Morphological and molecular investigations reveal that Paphia malabarica from Indian waters is not synonymous with Paphia (Protapes) gallus

Paphia malabarica Chemnitz, 1782 is an economically important species of Venerid clam in Indian waters. The fishery of P. malabarica from Ashtamudi estuary, Kollam, Kerala has been certified by marine stewardship council as sustainable and the fishery is now managed by a set of fishery management plans. The name P. malabarica is invalid now as it has been synonymized as Paphia (Protapes) gallus (Gmelin, 1791) in subsequent taxonomic investigations. We examined the taxonomic status of P. malabarica using morphological and molecular methods. Morphological characteristics of the shell mainly, shell structure, size and internal features were compared between P. gallus and P. malabarica indicating significant differences in morphology. Molecular investigations were carried out by amplifying and sequencing mitochondrial Cytochrome C Oxidase 1 (COI) and 16SrRNA sequences of P. malabarica collected from Ashtamudi (Kollam), Dharmadam, Kannur (3 locations in Kerala), Goa, Maharashtra, Gujarat and Tuticorin in order to clear the taxonomic ambiguity and validate the synonymy. Sequences of P. malabarica were compared with sequences of P. gallus and other Paphia species. Substantial genetic divergence was detected between P. malabarica and P. gallus with a K2P genetic distance value of 28.9% and distinct clustering in phylogenetic tree demonstrating that P. malabarica is well diverged from P. gallus. We suggest retaining the name P. malabarica considering that the synonymy with P. gallus is invalid. •Paphia malabarica is an economically important species of clam in Indian water.•The name P. malabarica has been synonymized as Paphia (Protapes) gallus recently.•The validity of the synonymy investigated using molecular and morphological methods.•Substantial genetic and morphological divergence detected between both species.•The name P. malabarica should be retained as it is well diverged from P. gallus.