Size as a Proxy for Survival in Aedes aegypti (Diptera: Culicidae) Mosquitoes

Abstract

The Aedes aegypti mosquito is the primary vector of dengue, yellow fever, chikungunya, and Zika viruses. Infection with the dengue virus alone occurs in an estimated 400 million people each year. Likelihood of infection with a virus transmitted by Ae. aegypti is most commonly attributed to abundance of the mosquito. However, the Arizona-Sonora desert region has abundant Ae. aegypti in most urban areas, yet local transmission of these arboviruses has not been reported in many of these cities. Previous work examined the role of differential Ae. aegypti longevity as a potential explanation for these discrepancies in transmission. To determine factors that were associated with Ae. aegypti longevity in the region, we collected eggs from ovitraps in Tucson, AZ and reared them under multiple experimental conditions in the laboratory to examine the relative impact of temperature and crowding during development, body size, fecundity, and relative humidity during the adult stage. Of the variables studied, we found that the combination of temperature during development, relative humidity, and body size produced the best model to explain variation in age at death. El mosquito Aedes aegypti es el vector primario de los virus de dengue, fiebre amarilla, chikungunya y Zika. Solamente las infecciones con los virus de dengue ocurren en aproximadamente 400 millones de personas cada año. La probabilidad de infección con un virus transmitido por Ae. aegypti es frecuentemente atribuido a la abundancia del mosquito. No obstante, la región del desierto de Arizona-Sonora tiene una abundancia de Ae. aegypti en la mayoría de las áreas urbanas, pero la transmisión local de estos arbovirus no ha sido reportada en muchas de estas ciudades. Trabajos previos han examinado el rol de las diferencias de longevidad en Ae. aegypti como explicación potencial por estas discrepancias en la transmisión. Para determinar que factores fueron asociados con longevidad en Ae. aegypti en la región, colectamos huevos de ovitrampas en Tucson, Arizona y los criamos debajo de múltiples condiciones experimentales en el laboratorio para examinar el impacto relativo de temperatura y competencia para nutrición durante desarrollo, tamaño del cuerpo, capacidad reproductiva, y humedad relativa durante adultez. De las variables estudiados, encontramos que la combinación de temperatura durante desarrollo, humedad relativa, y tamaño del cuerpo produjo el mejor modelo para explicar variación en edad al tiempo de la muerte.

Keywords: Aedes aegypti; body size; longevity.

Fig. 1.

Nested treatment conditions during development.

Fig. 2.

Nested treatment conditions during adulthood.

Fig. 3.

Age at death by average temperature during development.

Fig. 4.

Path analysis of direct and indirect effects on age at death. Path values are standardized regression coefficients. Solid lines signify significant relationships, dashed lines are insignificant pathways that were omitted from the final analyses. *P < 0.05, **P < 0.01, ***P < 0.001 n.s. = Nonsignificant effect. (A) Shows all factors for explaining age at death in one model (AIC = 1,122.23, r² = 0.15). (B) shows the model with insignificant relationships omitted, such as those between crowding and age at death, and the development time and age at death. This model had the lowest AIC score (AIC = 1,108.11, r² = 0.15).