Patterns and mechanisms of growth of fifth-instar Manduca sexta caterpillars following exposure to low- or high-protein food during early instars.
For many insect herbivores, variation in protein availability is a pervasive part of the environment. I explore how variable protein availability affects growth rates of fifth-instar Manduca sexta caterpillars and how growth is related to behavior and physiology. Groups of larvae were reared on low- or high-protein artificial diets (5.9% and 17.7% casein by dry weight, respectively) and then transferred in the fifth instar to the same or opposite diet. During or after the 24-h period following transfer, I measured growth rate, consumption rate, growth efficiency, midgut proteolytic activity, and masses of midgut contents and tissues. Fifth-instar caterpillars reared in earlier instars on high-protein diet grew about 20% more rapidly over 24 h than did caterpillars reared on low-protein diet. This growth pattern appears to be caused by differences in consumption and growth efficiency: caterpillars reared on high protein consumed more food, and used it more efficiently, than did caterpillars reared on low-protein diet. Over the short term (24 h), in contrast, fifth instars that received low-protein diet grew as rapidly as caterpillars that received high-protein diet. Increased (compensatory) consumption appears to be the primary mechanism by which caterpillars consuming low-protein food maintained growth rates.
Woods
H A
HA
Department of Zoology, University of Washington, Seattle, WA, 98195, USA. art.woods@asu.edu
D000222:Adaptation, Physiological; D000818:Animals; D004044:Dietary Proteins / Q000008:administration & dosage / Q000494:pharmacology; D004777:Environment; D007814:Larva / Q000254:growth & development; D018402:Manduca / Q000254:growth & development*
D004044:Dietary Proteins