<em>Hematodinium perezi</em> (Dinophyceae: Syndiniales) in Morocco: First Record on the African Atlantic Coast, and First Country Record of a Parasite of the Invasive Blue Crab <em>Callinectes sapidus</em>

Abstract

Dinoflagellates belonging to Hematodinium are important parasites of marine crustaceans, primarily dec-apods. In this study, we document the first report of H. perezi Chatton & Poisson, 1930 on the African Atlantic coast. This is also the first parasite record in the invasive American blue crab Callinectes sapidus Rathbun, 1896 in Morocco. Specimens of C. sapidus were sampled in winter 2023 from two Ramsar sites on the Atlantic coast of Morocco, namely Merja Zerga and Oualidia Lagoons, and were screened to detect the presence of parasites in their hemolymph. Based on staining fresh hemolymph smears, we did not de-tect Hematodinium in any of the 36 investigated individuals (20 and 16 from Merja Zerga and Oualidia lagoons, respectively), probably due to methodological artifacts. The PCR-based method was revealed to be more accurate in diagnosing the Hematodinium parasite. It showed that 13 blue crabs were infected by the parasite at Merja Zerga Lagoon (prevalence 65%) and four individuals at Oualidia Lagoon (25%). Ge-netic analysis, based on the ITS1 rDNA gene from Hematodinium, confirmed the sequences as being those of Hematodinium perezi.