Not one but two invasions of the Atlantic Ocean from the Indo-Pacific: Genetic and morphologic study of the slug genus Vayssierea Risbec, 1928 (Mollusca, Nudibranchia)

Abstract

Vayssierea is an understudied nudibranch genus characterized by its orange colouration and small size of up to 5 mm long. There are four described species so far, distributed in the Indo-Pacific Ocean. Here, individuals of Vayssierea have been recorded for the first time in the North Atlantic Ocean, in the Canary Islands (Spain). This study aims to evaluate the systematic and taxonomy status, and distribution of the genus through a multilocus phylogenetic analysis and a morphological and radular analysis. Phylogenetic results show the monophyly of the genus, with a particularly long branch that may represent its fast evolutionary rate compared to its counterparts. The systematics of the genus are clarified, and we provide evidence that Vayssierea is included in the new subfamily Okadaiinae stat. nov. within Polyceridae. According to the species delimitation test, four different species have been sequenced from Russia to Australia in the Indo-Pacific plus our records from the Atlantic, but more information is needed to identify them. Nevertheless, our specimens from the Canary Islands correspond to two different species, one identical to the Australian species. Bearing in mind they lack a planktonic larval phase, we hypothesize that they have arrived by shipping transportation or aquarium releases, becoming an invasive species of the Atlantic Ocean.