Meeting Abstract
In insects, fitness tradeoffs exist between maximizing body size and developmental speed. In the tobacco hornworm, Manduca sexta, growth is dependent on two size assessment points, the critical weight and the threshold weight. In Drosophila, the insulin/TOR signaling pathway has been shown to affect metamorphic timing and the size-assessment point. In this study, insulin/TOR signaling was inhibited by feeding rapamycin to JH-deficient and wild type Manduca larvae. Critical weight was not affected by rapamycin treatments although the final body size was significantly increased in rapamycin-treated JH-deficient larvae. Our study demonstrates that both a nutrient sensitive pathway, mediated by insulin/TOR pathway, and a size sensing pathway, mediated by the JH pathway, exists in Manduca, and that JH overrides the role of insulin/TOR signaling to maximize body size. The mechanism underlying the threshold weight is presently under investigation.
