Ultrastructure and cytochemistry study of Eimeria sparis (Protozoa: Apicomplexa) stages from the intestine of gilthead sea bream Sparus aurata L (Pisces: Teleostei)

The ultrastructure and cytochemistry of merogonial, gamogonial, and early sporogonial stages of Eimeria sparis in the intestine of Spartus aurata were studied. Mature stages showed the typical pellicle, which was lost in some transitional stages. An apparent unit membrane was seen in some immature stages. A parasitophorous vacuole, sometimes with membrane vesicular invaginations, was usually observed. We propose that the stages located over the epithelium and the so-called epicellular stages be termed supraepithelial stages. Endomerogony was observed in intraepithelial and supraepithelial positions. Intraepithelial stages apparently starting ectomerogony were also detected. Electron-dense granules similar to wall-forming-like bodies of types 1 and 2 were observed. Microgametes exhibited two flagella. Cytochemistry study revealed scarce polysaccharides, if any, in merogonial stages and in microgamonts. The occurrence of polysaccharides and amylopectin granules increased progressively in macrogamonts, macrogametes, zygotes, and early oocysts. Lipidic droplets were scarce or absent in merogonial stages and abundant in maturing macrogamonts. Some glycoproteins were demonstrated in certain merogonial stages.