Metabolism larvae

Hurst (19) discusses the similarity in action of the pyrethrins and of DDT as indicated by a dispersant action on the lipids of insect cuticle and internal tissue. He has developed an elaborate theory of contact insecticidal action but provides no experimental data. Hurst believes that the susceptibility to insecticides depends partially on the cuticular permeability, but more fundamentally on the effects on internal tissue receptors which control oxidative metabolism or oxidative enzyme systems. The access of pyrethrins to insects, for example, is facilitated by adsorption and storage in the lipophilic layers of the epicuticle. The epicuticle is to be regarded as a lipoprotein mosaic consisting of alternating patches of lipid and protein receptors which are sites of oxidase activity. Such a condition exists in both the hydrophilic type of cuticle found in larvae of Calliphora and Phormia and in the waxy cuticle of Tenebrio larvae. Hurst explains pyrethrinization as a preliminary narcosis or knockdown phase in which oxidase action is blocked by adsorption of the insecticide on the lipoprotein tissue components, followed by death when further dispersant action of the insecticide results in an irreversible increase in the phenoloxidase activity as a result of the displacement of protective lipids. This increase in phenoloxidase activity is accompanied by the accumulation of toxic quinoid metabolites in the blood and tissues—for example, O-quinones which would block substrate access to normal enzyme systems. The varying degrees of susceptibility shown by different insect species to an insecticide may be explainable not only in terms of differences in cuticle make-up but also as internal factors associated with the stability of oxidase systems. 

Urban, J.F. Jr and Douvres, F.W. (1981) In vitro development of Ascaris suum from third- to fourth-stage larvae and detection of metabolic antigens in multi-well culture systems. Journal of Parasitology 67, 800-806. 

Vanover, L. and Komuniecki, P.R. (1989) Effect of gas phase on carbohydrate metabolism of Ascaris suum larvae. Molecular Biochemical Parasitology 36, 29-40. 

Gatterdam, P.E., L.A. Wozniak, M.W. Bullock, G.L. Parks, and J.E. Boyd. 1967. Absorption, metabolism, and excretion of tritium-labeled famphur in the sheep and calf. Jour. Agricul. Food Chem. 15 845-853. Gingrich, R.E., O. Drummond, and W.J. Gladney. 1972. Use of white mice experimentally infested with larvae of a rodent hot fly for screening systemic insecticides. Jour. Econ. Entomol. 65 742-745. 

Cravedi, J.P., C. Gillet, and G. Monod. 1995. In vivo metabolism of pentachlorophenol and aniline in Arctic charr (Salvelinus alpinus L.) larvae. Bull. Environ. Contam. Toxicol. 54 711-716. 

Sediments and biota collected from the Hersey River, Michigan, in 1978, were heavily contaminated with phenanthrene, benz[a]anthracene, and benzo[a]pyrene when compared to a control site. Elevated PAH concentrations were recorded in sediments, whole insect larvae, crayfish muscle, and flesh of lampreys (family Petromyzontidae), brown trout (Salmo trutta), and white suckers (Catostomus commersoni), in that general order (Black et al. 1981). The polluted collection locale was the former site of a creosote wood preservation facility between 1902 and 1949, and, at the time of the study, received Reed City wastewater treatment plant effluent, described as an oily material with a naphthalene-like odor (Black et al. 1981). In San Francisco Bay, elevated PAH concentrations in fish livers reflected elevated sediment PAH concentrations (Stehr et al. 1997). In Chesapeake Bay, spot (Leiostomus xanthurus) collected from a PAH-contaminated tributary (up to 96 mg PAHs/kg DW sediment) had elevated cytochrome P-450 and EROD activity in liver and intestine microsomes (Van Veld et al. 1990). Intestinal P-450 activity was 80 to 100 times higher in fish from highly contaminated sites than in conspecifics from reference sites intestinal EROD activity had a similar trend. Liver P-450 and EROD activity was about 8 times higher in spot from the contaminated sites when compared to the reference sites. Liver P-450 activity correlated positively with sediment PAH, but intestinal P-450 activity seemed to reflect dietary exposure (Van Veld et al. 1990). The poor correlation between hepatic concentrations of PAHs and P-4501A is attributed to the rapid metabolism of these compounds (van der Weiden et al. 1994). 

When larvae were exposed to an equivalent concentration of radio-labeled naphthalene complexed with bovine serum albumin (BSA), the maximum value for accumulated metabolites was 21%. Radio-labeled naphthalene was almost entirely depurated in 24-36 hr, whereas metabolic products were strongly resistant to depuration... 

Little has been done to study phthalate ester metabolism in other individual species. Mosquito larvae and salt marsh caterpillar larvae, however, were each shown to transform dioctyl... 

Experiments in this study, done exclusively with midge larvae, include 1) 24-hr toxicity data for representative insecticides, with and without synergists 2) in vivo absorptive uptake and metabolic studies of aldrin and dieldrin, with and without piperonyl butoxide (PBO) 3) body depuration rate (loss to water) for dieldrin 4) determination of optimal in vitro... 

However, there are some potential effects of spilled oil on fish. The impacfs on fish are primarily to fhe eggs and larvae, wifh limited effecfs on fhe adulls. The sensitivity varies by species pink salmon fry are affected by exposure to water-soluble fractions of crnde oil, and pink salmon eggs are very tolerant to benzene and water-soluble petroleum. The general effects are difficnlt to assess and document quantitatively, dne to the seasonal and natural variability of the species. Fish rapidly metabolize aromatic hydrocarbons, due to their enzyme system. 

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