Integrative taxonomy reveals the first record of Cerebratulus cf. maldivensis (Nemertea: Heteronemertea) from the Indian subcontinent

Abstract

Cerebratulus maldivensis , originally described from the Miladhunmadulu Atoll, Maldives, has remained a poorly studied species with no available molecular data. The present study documents the first record of C. cf. maldivensis from the Indian subcontinent based on specimens collected from the Sundarbans Estuarine System. Species identification was established using an integrative taxonomic framework combining detailed morphological examination with mitochondrial cytochrome c oxidase Subunit I (mtCOI)-based DNA barcoding. Morphological observations corresponded with the original description of the species and revealed a distinctive combination of characters, including a uniformly white dorsoventrally flattened body, absence of eyes, prominent lateral cephalic slits, and a stout caudal cirrus. To further validate species identity, the mtCOI region was sequenced for C. cf. maldivensis , thereby generating the first molecular barcode reference for this species. The obtained sequence was analysed alongside 234 congeneric sequences retrieved from NCBI GenBank and BOLD databases. Maximum Likelihood phylogenetic reconstruction using the GTR + G + I substitution model demonstrated clear genetic separation of C. cf. maldivensis from all other available Cerebratulus species. The generated sequence exhibited an overall mean interspecific p-distance of 18.0% ± 1.0% from the examined congeneric sequences, strongly supporting its distinct taxonomic status. By establishing the first molecular barcode for Cerebratulus cf. maldivensis , this study provides a crucial molecular baseline and highlights the importance of integrative taxonomy in resolving ambiguities in nemertean phylogeny.