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 (2021) "The sea slugs of Barcelona" in OPK-Opistobranquis. Published: 25/07/2020. Accessed: 14/04/2021. Available at (

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Pontes, Miquel

Informàtic de profesió, és fotògraf submarí i naturalista aficionat. Submarinista des del 1994, el seu “logbook” compta amb centenars d'immersions al mar Mediterrani i als oceans Atlàntic, Índic i Pacífic. Ha participat i participa en tota mena de projectes divulgatius (llibres, revistes, webs, conferències, exposicions…) com a mitjà per difondre el seu interès principal: protegir els mars i els éssers que hi habiten. Fundador del Grup d’Estudis M@re Nostrum ( Soci fundador del GROC (Grup Recerca d’Opistobranquis der Catalunya). Soci Fundador del VIMAR (Vida Marina). Va descobrir l’interessant mon dels opistobranquis el 1997 de la ma dels seus companys d’immersió i des de llavors ha estat una línia de treball continuada, aportant fotos submarines, observacions fetes al medi i donant suport informàtic per a la difusió d’aquests continguts.