MOLECULAR EPIZOOTIOLOGY OF THE EUROPEAN MARTEILIA SPP., INFECTING MUSSELS (MYTILUS GALLOPROVINCIALIS AND M. EDULIS) AND OYSTERS (OSTREA EDULIS): AN UPDATE

The internal Transcribed Spacer 1 (ITS-1) region from Marteilia spp. parasitizing Mediterranean mussels (Mytilus galloprovincialis) from Italy and flat oysters (Ostrea edulis) from Greece were characterized by RFLP with endonuclease Hhal and sequenced. Profiles "O" (Marteilia refringens), previously associated with heavy mortalities, and "M" (Marteilia maurini) were found in both mussels and oysters and coinfection with the two types was common. In addition, all the available molecular information on Marteilia spp. ITS-1 region in Europe was compared and summarized. All these molecular data, in addition to molecular data from other regions and ultrastructural evidence, support the synonymy of M. maurini, the parasite originally described from mussels, with M. refringens, which was originally described from oysters and has taxonomic priority. This emphasises the need for further molecular and biological studies to reach scientifically based conclusions regarding control of Marteiliosis.