Gametocyte Maturation,Exflagellation and Fertilization in Parahaemoproteus (=Haemoproteus) velans (Coatney & Roudabush) (Haemosporidia: Haemoproteidae): an Ultrastructural Study*

SYNOPSIS. The structural changes in macro and microgametocytes of Parahaemoproteus velans following removal of infected blood from the avian host were studied in the light and electron microscope. Gametocytes of both sexes round up and soon escape from their host cells. Shortly thereafter they assume a dumbbell shape. The microgametocyte undergoes exflagellation forming 8 slender microgametes. During fertilization the entire microgamete appears to enter the female. The most striking ultrastructural change in the formation of the macrogamete is the condensation and enclosure by a membrane of abundant amophorus dense material seen in the cytoplasm of the immature gametocyte. Maturation of the microgametocyte begins prior to its escape from the host cell. Axonemes are present in the cytoplasm and nuclear reorganization occurs while the parasite is intracellular. Bundles of microtubules associated with condensed chromatin are found in the peripheral cytoplasm of maturing forms and apparently participate in the formation of small compact microgamete nuclei. Each of these filiform structures consists of a dense, centrally located nucleus and a single axoneme lying in flocculent cytoplasm. The nucleus and axoneme of the microgamete are seen free in the cytoplasm of a fertilized macrogamete.     

Ultrastructural observations on Barroussia schneideri (apicomplexa,eucoccidiida) in the centipede Lithobius forficatus

The ultrastructure of the principal stages of Barroussia schneideri in the intestinal cells of the centipede, Lithobius forficatus, is described. The structure of the merozoites has much in common with that of other Eimeriidae: pellicle of an outer and two inner membranes, microtubules, mitochondria, micronemes, rhoptries, endoplasmic reticulum, and polysaccharide granules. The mature macrogamete has a large nucleus with a distinct nucleolus, wall-forming bodies of type 1 (WFB1), and presumably of type 2 (WFB2), and a large number of polysaccharide granules. The microgametocyte includes smaller polysaccharide granules closely associated with the cisternae of the endoplasmic reticulum. The microgametocyte surface is smooth in outline and has peripherally arranged nuclei. Microgametes have a curved nucleus, a mitochondrion, polysaccharide granules, and two flagella. One of the flagella is attached for some distance along the body.     

Studies of Growth and Development of Gametocytes in Haemoproteus columbae Kruse*

SYNOPSIS As determined by their ability to exflagellate and round up, it took the macrogametocyte and the microgametocyte of Haemoproteus columbae in pigeons 68 and 116 h, respectively, after patency to reach maturity. Pigment granules appeared in the undifferentiated gametocytes 8 h after invasion of blood. Vacuoles were observed in young gametocytes and persisted in the older forms. The growth curve of H. columbae is close to the sigmoidal curve for growth in protozoa. Multiple infection was noticed in pigeons with high levels of parasitemia, but no more than 2 gametocytes reached maturity; such multiple infections were rare in relapses. The sex ratio of the gametocytes was 1:1. Strong lateral displacement of the nuclei of infected erythrocytes was the rule; hypertrophy was negligible.