Ovipositional periodicity of caged Anopheles gambiae individuals
DOI:
https://doi.org/10.1186/1740-3391-6-2Abstract
Background: Anopheles gambiae s.s. Giles is a major malaria vector in Sub-Saharan Africa. Studies of the basic biology of this mosquito, including oviposition, provide a background for assessing which attributes might be exploited for suppressingA. gambiaepopulations. Here, we report on when during the diel cycleA. gambiaeindividuals deposit eggs as compared to the ovipositional patterns of groups.Methods: Battery-powered wall clocks were modified so as to present a unique section of dark and wet ovipositional substrate at hourly intervals over two consecutive 12 h periods. Ovipositional periodicity of mosquito groups (Kisumu laboratory strain or feral females) and individuals was determined by counting the number of eggs present on each section of the ovipositional substrate. Capacity for mid-afternoon oviposition by groups of Kisumu laboratory strainA. gambiaewas determined by presenting hypergravid females with an ovipositional substrate exclusively between 1200 and 1600 h.
Results: On equatorial time, caged laboratory strainA. gambiaegroups deposited 65% of their total eggs between 1800 and 0 h, and the remaining 35% were spread between 0 and 1000 h. Caged house-collectedA. gambiaegroups deposited 74% of their total eggs between 1800 and 200 h, ceased oviposition for 3 h, and then spread the remaining 26% of their eggs near or after dawn. Ninety-six percent of individualA. gambiaefemales spread their eggs over a continuous 2–4 h period without interruption. In tests of capacity for mid-afternoon oviposition, females given evening access to an ovipositional resource deposited 2% of their total eggs between 1200 and 1700 h.A. gambiaefemales given only access to an ovipositional resource between 1200 and 1700 h deposited 3 times more eggs during that time period than did females previously given evening access.
Conclusion: Confined individualA. gambiaeoviposit in a single ca. 2–4 h continuous bout per 24 h. Oviposition is most probable in early scotophase, mid scotophase, or early photophase. However, some oviposition can occur at any hour during 24 h, especially if females were previously deprived of ovipositional substrate.
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