West Jessica M, Klukowski Matthew
Biology Department, Middle Tennessee State University, Murfreesboro, TN 37132, USA.
Gen Comp Endocrinol. 2018 Jun 1;262:71-80. doi: 10.1016/j.ygcen.2018.03.016. Epub 2018 Mar 13.
Seasonal changes in glucocorticoids and their influence on the immune system are widespread in vertebrates, but whether this occurs in lesser studied taxa like turtles is unclear. The purpose of this study was to test for seasonal changes in baseline corticosterone (CORT), innate immunity, body condition, and metabolic factors (triglycerides, uric acid) in free-ranging Eastern Box Turtles (Terrapene carolina carolina), a species which is in decline across its range. In addition, the effect of handling and confinement on CORT levels was measured. In both years of the seasonal study, baseline CORT concentrations were significantly higher in fall than in spring, but summer CORT levels differed between the years. The annual variation in CORT levels may be related to weather conditions or associated with opportunistic mating. CORT levels of turtles confined for one hour were higher than turtles bled as quickly as possible, and unlike the seasonal study, females had higher baseline and post-stressor CORT levels than males. Baseline CORT levels were positively correlated with hemolysis titer, indicating a possible immunoenhancing effect of CORT. Triglycerides were positively correlated with body condition and were higher in females than males. The higher triglyceride level in females was likely associated with the energetic demands of reproduction and nesting. Males had a lower body condition in the fall than in both spring and summer, while females exhibited no seasonal differences in body condition. Uric acid and innate immunity measures failed to exhibit significant seasonal or sex related differences. Overall our findings of substantial annual, seasonal, and sexual variation in turtle physiology are consistent with the findings reported for other vertebrates and indicate the importance of incorporating these sources of variation into the design of future studies.
糖皮质激素的季节性变化及其对免疫系统的影响在脊椎动物中广泛存在，但在像海龟这样研究较少的类群中是否如此尚不清楚。本研究的目的是测试自由放养的东部箱龟（Terrapene carolina carolina）的基础皮质酮（CORT）、先天免疫、身体状况和代谢因子（甘油三酯、尿酸）的季节性变化，该物种在其分布范围内数量正在减少。此外，还测量了处理和禁闭对CORT水平的影响。在季节性研究的两年中，基础CORT浓度秋季显著高于春季，但夏季CORT水平在两年间有所不同。CORT水平的年度变化可能与天气条件有关或与机会性交配有关。禁闭一小时的海龟的CORT水平高于尽快采血的海龟，并且与季节性研究不同，雌性的基础和应激后CORT水平高于雄性。基础CORT水平与溶血效价呈正相关，表明CORT可能具有免疫增强作用。甘油三酯与身体状况呈正相关，且雌性高于雄性。雌性较高的甘油三酯水平可能与繁殖和筑巢的能量需求有关。雄性秋季的身体状况低于春季和夏季，而雌性的身体状况没有季节性差异。尿酸和先天免疫指标未表现出明显的季节性或性别相关差异。总体而言，我们关于海龟生理存在大量年度、季节和性别差异的研究结果与其他脊椎动物的报道结果一致，并表明在未来研究设计中纳入这些差异来源的重要性。
