Paracartia grani (Copepoda) has been identified as a potential intermediate host in the life cycle of Marteilia refringens , a paramyxean parasite infecting flat oysters. However, no intermediate host has yet been identified for Marteilia maurini that infects mussels. A better understanding of the life cycle of these two Marteilia types would clarify their taxonomic relationship and hypothesized co‐specificity. For this purpos...