The sea slugs of Barcelona

The article “Sea slugs (Mollusca, Gastropoda, Heterobranchia): the other Inhabitants of the city of Barcelona (Spain)” written by Alex Parera, Miquel Pontes, Xavier Salvador and Manuel Ballesteros has been published in number 84 of the Catalan Institute of Natural History Bulletin (BICHN),  in which an inventory of the species of these interesting molluscs is made along the coastal front of the city of Barcelona.

Algunas babosas marinas de las costas de la ciudad de Barcelona

Some sea slugs found in the waterfront of the city of Barcelona

This work has been carried out within the framework of a citizen science project known as the DIVA Project, designed by members of the Research Group in Benthic Biology and Ecology of the Faculty of Biology of the University of Barcelona, ​​coordinated by VIMAR and with logistical support from FECDAS and Saita Diving Center. The results obtained by VIMAR divers, underwater photographer Xavier Salvador and other Internet published sources demonstrates, once again, that collaboration between professional scientists and society can give tangible results for science.

Sea slugs in the broad sense (until recently known as «opisthobranchs» and today classified within the Heterobranchia subclass of the Gastropoda) have aroused the interest of naturalists since they became known in the late XVIIIth century. Their flashy coloration schemes and varied shapes make them very attractive to study and photograph, while scientists discover interesting adaptations to survive in the environment, such as chemical defenses or highly advanced camouflage techniques.

Many are the works that have been published about the biodiversity of these molluscs in all marine regions, but few are the studies carried out to know the species that inhabit highly anthropized areas such as the interior of commercial ports, sport marinas, artificial substrates or coastal areas of large cities.

In this paper, the authors present the results of a study of the biodiversity of marine heterobranchs carried out on the coast of the city of Barcelona (Spain). In just under two years, numerous specimens of 73 different species of sea slugs, belonging to 5 orders have been counted: 4 species of Aplysiida, 5 of Cephalaspidea, 3 of Runcinida, 47 of Nudibranchia and 4 of Pleurobranchida, and one superorder: 10 species of Sacoglossa, including two alien species, Polycerella emertoni and Bursatella leachii, of wide circumtropical distribution.

All the species are illustrated with excellent images that will allow readers to identify many findings on the beaches, not only in Barcelona, ​​but on the entire Catalan coast. The locations where it is easier to observe every species are detailed, being the result of dozens of dives along the city’s shoreline and hundreds of records of these interesting animals.

The article concludes that in the artificial structures created with the construction of marinas, jetties or submerged bars establish new environments suitable to be colonized by algae and a multitude of marine invertebrates. The high biodiversity found in terms of marine heterobranchs, even in waters with abundant organic matter and subject to high anthropic pressure, is a surprising result in this study.

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Cite this article as:

Pontes, Miquel (2023) "The sea slugs of Barcelona" in OPK-Opistobranquis. Published: 25/07/2020. Accessed: 04/03/2024. Available at (

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Pontes, Miquel

Informático de profesión, es fotógrafo submarino y naturalista aficionado. Submarinista desde 1994, su “logbook” cuenta con centenares de inmersiones en el mar Mediterráneo, mar Caribe y mar Rojo y en los océanos Atlántico, Índico y Pacífico. Fundador del Grupo de Estudios M@re Nostrum en 1996, socio fundador de Grup de Recerca en Opistobranquis de Catalunya en 2010, socio fundador del Grup de Recerca VIMAR (Vida Marina) en 2012. Co-autor y webmaster del web dedicado a los moluscos opistobranquios del Mediterráneo e Iberia OPK - Opistobranquis, co-autor del libro "Els nudibranquis del mar català" publicado en 2020 por Brau Edicions, descubrió el interesante mundo de los opistobranquios en 1997 de la mano de sus compañeros de inmersión y desde entonces ha sido una línea de trabajo continuada, aportando fotos submarinas, observaciones hechas en el medio natural y colaborando en la difusión de este área del conocimiento. Autor y co-autor de múltiples publicaciones científicas sobre moluscos opistobranquios (y otros grupos animales), ha participado y participa en todo tipo de proyectos divulgativos (libros, revistas, webs, conferencias, exposiciones …) como medio para difundir su interés principal: proteger los mares y los seres que los habitan. Desde 2019 es coordinador del grupo VIMAR (Vida Marina) y es webmaster de esta página web.