New distribution record of Crassostreine oyster Magallana gryphoides (Schlotheim, 1820) in Kerala, India

The Crassostreine oyster Magallana gryphoides (Bivalvia: Ostreidae) has been recorded for the first time on the Kerala coasts from Dharmadom estuary, Kannur, Kerala, India. The report indicates the range extension of M. gryphoides on the South-west coast of India. The external morphological characters were phenotypic and insufficient for species identification as it resembles Magallana bilineata. However, internal shell characters gave important information, especially the adductor muscle scar. The accurate species determination was achieved from the mitochondrial COI and 16S gene sequencing, followed by molecular phylogenetic analysis. The native oyster M. bilineata and M. gryphoides were found to co-exist in the same habitat sharing similar ecological conditions, sharing a sister group relationship.