DISEASES AND PARASITES OF RAFTED MUSSELS (MYTILUS-GALLOPROVINCIALIS LMK) - PRELIMINARY-RESULTS

A detailed histopathology-based survey of a total of 330 cultured mussels collected from three locations on mussel rafts in the Ria de Arosa (NW, Spain) was carried out over a 1-year period between 1985 and 1986. The populations were "healthy" at the time of sampling. The commonest parasites found in histology were Rickettsiae (up to 50% of histological samples demonstrated clear "inclusions"), the Ascetosporan Marteilia (possibly M. maurini) (up to 35%), and the "redworm" copepod Mytilicola intestinalis (up to 80%). A gill ciliate similar to Ancistrum mytili was found on all samples examined. ranging in frequency from 60-95%. Specific host-tissue reponses were detected in association with the plasmodial and spore stages of Marteilia sp. infections, as well as with ovarian infection by the microsporidian parasite Steinhausia mytilovum, and there was a marked haemocyte encapsulation response to tissue penetration by a copepod. No tissue responses could be detected in association with the other parasites observed.