A comparative genetical study of DDT resistance in adults and larvae of the mosquito Aedes aegypti L

Inheritance of DDT resistance has been studied in crosses between the highly resistant ‘T’ strain ofA. aegypti(constituted by inbreeding from the TRINIDAD DDT-resistant stock) and the ‘64’ susceptible strain.

Larval DDT resistance derives from a major geneRDDT1on linkage group II, the order beingRDDT1–s–y. Linkage group III may also contribute to larval resistance. Linkage group I makes no contribution.

Adult DDT resistance derives from a major geneRDDT2, 18·2 ± 2·1 units from the marketblton linkage group III. Linkage group II has no influence on adult resistance.

Selection with DDT to retain onlyRDDT1/+ segregants in larvae of backcrossesRDDT1/+×+/+ did not increase resistance in resulting adults, confirming the difference in genetic mechanism at the two stages.

The F1progenies from reciprocal crosses between ‘T’ and ‘64’ differed slightly but significantly in larval resistance, modifying the influence of the major geneRDDT1in the heterozygote.

The early developmental stages of theRDDT1/+ phenotype (up to the fourth larval stage) were more viable than the +/+ phenotype in backcross segregation. The difference in mortality probably exceeded 30%.

Nicotinamide-adenine dinucleotide phosphate enzymes in the mosquito during growth and aging

1. Optimum conditions were established for determining the activities of the NADP(+)-linked enzymes, glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and isocitrate dehydrogenase, in mosquito tissues. 2. The activity of each dehydrogenase was determined in samples of mosquitoes of different ages throughout the life-span. The specific-activity curves attained maximal values in the pupal or early adult period. From these maxima an 81% decrease in glucose 6-phosphate-dehydrogenase and 67% decrease in 6-phosphogluconate-dehydrogenase activities occurred after the tenth day of adult life; a 77% decrease in isocitrate-dehydrogenase activity occurred before the fifth day. 3. The activity differences were found in different body regions as well as in whole organisms. 4. Starvation of the larva or adult did not result in decreases in enzyme activity. 5. These findings support the hypothesis that the activities of enzymes that form NADPH are related to the biosynthetic activity, for the enzyme activities increased during the period of cellular growth and decreased during the aging period.

Effects of high-intensity light flashes on mortality and reproduction of Aedes aegypti (L.) (Diptera: Culicidae)

Dose/effect relationships for radiant energy from high-intensity flash discharges causing mortality and sterility in male and female adults of Aedes aegypti (L.) were established. The rate of progression of effect changed markedly at a particular stage of the voltage range used. This is attributed to a change in the wavelength content of the light emitted at the higher voltages.