An ultrastructural study of the sporogonic development of Plasmodium falciparum in Anopheles gambiae

Abstract

This paper describes the fine structure of the sporogonic development of Plasmodium falciparum in its natural vector Anopheles gambiae (Species A) as seen by scanning and transmission electron microscopy. The parasite was derived from naturally infected volunteers and the vector maintained under natural conditions at the MRC Laboratories, Fajara, The Gambia. Sporogonic development of P. falciparum is similar to that described for other Plasmodium spp. There are however greater similarities between P. falciparum and the avian malaria parasites, than those mammalian (primarily rodent) species described to date--particularly with respect to mitochondrial development, crystalloid morphology and nucleolar organization. Nuclear development is similar to that of the murine malaria parasites, but reconstruction of complete mitotic spindles from serial sections suggest the haploid genome of P. falciparum contains 14 chromosomes compared to eight to ten in the murine plasmodia. Sporoblast formation involves a unique process of cleft formation based on the expansion of the cisternal space of the endoplasmic reticulum. Sporozoite budding is almost exclusively confined to these inner membrane surfaces and results in a characteristic sporozoite distribution in the oocyst. High resolution scanning electron microscopy of free sporozoites provides the first surface view of the micropore of Plasmodium.

Cytoskeleton of Apicomplexan Parasites

“…Partitioning of the spindle pole plaque has also been observed by electron microscopy. A band of striated fibers termed the couche fibrillaire spans the separating plaques (42,140,161). This structure may represent centrin fibers, since similar structures are observed in algae and yeast (89,164,192).…”

“…Nuclear division proceeds without nuclear membrane breakdown (12,26,59,79,130,161). Spindle microtubules are nucleated from electron-dense, amorphous plaques associated with nuclear invaginations and embedded in the nuclear membrane (12,26,82,109,140,146,157).…”

In Vitro Generation of Plasmodium falciparum Ookinetes

“…Gametocytes had a surrounding erythrocyte membrane, whereas crosssections of ookinetes did not. 41,[49][50][51][52][53][54][55] Examination of erythrocyte-free elongated parasites showed definitive ookinete ultrastructure, including the apical complex and a pellicle, which was not observed in gametocytes ( Figure 5 ). The apical complex consists of an apical polar ring and micronemes.…”

“…NF54 is one of the 13 initial Nijmegen Falciparum (NF) isolates derived from a Dutch patient. [52][53][54] This strain was maintained in continuous asexual culture according to standard protocol 26 with the exception that no antibiotics were used in the complete medium: RPMI 1,640, 25 mM Hepes, 2 mM l-glutamine, 2.4 g/L NaHCO3, 50 mg/L hypoxanthine, and 10% heat-inactivated AB+ human serum (Interstate Blood Bank, Memphis, TN). Asynchronous asexual stage cultures at 8-15% parasitemia were used to start gametocyte cultures.…”

The biology of malarial parasite in the mosquito: a review

“…stephensi mosquitoes (Meis et al 1992b), confirming previous results observed with P. falciparum in naturally infected An. gambiae (Sinden & Strong 1978). Recent reports described an enhancement of oocyst development in vitro for P. berghei (Syaffruddin et al 1992), P. gallinaceum and P. falciparum (Warburg & Schneider, 1993), when insect cell lines were added into the culture medium.…”