Vera Luisa Maria, Cairns Louise, Sánchez-Vázquez Francisco Javier, Migaud Hervé
Institute of Aquaculture, University of Stirling, UK.
Chronobiol Int. 2009 May;26(4):666-81. doi: 10.1080/07420520902926017.
Behavioral rhythms of the Nile tilapia were investigated to better characterize its circadian system. To do so, the locomotor activity patterns of both male and female tilapia reared under a 12:12 h light-dark (LD) cycle were studied, as well as in males the existence of endogenous rhythmicity under free-running conditions (DD and 45 min LD pulses). When exposed to an LD cycle, the daily pattern of activity differed between individuals: some fish were diurnal, some nocturnal, and a few displayed an arrhythmic pattern. This variability would be typical of the plastic circadian system of fish. Moreover, reproductive events clearly affected the behavioral rhythms of female tilapia, a mouth-brooder teleost species. Under DD, 50% (6 of 12) of male fish showed circadian rhythms with an average period (tau) of 24.1+/-0.2 h, whereas under the 45 min LD pulses, 58% (7 of 12) of the fish exhibited free-running activity rhythms with an average tau of 23.9+/-0.5 h. However, interestingly in this case, activity was always confined to the dark phase. Furthermore, when the LD cycle was reversed, a third of the fish showed gradual resynchronization to the new phase, taking 7-10 days to be completely re-entrained. Taken together, these results suggest the existence of an endogenous circadian oscillator that controls the expression of locomotor activity rhythms in the Nile tilapia, although its anatomical localization remains unknown.
为了更好地描述尼罗罗非鱼的昼夜节律系统，对其行为节律进行了研究。为此，研究了在12:12小时明暗（LD）循环条件下饲养的雄性和雌性罗非鱼的运动活动模式，以及雄性罗非鱼在自由运行条件下（持续黑暗[DD]和45分钟LD脉冲）内源性节律的存在情况。当暴露于LD循环时，个体之间的每日活动模式有所不同：一些鱼是昼行性的，一些是夜行性的，还有一些表现出无节律模式。这种变异性是鱼类可塑性昼夜节律系统的典型特征。此外，繁殖事件明显影响了雌性尼罗罗非鱼（一种口孵硬骨鱼）的行为节律。在DD条件下，50%（12条中的6条）的雄鱼表现出昼夜节律，平均周期（tau）为24.1±0.2小时，而在45分钟LD脉冲条件下，58%（12条中的7条）的鱼表现出自由运行的活动节律，平均tau为23.9±0.5小时。然而，有趣的是，在这种情况下，活动总是局限于黑暗阶段。此外，当LD循环颠倒时，三分之一的鱼显示出逐渐重新同步到新阶段，需要7 - 10天才能完全重新适应。综上所述，这些结果表明存在一个内源性昼夜节律振荡器，它控制着尼罗罗非鱼运动活动节律的表达，尽管其解剖定位仍然未知。
