Kondo Yuki, Kobayashi Ryotaro, Kobayashi Yuya, Awata Satoshi
Laboratory of Animal Sociology, Department of Biology, Graduate School of Science, Osaka Metropolitan University, Osaka, 558-8585, Japan.
Sci Rep. 2025 Aug 7;15(1):26576. doi: 10.1038/s41598-025-11082-y.
Understanding the biological phenomena in model organisms typically relies on laboratory studies. However, the ecological validity of these findings is often uncertain when natural behaviors remain understudied. The medaka (Oryzias latipes) is a widely used model in reproductive and behavioral research; however, the timing of spawning in natural settings has rarely been directly observed. Recent fieldwork has suggested that medaka spawn several hours before sunrise, in contrast to the common assumption in laboratory-based studies that spawning occurs within an hour before or after exposure to light. In this study, we conducted continuous 24 h video recordings of medaka pairs under controlled laboratory conditions (14 L:10D photoperiod) to quantify diel variations in courtship and spawning behavior. Spawning occurred mostly between 08:00 and 11:00, peaking immediately after lights were turned on (08:00). Courtship behavior began during the dark period, increased before lights-on, and peaked between 07:00 and 09:00. These results exhibited a consistent delay of 3-4 h compared to (semi-)natural conditions. Our results highlight the influence of environmental conditions on reproductive timing in medaka. The temporal shifts observed in this study underscore the importance of incorporating natural temporal dynamics into experimental protocols to ensure accurate behavioral studies with model organisms.
了解模式生物中的生物学现象通常依赖于实验室研究。然而，当自然行为仍未得到充分研究时，这些发现的生态有效性往往不确定。青鳉（Oryzias latipes）是生殖和行为研究中广泛使用的模式生物；然而，在自然环境中产卵的时间很少被直接观察到。最近的野外工作表明，青鳉在日出前几个小时产卵，这与基于实验室的研究中普遍认为的产卵发生在光照前后一小时内的假设相反。在本研究中，我们在受控实验室条件下（14小时光照：10小时黑暗光周期）对青鳉配对进行了连续24小时的视频记录，以量化求偶和产卵行为的昼夜变化。产卵大多发生在08:00至11:00之间，在灯打开后立即达到峰值（08:00）。求偶行为在黑暗期开始，在开灯前增加，并在07:00至09:00之间达到峰值。与（半）自然条件相比，这些结果显示出3-4小时的一致延迟。我们的结果突出了环境条件对青鳉生殖时间的影响。本研究中观察到的时间变化强调了将自然时间动态纳入实验方案以确保对模式生物进行准确行为研究的重要性。
