Effect of Temperature and pH on Egg Viability and Pupation of Anopheles arabiensis Patton (Diptera: Culicidae): Prospect for Optimizing Colony Reproduction Procedures

Abstract

Optimizing procedures for mass rearing mosquitoes for practices akin to the sterile insect techniques or routine laboratory activities is crucial. The present study evaluated the impact of nutrients, temperature, egg storage period and pH on egg hatchability and pupation rate, respectively, of Anopheles arabiensis mosquitoes. First, twenty eggs, collected from female mosquitoes and raised on different diet types (Rastrineobola argentea, Tetramin® Baby fish food and Bakers’ active yeast) in their larval stages, were stored at different time periods at two temperature regimes; 22 – 23OC and 28 – 29OC and later dispensed in plastic cups (4.0 cm top × 3.5 cm bottom × 2.7 cm height) containing 25cm3 of water and left to hatch. Secondly, twenty L4s were placed individually in 100 Ml of larval rearing media of different pH regimes in plastic cups (7.5 cm top × 5.0 cm bottom × 8 cm height) and left to pupate and emerge as adults. The media were of pH 6, 6.8 (clean borehole water), 7, 8, 9 and cow dung solution. It was found that eggs incubated at 28-29OC were less viable than those incubated at 22-23OC (p < 0.05). Eggs remained hatchable for 8 days. Mean pupation time for L4 larvae maintained in untreated tap water (pH 6.8) differed significantly compared to other rearing media (p p < 0.05). Mean pupation time was neither influenced by sex (p = 0.124) or size (p = 0.801) of emerged mosquitoes. It was concluded that pH (6.8) and temperatures of 22-23OC were optimal for pupation and egg hatchability, respectively.