Wolbachia sp. (Rickettsiales: Rickettsiaceae) a symbiont of the almond moth,Ephestia cautella: Ultrastructure and influence on host fertility

Wolbachia sp. is a maternally inherited symbiont of the almond moth, Ephestia cautella. It is transmitted through the cytoplasm of the egg and occurs normally in the gonads of all stages of the moth. The symbiont is responsible for reproductive cytoplasmic incompatibility between crosses of experimental laboratory strains of aposymbiotic female moths and symbiotic (normal) males. Although female moths were inseminated in laboratory tests, their eggs failed to hatch and exhibited no signs of embryonic development. The reciprocal cross, i.e., symbiotic female months × aposymbiotic males, produced normal progeny.The ultrastructure of Wolbachia was studied in sections of E. cautella larval testes. Symbionts, minute rod-shaped structures, were abundant in the cytoplasm of hypertrophied spermatids. There was no indication of deleterious influence of symbionts on sperm production or activity. Strains of Wolbachia occur in allopatric populations of insects where they may function as a genetic isolation mechanism. Microorganismal reproductive incompatibility has been suggested as a possible approach for insect control.