Mono-Oxygenase Activity and Nutritional Ecology of Larvae of the Gypsy Moth, Lymantria Dispar
Anelli, Carol Madeline
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Permalink
https://hdl.handle.net/2142/71111
Description
Title
Mono-Oxygenase Activity and Nutritional Ecology of Larvae of the Gypsy Moth, Lymantria Dispar
Author(s)
Anelli, Carol Madeline
Issue Date
1988
Department of Study
Entomology
Discipline
Entomology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Entomology
Abstract
Although considered to be polyphagous herbivores, larvae of the gypsy moth, Lymantria dispar, exhibit certain host plant preferences: oak species are favored by all larval instars; pine may serve as an alternate host for older instar larvae, but first instar larvae suffer 100% mortality on pine (Barbosa et al., 1986). Since pine contains high concentrations of potentially toxic terpenoids, we hypothesized that older instar larvae have inducible mono-oxygenases (MFOs) that can detoxify pine terpenoids. To test this hypothesis, NADPH oxidase and O-demethylase specific activities were determined using midgut microsomes from gypsy moth and other polyphagous, lepidopterous larvae fed foliage or artificial diets containing MFO inducers ($\alpha$-pinene or pentamethylbenzene). Our results indicate that basal MFO activity levels are relatively low in gypsy moth larvae, and that ingestion of pine foliage or inducer-containing diets has little or no effect on gypsy moth MFO activity. To investigate whether gypsy moth performance differs on oak vs. pine foliage, quantitative nutritional indices were measured for 3rd instar larvae. Significant trends were evident: Efficiency of conversion of digested food is higher in oak vs. pine fed larvae, but pine feeders have higher relative consumption rates than do oak feeders. Larval relative growth rate (RGR) varies with plant phenology, such that RGR is higher in larvae fed early season oak vs. pine, but this relationship is reversed with late season foliage feeders. Lower RGR on late season oak vs. pine is not attributable to lower foliar nitrogen, since oak contains more N per dry weight than does pine; however, foliar water content is higher in late season pine compared with oak. Use of a model system, in which larvae were reared on artificial diets prepared from lyophilized oak or pine foliage, permitted quantitative manipulation of dietary N levels. Larval nutritional indices, development rates and pupal weights from these experiments suggest that dietary N content per se does not account for larval performance on oak vs. pine. Results of parallel experiments with the natural and model systems indicate that poor RGR is correlated with both lower larval percent dry weight and diminished larval lipid content. Thus, larvae fed a poor quality food may incur increased metabolic costs and decreased lipid stores.
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