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|Title:||Dietary Self-Selection by the Corn Earworm, Heliothis Zea: Testing the Malaise Hypothesis|
|Author(s):||Schiff, Nathan Mark|
|Doctoral Committee Chair(s):||Waldbauer, G.P.; Friedman, Stanley,|
|Department / Program:||Entomology|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
Agriculture, Plant Culture
|Abstract:||When last instar H. zea larvae were presented with two diets that were nutritionally complete except that one lacked protein and the other lacked utilizable carbohydrate, they self-selected a complete diet. Two alternative hypotheses have been developed to explain this self-selection behavior: first, the Malaise Hypothesis, which states that a metabolic upset is caused by a dietary deficiency and is relieved by a metabolic feedback produced when the missing nutrient(s) is eaten; second, a taste hypothesis which states that the larva has an innnate desire to eat the appropriate nutrients, each of which it detects by chemosensory stimuli. These hypotheses were tested by offering larvae the chance to self-select for a carbohydrate that is stimulating but non-utilizable and one that is non-stimulating but readily utilizable.
Several carbohydrates were tested to determine both their ability to stimulate biting, and their utilizability to larvae. Sucrose and fructose were both stimulating and utilizable. Sorbose was stimulating but non-utilizable, and mannitol was not stimulating but readily utilizable.
Sorbose was not selected for, eliminating the taste hypothesis. Mannitol was selected for in four different experiments. First, larvae offered a mixture of sorbose and mannitol ate more mannitol, per se, than when offered a diet that contained mannitol alone. Second, larvae were offered two protein diets that were equally stimulating because they contained the same amount of protein but one was more utilizable because it contained mannitol. Larvae ate significantly more from the mannitol containing diet. Third, when larvae were offered diets with high concentrations of sucrose their response was to reduce their volume of diet eaten. Larvae offered a similar series of diets with a fixed low concentration of sucrose that was progressively increased by the addition of mannitol, also reduced their volume eaten. Finally, larvae offered a diet with a reduced concentration of sucrose responded by increasing protein consumption. If mannitol was substituted for some of the sucrose there was no increase in protein consumption. Because larvae selected for mannitol, which is not stimulating, as they did for sucrose, they must have responded to the mannitol metabolically thus supporting the malaise hypothesis.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1988.
|Date Available in IDEALS:||2014-12-16|