Balanced amino acid composition essential for infusion-induced egg development in the mosquito ( Culex pipiens pallens)

Abstract

Amino acid mixtures, in which one or more amino acids were omitted from a basal mixture of 17 amino acids, were infused into the hemocoels of female Culex pipiens pallens mosquitoes. The resulting oögenesis was compared with previous studies of oögenesis induced by the basal mixture to evaluate the oögenic stimulatory effect of individual amino acids. Infusion of solutions deficient in isoleucine, leucine, lysine, phenylalanine, threonine, tryptophan or valine, which are known to be absolutely essential for producing mature eggs, failed even to initiate oögenesis. Removal of arginine (also absolutely essential for egg production), cysteine, histidine or methionine from the basal mixture resulted in decreased activation of oögenesis. Single elimination of other amino acids (alanine, glycine, proline and serine) resulted in high percentages of oögenesis and egg maturation, comparable to the levels produced by basal mixture infusion. The combination of asparagine and glutamine, which were reported to increase in the hemolymph of blood-fed females, can be substituted for asparagine and glutamate in the basal mixture to give a high level of oögenesis. On the other hand, infusion of a mixture comprised of the eight amino acids absolutely essential for egg production showed only a slight stimulation of oögenesis initiation. Single amino acid infusion of isoleucine or threonine also failed to stimulate mosquito oögenesis. Thus, we have concluded that initiation of mosquito oögenesis requires an appropriate balance in increased hemolymph amino acids rather than just one or a few special trigger amino acids.