Description of a new species in the genus Sarcothelia Verrill, 1928 (Alcyonacea: Xeniidae) from reefs of Gulf of Mannar, South-eastern India

Sarcothelia Verrill, 1928 has been considered a monotypic and endemic reef-dwelling octocoral genus geographically restricted to the Hawaiian Islands. In this paper we present a new species Sarcothelia indica sp. nov. from the Gulf of Mannar reefs, south-eastern India. The dense growth of blue monomorphic polyps was noticed on artificial reefs, live molluscan shells, dead corals and coral rubbles at 3–5 m depth. The species was identified using an integrated morpho-molecular method. Sarcothelia is characterised by the “presence of membranous and stolonal colonies, blue or brown coloration, zooxanthellate, and platelet-like sclerites”. Sarcothelia indica sp. nov. is distinguishable from S. edmondsoni by its pulsating polyps, by a rugged microstructure on the surface of platelet-like sclerites, and by a significant genetic difference. In S. indica sp. nov. platelet-like sclerites are abundantly distributed in the tentacles and the polyp body, but are only rarely seen on the membranous base or ribbon-like stolons of the colonies investigated. Based on partial mtMutS and 28S rDNA sequences, the newly collected specimens belong to a well-supported group that includes Xenia , Sansibia, Yamazatum , Quattuoria, Latissimia and Unomia . In particular, the mitochondrial and ribosomal DNA sequences show high degree of similarity with other Sarcothelia sequences available on GenBank, confirming the generic identity of the specimens investigated.