Horizontal transmission and subsequent development of Amblyospora californica (Microsporidia: Amblyosporidae) in the intermediate and definitive hosts

Abstract

Amblyospora californica (type species) was transmiitted horizontally byfeeding meiospores from larvae of Culex tarsalis (definitive host) tothe copepod Macrocyclops albidus (a new intermediate host) and,conversely, by feeding spores produced in adult copepods to larvalmosquitoes. Key features of the developmental sequence resulting fromthe 2 transmissions were demonstrated with both light and electronmicroscopy. Development in the copepod started with uninucleatesporoplasms from the ingested meiospores, included merogony by binarydivision of uninucleate meronts, sporogony by binary (usually) ormultiple division and production of uninucleate-lanceolate spores withinindividual envelopes. Development in the mosquito began with uninucleatesporoplasms from the ingested lanceolate spores, included a firstmerogony (gametogony), plasmogamy, nuclear association, a secondmerogony and disporous sporulation with the production of Nosema-likespores in the adult female. This female represents a parental generationthat transmits the infection transovarially (vertically) to male andfemale progeny. By combining results of this study with published dataon development in filial generation mosquitoes, it was possible tooutline the complete life cycle.