One of the previously discovered hermit crab species, Diogenes curvimanus. / BRUNO ALMÓN/CSIC

Three new crab species discovered in Andalusian waters

The exciting findings have been published in the journals Ecology and Evolution and the Journal of Crustacean Biology


Researchers from the Consejo Superior de Investigaciones Científicas (CSIC) have discovered and described two new species of hermit crab, of the genus Diogenes, and one of spider crab of the genus Inachus in Andalusian waters.

In a statement, the CSIC said these discoveries have come about thanks to the molecular and morphological studies carried out on the decapod (ten-footed crustacean) populations off the Andalusian coast.

The discovery of the two new hermit crabs, Diogenes erythromanus and Diogenes arguinensis was made by Bruno Almón, from the Oceanographic Centre of Vigo (IEO/CSIC), in his doctoral thesis on the study of the hermit crabs of the Iberian Peninsula, with the co-authorship of José Antonio Cuesta, from the Institute of Marine Sciences of Andalusia (Icman/CSIC), and Enrique García-Raso, professor at the University of Malaga.

The detection of the new species of spider crab, Inachus gaditanus, came after one of the publication authors, Enrique González-Ortegón (Icman-CSIC), in a separate study, compared samples to those of other spider crabs collected in Wales.

"In both studies, the role of molecular techniques has been fundamental in confirming that these were new species, since morphology alone does not always allow us to reach these conclusions with certainty," Cuesta said.

The three species described in these two studies possibly share the same origin.

"Everything suggests that they are African species that have their northern distribution limit in the waters of the Iberian Peninsula," González-Ortegón said.

In the case of the spider crab, Inachus gaditanus, it is a species that until now was known by another name, Inachus phalangium, and which is relatively common in the rocky intertidal zone, where it can be found under the anemones that protect it. An important population of this new species is found on the La Caleta beach in Cadiz.

These three species join two others: a pea crab, Pinnotheresbicristatus, and another hermit crab, Diogenes armatus, also described in 2019 and 2021 by this group of CSIC researchers in these same Andalusian waters.

Further discoveries are pending. "There are still several more new species to be described, also from Andalusian waters and from other parts of the Iberian Peninsula, but it is a slow process, until all the data are gathered to confirm that we are dealing with a new species for science and we carry out its description," Cuesta said.