QEIB: Gas Exchange Across Insect Eggshells

University Of Texas At Austin, Austin TX

Investigators

Abstract

Despite a large literature on insect eggshell morphology, little is known about the relationship between eggshell morphology and gas transport. This award will support the development of a mathematical model that explicitly connects gas flux to eggshell morphology. The equations will incorporate 6 - 8 of what appear a priori to be important eggshell morphological parameters. The model will then be solved numerically and used in two primary ways. (i) Sensitivity analyses will identify which morphological parameters have the strongest influence on gas flux. Subsequent morphological work on a common North American moth, Manduca sexta, will concentrate on getting the best measures of the most important parameters. (ii) Once the morphological parameters have been obtained, they will be used in conjunction with the model to predict total eggshell permeability to each of the three gases. These predictions will then be compared with direct measures of the permeability from other experimental work currently in progress. A good match will indicate that all significant factors affecting eggshell permeability have been accounted for and understood. A poor match will lead to additional mathematical and experimental work to identify the source of error (and in the process an important component of eggshell function). Thus, by design the mathematical and experimental progress will be iterative and co-dependent. The outcome will be a robust model that captures the essential elements of eggshell function. Such a model will be useful in a number of ways. (i) Many species, including Manduca sexta, have geographic ranges that span a variety of temperature and humidity conditions. The model will provide a tool for predicting how eggshell structure may vary intra-specifically across abiotic environmental gradients. (ii) Insects as a group exhibit spectacular diversity in eggshell form. The model will provide a way to predict how this morphological diversity affects permeability characteristics. (iii) An important methodology for controlling some crop pests, especially pests of stored-grains, is atmosphere manipulation. In conjunction with morphological data on eggs of pests species, the model will provide a way of evaluating atmosphere-based control strategies. (iv) Student training in mathematics and modeling is increasingly important in biology. The project provides an ideal vehicle for training students to think about the relationship between models and experimental work. The award will support a graduate student to participate in model development and parameterization, and it is highly likely that additional undergraduates will also participate.