Presence of the parasite Marteilia sp. in the flat oyster (Ostrea edulis L) in Greece

Native oyster (Ostrea edulis L) beds of the gulf of Thessaloniki were totally extinct in the past 10 years. A cause for this extinction is the presence of the parasite Marteilia sp., as was proven by an earlier study conducted by the same workgroup. Furthermore, a parasite of the same species affects mussels (Mytilus galloprovincialis Lam) in the same gulf. To determine the degree of this infection throughout Greece, the present research was carried out. Oyster samples were collected from four different areas (Thessaloniki, Argos, Stilida, Igoumenitsa). Cytological procedures and histology were used to examine the samples. The parasite was detected only in the oysters originating from the gulf of Thessaloniki, in a high prevalence (46%).