New records of three vent-endemic scale worms (Annelida, Polynoidae) from the northern Central Indian Ridge fill regional distributional gaps

The tribe Lepidonotopodini (Polychaeta, Polynoidae) consists of 61 species in 12 genera. Species in this tribe lack eyes and lateral antennae and exhibit pronounced sexual dimorphism; some have external branchiae. Here, we report new records of three species of Lepidonotopodini — Cladopolynoe jiaolongae, Photinopolynoe kaireiensis, and Themis longqiensis — from hydrothermal vents on the northern Central Indian Ridge (nCIR) based on morphological characteristics and COI barcodes.

Morphological characters missing in the original description papers are also provided here to complement and refine these species’ diagnoses. The COI barcodes of all three species showed low intraspecific divergence (0.00–1.55 %), substantially lower than interspecific divergence within the genus (7.77–24.47 %). These findings expand the known distribution ranges and clarify the species boundaries of these taxa in nCIR vent fields.

Consequently, this study contributes to a better understanding of regional biodiversity and helps establish biological baselines for environmental management within the contract areas.