Effects of Larval Nutrition, Adult Body Size, and Adult Temperature on the Ability of Anopheles gambiae (Diptera: Culicidae) to Melanize Sephadex Beads

A Plasmodium-refractory strain (L35) of the mosquito Anopheles gambiae Giles melanizes late ookinetes on the basal surface of the midgut, resulting in the death of the parasites. This strain also melanizes CM C-25 Sephadex beads, which serve as a model system for investigating the melanization response. The effects of larval nutrition, adult body size, and temperature of the adult environment on the ability of refractory females to melanize CM C-25 beads were studied. Nutritional deprivation during the larval stages significantly decreased the ability of adults to melanize beads. In addition, bead melanization decreased progressively as the environmental temperature of the adults increased from 24 to 30 degrees C. We conclude that environmental stress may affect the immune responses of An. gambiae.