Data from: Temporal shifts in ovulation between laboratory and semi-natural environments in the model fish medaka

Research on model organisms in controlled laboratory settings has enabled
fundamental biological discoveries. However, the ecological validity of
these findings remains uncertain when natural ecology is poorly
understood. Medaka (Oryzias latipes) has served as a model fish for over a
century. Recent studies on medaka have shown that the timing of daily
mating behaviour differs by 3–4 h between laboratory and natural
conditions; however, the underlying physiological timing of reproduction
remains unclear. This study compared daily ovulation timing in medaka that
spawn under standard laboratory conditions (artificial photoperiod,
constant water temperature) and semi-natural conditions (natural light,
daily temperature fluctuations) by dissecting ovaries sampled hourly to
assess ovulation status. The time when 50% of individuals had ovulated was
4.2 h before sunrise in semi-natural conditions and 0.7 h before lights-on
in laboratory conditions, indicating a 3.5 h (2.6–4.3 h) shift. These
quantitative results revealed the significant physiological differences
between laboratory and natural conditions despite the controlled
conditions typical of laboratory reproductive studies. These findings have
important implications for studies on circadian rhythms and reproductive
physiology. They also emphasise the necessity of incorporating ecological
context into an experimental design to ensure the biological relevance and
reproducibility of model organism research.