ULTRASTRUCTURAL OBSERVATIONS ON MICROGAMETOGENESIS AND THE STRUCTURE OF THE MICROGAMETE OF ISOSPORA FELIS

Abstract

The endogenous forms of I. felis were observed within the epithelial cells of the small intestine of the cat. They were situated within a parasitophorous vacuole which was limited by a multimembranous wall. The ultrastructural features of microgametogenesis were studied at 8 days postinfection. The initial phase of microgamont development consisted of cytoplasmic growth accompanied by nuclear divisions. The gamont was enclosed by a pellicle and its surface area was greatly increased by deep invaginations. In the later stages of development the numerous nuclei were situated close to the pellicle. Each nucleus has peripherally condensed chromatin. Formation of the microgametes occurred as protrusions from the microgamont surface. Two basal bodies, the dense portion of a nucleus and a mitochondrion entered each protrusion. The microgametes matured while still attached to the gamont from which they finally budded off into the parasitophorous vacuole, leaving a large residual cytoplasmic mass. The mature microgamete consisted of an elongate nucleus which overlaps with a mitochondrion towards the anterior end of the organism. The anterior portion contains a dose of perforatorium and 2 basal bodies with attached flagella. Microtubules (5-9) ran longitudinally from the basal body region.