Shephard A M, Lagon S R, Jacobsen S, Millar K, Ledón-Rettig C C
Department of Biology, Indiana University Bloomington, Myers Hall, 915 East 3rd Street, Bloomington IN 47405, USA.
Integr Org Biol. 2024 Apr 24;6(1):obae012. doi: 10.1093/iob/obae012. eCollection 2024.
Stressful experiences in early life can have phenotypic effects that persist into, or manifest during, adulthood. In vertebrates, such carryover effects can be driven by stress-induced secretion of glucocorticoid hormones, such as corticosterone, which can lead to developmental reprogramming of hypothalamic-pituitary-adrenal/interrenal axis activity and behavior. Nutritional stress in the form of early life nutrient restriction is well known to modify later life behaviors and stress activity through corticosterone-related mechanisms. However, it is not known whether corticosterone is also mechanistically involved in carryover effects induced by a different form of nutritional variation: the use of alternate or entirely novel types of dietary resources. The plains spadefoot () presents an excellent system for testing this question, since larvae of this species have evolved to use 2 alternate diet types: an ancestral detritus-based diet and a more novel diet of live shrimp. While previous work has shown that feeding on the novel shrimp diet influences juvenile (i.e., post-metamorphic) behavior and corticosterone levels, it is unclear whether these diet-induced carryover effects are mediated by diet-induced corticosterone itself. To test for the mechanistic role of corticosterone in diet-induced carryover effects, we experimentally treated larvae with exogenous corticosterone and measured subsequent effects on juvenile behavior and corticosterone levels. We found that while shrimp-fed larvae had elevated corticosterone levels, treatment of larvae with corticosterone itself had effects on juvenile behavior that partially resembled those carryover effects induced by the shrimp diet, such as altered food seeking and higher locomotor activity. However, unlike carryover effects caused by the shrimp diet, larval corticosterone exposure did not affect juvenile corticosterone levels. Overall, our study shows that corticosterone-related mechanisms are likely involved in carryover effects induced by a novel diet, yet such diet-induced carryover effects are not driven by corticosterone alone.
生命早期的应激经历会产生表型效应，并持续到成年期或在成年期显现出来。在脊椎动物中，这种遗留效应可能由应激诱导的糖皮质激素分泌驱动，比如皮质酮，它会导致下丘脑 - 垂体 - 肾上腺/肾间轴活动和行为的发育重编程。众所周知，生命早期营养限制形式的营养应激会通过与皮质酮相关的机制改变后期行为和应激活动。然而，尚不清楚皮质酮是否也在由另一种营养变化形式——使用替代或全新类型的饮食资源所诱导的遗留效应中发挥机制性作用。平原锄足蟾（）提供了一个绝佳的系统来测试这个问题，因为该物种的幼虫已经进化到可以使用两种替代饮食类型：一种基于碎屑的祖传饮食和一种更新颖的活虾饮食。虽然之前的研究表明，食用新颖的虾类饮食会影响幼体（即变态后）行为和皮质酮水平，但尚不清楚这些饮食诱导的遗留效应是否由饮食诱导的皮质酮本身介导。为了测试皮质酮在饮食诱导的遗留效应中的机制性作用，我们用外源性皮质酮对 只幼虫进行了实验处理，并测量了随后对幼体行为和皮质酮水平的影响。我们发现，虽然喂食虾类的幼虫皮质酮水平升高，但用皮质酮本身处理幼虫对幼体行为产生的影响部分类似于虾类饮食诱导的那些遗留效应，比如觅食行为改变和更高的运动活性。然而，与虾类饮食引起的遗留效应不同，幼虫期暴露于皮质酮并未影响幼体的皮质酮水平。总体而言，我们的研究表明，与皮质酮相关的机制可能参与了由新颖饮食诱导的遗留效应，但这种饮食诱导的遗留效应并非仅由皮质酮驱动。
