The genus Ilia Leach, 1817 consist of two species, Ilia nucleus and I. spinosa Miers 1881. In European continental waters the genus is represented solely by I. nucleus, a common species distributed from the Mediterranean to the Cape Verde Islands. However, during a biodiversity monitoring project carried out in the Gulf of Cádiz in 2013, an unusual specimen of Ilia was collected. The sample was identified as I. spinosa through an integrative approach combining morphological and molecular data, and is therefore reported here for the first time within European waters. Ilia spinosa is native to the West African coast, from Mauritania to Angola and the Canary Islands. Unlike its congener, I. spinosa possesses four well-defined and acute posterior spines, allowing for a clear morphological distinction whereas I. nucleus is characterized by short more or less triangular, and rounded posterior tubercles on the cephalothorax. The present study reports the first record of this African crab species in European continental waters, providing further evidence of the tropicalization process and range of northwards expansion of African marine fauna from the Mauritanian province. At the same time, due to the morphological variability of the species, it is also possible that I. spinosa has been previously overlooked or remained undetected in European waters.
Muñoz et al. (Thu,) studied this question.
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