Lipids of DDT-Resistant and Susceptible Larvae of Aedes aegypti

Abstract

No significant difference between DDT-resistant and susceptible strains of 3 different American stocks was found in total lipid or phospholipid content of the larvae. Two DDT-resistant strains of an Asiatic stock, one developed by malathion selection, contained 10%–25% more phospholipid than the susceptible strain, and the interstrain difference in the larval heads was even greater. However towards the end of the investigation the phospholipid content of the susceptible strain increased, to equal that of the resistant strains. Breakdown of phospholipid and total lipid was equally fast in the resistant and susceptible strains, both in DDT-contaminated and in distilled water. Isolated nerve cords of the 2 DDT-resistant Asiatic strains developed symptoms of DDT-poisoning as fast as the susceptible strain. The DDT-resistant strain developed by malathion pressure absorbed radioactive DDT one-half as fast, and retained twice as much DDT in the gut, as the susceptible strain. The principal fatty acid of neutral lipids and phospholipids in Aedes aegypti was palmitoleic acid; the principal phospholipid fraction was cephalin, as in other Diptera. No qualitative differences in the lipids and phospholipids were found between resistant and susceptible strains, except in one of the American stocks.