Hidden beauty of the north: a description of Eubranchus scintillans sp.n. (Gastropoda: Nudibranchia) from the Barents Sea and North-East Atlantic

Abstract

This paper represents results of an integrative analysis of specimens identified as Eubranchus exiguus (Alder et Hancock, 1848), a common nudibranch species inhabiting hydroid colonies in Northeast Atlantic marine communities. Our study included a molecular analysis, based on mitochondrial COI and 16S rRNA and nuclear histone H3 and 18S rRNA molecular markers. Phylogenetic relationships among species of Eubranchus Forbes, 1838 were estimated by phylogenetic reconstruction using two algorithms -Bayesian inference and maximum likelihood approaches. The phylogenetic hypotheses were accompanied by species delimitation methods: Assemble Species by Automatic Partitioning (ASAP), Bayesian implementation of the Poisson Tree Processes (bPTP) and General Mixed Yule Coalescent (GMYC). We used COI data to reconstruct a haplotype network for population structure analysis. Morphological defining features were analyzed with a light microscopy and scanning electron microscopy (SEM). Colouration and external appearance of specimens were studied with photographs. Results of the integrative approach indicated the existence of a pseudocryptic new species described herein under the name Eubranchus scintillans sp.n. This new species was found sympatrically with E. exiguus in all studied regions (the Barents and the North Seas). Also, we provide a comprehensive comparison of the new species with E. exiguus, as well as E. pallidus (Alder