HORIZONTAL TRANSMISSION AND SUBSEQUENT DEVELOPMENT OF AMBLYOSPORA-CALIFORNICA (MICROSPORIDA, AMBLYOSPORIDAE) IN THE INTERMEDIATE AND DEFINITIVE HOSTS

Amblyospora californica (type species) was transmiitted horizontally by feeding meiospores from larvae of Culex tarsalis (definitive host) to the copepod Macrocyclops albidus (a new intermediate host) and, conversely, by feeding spores produced in adult copepods to larval mosquitoes. Key features of the developmental sequence resulting from the 2 transmissions were demonstrated with both light and electron microscopy. Development in the copepod started with uninucleate sporoplasms from the ingested meiospores, included merogony by binary division of uninucleate meronts, sporogony by binary (usually) or multiple division and production of uninucleate-lanceolate spores within individual envelopes. Development in the mosquito began with uninucleate sporoplasms from the ingested lanceolate spores, included a first merogony (gametogony), plasmogamy, nuclear association, a second merogony and disporous sporulation with the production of Nosema-like spores in the adult female. This female represents a parental generation that transmits the infection transovarially (vertically) to male and female progeny. By combining results of this study with published data on development in filial generation mosquitoes, it was possible to outline the complete life cycle.