The genus Jorunna (Nudibranchia: Discodorididae) in Europe: A new species and a possible case of incipient speciation

Abstract

To investigate the conspecificity of different morphotypes of Jorunna tomentosa (Cuvier, 1804) (type species of genus Jorunna Bergh, 1876), we studied specimens sampled from across part of the geographical distribution of the species, using a combination of morphoanatomical characters and molecular phylogenetics. Bayesian and maximum likelihood phylograms were inferred based on the mitochondrial genes cytochrome c oxidase subunit I (COI) and 16S ribosomal RNA, and the nuclear gene histone H3. We used the automatic barcode gap discovery method to aid in species delimitation. COI genetic uncorrected p-distances were estimated between and within species. Animals were dissected and the reproductive system, radulae and labial cuticles were examined; scanning electron microscopy was employed to study ultrastructural elements of anatomical characters. The results revealed the presence of a new species (Jorunna artsdatabankia n. sp.) and a possible case of incipient speciation in J. tomentosa with our COI data indicating the presence of two morphoanatomically indistinct lineages that are separated from each other by distances of 3.2–5.0%. The genetic distance between J. artsdatabankia n. sp. and its sister species J. tomentosa was 9.0–12.3%; the former species is characterized by a plain white to yellow background colour with irregularly placed small brown spots, smooth radular teeth and a longer vas deferens, wider vagina and a longer copulatory spine (up to 600 μm longer) than the latter. A diagnostic comparison of all species of European Jorunna is included, as well as a discussion of the assignment of J. lemchei to the genus Gargamella.