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Mathematical modeling of digestion modulation in grasshoppers
We develop a phenomenological model for insect digestion and gustatory responsiveness using chemical reactor models for the digestive structures with feedbacks from nutrient titers in the hemolymph. The model provides explanatory links between foraging and digestion. We first consider the case of a single substrate-enzyme reaction and show that digestion, modified by temperature, is an important rate-limiting step in nutrient acquisition. We allow for external temperature effects, variable food quality, and random foraging times. ^ The model is further developed to include multi-dimensional nutrient space and uses the concepts of nutrient targets and nutrient rails to define the nutritional status and requirements of the insect. We introduce control variables to simulate both pre- and post-ingestive compensatory behavior that insects exhibit when feeding on a single suboptimal food. The control variables act to shorten intermeal intervals, and to limit the absorption of nutrients that occur in excessive concentrations in the hemolymph. ^ In both the single and multi-dimensional cases we use numerical simulations to make qualitative and quantitative predictions of intermeal behavior, as well as substrate and nutrient concentrations in the digestive structures (crop, midgut, and hemolymph system). The model makes strong inferences about the regulatory role that temperature has on digestion and foraging behavior. The models are developed primarily for grasshoppers and locusts, but many of the results apply to insects in general. ^
Biology, Biostatistics|Biology, Ecology|Biology, Entomology|Biology, Animal Physiology|Biology, Zoology
Wolesensky, William Robert, "Mathematical modeling of digestion modulation in grasshoppers" (2002). ETD collection for University of Nebraska - Lincoln. AAI3074110.