Five new myxosporean species (Myxozoa: Myxosporea) infecting the Nile tilapia Oreochromis niloticus in Bahr Shebin, Nile Tributary, Nile Delta, Egypt.

Five new myxosporean species belonging to three different genera were described from the Nile tilapia Oreochromis niloticus in Bahr Shebin, Nile Tributary, Nile Delta, Egypt. These species are: Zschokkella nilei sp. n., Ortholinea africanus sp. n., Triangula egyptica sp. n., Myxobolus fomenai sp. n., and Myxobolus branchiophilus sp. n. Morphometry, light microscopy, and hand drawing of mature spores and plasmodia were presented for each species.

Endogenous stages of Eimeria arvicanthi infecting the field rat Arvicanthis niloticus niloticus from Egypt.

The endogenous stages of Eimeria arvicanthi were studied after experimental infection with pure strain in the rat Arvicanthis n. niloticus. The prepatent period was 5 days, while the patent period extended to the 11th day p.i. Two asexual generations were determined in the epithelial cells of the upper part of the colon, while the sexual one was found in the crypts of Lieberkühn. Schizonts of the 1st generation were found 60 hrs p.i., measuring 9 X 4 microns and contained 4-8 merozoites, however those of the 2nd generation were found at 96 hrs p.i., measured 14 X 10 microns and contained 8-12 merozoites. Gamonts were firstly recorded at 108 hrs p.i., after growth they differentiated and gave rise to gametes. Macrogametes were 19 X 17 microns with large nuclei and wall-forming bodies in their cytoplasm. Microgamonts (14 X 11 microns) were irregular in shape and after many nuclear divisions produce many microgametes. Eimeria arvicanthi was pathogenic and about 60% of the experimentally infected rats with 3-5 X 10(5) sporulated oocysts were died till the 9th day p.i.

Light and electron microscopic studies of Isospora chalchidis (Amoudi, 1989) infecting Chalcides ocellatus in Egypt.

Oocysts of Isospora chalchidis (Amoudi, 1989) were described from the faeces of the skink Chalcides ocellatus in Egypt. Non-sporulated oocysts were spheroidal, measuring 20 (18.5-21) microns in diameter and contained granulated zygotes. Sporulated oocysts had the same dimensions of the nonsporulated ones and each contained two sporocysts. Sporocysts were ovoid with stieda and sporocyst residual bodies. Sporulation time was 50 hours at room temperature. Merogony and gamogony occurred in the intestinal mucosa. Electron microscopic investigations showed that meronts, merozoites, gamonts and gametes developed in a narrow parasitophorous vacuole within the host-cell nucleus. Nuclei of meronts were surrounded by rough endoplasmic reticulum. Merozoites showed the main characteristics of motile stages of Apicomplexa. Macrogametes contained a large nucleus, two types of wall-forming bodies and a large amount of lipid inclusions. Nuclei of microgamonts were peripherally arranged and lacked nucleoli. Microgametes were flagellated.

Transmission electron microscopic studies on the effects of toltrazuril on Glugea anomala, Moniez, 1887 (Microsporidia) infecting the three-spined stickleback Gasterosteus aculeatus.

A symmetric triazinone, toltrazuril, was tested in vivo against Glugea anomala parasitizing the connective tissue of sticklebacks (Gasterosteus aculeatus). Naturally infected sticklebacks were incubated in toltrazuril-containing water as intermittent therapy (3 x 2 micrograms/ml for 6 h at 3-day intervals or 3 x 2 micrograms/ml for 24 h at 2-day intervals). As seen at the ultrastructural level, the drug caused severe damage to all developmental stages of G. anomala. When treatment was carried out for 6 h, the xenoma wall exhibited a network appearance. The multinucleate meronts showed tapering at one end and were lysed at places; disintegration of the nuclei was also observed. The sporogonial plasmodia were partially fragmented, and the dumbbell-shaped nuclei of the sporoblast mother cells showed damaged spindle fibres and lysis of the chromosomal material and nuclear membranes. The shape of the mature spores was altered as well. When treatment was done for 24 h, the xenoma wall was completely destroyed. The uni- and multinucleate meronts were completely destroyed and lacked their nuclei, and the sporogonial plasmodia were frequently totally fragmented. The development of the sporophorous vesicle stopped in many cases. In the sporoblasts and their mother cells, vacuolization of the cytoplasma and lysis of the nuclei were observed. Destroyed spores with damaged polar tubes and polaroblasts were frequently detected. It seems likely that toltrazuril could be successfully applied against Microsporidia in fish when used as intermittent therapy at low doses and with prolonged exposure.