School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA.
J Exp Biol. 2013 Dec 1;216(Pt 23):4334-40. doi: 10.1242/jeb.093120.
Rearing oxygen level is known to affect final body size in a variety of insects, but the physiological mechanisms by which oxygen affects size are incompletely understood. In Manduca sexta and Drosophila melanogaster, the larval size at which metamorphosis is initiated largely determines adult size, and metamorphosis is initiated when larvae attain a critical mass. We hypothesized that oxygen effects on final size might be mediated by oxygen effects on the critical weight and the ecdysone titers, which regulate growth rate and the timing of developmental transitions. Our results showed that oxygen affected critical weight, the basal ecdysone titers and the timing of the ecdysone peak, providing clear evidence that oxygen affected growth rate and developmental rate. Hypoxic third instar larvae (10% oxygen) exhibited a reduced critical weight, slower growth rate, delayed pupariation, elevated baseline ecdysone levels and a delayed ecdysone peak that occurred at a lower larval mass. Hyperoxic larvae exhibited increased basal ecdysone levels, but no change in critical weight compared with normoxic larvae and no significant change in timing of pupariation. Previous studies have shown that nutrition is crucial for regulating growth rate and the timing of developmental transitions. Here we show that oxygen level is one of multiple cues that together regulate adult size and the timing and dynamics of growth, developmental rate and ecdysone signaling.
已知饲养氧气水平会影响各种昆虫的最终体大小，但氧气影响大小的生理机制尚不完全清楚。在烟青虫和黑腹果蝇中，启动变态的幼虫大小在很大程度上决定了成虫大小，当幼虫达到临界质量时就会启动变态。我们假设，氧气对最终大小的影响可能是通过氧气对临界体重和蜕皮激素滴度的影响来介导的，蜕皮激素调节生长速度和发育转变的时间。我们的结果表明，氧气影响临界体重、基础蜕皮激素滴度和蜕皮激素峰值的时间，这为氧气影响生长速度和发育速度提供了明确的证据。低氧（10%氧气）的第三龄幼虫表现出临界体重降低、生长速度较慢、化蛹延迟、基础蜕皮激素水平升高以及蜕皮激素峰值出现在较低的幼虫质量。与常氧幼虫相比，高氧幼虫表现出基础蜕皮激素水平升高，但临界体重没有变化，化蛹时间也没有明显变化。先前的研究表明，营养对调节生长速度和发育转变的时间至关重要。在这里，我们表明，氧气水平是调节成虫大小以及生长、发育速度和蜕皮激素信号的时间和动态的多种线索之一。
