AOSTnACT: A new species of oyster pathogen, Marteilia syd11eyi, from Australian oysters, Crassostrea commercialis, is described incorporaling light and electron micro~ropr obsrrvatious. The pathogen is a hnplosporidan w hich e,ists n.s a plasmodiwn in the oyste r hepatopnncreas. Upon sporulation, 8 to 16 uninuc lcate sporangial prlmordia a re internally cleaved (endogenously budded) from each plasmodium; thus c.-onver:;ion lo a sporangiosorus occurs. Each spornngium enlnrsres and internally cleaves into 2 or 3 spore primordia each of w hich, in turn, internally cleaves into 3 uninuclcalc sporoplnsms of graded sizes, the largest containing the \ mailer 2 in u va cuole and the inte m1ediale-~izcd one containing the smallest in a vacuole. The spore wall Is continuous without an orifice ur upt•rculum.

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Muscle activity and function appear to be related to ionic concentrations in the muscle. We investigated whether muscle paresis induced by injection of Botulinum toxin A (Botox) in 16-week-old pigs over a 56-day period is associated with ionic changes in the affected muscles. Tissue samples were taken from the masseter, temporalis, medial pterygoid, and geniohyoid muscles by a standardized method and used for energy-dispersive x-ray microanalysis in an environmental scanning electron microscope. The largest increase in Na(+) was measured in the right and left sides of the masseter muscle in treated animals. Additionally, a significant elevation of Na(+) was measured in the anterior part of the temporalis muscle and in the pterygoid muscle (P < 0.05). In temporalis and pterygoid muscles, an increase in sulfur in both sides of treated pigs' heads was observed. Botox((R)) has an indirect impact on ion concentrations, resulting in changes in muscle functional capacity and adaptive compensation of paretic muscle function by other muscles.

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A pediinculated tumor within the pericardial cavity of a Sydney rock oyster (Crassostrea commercialis) was discovered during a routine dissection. The tumor measured 5 x 4.8 x 4.5 mm, was lobulated and was attached to the dorsal parietal pericardium over the ventricle, close to the anterior aorta. Associated with it were three smaller nodular lesions, also on the parietal pericardium. All four masses were composed chiefly of vesicular connective tissue (Leydig cells of oysters) within which mild inflammatory cell infiltration and fibrosis were present. The mesothelium overlying or enveloping the tumors was moderately hyperplastic. These apparently multicentric lesions present a problem in differential diagnosis among ( I ) slow-growing, multi- centric, benign neoplasms of Leydig cell origin, ( 2 ) developmental anomaly, including hamartoma, ( 3 ) hyperplasia secondary to inflammation and repair. The authorsconsider the first of these possibilities to be the most acceptable. The tumors in this specimen appear to belong in a group with three similar ones previously recorded in the literature. Their precise nature in relation to neoplastic processes remains unsettled.

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