Effects of Temperature and Nutrition during the Larval Period on Life History Traits in an Invasive Malaria Vector Anopheles stephensi

SIMPLE SUMMARY: Anopheles stephensi is an Asian malaria vector, and it has recently been discovered in Africa since 2012 and is still likely to expand its distribution there. Anopheles stephensi differs from other African malaria vectors in that it breeds in artificial containers in urban areas. Therefore, there is concern that this mosquito may spread malaria to areas where malaria has not been known. We raised larvae under variable conditions and provided blood infected with Plasmodium berghei at a constant temperature of 19 °C, the optimum temperature for growth of P. berghei. As a result, the survival rate of adults was affected by temperature and nutrient conditions at the larval stage. None of the mosquitoes that were raised at a high temperature (32 °C) and low nutrition conditions at the larval stage became infected with P. berghei. Adults’ infection rate and their larval experience were independent. At higher temperatures, only better-fed mosquitoes survived long enough to become infected. Mosquitoes’ wing length reflects their larval environment. Higher temperatures may reduce infective A. stephensi; however, larger-sized individuals can still be infected. We suggest that wing length can be a useful indicator to predict malaria risk in the field. ABSTRACT: Anopheles stephensi is an Asian and Middle Eastern malaria vector, and it has recently spread to the African continent. It is needed to measure how the malaria parasite infection in A. stephensi is influenced by environmental factors to predict its expansion in a new environment. Effects of temperature and food conditions during larval periods on larval mortality, larval period, female wing size, egg production, egg size, adult longevity, and malaria infection rate were studied using a laboratory strain. Larval survival and female wing size were generally reduced when reared at higher temperatures and with a low food supply during the larval period. Egg production was not significantly affected by temperature during the larval period. Egg size was generally smaller in females reared at higher temperatures during the larval period. The infection rate of mosquitoes that fed on blood from malaria-infected mice was not affected by rearing temperature or food conditions during the larval period. Higher temperatures may reduce infection. A. stephensi; however, larger individuals can still be infective. We suggest that routinely recording the body size of adults in field surveys is effective in finding productive larval breeding sites and in predicting malaria risk.