, have brought in valuable information on status of the species. These findings were further established by Maximum Likelihood Analysis, using the PCR amplicons of 18S rRNA. The phylogram prepared out of the sequence clearly reveals the candidate species' phylogenetic proximity to other members of the genus Barytelphusa. Further, the species' monophyletic status (with a BS value of 81%) suggests its early divergence from its congeners. The K2P pairwise genetic 'p' distance analysis (p = nd/n) of the 18S rRNA has helped us not only to further ascertain the extent of its genetic identity with its congeners, but as well has clearly provided us with the valuable cues per precise identification of the species. Interpretation: Along with the morphological parameters, the present study, using molecular tools, provides valuable information for precise identification of the commercially important freshwater crab. Key words: Barytelphusa cunicularis, Crustacea, Freshwater crab, Gecarcinucidae, Phylogram, Taxonomy