ARS | Publication request: EVOLVING LIFE CYCLES OF COMPLEX MICROSPORIDIA IN MOSQUITOES

Submitted to: Meeting Abstract
Publication Type: Abstract
Publication Acceptance Date: August 6, 2006
Publication Date: N/A

Technical Abstract: Polymorphic microsporidia in mosquitoes are characterized by intricate life cycles involving multiple spore types responsible for horizontal (per os) and vertical (transovarial) transmission. They affect two generations of the mosquito and some involve an obligate copepod intermediate host. Polymorphic microsporidia are generally very host and tissue specific with complex developmental sequences comprised of unique stages and events. Amblyospora californica, a parasite of Culex tarsalis, has developmental sequences in larvae that involve gametogony followed by plasmogamy and nuclear association to form diplokarya. These diplokaryotic stages then form binucleate spores responsible for transovarial transmission in adult mosquitoes. In the filial generation, haplosis is by meiosis to produce spores infectious for a copepod intermediate host. A third spore type is formed in the intermediate host responsible for infection in a new generation of the mosquito host. Edhazardia aedis a parasite of Aedes aegypti and Culicospora magna, a parasite of Culex restuans, have similar developmental sequences in larvae and adults except that haplosis occurs as a result of nuclear dissociation to produce uninucleate spores directly infectious to larval mosquitoes without the involvement of a copepod host. Edhazardia aedis undergoes an additional sporulation sequence that involves meiosis but this process aborts and does not form functional meiospores. This apparent shift in the mechanism of haplosis from meiosis to nuclear dissociation, with E. aedis as an intermediate form, may represent an example of regressive evolution wherein microsporidia in multivoltine mosquitoes with overlapping generations may be evolving away from meiosis and two host systems to simpler, more efficient one host systems.