CERATOMYXA DREPANOPSETTAE IN THE GALLBLADDER OF ATLANTIC HALIBUT, HIPPOGLOSSUS-HIPPOGLOSSUS, FROM THE NORTHWEST ATLANTIC-OCEAN

Trophozoites of Ceratomyxa drepanopsettae Averintsev, 1907 (Myxosporea : Ceratomyxidae) containing prominent refractile granules were found i n the gallbladders of all but one of eight halibut, the exception bein g a single juvenile. They ranged in shape and size from globular forms 5-10 mu m in diameter, to rounded structures with pseudopodia and one or more processes that were up to 500 mu m in length and packed with refractile granules. Some trophozoites were free in the bile, while ot hers were attached to the epithelium of the gallbladder wall by pseudo podia which extended between the microvilli. Many free trophozoites we re attached to each other by septate junctions between their pseudopod ia. There were small cylindrical papillae on the surface of the tropho zoites, and the rounded portions contained two vegetative nuclei, gene rative cells (some attached by junctions) and, in many cases, feeding vacuoles. During sporogony, a binucleate sporoplasmic cell and the cap sulogenic cells of some sporoblasts were engulfed by valvogenic cells before they began to differentiate; whereas other sporoblasts consiste d of six cells attached to each other, two being capsulogenic cells co ntaining external tubes, two sporoplasmic cells and two valvogenic cel ls. There was a septate junction around the opening of the rounded pol ar capsule of the spore, between the capsulogenic and valvogenic cell. Sporoplasmosomes appeared to form in smooth membraned vesicles, possi bly part of the Golgi apparatus. Spores had a thin, delicate membrane, and elongate shell-valves, most of which were asymmetric, and bent or folded, A sporoplasm extended on either side of the distinct, straigh t suture line, but did not penetrate into the valves.