The occurrence of Callinctes sapidus Rathbun, 1896 (Decapoda, Brachyura, Portunidae) in the Salento Peninsula coastal habitats: temporary visitor or permanent resident?

Coastal marine ecosystems world-wide are threatened by invasions of non-indigenous invertebrate species, altering population, community and ecosystem processes. Here, we report on the occurrence of the Atlantic blue crab Callinectes sapidus in coastal habitats of the Salento peninsula (South-East of Italy). Blue crabs and other indigenous crab species were sampled monthly in Acquatina and Torre Colimena basins (Adriatic and Ionian Sea, respectively). Specimens were enumerated, and sexed. In addition, their hemolymph was collected and analyzed using histological techniques. C. sapidus occurred episodically in the Acquatina basin, whereas it was collected during the whole sampling period in the Torre Colimena basin. Immature and mature individuals of both sexes were sampled; in addition, the ubiquitous occurrence in the hemolymph of both C. sapidus and indigenous crab species of the parasite Hematodinium sp. suggested the occurrence of an established population in the basin. A preliminary evaluation of the molecular approaches to be implemented on C. sapidus and its parasites from Torre Colimena to assess the relationship with other established populations in Croatian and Albanian waters is presented. In particular, the transmission of parasites between invasive and indigenous species is generally poorly investigated, and molecular techniques may provide a rapid and effective screening methodology.