The Effect of Egg Storage of Laboratory Reared Anopheles arabiensis (Diptera: Culicidae) on Egg Hatch Synchronisation, Pupation Success and Pupal Production Time

Abstract

Use of the sterile insect technique (SIT) targeting the malaria vector Anopheles arabiensis has been proposed and is currently under investigation. The SIT requires production of large numbers of sterile males and therefore mass-rearing of the target species is required. One critical factor during mass-rearing for sterile releases is the need to synchronise developmental life stages to assist in pupae and adult harvesting during production. However, by nature An. arabiensis egg hatching, and subsequent development is staggered as a survival strategy resulting in unsynchronised production. This causes a loss in efficiency during mass-rearing. This study aimed to investigate the effect of egg storage on egg hatch synchronisation, survival rate of aquatic life stages and the subsequent effect on production lead-time of a laboratory-reared An. arabiensis strain. Eggs from colonised An. arabiensis were collected, drained onto a filter paper to remove excess water, and stored for an increasing number of days, up to four days. After the storage time, proportion hatching and pupating as well as the time to hatch and pupation were measured and analysed using a one-way ANOVA and a Kaplan-Meier Survival analysis, respectively. No significant difference was observed in the proportion hatching or pupating between the different storage durations. However, there was a significant reduction in time to hatch and pupate. In conclusion, egg storage is a viable method to synchronise hatching, which could, in combination with other factors, assist in synchronous production of pupae for this strain without having adverse effects on survival.