NEW FINDINGS ON THE DEVELOPMENTAL PROCESS OF ASCOGREGARINA TAIWANENSIS AND ASCOGREGARINA CULICIS IN AEDES ALBOPICTUS AND AEDES AEGYPTI

Abstract

Infection in different stages of larvae of Aedes aegypti and Ae. albopictus with Ascogregarina taiwanensis and A. culicis, respectively, revealed that the oocysts of Ascogregarina spp. are able to infect any instar and can complete their life cycle within 9.5 +/- 1 days. When early instars ingested oocysts, parasite development was synchronized to larval-pupal ecdysis and oocyst dissemination occurred at the time of adult emergence, oviposition, or both. The parasites also developed normally when infecting 2nd, 3rd, and early 4th instars and oocysts were released only during oviposition. The parasitic development stopped at the gamont stage when oocysts were ingested by late 4th instars (6 days old). The release of sporozoites in the midgut of any larval stage started within 45 min of oocyst ingestion. About 98% of oocysts of both A. taiwanensis and A. culicis were emptied within 2-3 h of their ingestion in their respective hosts. The oocysts of both species remained viable on desiccated filter paper stored at 27 degrees C and 65 +/- 5% relative humidity, indicating that the oocysts were resistant to dryness. The oocysts of A. culicis could survive up to 6 months, whereas those of A. taiwanensis survived up to 4 months. These biological characteristics relating to parasite development might enhance the distribution of Ascogregarina spp. widely in nature and facilitate the species to be considered for biological control of Aedes mosquitoes in the future.