Diversity and biogeography of scale worms in the subfamily Lepidonotopodinae (Annelida: Polynoidae) from Indian Ocean hydrothermal vents with descriptions of four new species

Abstract

Abstract Lepidonotopodinae is a subfamily of Polynoidae endemic to deep-sea chemosynthetic ecosystems around the world. Nevertheless, their species composition and phylogeny have only been systematically studied in hydrothermal vents of the Eastern and Western Pacific. Here, we morphologically and genetically examined worms in Lepidonotopodinae from vents across three Indian Ocean ridges, revealing two new Branchinotogluma species (B. jiaolongae sp. nov. and B. kaireiensis sp. nov.) and two new Levensteiniella species (L. pettiboneae sp. nov. and L. longqiensis sp. nov.). Primary morphological characters distinguishing them from other congeners include the number and arrangement of both pharyngeal papillae and ventral papillae. The reconstructed molecular phylogeny of Lepidonotopodinae supports a monophyletic Levensteiniella, with the two new Indian Ocean species recovered as sisters. As revealed in previous studies, a paraphyletic Branchinotogluma was also found, with the three Indian Ocean species separated into distinct clades with sister-relationships to species from the Mid-Atlantic, Alarcon Rise, and Manus Basin, respectively. This indicates three separate historical invasions to Indian Ocean vents. Our findings increase the number of Indian Ocean Lepidonotopodinae worms to seven, now the most diverse annelid group there, and help to elucidate the biodiversity, distribution, and biogeography of this subfamily in the Indian Ocean.