Sporogonic development of Haemoproteus meleagridis (Haemosporina: Haemoproteidae) in Culicoides edeni (Diptera: Ceratopogonidae)

Abstract

Mature oocysts of Haemoproteus meleagridis developed in specimens of Culicoides edeni within 3–6 days after the midges took a blood meal from an infected domestic turkey. Approximately 50 sporozoites budded from the surface of a single sporoblast body. Sporogonic development was similar to that of reptilian, avian, and mammalian haemoproteids that are transmitted by ceratopogonid and tabanid flies, but unlike that of hippoboscid-transmitted species in birds, which form large, slowly developing oocysts with multiple sporoblast bodies. Ultrastructural features of developing oocysts included nuclei with prominent nucleoli, mitochondria, and sandwich-like arrays of crystalloid particles and smooth endoplasmic reticulum (ER) that were present on the outer surface of developing lipid droplets during early stages of sporogony. During budding of sporozoites, crystalloid particles measuring 30–40 nm in diameter were associated with the inner membrane complex of the sporozoite pellicle, arranged in rows between subpellicular microtubules. Mature sporozoites contained an apical complex composed of a polar ring with two anterior apical rings, from two to eight elongate rhoptries, 22 evenly spaced subpellicular microtubules, and a small anterior crystalloid body. Morphological similarities between the ER–crystalloid arrays and the ER–microperoxisome arrays that have been described in cells actively engaged in lipid biosynthesis suggest that the crystalloid body contains enzymes important in lipid metabolism.