The surface of the malaria parasite: I. Scanning electron microscopy of the oocyst

Abstract

Scanning electron microscopy has been used to study surface characteristics of the early sporogonic stages of Plasmodium gallinaceum and Plasmodium berghei. Observations upon oocysts from 9-day old infections of P. gallinaceum in Aedes aegypti and 14-day old infections of P. berghei in Anopheles stephensi indicate the oocyst surface is relatively smooth, although an outline of the underlying sporozoites can easily be recognized in the mature oocyst. Although all infections with each species were the same age, the stage of development of each oocyst appeared highly variable even within an individual mosquito. Oocysts appear to be covered by the overlying basement membrane which separates them from direct contact with the hemolymph as well as hemocytes. Small buds designated as satellite bodies were often seen attached to large oocysts of P. gallinaceum. Neither their origin nor their significance is yet known. During the study, numerous observations were made of the liberated sporozoites of both species. In each species the sporozoites are comma-shaped; however, those of P. gallinaceum are shorter, more strongly curved and stouter than those of P. berghei.