A. Ralph Barr

The ultrastructure and symbiotic relationships of Wolbachia of mosquitoes of the Aedes scutellaris group.

Although the ultrastructure of the wolbachiae in the Aedes scutellaris group is similar to that of Wolbachia pipientis, this study of the ultrastructure of wolbachiae in ovaries of Ae. cooki, Ae. polynesiensis, Ae. albopictus, Ae. riversi, and the Tafahi species revealed no virus-like particles. Crystalloids were found in abnormal wolbachiae from old nulliparous mosquitoes. The volume fraction of wolbachiae in nulliparous resting-stage oocytes was 2–3% in 4.5-day-old Aedes polynesiensis and 12–26% in 24.5-day-old adults of this species. The nurse cells of the scutellaris group (unlike those in Culex pipiens) are rarely infected. An association of wolbachiae with the spindle apparatus of dividing cystocytes and the rough endoplasmic reticulum of resting-stage oocytes was observed, although the relationship may have been fortuitous. Such associations may have significance in the development of symbiotic relationships.

The ultrastructure of the rickettsia-like microorganism Wolbachia pipientis and associated virus-like bodies in the mosquito Culex pipiens.

Details of the ultrastructure of Wolbachia pipientis (Rickettsiales: Wolbachieae) from the ovaries and testes of autogenous Culex pipiens (Diptera: Culicidae) are described. Although similar to the rickettsia and certain insect symbionts, W. pipientis exhibits a peculiar form of cell division. Particles resembling Bradleys (Bacteriol. Rev. 31, 230, 1967) type C bacteriophage in size, with a nucleoid similar to herpesvirus, are frequently encountered in wolbachiae that appear to be lysing. Mature virus particles possess a toroidal nucleoid and may have a short tailpiece; they are polyhedral in shape.

Wolbachia and the normal and incompatible eggs of Aedes polynesiensis (Diptera: Culicidae)

Abstract The development of eggs resulting from compatible and incompatible crosses of Aedes polynesiensis strains was studied. No difference was seen between newly laid compatible and incompatible eggs. Very little development occurs in most of the incompatible eggs; the eggs that develop mature but often produce abnormal embryos. Embryos developed in as many as 10% of the incompatible eggs and these developed into both males and females, which indicates that the surviving embryos were not parthenogenetic. In eggs infected with Wolbachia, the pole cells are infected at the time of formation and provide infection for the germ cells which develop later. Embryos that survive the incompatibility reaction and hatch from the egg develop normally.

Chromosomal evidence on the sporogony of Amblyospora californica (Microspora: Amblyosporidae) in Culex tarsalis (Diptera: Culicidae).

ABSTRACT. Amblyospora californica is a polymorphic, eukaryotic microsporidian. Three types of sporogony producing three types of spores occur in male larvae and female adults of its mosquito host, Culex tarsalis, and an alternate copepod host, Acanthocyclops vernalis. Development of A. californica in male larvae includes merogony and sporogony. Karyogamy and meiosis was observed in sporogony in male larvae but not in the female adult or in the copepod. Chromosomal evidence showed that sporogony included two consecutive meiotic divisions and a subsequent mitosis forming an octosporont, ultimately containing eight haploid, uninucleate mature spores. In this species, the haploid number of chromosomes is nine. Macrosporoblasts and macrospores, containing 1, 2 or more nuclei, can be seen in infected male larvae. The stage of sporogony in which cytokinesis was arrested seems to determine the number of nuclei. Those with only one nucleus, we believe are due to failed nuclear division at meiosis. Although A. californica displayed a process of karyogamy and meiosis similar to that of the species from Cx. salinarius, they may not be the same species because of the difference in their chromosome numbers.