Molecular and morphological data reveal three new species of Thouarella Gray, 1870 (Anthozoa: Octocorallia: Primnoidae) from the Southern Ocean

Abstract

Thouarella Gray, 1870, is one of the most speciose genera among primnoid gorgonians. It has a worldwide distribution that includes Antarctic and sub-Antarctic regions. Based on a combination of detailed morphological studies and analyses using mitochondrial and nuclear DNA markers, we describe and illustrate three new species of bottlebrush-shaped Thouarella from the Weddell Sea, Southern Ocean: T. islai sp. nov., T. weddellensis sp. nov. and T. polarsterni sp. nov. For the morphological description, we used macro-structural characters, such as branching pattern and polyp arrangement, along with axis and micro-structural characters, such as architecture and shapes of scales and their arrangement in polyps. Additionally, we amplified two mitochondrial (mtMutS and Cox1) and one nuclear loci (28S rDNA) obtaining optimal topologies under a Bayesian approach. Resulting molecular phylogenies corroborated the status of the new taxa and elucidated their relationships to closely related species. With the three new species here described, the global diversity of Thouarella has increased to 38 species, 12 of which are endemic to Antarctic and sub-Antarctic waters. The high number of species from higher latitudes of the Southern Hemisphere, the high grade of endemism in this biogeographic area and recent phylogenetic analyses support the idea that the Southern Ocean was likely a centre for Thouarella species radiation.