Oliveira Catarina C V, Figueiredo Filipe, Soares Florbela, Pinto Wilson, Dinis Maria Teresa
CCMAR, Universidade do Algarve, Campus de Gambelas, Edifício 7, 8005-139, Faro, Portugal.
Norwegian College of Fishery Science, UiT The Arctic University of Norway, 9037, Tromsø, Norway.
Fish Physiol Biochem. 2018 Jun;44(3):885-893. doi: 10.1007/s10695-018-0478-0. Epub 2018 Mar 2.
The present study reveals the first characterization of the plasma melatonin rhythms of the meagre (Argyrosomus regius) under aquaculture conditions. Melatonin levels were monitored during a 24 h cycle under a photoperiod of 16 L:8D and under constant darkness (DD), respectively to characterize the daily rhythm of this indoleamine and to test its endogenous origin. Besides, to identify which light intensities are perceived as night or day by this species, the degree of inhibition of nocturnal melatonin production caused by increasing intensities of light was tested (3.3, 5.3, 10.5, and 120 μW/cm), applying 1 h light pulses at Mid-Dark. The result for melatonin daily rhythm in plasma showed a typical profile: concentration remained low during all daytime points, increasing greatly during dark points, with maximum values at 16:00 and 22:00 h, zeitgeber time. Under DD conditions, the plasma melatonin profile persisted, with a similar acrophase but with a lower amplitude between subjective day and night periods, indicating this rhythm as being endogenously driven. Moreover, meagre seemed to be very sensitive to dim levels of illumination during the night, since an intensity of just 3.3 μW/cm inhibited melatonin production. However, only the pulse of 5.3 μW/cm caused a melatonin drop till daytime concentrations. Thus, the threshold of light detection by the pineal organ was suggested as being located between 3.3 and 5.3 μW/cm. Such results are an added value for this species biology knowledge, and in consequence to its adaptation to aquaculture conditions, allowing the improvement of culture husbandry protocols.
本研究首次揭示了水产养殖条件下军曹鱼（Argyrosomus regius）血浆褪黑素节律的特征。分别在16L:8D光周期和持续黑暗（DD）条件下，对褪黑素水平进行了24小时监测，以表征这种吲哚胺的每日节律并测试其内源起源。此外，为了确定该物种将何种光强度视为白天或夜晚，测试了在午夜增加光强度（3.3、5.3、10.5和120μW/cm²）对夜间褪黑素分泌的抑制程度，施加1小时的光脉冲。血浆中褪黑素的每日节律结果显示出典型的特征：在所有白天时段浓度保持较低，在黑暗时段大幅增加，在授时时间16:00和22:00达到最大值。在DD条件下，血浆褪黑素特征持续存在，相位相同但主观白天和夜晚期间的振幅较低，表明这种节律是内源性驱动的。此外，军曹鱼似乎对夜间微弱的光照水平非常敏感，因为仅3.3μW/cm²的强度就抑制了褪黑素的分泌。然而，只有5.3μW/cm²的脉冲导致褪黑素下降至白天浓度。因此，松果体器官的光检测阈值被认为位于3.3和5.3μW/cm²之间。这些结果为该物种的生物学知识增添了价值，从而有助于其适应水产养殖条件，改进养殖管理方案。
