Meeting Abstract

P3.140  Sunday, Jan. 6  Diet-induced enlargement of the gastrointestinal tract increases nutrient absorption rates in locusts by allowing larger meals rather than better absorptive efficiency. CLISSOLD, F.J.*; BROWN, Z.; SIMPSON, S.J.; The Univ. of Sydney, Australia; The Univ. of Sydney, Australia; The Univ. of Sydney, Australia fiona.clissold@sydney.edu.au

Increasing the size of the gastrointestinal tract (GIT) is a plastic response commonly seen when animals feed on poor quality diets. This increase may simply function to permit larger meal sizes, but it has also been suggested that plastic growth of the GIT may serve as a means of rebalancing nutritionally imbalanced ingesta by allowing selective absorption of limiting nutrients. We determined the dietary conditions that induced GIT plasticity in an insect herbivore, the locust. In an insect herbivore, the migratory locust, a synthetic diet with a high ratio of protein to carbohydrate was found to induce weight enhancement of the GIT. Increases to the mass of the foregut and midgut caeca resulted in a similar, 20-30% increase in absorption rates of both protein and carbohydrate when feeding from three biomechanically and chemically different grasses. Greater net absorption of macronutrients occurred because these locusts ate meals that were larger, but transited at the same time and with the same digestive efficiency as in locusts where the GIT was unenhanced. Thus, volumetric plasticity of the GIT did not improve nutritional homeostasis, but increased the rate of nutrient uptake.