Meeting Abstract

P2.105  Thursday, Jan. 5  The effects of diet on the timing of larval molts in the tobacco hornworm, Manduca sexta. KEMIREMBE, K**; LIEBMANN, K.L.*; SMITH, W.A.; SUZUKI, Y; Wellesley College; Wellesley College; Northeastern University; Wellesley College

In insects, juvenile growth occurs by molting, in which the animal sheds its old skin and acquires a new one. It is known that the release of the steroid hormone, ecdysone, plays a key part in the initiation of the molt, but the signals that trigger the timing of its release remain poorly understood. Previous studies have shown that nutritional inputs influence the timing of a molt. In order to determine the role of diet on molt timing, fourth instar Manduca sexta were fed different diets lacking specific nutrients. Animals were monitored, weighed daily and sacrificed for dissection of the prothoracic gland, from which ecdysone is released. Animals fed amino acid-deficient diets failed to molt. All essential amino acids were discovered to be necessary for molting, although those animals fed diets lacking tryptophan were found to be capable of surviving for more than three times the usual instar duration. Rapamycin, an inhibitor of amino acid sensor target of rapamycin (TOR) signaling, was found to delay molting without dramatic retardation of growth. Furthermore, the growth of prothoracic gland was found to be particularly sensitive to nutritional intake. A model linking nutrients to the timing of a larval molt will be presented.