Centre for Evolutionary Biology, School of Animal Biology (M092), The University of Western Australia, Crawley, WA, 6009, Australia.
J Anim Ecol. 2013 Jan;82(1):235-44. doi: 10.1111/j.1365-2656.2012.02018.x. Epub 2012 Jul 31.
Immune function is costly and must be traded off against other life-history traits, such as gamete production. Studies of immune trade-offs typically focus on adult individuals, yet the juvenile stage can be a highly protracted period when reproductive resources are acquired and immune challenges are ubiquitous. Trade-offs during development are likely to be important, yet no studies have considered changes in adult responses to immune challenges imposed at different stages of juvenile development. By manipulating the timing of a bacterial immune challenge to the larvae of the cotton bollworm moth, we examined potential trade-offs between investment into immunity at different stages of juvenile development (early or late) and subsequent adult reproductive investment into sperm or egg production. Our data reveal an age-dependent trade-off between juvenile immune function and adult male reproductive investment. Activation of the immune response during late development resulted in a reduced allocation of resources to eupyrene (fertilizing) sperm production. Immune activation from the injection procedure itself (irrespective of whether individuals were injected with an immune elicitor or a control solution) also caused reproductive trade-offs; males injected early in development produced fewer apyrene (nonfertilizing) sperm. Contrary to many other studies, our study demonstrates these immune trade-offs under ad libitum nutritional conditions. No trade-offs were observed between female immune activation and adult reproductive investment. We suggest the differences in trade-offs observed between male sperm types and the absence of reproductive trade-offs in females may be the result of ontogenetic differences in gamete production in this species. Our data reveal developmental windows when trade-offs between immune function and gametic investment are made, and highlight the importance of considering multiple developmental periods when making inferences regarding the fundamental trade-offs expected between immune function and reproduction.
免疫功能是有代价的，必须与其他生活史特征（如配子产生）相权衡。免疫权衡的研究通常集中在成年个体上，但幼体阶段可能是一个高度延长的时期，在此期间会积累生殖资源并面临普遍的免疫挑战。发育过程中的权衡可能很重要，但尚无研究考虑成年个体对在幼体发育的不同阶段施加的免疫挑战的反应变化。通过操纵对棉铃虫幼虫的细菌免疫挑战的时间，我们研究了在幼体发育的不同阶段（早期或晚期）对免疫的投资与随后对成年生殖投资（精子或卵子产生）之间的潜在权衡。我们的数据揭示了幼体免疫功能与成年雄性生殖投资之间的年龄依赖性权衡。晚期发育过程中免疫反应的激活导致资源分配减少到有生育力（受精）精子的产生。注射程序本身（无论个体注射的是免疫诱导剂还是对照溶液）的免疫激活也会引起生殖权衡；在早期发育时接受注射的雄性产生的非有生育力（非受精）精子较少。与许多其他研究相反，我们的研究在自由营养条件下证明了这些免疫权衡。在雌性免疫激活和成年生殖投资之间没有观察到权衡。我们认为，在雄性精子类型中观察到的权衡差异以及在雌性中不存在生殖权衡可能是由于该物种配子产生的个体发生差异造成的。我们的数据揭示了在免疫功能和配子投资之间做出权衡的发育窗口，并强调了当考虑到免疫功能和生殖之间预期的基本权衡时，考虑多个发育阶段的重要性。
