One Health perspectives on marine invasions: the case of Callinectes sapidus and parasite transmission in Moroccan lagoons

Abstract

Crustaceans are key components of coastal ecosystems, playing essential roles in benthic regulation, sediment stabilization, and nutrient cycling. In Morocco, native crab species such as Carcinus maenas and Afruca tangeri contribute to ecological stability, enhance nutrient cycling and support the productivity of local fisheries. However, the introduction of the invasive Atlantic blue crab Callinectes sapidus, native to the western Atlantic and established along Moroccan coasts since 2017, presents significant ecological and economic concerns. Invasion biology increasingly recognizes the role of parasites in mediating invasion success and impact. Parasites can influence host population dynamics, facilitate or hinder establishment (via enemy release, spillover, or spillback), and disrupt native host-parasite networks. Understanding parasite-host relationships is thus relevant for predicting invasion outcomes, managing associated risks and safeguarding socio-economic systems under an integrative (One Health) framework. Our efforts combine multiple approaches to investigate the invasion dynamics of C. sapidus and its interactions with the selected native crab species in Moroccan lagoons. A total of 110 C. sapidus specimens from four sites (Merja Zerga, Sidi Moussa, Oualidia, and Marchica) were analyzed using a 572 bp fragment of the mitochondrial COI gene. Haplotype network analysis revealed high genetic variation within Moroccan populations and suggest multiple introduction events from the native range along the eastern coast of North America. Comparative analyses with native and other non-native populations highlight complex invasion dynamics. These results provide key insights into introduction pathways and potential sources of parasite co-introduction. To assess parasite diversity, 165 crab specimens (C. sapidus, C. maenas, A. tangeri) from Merja Zerga were examined through hemolymph and organ analysis. Hematodinium sp., a parasitic dinoflagellate of major concern in crustacean health, was detected in all three species. Additionally, C. sapidus harbored digenean trematodes and microsporidians; C. maenas and A. tangeri carried haplosporidians; and amoebae and ciliates were found in C. maenas. These findings suggest parasite exchange between native and invasive hosts, raising concerns spillback events. By integrating molecular and parasitological data, this study emphasizes the importance of parasite surveillance in invasion biology. Monitoring invasive species like C. sapidus and their associated symbionts is essential for evaluating ecological risks, protecting native biodiversity, and informing effective coastal management strategies within a One Health framework.