Chronobiology applied to spawning and gamete withdrawal: importance of daily rhythms

Abstract

Chronobiology is the field of science which studies the biological rhythms and the mechanisms by which the organisms adapt to a constantly changing environment. Animals synchronize their rhythms with environmental cycles choosing the most suitable moment to feed, reproduce or be active, thereby optimizing biological processes. In fish, the study of circadian activity and feeding rhythms has been profusely investigated lately; however, reproduction rhythms are often neglected. Fish species reproduce once a year around a species specific season, but many of them can also present lunar reproduction rhythms and may even select the best moment of the day to spawn (Oliveira & Sánchez-Vázquez 2009). Knowing the moment of the day spawning occurs can improve egg collection protocols and provide insides about time of ovulation. This kind of knowledge can be very useful for gamete collection and in vitro fertilization procedures. In fact, for species like red snapper, red sea bream or bambooleaf wrasse, daily maturation rhythms have been observed (Matsuyama et al. 1988, 1998; Jackson et al. 2006). Thus the objective of this work is to review the evidences of daily rhythms of reproduction in teleost species (e.g. Senegal sole, Solea senegalensis, gilthead seabream, Sparus aurata, European sea bass, Dicentrarchus labrax, white seabream, Diplodus sargus, and zebrafish, Danio rerio), highlighting the importance of the time of day in gamete studies.