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|Title:||Factors affecting the latent toxicity of aldrin, DDT, and heptachlor to resistant and susceptible strains of the house fly|
|Authors:||Sanchez, Fernando Flores|
|Keywords:||Insecticides -- Toxicology|
Flies -- Resistance to insecticides
|Abstract:||Latent toxicity is that phenomenon in which the full lethal effect of an insecticide applied to a larva is not apparent until it has differentiated into an adult. It was found that appreciable latent toxicity occurred when aldrin, heptachlor, and DDT were applied to larvae of a susceptible strain of the house fly, Musca domestica L., while little or no latent toxicity occurred when these insecticides were applied to a resistant strain. This study was undertaken to determine the effect of a number of factors on the latent toxicity of aldrin, DDT, and heptachlor to susceptible and resistant strains of the house fly. The factors investigated were: (1) rate of cuticular penetration of the insecticide; (2) rate of degradation of the insecticide in the insect body; and (3) amount of carry-over of the insecticide and/or its metabolites from the larval to the adult stage. The insecticides were topically applied to larvae of the resistant (Hawaiian) strain and the susceptible (SCR-60) strain of the house fly and their metabolism followed by the use of electron capture gas chromatography. It was found that aldrin and heptachlor were rapidly converted to their epoxides, dieldrin and heptachlor epoxide, respectively, while DDT was converted to the non-toxic metabolite dichlorodiphenyldichloroethylene (DOE). The rate of cuticular penetration of the three insecticides was somewhat faster with the susceptible than with the resistant strain. Resistance of the larvae of the Hawaiian strain to DDT is attributable to its rapid conversion to the non-toxic derivative DOE. No internal DDT was recovered from the Hawaiian strain at any time, indicating complete dehydrochlorination of all the DDT that penetrated. Measurable amounts of DDT could be recovered from the susceptible SCR-60 larvae one hour after topical application. The larvae of the SCR-60 strain were limited in their ability to detoxify DDT to DOE. The latent toxicity of DDT to the susceptible SCR-60 strain was due to the carry-over of sufficient amounts of unchanged DDT from the larval to the adult stage to cause mortality. in the flies shortly after emergence. The living flies contained very little DDT. There was no carry-over of DDT in the restant Hawaiian strain. Only DOE was found internally, indicating complete detoxification of the absorbed DDT. There was sufficient carry-over of dieldrin and heptachlor epoxide from the larva to the adult to account for the latent toxicity in the susceptible SCR-60 flies. The failure to elicit the phenomenon of latent toxicity by aldrin and heptachlor to the resistant strain is difficult to explain. The amount carried over to the adult stage was practically the same in both strains. Thus, it appears that the ability to convert aldrin and heptachlor to their corresponding epoxides cannot explain resistance or the latent toxicity of these two compounds. Latent mortality occurred only in the susceptible SCR-60 flies despite the comparable pattern of metabolism in the two strains. Also, the levels of dieldrin and heptachlor epoxide found in SCR-60 flies was practically the same in the living as in those that died of latent toxicity .|
Thesis (Ph. D.)--University of Hawaii, 1965.
Bibliography: leaves -54.
xi, 54 l mounted illus., tables
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|Appears in Collections:||Ph.D. - Entomology|
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