School of Biological Sciences, Illinois State University, Normal, Illinois.
Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, Tennessee.
J Exp Zool A Ecol Integr Physiol. 2019 Nov;331(9):485-493. doi: 10.1002/jez.2315. Epub 2019 Aug 22.
Correlated and repeatable patterns of behavior, termed behavioral types, can affect individual fitness. The most advantageous behavioral type may differ across predictable environments (e.g., seasonally), and maternally mediated effects may match hatchling behavior to the environment. We measured righting response, an indicator of behavioral type, of juvenile red-eared slider turtles (Trachemys scripta) emerging from early and late season clutches to understand if the production of behavioral types differs across the nesting season. There was a significant effect of season, with early season hatchlings righting more quickly than late season hatchlings, and we explored two potential underlying mechanisms, maternal estrogens and maternal investment (e.g., yolk allocation). We dosed early season eggs with an estrogen mixture to mimic late season eggs and assayed hatchling righting response, but found no significant effect of this maternal effect. We assessed maternal investment by measuring egg, hatchling, and residual yolk masses. We found a seasonal pattern in yolk allocation, where early season eggs have more yolk than late season eggs. Early season hatchlings used more yolk for growth rather than maintenance of existing tissues, resulting in larger hatchlings. Interestingly, across both seasons, hatchlings that received less maternal yolk appeared to be more efficient at converting yolk to tissue, but we found no direct correlation with righting behavior. We demonstrate that the prevalence of behavioral types varies across the nesting season, creating correlated suites of seasonal phenotypes in turtle hatchlings, but it appears that neither maternal estrogens or investment in yolk directly underlie this shift in behavior.
相关且可重复的行为模式，称为行为类型，可以影响个体的适应度。最有利的行为类型可能因可预测的环境（例如，季节性）而异，并且母体介导的效应可能使幼体行为与环境相匹配。我们测量了幼红耳龟（Trachemys scripta）从早季和晚季卵中孵化出的翻身反应，这是行为类型的一个指标，以了解在产卵季节是否会产生不同的行为类型。季节有显著影响，早季孵化的幼龟翻身速度快于晚季孵化的幼龟，我们探讨了两种潜在的潜在机制，即母体雌激素和母体投资（例如，卵黄分配）。我们用雌激素混合物处理早季卵，以模拟晚季卵，并测定幼龟的翻身反应，但未发现这种母体效应有显著影响。我们通过测量卵、幼龟和残余卵黄的质量来评估母体投资。我们发现卵黄分配存在季节性模式，即早季卵的卵黄比晚季卵多。早季孵化的幼龟用更多的卵黄来生长，而不是维持现有组织，因此孵化出的幼龟更大。有趣的是，在两个季节中，接收较少母体卵黄的幼龟似乎更有效地将卵黄转化为组织，但我们没有发现与翻身行为的直接相关性。我们证明，行为类型的流行度在产卵季节会发生变化，在龟类幼体中产生相关的季节性表型丛，但似乎母体雌激素或卵黄投资都不是这种行为变化的直接基础。
