A new species of glass sponge (Hexactinellida: Sceptrulophora: Uncinateridae) from a seamount of the Central Indian Ridge reveals a range extension of the genus Tretopleura to the Indian Ocean

The present study describes a new species of deep-sea hexactinellid sponge in the genus Tretopleura, collected from the off-axis seamount of the Central Indian Ocean Ridge (CIR). The specimen possesses a paraulocalycoid dictyonal framework with multiaxial longitudinal strands, along with uncinates and scopules, supporting its classification within the family Uncinateridae Reiswig, 2002. The new species is distinguished from its congeners by the absence of swollen dermal spurs and the presence of of oxyhexasters, club-shaped terminals on discoscopules and discohexasters. Molecular phylogenetic analyses using mitochondrial COI and 16S rRNA gene sequences further confirm its taxonomic placement. This study provides the first record of the genus Tretopleura in the Indian Ocean, extending its known geographic range and underscoring the biogeographic connectivity of deep-sea sponge fauna.