Research

Ovipositional periodicity of caged Anopheles gambiae individuals

Megan L Fritz¹ , Juan Huang¹ , Edward D Walker² , M Nabie Bayoh³ , John Vulule³ and James R Miller¹

¹  Department of Entomology, Michigan State University, 203 Center for Integrated Plant Systems, East Lansing, MI, 48824, USA

²  Department of Microbiology and Molecular Genetics, Michigan State University, 6169 Biomedical Physical Sciences Building, East Lansing, MI, 48824, USA

³  Centre for Global Health Research, Kenya Medical Research Institute (KEMRI), P.O. Box 1578, Kisumu, Kenya

author email corresponding author email

Journal of Circadian Rhythms 2008, 6:2doi:10.1186/1740-3391-6-2

Published:	25 January 2008

Abstract

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 suppressing A. gambiae populations. Here, we report on when during the diel cycle A. gambiae individuals 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 strain A. gambiae was determined by presenting hypergravid females with an ovipositional substrate exclusively between 1200 and 1600 h.

Results

On equatorial time, caged laboratory strain A. gambiae groups deposited 65% of their total eggs between 1800 and 0 h, and the remaining 35% were spread between 0 and 1000 h. Caged house-collected A. gambiae groups 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 individual A. gambiae females 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. gambiae females 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 individual A. gambiae oviposit 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.