Ikeya Koki, Kume Manabu
Gifu World Freshwater Aquarium, Kakamigahara, Gifu , Japan.
Zoolog Sci. 2011 Aug;28(8):545-9. doi: 10.2108/zsj.28.545.
The Mekong giant catfish Pangasianodon gigas is endemic to the Mekong River basin, and is recognized as endangered species, largely due to overfishing and development of the river basin. We monitored food intake of P. gigas in a stable environment in an aquarium over a 6-year period and analyzed their feeding rhythm and fasting periods. The daily food intake for each fish was recorded from 18 June 2004 to 17 June 2010. The feeding rhythm or pattern was determined by the fast Fourier transform (FFT) analysis. The FFT analysis revealed that different cycles of feeding rhythm (168.8, 313.1, and 365.3 days) in three catfishes and no observable cycles in two catfishes. However, three catfishes showed subordinate peaks with approximately 365 days (365.3 days for all). These suggest that, at least, four of five catfish had have approximately 365-days feeding cycle. We also showed that all catfish undergo long-term fasting periods (> 20 days). Of note, the feeding/fasting pattern coincides with the wet/dry seasons in Thailand, which also corresponds to the abundance of the catfish food resource (Cladophora spp.). We found that P. gigas exhibit a seasonal feeding rhythm that is synchronized by food availability. Furthermore, we found that the seasonal feeding rhythm was gradually dampened over time, suggesting that the observed seasonal feeding rhythm with long-term fasting of the catfish is likely controlled by an endogenous clock system. To our knowledge, this is the first case of quantification of the seasonal feeding rhythm with fasting periods in teleost fish.
湄公河巨鲶（Pangasianodon gigas）是湄公河流域的特有物种，被认定为濒危物种，这主要是由于过度捕捞和流域开发所致。我们在水族箱的稳定环境中对湄公河巨鲶的食物摄入量进行了为期6年的监测，并分析了它们的摄食节律和禁食期。从2004年6月18日至2010年6月17日记录了每条鱼的每日食物摄入量。通过快速傅里叶变换（FFT）分析确定摄食节律或模式。FFT分析显示，三条鲶鱼存在不同周期的摄食节律（168.8、313.1和365.3天），两条鲶鱼未观察到明显周期。然而，三条鲶鱼显示出约365天的次要峰值（均为365.3天）。这些表明，至少五条鲶鱼中有四条具有约365天的摄食周期。我们还表明，所有鲶鱼都经历长期禁食期（>20天）。值得注意的是，摄食/禁食模式与泰国的湿/干季节相吻合，这也与鲶鱼食物资源（刚毛藻属）的丰度相对应。我们发现湄公河巨鲶表现出受食物可获得性同步的季节性摄食节律。此外，我们发现季节性摄食节律随时间逐渐减弱，这表明观察到的鲶鱼季节性摄食节律和长期禁食可能受内源性时钟系统控制。据我们所知，这是硬骨鱼中首次对带有禁食期的季节性摄食节律进行量化的案例。
