~ 28 ~ International Journal of Mosquito Research 2014; 1 (2): 28-34 ISSN: 2348-5906 CODEN: IJMRK2 IJMR 2014; 1 (2): 28-34 © 2014 IJMR Received: 23-03-2014 Accepted: 25-04-2014 Albert O. Mala (a)Human Health Division, International Centre of Insect Physiology and Ecology, P.O. Box 30772-00100, Nairobi, Kenya. (b)College of Health Sciences, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya. P.O. Box 62000-00100, Nairobi, Kenya. Lucy W. Irungu College of Biological and Physical Sciences, School of Biological Sciences, University of Nairobi, Kenya. Email: lirungu@uonbi.ac.ke Elizabeth K. Mitaki College of Health Sciences, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya. P.O. Box 62000-00100, Nairobi, Kenya. Email: mitakielizabeth@gmail.com Josephat I. Shililu Human Health Division, International Centre of Insect Physiology and Ecology, P.O. Box 30772-00100, Nairobi, Kenya Email: jshililu@yahoo.com Charles M. Mbogo Centre for Geographic Medicine Research Coast, Kenya Medical Research Institute, P.O. Box 230 Kilifi 80108, Kenya Email: cmbogo@kemri-wellcome.org Joseph K. Njagi Malaria Control Unit (MCU) Ministry of Health P.O. Box 20750, Nairobi Email: knjagi@domc.or.ke John I. Githure Human Health Division, International Centre of Insect Physiology and Ecology, P.O. Box 30772-00100, Nairobi, Kenya. Email: jgithure@icipe.org. For Correspondence: Albert O. Mala a)Human Health Division, International, Centre of Insect Physiology and Ecology, P.O. Box 30772-00100, Nairobi, Kenya. (b)College of Health Sciences, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya. P.O. Box 62000-00100, Nairobi, Kenya. Email: amala@jkuat.ac.ke Gonotrophic cycle duration, fecundity and parity of Anopheles gambiae complex mosquitoes during an extended period of dry weather in a semi arid area in Baringo County, Kenya Albert O. Mala, Lucy W. Irungu, Elizabeth K. Mitaki, Josephat I. Shililu, Charles M. Mbogo, Joseph K. Njagi, John I. Githure ABSTRACT An entomological longitudinal survey was carried out over a 22 month period in two semi-arid villages in Baringo District in Kenya to study how adult malaria vectors survive under semi-arid conditions and during extended periods of dry weather. Methods: Wild caught female mosquitoes were dissected to examine ovarian lobes for parity status and to determine number of gonotrophic cycles they had undergone. Duration of the first and second gonotrophic cycles were estimated using cage-reared F1 females. Blood-fed females were kept individually in plastic vials and percent oviposition incidence recorded. Results: Significantly fewer mosquitoes laid eggs during the dry than the wet season. The average duration of the first gonotrophic cycle in the wet season was 4.1 d after blood feeding, 1.1 d (36%) longer than the dry season (3.0 d). The average duration of the second gonotrophic cycle in the wet season was 2.9 d after second blood meal, 0.7 d (31.8%) longer than those in the dry season. Chi-square tests showed the gonotrophic cycle duration was significantly shorter during the dry than the wet season. Both gonotrophic cycle duration and physiological age varied significantly between wet and dry seasons. Conclusion: These findings suggest the duration of gonotrophic cycle among Anopheles gambiae in dry lands with scarce breeding sites is shorter during the dry than wet season. Low fecundity rates during the dry season could be a sign of reduced reproductive activity. However lack of variation in seasonal mating frequency is a clear indication that oviposition and mating kinetics are influenced differently even under the same environmental conditions. It is likely that the results of this study will shed an understanding on spatial and temporal heterogeneities experienced in malaria transmission in semi-arid regions of the world where malaria and indeed mosquito-borne diseases are a public health menace. Keywords: Anopheles gambiae, Gonotrophic cycle duration, fecundity, mating behavior. 1. Introduction Semi-arid areas experience deficits of rain accompanied by high temperatures during dry seasons and extended periods of dry weather. It is observed that the abundance of the malaria vector species drops dramatically with the onset of the dry season, and this may depress the incidence of severe malaria [1, 2] . The onset of the rains, however, brings a rapid explosion in mosquito numbers and a concomitant increase in malaria [3, 4] . Data on the Anophelinae are not conclusive with respect to how each life stage contributes to long-term survival in semi-arid conditions and the rapid population rise that occurs following the onset of the rains. Contributions to long-term survival during the dry season and in semiarid zones could be made during the egg, larval, and/or adult (including pupal) stages. Adult stages make an important contribution to dry season/ semi-arid population dynamics. Small changes in the temperature of malaria vector resting sites in the relatively hot semi-arid areas may have a significant impact on the kinetics of mosquito blood digestion and consequently in their overall breeding ecology [5] . Subsequently, effects may be seen on population reproduction rates through changes in the duration of the gonotrophic cycle. Mosquito vectors require blood meals for egg development, and the rate of digestion of these blood meals is normally directly proportional to increase in temperature.