Perkinsus qugwadi sp.nov. (incertae sedis), a pathogenic protozoan parasite of Japanese scallops, Patinopecten yessoensis, cultured in British Columbia, Canada

Abstract

The pathogenic protozoan that has caused high mortalities among cultured Japanese scallops, Patinopecten yessoensis (introduced into British Columbia in 1983), is described as a new species, Perkinsus qugwadi. As in other species in the genus Perkinsus, vegetative multiplication occurred in the intercellular spaces and haemolymph sinuses of all organs of the host. Although the morphology of all developmental stages was similar to that of other Perkinsus spp., differences were observed in the ultrastructural morphology of some organelles in the biflagellate zoospore of P. qugwadi. Also, unlike all other Perkinsus spp., P. qugwadi multiplied and was pathogenic at low temperatures (8-15°C), the development of zoospores was found to occur only within the interstitial spaces of living hosts (and only in some heavily infected juvenile scallops that were less than 50 mm in valve height), and the thioglycollate culture technique that is a diagnostic test for all previously described Perkinsus spp. was negative for P. qugwadi.