Studying marine crab genetic diversity in the Atlantic and Mediterranean ocean barriers

Genetic biodiversity of the Liocarcinus depurator crab –known as false swimcrab or soup crab- varies over the years and responding to the Atlantic water entering in the Mediterranean, according to a study published in the journal Scientific Reports and directed by Professor Marta Pascual, from the Department of Genetics, Microbiology and Statistics and the Biodiversity Research Institute (IRBio) of the University of Barcelona. The article is also signed by the experts Aymée Robainas Barcia, Francesc Mestres and Tània Roda (UB and IRBio), Ferran Palero and Enrique Macpherson (Blanes Center for Advanced Studies, CEAB-CSIC); Pere Abelló (Institute of Marine Sciences, ICM-CSIC) and Víctor Hugo García-Merchán (University of Quindio, Colombia).

This nocturnal decapod crustacean is found around the east coasts of the Atlantic, from Mauritania and Canary Islands to Norway, as well as around the Mediterranean. With great colonization abilities, its natural habitat is the muddy sands of the continent platform. As it reproduces during the winter, Liocarcinus depurator is very sensitive to the effects of the global warming.

Getting to know the genetic evolution in time and space

Experts analyzed genetic temporal and spatial diversity in this marine species through the main oceanographic discontinuities in the Atlantic and Mediterranean: Strait of Gibraltar, Almería-Oran Front, and Ibiza Channel, authentic marine barriers that can affect the gene flow of the species among different areas. To study this variation, the researchers analyzed an extract of the mitochondrial gen citocrom oxidasa I (COI) in 366 samples from five areas in two areas of each discontinuity (Cadiz, Malaga, Alicante, Valencia and Ebro Delta) and during different timeframes.

The study shows the importance of creating temporal series to understand the structure and genetic evolution of the species. According to Professor Marta Pascual, “it is hard to define the relative importance of older and current processes on the space distribution of genetic diversity because time and space may not be independent. Therefore, it is necessary to have samples in the same areas and during different periods of time to see if genetic variation is due a historical cause or current processes”.

According to the results, apart from genetic fluctuations with inter-annual character seen in the samples of different areas, the experts also saw a significant gradient of mitochondrial polymorphism along the coast.

“The new scientific work –says Marta Pascual- shows that historical processes and current ones affect the genetic structure of Liocarcinus depurator, which could explain certain discrepancies in the results of previous studies with other species where temporal factors were not taken into account. The persistency of a pattern of isolation with distance in the transition area of the Atlantic and Mediterranean, together with local fluctuations, suggests a complex balance of dispersion and natural selection”.

Image: Liocarcinus depurator crab, known as false swimcrab or soup crab, is an nocturnal decapod crustacean.