The co-occurrence of Callinectes sapidus Rathbun, 1896 (Brachyura: Portunidae) and the parasitic dinoflagellate Hematodinium sp. (Dinoflagellata: Syndinidae) in two transitional water ecosystems of the Apulia coastline (South-Italy)

1 - Coastal marine and transitional water ecosystems are threatened world-wide by invasions of nonindigenous invertebrate species, altering community structure and ecosystem functioning. 2 - Here, we report on the occurrence of the Atlantic blue crab Callinectes sapidus in transitional water ecosystems of the Apulia coastline (Salento peninsula, SE Italy). 3 - Blue crabs were sampled seasonally, every three months over a whole-year period in the Torre Colimena basin (Ionian Sea) and Acquatina lagoon (Adriatic Sea). Specimens were identified and enumerated. In addition, their hemolymph was screened for parasite infections using histological techniques. 4 - Callinectes sapidus was sampled in the Torre Colimena basin, where no other crab species were collected during the whole experimental period. In contrast, in the Acquatina Lagoon four crab species were sampled, including C. sapidus. 5 - The parasitic dinoflagellate Hematodinium sp., known to determine in C. sapidus the degenerative “bitter crab syndrome” in its native habitats, was ubiquitously detected in the hemolymph of blue crabs from both habitats and in autochthonous brachyurans collected in the Acquatina Lagoon. 6 - An assessment of the diverse spectrum of potential ecological effects triggered by the Callinectes-Hematodinium interaction on autochthonous brachyuran species is presented, together with a preliminary evaluation of the molecular approaches to be implemented in order to verify the species-specificity of the host-parasite interaction.