Amblyospora connecticus sp. nov. (Microsporida: Amblyosporidae): Horizontal transmission studies in the mosquito Aedes cantator and formal description

Abstract

The morphology, development, and ultrastructure of an Amblyospora (Microsporida) species parasitic in the salt marsh mosquito, Aedes cantator, were investigated following horizontal transmission of infection from the intermediate copepod host, Acanthocyclops vernalis. Infections were readily transmitted to A. cantator in the laboratory when larvae were allowed to feed on spores harvested from A. vernalis. The microsporidium was observed to initially invade the midgut and gastric caeca of host larvae and then spread to the muscles, oenocytes, and Malpighian tubules. It divides by binary fission within these host tissues and produces uninucleated gametes that undergo plasmogamy to form diplokaryotic stages in adult hosts. Diplokaryotic sporonts sporulate in adult female hosts only when a blood meal is taken and this results in the formation of binucleated spores that are responsible for transovarial transmission to the next host mosquito generation. Quantitative studies show that male mosquito hosts are more susceptible and develop more progressive infections than females. However, the microsporidium never sporulates in males and the fate and function of these infections in male hosts remain unknown. A new species, Amblyospora connecticus, is proposed for this isolate and a formal taxonomic description is given based on its entire life cycle in both hosts.