Meeting Abstract

P2.181  Monday, Jan. 5  The importance of threshold size for the initiation of metamorphosis in the insect Tribolium castaneum PREUSS, K.M.*; NIJHOUT, H.F.; Duke University; Duke University kevin.preuss@duke.edu

Proper timing is critical for the initiation of metamorphosis because cessation of the larval developmental period determines the final body size of adult insects. Although many of the processes involved in metamorphosis have been well characterized, little is known about the timing of the initiation of metamorphosis. I used the red flour beetle, Tribolium castaneum, to investigate the initiation of metamorphosis. T. castaneum has a highly plastic larval developmental period, which can vary in length by over two weeks. Using different strains and varied nutritional conditions, I was able to document the existence of a threshold size, which determines when the larva becomes competent to metamorphose. Threshold size, however, does not dictate the exact timing of initiation. The exact timing for the initiation of metamorphosis is determined by a pulse of the molting hormone, ecdysone, but only after threshold size has been reached. Ecdysone pulses before the larva attains threshold size only cause the larva to molt to another larval instar. These results indicate the timing of metamorphosis initiation is controlled by two factors: (1) attainment of threshold size, at which the larva becomes competent to initiate metamorphosis and (2) the timing of an ecdysone pulse after attaining threshold size. Using these factors, I have developed a predictive model of the larval developmental period for T. castaneum.