Department of Biological Sciences, North Dakota State University, Fargo, ND 58108-6050;
Agricultural Research Service-Insect Genetics and Biochemistry, Red River Valley Agricultural Research Center, United States Department of Agriculture, Fargo, ND 58102.
Proc Natl Acad Sci U S A. 2017 Oct 10;114(41):10924-10929. doi: 10.1073/pnas.1703008114. Epub 2017 Sep 25.
Body size is an important phenotypic trait that correlates with performance and fitness. For determinate growing insects, body size variation is determined by growth rate and the mechanisms that stop growth at the end of juvenile growth. Endocrine mechanisms regulate growth cessation, and their relative timing along development shapes phenotypic variation in body size and development time. Larval insects are generally hypothesized to initiate metamorphosis once they attain a critical weight. However, the mechanisms underlying the critical weight have not been resolved even for well-studied insect species. More importantly, critical weights may or may not be generalizable across species. In this study, we characterized the developmental aspects of size regulation in the solitary bee, We demonstrate that starvation cues metamorphosis in and that a critical weight does not exist in this species. Larvae initiated pupation <24 h after food was absent. However, even larvae fed ad libitum eventually underwent metamorphosis, suggesting that some secondary mechanism regulates metamorphosis when provisions are not completely consumed. We show that metamorphosis could be induced by precocene treatment in the presence of food, which suggests that this decision is regulated through juvenile hormone signaling. Removing food at different larval masses produced a 10-fold difference in mass between smallest and largest adults. We discuss the implications of body size variation for insect species that are provided with a fixed quantity of provisions, including many bees which have economic value as pollinators.
体型是一个重要的表型特征，与性能和适应性相关。对于定态生长的昆虫来说，体型的变化取决于生长速度和在幼体生长结束时停止生长的机制。内分泌机制调节生长停止，它们在发育过程中的相对时间决定了体型和发育时间的表型变化。幼虫通常被假设一旦达到临界体重就会开始变态。然而，即使对于研究得很好的昆虫物种，临界体重的机制也尚未解决。更重要的是，临界体重在不同物种之间可能存在或不存在通用性。在这项研究中，我们描述了独居蜜蜂的大小调节的发育方面。我们证明，饥饿信号会引发 的变态，而且该物种不存在临界体重。在没有食物的情况下，幼虫在<24 小时内开始化蛹。然而，即使是自由进食的幼虫最终也会经历变态，这表明当食物没有完全消耗时，某些次要机制会调节变态。我们表明，即使在有食物的情况下，用 Precocene 处理也可以诱导变态，这表明这个决定是通过保幼激素信号来调节的。在不同的幼虫质量下移除食物会导致成虫之间的质量差异达到 10 倍。我们讨论了体型变化对那些提供固定数量食物的昆虫物种的影响，包括许多作为传粉媒介具有经济价值的蜜蜂。
