New distributional record of Athanas polymorphus Kemp, 1915 (Crustacea: Decapoda: Alpheidae) from the Vellar estuary, Southeastern India: An integrated taxonomic approach

This study documents the occurrence of Athanas polymorphus in the Vellar estuary on the southeast coast of India, representing a distributional record that further substantiates its presence in estuarine environments. Seven specimens were examined using detailed morphological analysis and molecular confirmation based on mitochondrial 16S rRNA gene sequences. The examined material conforms closely to previously published descriptions of the species, with minor variations observed in the number of meral teeth on the major cheliped and the position of the pterygostomian tooth. Molecular analysis of a 549 bp fragment of the 16S rRNA gene showed 100% similarity with A. polymorphus sequences available in GenBank, confirming the species identity. Phylogenetic analysis further supported the placement of the Vellar specimens within the A. polymorphus clade. The occurrence of ovigerous females indicates that the species is reproducing within the estuarine environment, suggesting tolerance to fluctuating salinity conditions. This study expands the known habitat range of A. polymorphus and highlights the importance of estuarine biodiversity surveys for improving the understanding of caridean shrimp distribution in Indian coastal waters.