Microparasite screening across four species of decapod crustaceans (Decapoda: Brachyura, Astacidea) in Ireland

Decapod crustaceans and their associated fisheries are an important resource globally, and demand for seafood continues to grow alongside a growing human population. With a combined 2023 value of €36 million in Ireland, three species of brachyuran crabs, the velvet crab (Necora puber Linnaeus, 1767), edible crab (Cancer pagurus Linnaeus, 1758), spider crab (Maja squinado Herbst, 1788)), and the European lobster (Homarus gammarus Linnaeus, 1758) are decapods of commercial importance. These species are also important components of their respective ecosystems. Parasite infection can affect the health of crustaceans and may affect population productivity. Microparasites, including paramyxids (Hematodinium spp.) and microsporidians can infect decapod crustaceans and have a range of effects on their hosts. We assessed three microparasites in four crustacean species. Paramarteilia canceri was found in all three crab species, and we provide the first genetic confirmation in spider crabs. A microsporidian associated with cotton crab disease, Ameson sp., was identified in N. puber, along with a second species of microsporidian which will require further classification. None of the three parasite groups were identified in Homarus gammarus. Species of Hematodinium were not identified in any of the species studies. Our work highlights the need for parasite surveys to uncover parasite diversity and prevalence in crustaceans to help elucidate host-parasite interactions, and the potential impacts of parasites.