ISOLATION AND PURIFICATION OF DEVELOPMENTAL STAGES OF PERKINSUS-KARLSSONI (APICOMPLEXA, PERKINSEA), A PARASITE AFFECTING BAY SCALLOPS ARGOPECTEN-IRRADIANS

Isolation and purification of the trophozoite and schizont stages of t he protozoan Perkinsus karlssoni, a parasite affecting Argopecten irra dians, was achieved by macerating infected host tissue. Prior culture of infected tissue in fluid thioglycollate medium was unnecessary eith er for detecting Perkinsus karlssoni in the host tissue, or for collec ting developmental stages of the parasite for further studies. The mac eration technique is rapid and simple to perform, yielding numerous vi able trophozoites and schizonts which are relatively free of contamina ting host material. Trophozoites and schizonts demonstrated good reten tion of structural integrity following isolation from host tissue. The se stages were further purified by separation from host material using a Percoll gradient and were harvested at the 50 to 60 % interface. De velopment of the successive parasite stages was observed to proceed in vitro when trophozoites and schizonts were transferred to petri dishe s containing sterile seawater fortified with antibiotics and incubated at 26-degrees-C. Light and electron microscopy were used to document the development of zoosporangia in vitro. The terminal stage of develo pment was the release of biflagellate zoospores after 3 d at 26-degree s-C. All stages of the parasite could be used for further studies incl uding development of specific diagnostic aids.