How micronutrients influence the physiology of mosquitoes

Abstract

Micronutrients or non-energetic nutrients (NEN) are needed in reduced amounts, but are essential for many mosquito physiological processes that influence biological traits from vector competence to reproductive capacity. The NEN include amino acids (AA), vitamins, salts, metals and sterols. Free AA plays critical roles controlling most physiological processes, from digestion to reproduction. Particularly proline connects metabolic pathways in energy production, flight physiology and ammonia detoxification. Metal, in particular iron and calcium, salts, sterol and vitamin homeostasis are critical for cell signaling, respiration, metabolism and reproduction. Micronutrient homeostasis influence the symbiotic relationships with microorganisms, having important implications in mosquitoes' nutrition, physiology and behavior, as well as in mosquito immunity and vector competence.

Fig. 1. Amino acid effects on mosquito physiology

Digestion of hemoglobin releases free amino acids in the midgut lumen that act as signaling molecules for meal retention and protease synthesis. Increases in AA titers in hemolymph, together with an increase in 20E synthesis in ovaries, stimulate vitellogenin synthesis by the fat body. An increase in proline connects metabolic pathways in energy production, flight physiology and ammonia detoxification. AA: amino acids; 20E: 20-hydroxyecdysone; VG: vitellogenin.

Fig. 2. Iron effects on mosquito physiology

Digestion of hemoglobin releases heme and iron that promote lipid peroxidation and increases in free radical formation. Heme promotes the generation of xanthurenic acid that binds heme and iron. Iron increases upregulate the expression of antioxidant proteins, which block lipid peroxidation. Iron stimulates the proliferation of gut microbiota and increases ferritin titers in hemolymph. Most iron is eliminated in the feces; smaller amounts are incorporated into the eggs or stored in tissues. XA: xanthurenic acid.