Sporogonic Development of the Gregarine Ascogregarina taiwanensis (Lien and Levine) (Apicomplexa: Lecudinidae) in Its Natural Host Aedes albopictus (Skuse) (Diptera: Culicidae)

Abstract

ABSTRACT. Sexual reproduction of Ascogregarina taiwanensis occurred in pupal Malpighian tubules of its natural host Aedes albopictus, resulting in the formation of gametocysts within which oocysts developed. Sporogony proceeded in each newly formed unsporulated oocyst; eight sporozoites were formed after completion of nuclear divisions followed by the cytokinesis. Developing oocysts were separated by gradient centrifugation on percoll based on different buoyant densities. The slender sporozoite had a typical apical complex composed of a coiled conoid, polar rings, rhoptries with ductules, subpellicular microtubules and micronemes. An apical cavity was seen in the gland‐like rhoptries. Mitochondria of gregarines were not seen in any stage during the sporogony. Howeever, amylopectin granules were frequently seen in the cytoplasm. These starch‐related granules became scant when the sporozoite was formed. We assumed they were associated with the energy source. Since the apical complex was only present in the sporozoite stage, it was most likely related to the invasion of host epithelial cells of the midgut during the early phase of infection.

Fine structure of a septate gregarine trophozoite in the black tiger shrimp Penaeus monodon

“…from the frog Rana berlandieri (Desser & Weller 1973) and in Lankesteria culicis from the mosquito Aedes aegypti (Walsh & Callaway 1969). No typical mitochondria were observed in this gregarine species, but it is possible that they may exist in other forms (Landers 2002) or in other stages of development (Chen et al 1997). As regards the vesicles, features of their contents were similar to amylopectin as previously described in the gregarine Hemolivia mariae infecting the lizard Tiligua rugosa, and the clear feature in the vesicles may represent fat droplets.…”

Parasitism of Ascogregarina taiwanensis and Ascogregarina culicis (Apicomplexa: Lecudinidae) in larvae of Aedes albopictus and Aedes aegypti (Diptera: Culicidae) from Manaus, Amazon region, Brazil

“…Trophozoites grow and differentiate within the larval mid-gut, and gametocytes mature within the Malpighian tubules of pupae and adults. The production and fusion of gametes occur within the gametocytes (which produce oocysts), which produce eight sporozoites each (Chen et al, 1997a(Chen et al, , 1997bChen, 1999). Parasite dissemination depends on the oviposition behaviour of the infected female mosquito.…”

Apoptosis ofAscogregarina taiwanensis(Apicomplexa: Lecudinidae) which failed to migrate within its natural host

“…However, apoptosis may be beneficial to the parasite because cell death in response to limited resources may help promote the survival of genetically related individuals (James and Green, 2002). In addition, the Malpighian tubule lumen may not be large enough to endure the entry of all those trophozoites from which the numerous oocysts contained in large-sized gametocysts would ultimately form (Chen et al, 1997b). As a result, differential support of the survival of individual trophozoites may help optimize the parasite load within the host, indicating a form of social control of cell survival and cell death (Ameisen, 2002).…”

“…Preparation for electron microscopy followed a previously described method (Chen et al, 1997a;Chen et al, 1997b). In brief, dissected tissues (the midguts from both larvae and pupae) were fixed with 2% (v/v) glutaraldehyde in 0.1moll -1 cacodylate buffer for 2h at 4°C, washed with 0.2moll -1 cacodylate buffer three times, and then postfixed in 1% (w/v) osmium tetroxide in 0.1moll -1 cacodylate buffer for 2h at room temperature, finally washed three times with 0.2moll -1 cacodylate buffer and dehydrated through an ascending graded series of ethanol.…”

“…Development of the parasite is initiated upon entry of sporozoites released from the ingested oocysts into epithelial cells in the midgut of mosquito larvae (Chen et al, 1997a). After a short intracellular stage, sporozoites subsequently leave the invaded epithelial cells to form extracellular trophozoites that attach to the epithelium by their epimerites (Chen et al, 1997b). Such trophozoites are mostly found in the posterior part of the midgut in which vacuolar-type H + -ATPase (V-ATPase) is actively expressed (Huang et al, 2006).…”