Evolutionary affinity of a novel deep-sea coral from the Central Indian Ridge seamount, and its links to Pacific Ocean species

The family Victorgorgiidae Moore et al., 2017 comprises deep-sea gorgonian corals typically characterized by purple colonies and distinctive josephinae clubs in their polyp tentacles. Despite this, the family exhibits low species diversity and the ones from the deep Indian Ocean remain poorly unknown, remarking the need for more research to better understand their ecological role and evolutionary history. A new species, Victorgorgia indica sp. nov., was discovered on a seamount along the Central Indian Ridge (CIR) at depths of 1917–2053 m, representing the first record of Victorgorgiidae in the Indian Ocean. Among the nine known species of Victorgorgia López-González and Briand, 2002), V. indica sp. nov. is morphologically most similar to V. flabellata Li et al., 2020 and V. iocasica Li et al., 2020, particularly in the arrangement of the calyx, which is mainly isolated in three sides of the branches. However, this arrangement can vary in different parts of a colony and may be influenced by local habitat conditions. V. indica sp. nov. differs from these species by having tuberculate rods, a thorn club in the tentacle rachis, and curved rodlets with tall tubercules along their edges in the pinnules. Phylogenetic analysis at the family level using the MutS-like protein (MutS) gene supports Victorgorgiidae as a monophyletic group. The evolutionary relationships of the new CIR species suggest a close affinity with its Pacific Ocean congeners, including V. flabellata, V. iocasica and V. eminens Moore et al., 2017. This points to the CIR seamount system potentially acting as a link for gene flow between the Indian and Pacific Oceans. Analyses of the reproductions of these species showed that V. indica sp. nov. is a brooder, with planula larvae developing within clumped autozooids—the only mature polyps—and settling on dead deep-sea coral. Here we presented also the complete mitochondrial genome of V. indica sp. nov., which is 18,715 base pairs in size, and includes 14 protein-coding genes (PCGs), two ribosomal RNA genes (rrnS and rrnL), and one transfer RNA gene. The gene order of the mitogenome is identical to that of other sequenced Victorgorgiidae species.