Myxobolus and Myxosoma (Myxozoa:Myxosporea) of common carp (Cyprinus carpio) in Indonesia: Species description, spore development, and histopathology

Two species of myxosporean parasites in common carp (Cyprinus carpio) in West Java, Indonesia, were studied. Light and scanning electron microscopy descriptions of the morphological characteristics of spores for the identification of both species were made. A total of 150 tubificid worms collected from five localities were examined for the presence of the alternate stage of the parasite in the form of the epispores of Triactinomyxon. The epispores were not found. Attempts to experimentally inoculate both Myxobolus and Myxosoma spores into the tubificid worms were unsuccessful.; Myxobolus that formed unilocular and multilocular cysts in gill filaments was identified as Myxobolus koi. This species was confined to the gill lamellae and was characterized by its intralamellar plasmodial development. What appeared to be a direct transmission of the M. koi spores to the gill lamellae and its plasmodial developmental stage were observed. Sporogenesis characterized by the formation of the disporoblastic sporonts was described.; The Myxosoma species infecting muscle tissue of common carp was found to be undescribed. Spore morphological characteristics and sporogenesis of the monosporoblastic sporont development are discussed. The encysted form of this parasite, which occurred only in the muscle tissue, was apparently an intramuscular type. Unencysted individual spores were found within macrophages, and they diffusely infiltrated the trunk kidney, liver, spleen, heart, brain, and gills.; Histological lesions in the gill filaments due to the unilocular cysts in the Myxobolus infection were not prominent, but those of the multilocular infection were severe. The primary lesions of the gill lamellae associated with the multilocular infection were fusion, inflammation, congestion, and necrosis.; The most significant pathological changes in Myxosoma infections were found in trunk kidney and gill lamellae. Numerous spores of this parasite in the kidney caused the obstruction of glomerular capillaries and thickening of the basement membrane of the glomerular tuft. The dilation of lamellar capillaries and the hypertrophy of the epithelial tissue of gill lamellae were due to the accumulation of spores in the lamellae.