conference paper · ARPHA Conference Abstracts
The invasive Atlantic blue crab has established populations across Moroccan coastal lagoons, prompting investigations into its origins and parasite dynamics alongside native crab species. Genetic analysis reveals that Moroccan blue crabs exhibit high diversity originating from multiple introductions from eastern North America. Screening for parasites in the Merja Zerga lagoon identified the pathogenic dinoflagellate Hematodinium across the invasive blue crab and two native species, with high genetic similarity among parasite strains in the same area. The invasive blue crab harboured the highest overall parasite diversity, including trematodes and microsporidians, but the lowest prevalence of Hematodinium, while the native Carcinus maenas showed the highest Hematodinium prevalence. These patterns suggest potential parasite transmission and spillback between invasive and native species, posing risks to native marine biodiversity and coastal fisheries productivity.
Biological invasions can destabilise coastal ecosystems by introducing or amplifying diseases. Detecting shared parasites such as Hematodinium across invasive and native crabs indicates potential parasite spillback, which could threaten native marine biodiversity and the productivity of local fisheries that rely on healthy crustacean populations. Surveillance of host-parasite dynamics helps environmental managers evaluate disease risks and develop targeted strategies for lagoon management.
This work represents early-stage surveillance research that could inform biosecurity monitoring and coastal fisheries management. The findings provide diagnostic and genetic baselines that environmental authorities, marine park managers, and fisheries regulators can use to monitor crustacean disease spread and track invasive pathways. However, the abstract does not indicate a direct product, patentable technology, or immediate commercialisation pathway.
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Crustaceans play a fundamental role in the structure and functioning of coastal ecosystems, contributing to benthic regulation, sediment stabilization, and nutrient cycling. In Morocco, native crab species such as Carcinus maenas and Afruca tangeri are key components of the marine environment, supporting ecological stability, enhancing nutrient cycling, and sustaining 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, raises significant ecological and socio-economic concerns. In particular, the role of parasites in invasion biology is increasingly recognized within a One Health framework, as they can influence host population dynamics, mediate invasion success through mechanisms such as enemy release, spillover, or spillback, and disrupt native host–parasite networks. We aim to determine the origin and structure of Moroccan populations of C. sapidus , track their introduction pathways, inspect them for parasites, and investigate possible host–parasite interactions involving native crabs. A total of 110 specimens of C. sapidus were collected from four coastal lagoons (Marchica, Merja Zerga, Sidi Moussa, and Oualidia) and analyzed using a 572 bp fragment of the mitochondrial Cytochrome c oxidase subunit 1 (COI) marker. To assess parasite diversity, 165 crab specimens ( C. sapidus, C. maenas , A. tangeri ) from Merja Zerga were examined through hemolymph and internal organ screening. Incorporating all COI sequences currently available for C. sapidus enabled a global assessment of the species’ global population structure and invasive pathways. The results revealed high genetic variation within Moroccan populations and suggest multiple introduction events from the native range specifically from the eastern coast of North America. The pronounced genetic structuring across the native North and South American ranges mirrors patterns observed in other widely distributed marine crustaceans, while the introduced range reflects a limited number of founding events followed by expansion in the invaded range. A parasitic dinoflagellate belonging to Hematodinium , a lineage presenting a major concern for crustacean health, was detected in all three crab species. Haplotype network analysis based on the portion of the Internal Transcribed Spacer 1 (ITS-1) marker revealed high genetic similarity among parasites infecting different hosts within the same geographic area, alongside a clear separation between native and invasive ranges of C. sapidus . Looking at the entire parasite community, the species composition and infection parameters of parasite assemblages varied markedly among hosts: C. sapidus showed the highest parasite diversity but lowest prevalence of Hematodinium , also hosting digenean trematodes and microsporidians; Carcinus maenas exhibited the highest prevalence of Hematodinium , with haplosporidians, amoebae, and ciliates; while Afruca tangeri displayed intermediate infection levels and lower parasite diversity, lacking trematodes and microsporidians. These findings suggest potential parasite exchange between invasive and native hosts, raising concerns about spillback processes and their implications for marine disease dynamics, native biodiversity, and fisheries. By integrating molecular and parasitological approaches, this study highlights the importance of parasite surveillance in understanding invasion processes. Continued genetic monitoring and expanded sampling across the distribution range of C. sapidus , combined with additional molecular markers, will be essential to better resolve invasion pathways and assess ecological risks. Such efforts are critical for informing coordinated management strategies to mitigate the ecological and socio-economic impacts of this invasive species in Moroccan coastal ecosystems.
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DOI: 10.3897/aca.9.e202166
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