Cellular and molecular mechanisms of ion transport and excretion in insect and crustaceans

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This research examines how transporting epithelia excrete toxins and regulate the levels of water, ions, acids and bases within insects and crustaceans. Epithelia are layers of cells which form a barrier between two compartments, and which transport materials such as inorganic salts (sodium, chloride, etc.) and water between one fluid-filled compartment, often external, and a second internal compartment. Examples of fluids in external compartments include water flowing over the gills of an aquatic species, the contents of the digestive tract, and urine or blood filtrate contained within the excretory system. Examples of fluids in 'internal' compartments include the blood and extracellular fluids which transport nutrients to or from the gut and excretory system. The activities of epithelia which secrete or reabsorb ions, nutrients, waste materials, toxins or water from particular compartments can be controlled by hormones released into the circulatory system. The hormones bind to receptors in cell membranes and activate intracellular second messenger systems. This cascade of signaling often leads to activation of membrane proteins which transport particular ions. Research into the mechanisms and control of transporting epithelia in insects provides three benefits: 1) Knowledge of the cellular mechanisms and hormonal control of transporting epithelia in pest species of insect facilitates rational design of novel and environmentally-benign control measures. For example, understanding the mechanisms of excretion of toxic materials by epithelia aids development of compounds which block such excretion in pest insects. 2) Understanding the mechanisms of transporting epithelia is central to understanding how insects and crustaceans adapt to different environments, and how natural or man-made changes (e.g. environmental pollution) may have deleterious effects on these animals. 3) Epithelial tissues of insects and crustaceans provide useful model systems for understanding the cellular mechanisms of excretion and ion transport. The use of genetically well-characterized species, such as the fruit fly, allows us to examine the effects of mutations in genes controlling the expression of specific epithelial transporters.