Laboratóriode Cronobiologia Binacional Argentina-Brasil, Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brasil.
Laboratorio de Cronobiología Binacional Argentina-Brasil, Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja, Anillaco, Argentina.
J Biol Rhythms. 2022 Jun;37(3):283-295. doi: 10.1177/07487304221085105. Epub 2022 Apr 11.
Photoperiodism plays an important role in the synchronization of seasonal phenomena in various organisms. In mammals, photoperiod encoding is mediated by differential entrainment of the circadian system. The limits of daily light entrainment and photoperiodic time measurement can be verified in organisms that inhabit extreme photic environments, such as the subterranean. In this experimental study, we evaluated entrainment of circadian wheel-running rhythms in South American subterranean rodents, the Anillaco tuco-tucos ( aff. ), exposed to different artificial photoperiods, from extremely long to extremely short photophases (LD 21:3, LD 18:6, LD 15:9, LD 9:15, LD 6:18 and LD 3:21). Artificial photoperiods synchronized their activity/rest rhythms and clear differences occurred in (a) phase angles of entrainment relative to the LD cycle and (b) duration of the daily activity phase α. These photoperiod-dependent patterns of entrainment were similar to those reported for epigeous species. Release into constant darkness conditions revealed aftereffects of entrainment to different photoperiods, observed in α but not in the free-running period τ. We also verified if animals coming from summer and winter natural photoperiods entrained equally to the artificial photoperiods by evaluating their phase angle of entrainment, α and τ aftereffects. To this end, experimental animals were divided into "Matching" and "Mismatching" groups, based on whether the experimental photoperiod (short-day [L < 12 h] or long-day [L > 12 h]) matched or not the natural photoperiod to which they had been previously exposed. No significant differences were found in the phase angle of entrainment, α and τ aftereffects in each artificial photoperiod. Our results indicate that the circadian clocks of tuco-tucos are capable of photoperiodic time measurement despite their natural subterranean habits and that the final entrainment patterns achieved by the circadian clock do not depend on the photoperiodic history.
光周期在各种生物的季节性现象同步中起着重要作用。在哺乳动物中，光周期的编码是通过对生物钟系统的差异同步来介导的。在生活在极端光照环境中的生物中，可以验证日常光照同步和光周期时间测量的极限，例如地下生物。在这项实验研究中，我们评估了生活在地下的南美地下啮齿动物——阿尼拉科图科托斯（aff.）的昼夜节律轮跑节律的同步情况，这些动物暴露在不同的人工光周期下，从极长到极短的光相（LD 21:3、LD 18:6、LD 15:9、LD 9:15、LD 6:18 和 LD 3:21）。人工光周期使它们的活动/休息节律同步，并且在（a）相对于 LD 周期的同步相位角和（b）每日活动相α的持续时间方面出现了明显的差异。这些与报道的地上物种相似的光周期依赖性同步模式。进入持续黑暗条件下的释放揭示了不同光周期下的同步后效应，这些后效应表现在α中，但不在自由运行周期τ中。我们还通过评估它们的同步相位角α和τ的后效应，验证了来自夏季和冬季自然光周期的动物是否能够同样地适应人工光周期。为此，根据实验动物所经历的实验光周期（短日[L < 12 小时]或长日[L > 12 小时]）是否与它们之前暴露的自然光周期相匹配，将实验动物分为“匹配”和“不匹配”组。在每个人工光周期中，同步相位角α和τ的后效都没有发现显著差异。我们的结果表明，尽管图科托斯有其自然的地下习性，但它们的生物钟仍能够进行光周期时间测量，并且最终由生物钟实现的同步模式不依赖于光周期历史。
