The Pleurobranchida Berthella Stellata (risso, 1826) (mollusca: Gastropoda: Heterobranchia) in the Mediterranean: Morphology, Biology and Molecular Analysis of a Population in Es Caials (NE Spain)

Berthella stellata (Risso, 1826), a species of Pleurobranchidae characterized by a Y-shaped white patch on the dorsum, is distributed in the Mediterranean and Eastern Atlantic. In this paper we have compiled records of this species on the Catalonian coast (NE Spain) and studied a permanent population of B. stellata over time in the locality of Es Caials (Costa Brava, NE Spain). Live specimens were collected and photographed and details of their morphology, radula, and jaws, as well as molecular data were studied to compare them with other specimens from different parts of the species distribution range. Our results indicate that despite the color variation, the population of B. stellata from Es Caials shares both morphological and molecular traits with specimens from the Northeast Atlantic and the Mediterranean of Europe, the only regions where the species name B. stellata is applicable, populations from other regions belonging to different species. Also, that this population of this region has been studied over 20 years where we have found that its number of specimens has increased thanks to the stable temperature of the waters of the place and the availability of food.