Marquess, Richelle Renee (2016-12). The Role of Food Protein-Carbohydrate Content on Nutrient Regulation Strategies and Wing Morph Determination in the Wing Polymorphic Cricket Gryllus firmus. Master's Thesis.
Thesis
Field crickets in the genus Gryllus are wing polymorphic and have been used for many years as a model for trade-offs between dispersal and reproduction. There are two main morphs of adult crickets. The first has long hindwings but small ovaries and is capable of flight while the other has short hindwings and cannot fly but has much larger ovaries and therefore higher reproduction. This trade-off is well studied in adult crickets but very little work of any sort has been done with the nymphs. Previous studies have shown that the morph the nymphs will become is influenced by their genetics as well as environmental cues such as population density. The experiments in this thesis examine how the nymphs regulate their protein and carbohydrate intake and the extent to which food protein and carbohydrate content influences wing morph determination. Two experiments, using three cricket lines, were used. Two of these lines were selected to produce either long winged or short winged individuals; the third line was unselected and representative of field populations. First a choice experiment was conducted to determine the protein:carbohydrate (P:C) ratio nymphs from the different lines self-selected. The second experiment was a no-choice experiment that tested how the nymphs from the different lines regulated their protein-carbohydrate intake when they were restricted to a single diet as well as how those diets affected their performance and final wing morph. The results from these experiments are compared to nutrient regulation strategies in the adults of each morph, and discussed within the context of how food protein-carbohydrate content influences wing morph determination.
