ABSTRACT. In 1989, an unidentified protistan parasite, QPX (Quahaug Parasite X), was found in quahaugs Mercenaria mercenaria (Linnaeus, 1758) from a hatchery on Prince Edward Island, Canada, which was suffering extensive mortalities. The parasite was identical to one reported from mass mortalities of wild populations of quahaugs in the late 1960's. QPX eliclts a massive inflammatory response characterized by extensive infiltration of haemocytes with necrosis of the connective tissues in the digestive gland and within the musculature of the foot. Light microscopy revealed a range of paraslte stages including thick-walled cyst-like stages. The majority of QPX tissue stages were enclosed within a translucent 'halo' indicative of possible host tissue lysls. The same feature was observed in QPX isolated from quahaug tissue cultured on potato dextrose agar. Culture in sterile artificial seawater and on potato dextrose agar resulted in production of a blflagellate stage. Features of all developmental stages observed are described and compared with those of the Thraustochytriales and Labyrinthulales.

Chronic mortalities in lumpfish Cyclopterus lumpus raised in a saltwater recirculation system were associated with the presence of an intranuclear rnicrosporidian. Morphologic changes were characterized by infdtration of lymphocyte-like cells predominantly in the renal interstitium and also in the spleen, liver, gills, stomach, pyloric caecae, heart, ovary and mesenteric fat. Affected cell nuclei contained 1 to more than 6 spherical to oval eosinophilic bodies which stained poorly with hematoxylin and eosin and Giemsa. Ultrastructurally, spores were ovoid (2.1 X 1.0 pm) with a polar tube with 11 turns. The morphology of these spores place them in the genus Enterocytozoon. These spores resemble E. salmonis in salmonids, and Microsporidia rhabdophilia in the rodlet cells of salmonids.

The etiological agent of 'bumper car' disease in lobsters Homarus americanus is described as a new species of ciliate, Anophryoides haemophila (Scuticociliatida: Orchitophryidae). A. haemophila n, sp, is distinguished from other species in the genus by the curved rectangular oral polykinetid 2, a somatic kinety range of 16 to 18, and its relatively small size. The parasite is easy to maintain in vivo and in vitro for extended periods at 2 to 5°C. Apparently the ciliate can be a significant impediment to the economic viability of coldwater lobster impoundments in eastern North America. However, factors inducing epizootics of 'bumper car' disease are unknown.

No abstract

No abstract