Ultrastructure of the life-cycle stages of Goussia janae (Apicomplexa, Eimeriidae), with X-ray microanalysis of accompanying precipitates

Abstract

The ultrastructural features of the life-cycle stages of Goussia janae from the intestinal epithelium of the dace Leuciscus leuciscus and chub L. cephalus are described. All merogonial, gamogonial, and early sporogonial stages were localized in the microvillar region in an intracellular and extracytoplasmic position, covered by closely apposed enterocyte and parasitophorous vacuole membranes. Two types of location in the host cell were observed: (i) a more frequent "monopodial" type with a single zone of attachment to the host-cell cytoplasm, and (ii) a "spider-like" type with several isolated zones of attachment. Merozoites were formed by either ecto- or endo-merogony. Microgamonts produced elongated biflagellate microgametes at their periphery. The oocyst wall, produced exclusively by the parasite, was formed at the end of the intracellular phase of the life cycle. Exogenous sporulation resulted in the formation of elongated sporocysts with a thin sporocyst wall bearing a longitudinal suture accompanied by a narrow membranaceous veil. In the cytoplasm and cytoplasmic and parasitophorous vacuoles of the parasite, fine, dense precipitates were present. X-ray microanalysis of these precipitates from osmicated and non-osmicated samples revealed high levels of Ca and P, indicating the possible presence of hydroxyapatite.