Esterase Isozymes in the Mosquito Culex pipiens fatigans.1 Developmental and Genetic Variation2

Abstract

An electrophorctic analysis of esterases in developing Culex pipiens fatigans Wiedemann (Diptera: Culicidae), showed characteristic zymogram patterns for each of the major stages of metamorphosis. However, little qualitativevariation was observed within each of the major stages. There was an increase in esterase activity as the larvae developed, and adult males and females were differentiated by 4 weak zones of esterase activity. A genetic study of the larval polymorphism for the Esterase E (Est E) zone indicated that this esterase was specified by a pair of autosomal alleles inherited without dominance: Est E^a and Est E^b. Homozygotes showed the slow-moving (Est E^a) or the fast-movingh and (Est E^b) only. Heterozygotes had both parental bands and in addition a hybrid enzyme band. The formation of the hybrid molecule suggests that the Est E variants in Culex exist as a dimer. However, in vivo and in vitro hybridization tests showed a deficiency in the enzyme activity of the hybrid molecule. A partial characterization of the Est E zone indicated that this enzyme is probably an ali-esterase.