Reproductive ecology and larval morphology of the endangered freshwater oyster Pseudomulleria dalyi (E.A. Smith, 1898) (Mollusca; Bivalvia: Unionidae) from the Western Ghats, India

ABSTRACT

Pseudomulleria dalyi (E.A. Smith, 1898), an endemic and endangered freshwater bivalve of the Western Ghats, has long posed a taxonomic challenge because its larval morphology has remained unknown. Traditionally placed within the family Etheriidae based on its cemented shell morphology, its phylogenetic position has been debated, with molecular evidence instead suggesting affinities with Unionidae. In this study, we provide the first description of the reproductive biology and larval morphology of P. dalyi. Field surveys in the Tunga and Bhadra rivers in India revealed gravid females containing eggs, immature glochidia and mature glochidia in all four demibranchs. Scanning electron microscopy showed that the glochidia are hookless and D-shaped, consistent with the hypothesized placement of P. dalyi in the Unionidae. These findings provide important new evidence for the evolutionary relationships and reproductive biology of this species and underscore the diagnostic value of larval morphology in freshwater mussel systematics.