Koya Yasunori, Kodama Megumi, Maruyama Tsukasa, Kondo Yuki
Faculty of Education, Gifu University, Gifu, Japan.
Laboratory of Animal Sociology, Department of Biology, Graduate School of Science, Osaka Metropolitan University, Osaka, Japan.
J Exp Zool A Ecol Integr Physiol. 2025 Jul 30. doi: 10.1002/jez.70017.
Chemical communication between males and females is important for successful reproduction of animals. The activation of male courtship behavior by female olfactory cues has only been demonstrated in a limited number of teleost species. In the present study, we showed that in the model animal medaka, courtship behavior in males are activated by olfactory cues released by females and that at least one of them is released through urine. Male medaka perform a series of courtship behaviors, such as "following" (chasing the female), "positioning" (positioning slightly behind the female), and "quick-circle" (performing a somersault around the female's nose), before spawning. Males rarely showed courtship behavior toward post-spawning females; however, in the waters that had been reared ovulating female or other mating pairs, males significantly increased their following toward post-spawning females. Furthermore, males tended to make more frequent quick-circle toward post-spawning females in the water of other mating pairs had been spawned in it. When males were paired with post-spawning females in water supplemented with ovulating-female urine, only the frequency of quick-circle increased significantly. This suggested that the urine of ovulating females contains a component that induces the quick-circle and that the component inducing the following is a different component released via a route separate from urine. Ovulating females store more than ten times the amount of urine in their bladders than non-ovulating females and males, and releasing this urine during male courtship behavior may increase male motivation.
雌雄之间的化学通讯对于动物的成功繁殖至关重要。雌性嗅觉线索激活雄性求偶行为仅在有限数量的硬骨鱼物种中得到证实。在本研究中，我们表明，在模式动物青鳉中，雄性的求偶行为会被雌性释放的嗅觉线索激活，并且其中至少有一种是通过尿液释放的。雄性青鳉在产卵前会表现出一系列求偶行为，如“跟随”（追逐雌性）、“定位”（在雌性身后稍作定位）和“快速绕圈”（在雌性鼻子周围翻跟头）。雄性很少对产卵后的雌性表现出求偶行为；然而，在饲养过排卵雌性或其他交配配对的水中，雄性对产卵后雌性的跟随行为显著增加。此外，在其他交配配对已经在其中产卵的水中，雄性对产卵后雌性的快速绕圈行为往往更频繁。当雄性在添加了排卵雌性尿液的水中与产卵后雌性配对时，只有快速绕圈的频率显著增加。这表明排卵雌性的尿液中含有一种诱导快速绕圈的成分，而诱导跟随行为的成分是通过与尿液不同的途径释放的另一种成分。排卵雌性膀胱中的尿液储存量是非排卵雌性和雄性的十多倍，在雄性求偶行为期间释放这种尿液可能会增加雄性的积极性。
