Márquez-García Armando, Canales-Lazcano Jorge, Rantala Markus J, Contreras-Garduño Jorge
Departamento de Biología, División de Ciencias Naturales y Exactas, Universidad de Guanajuato, Noria Alta s/n, Noria Alta, 36050 Guanajuato, Mexico.
Posgrado en Ciencias Biomédicas, Instituto de Ecología, UNAM, Mexico.
Gen Comp Endocrinol. 2016 May 1;230-231:170-6. doi: 10.1016/j.ygcen.2016.03.027. Epub 2016 Mar 21.
Trade-offs are a central tenet in the life-history evolution and the simplest model to understand it is the "Y" model: the investment of one arm will affect the investment of the other arm. However, this model is by far more complex, and a "branched Y-model" is proposed: trade-offs could exist within each arm of the Y, but the mechanistic link is unknown. Here we used Tenebrio molitor to test if Juvenile Hormone (JH) could be a mechanistic link behind the "branched Y-model". Larvae were assigned to one of the following experimental groups: (1) low, (2) medium and (3) high doses of methoprene (a Juvenile Hormone analogue, JHa), (4) acetone (methoprene diluents; control one) or (5) näive (handled in the same way as other groups; control two). The JHa lengthened the time of development from larvae to pupae and larvae to adults, resulting in adults with a larger size. Males with medium and long JHa treatment doses were favored with female choice, but had smaller testes and fewer viable sperm. There were no differences between groups in regard to the number of spermatozoa of males, or the number of ovarioles or eggs of females. This results suggest that JH: (i) is a mechanistic link of insects "branched Y model", (ii) is a double ended-sword because it may not only provide benefits on reproduction but could also impose costs, and (iii) has a differential effect on each sex, being males more affected than females.
权衡是生活史进化的核心原则，理解这一原则的最简单模型是“Y”模型：一条臂的投资会影响另一条臂的投资。然而，这个模型要复杂得多，因此有人提出了“分支Y模型”：权衡可能存在于Y的每条臂内，但机制联系尚不清楚。在这里，我们利用黄粉虫来测试保幼激素（JH）是否可能是“分支Y模型”背后的机制联系。将幼虫分配到以下实验组之一：（1）低剂量、（2）中剂量和（3）高剂量的烯虫酯（一种保幼激素类似物，JHa）、（4）丙酮（烯虫酯稀释剂；对照一）或（5）未处理组（处理方式与其他组相同；对照二）。JHa延长了幼虫到蛹以及幼虫到成虫的发育时间，导致成虫体型更大。接受中剂量和高剂量JHa处理的雄性更受雌性青睐，但睾丸较小且活精子数量较少。各组雄性的精子数量、雌性的卵巢小管数量或卵子数量没有差异。这些结果表明，JH：（i）是昆虫“分支Y模型”的机制联系，（ii）是一把双刃剑，因为它不仅可能在繁殖方面带来益处，也可能带来成本，（iii）对每种性别有不同影响，雄性比雌性受影响更大。
