Dietary Sugars, Hemolymph Trehalose Levels, and Supernumerary Molting of Manduca sexta Larvae

Abstract

The influence of selected dietary factors on the prevention of starvation-induced supernumerary larval molt was studied. The incidence of supernumerary molting was greatly reduced when larvae were provided with sucrose during the starvation period. Neither casein nor a diet deficient only in sugar had such an effect. Among the various sugars tested, sucrose and fructose were the most effective in suppressing the supernumerary molt. Mannose and sorbose reduced supernumerary molting to a lesser extent. The percentage of larvae undergoing a supernumerary molt was inversely related to the concentration of sucrose, with 100% of those fed on 1% sucrose and 10% of those fed on 7% sucrose molting into sixth instars. The incidence of supernumerary molting was inversely correlated with hemolymph trehalose concentration but was not correlated with protein concentration. A hypothesis relating low hemolymph trehalose titers with activation of the brain-corpora allata system is proposed to explain the JH titer changes after starvation and during molting cycles.