ABSTRACT Photoperiod is believed to regulate growth in fish, although the mechanism involved is still unclear. In this paper, we report a relationship between leptin-receptor A1 (AsLRa1), melatonin-receptor (AsMR) and photoperiod in Atlantic salmon. Atlantic salmon (mean weight 1071.70 ± 155.54 g) were reared under six photoperiod regimes, four constant light regimes 24L:0D, 18L:6D, 12L:12D and 8L:16D, hours of light (L) and dark (D) and two varying light regimes, LL-SL = 24L:0D-8L:16D, and SL-LL = 8L:16D-24L:0D over a period of seven months. The results showed that AsLRa1 transcripts were mainly existed in the hypothalamus and saccus vasculosus (SV), AsMR was mainly expressed in the hypothalamus. Long photoperiod inhibited the expression of AsLRa1 and AsMR transcripts in the Atlantic salmon brain. The expression pattern of AsLRa1 was similar to the expression pattern of AsMR in the hypothalamus. Food intake was higher in fish with lower AsLRa1 transcript levels. This demonstrated that photoperiod influenced somatic growth by changing expression of AsLRa1 in the hypothalamus and SV to affect appetite. In addition, we found that the SV appears to act as a seasonal sensor regulating reproduction in a similar way to the hypothalamus.

中文翻译：

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光周期可通过大西洋鲑鱼（Salmo salar）下丘脑和血管囊中的瘦素受体 A1 调节生长

摘要 光周期被认为可以调节鱼类的生长，尽管其机制尚不清楚。在本文中，我们报告了大西洋鲑鱼中瘦素受体 A1 (AsLRa1)、褪黑激素受体 (AsMR) 和光周期之间的关系。大西洋鲑鱼（平均体重 1071.70 ± 155.54 g）在六个光周期条件下饲养，四个恒定光照条件 24L:0D、18L:6D、12L:12D 和 8L:16D、光照时间 (L) 和黑暗时间 (D) 以及两个在七个月的时间内，不同的光照条件，LL-SL = 24L:0D-8L:16D 和 SL-LL = 8L:16D-24L:0D。结果表明AsLRa1转录物主要存在于下丘脑和血管囊（SV），AsMR主要在下丘脑表达。长光周期抑制了大西洋鲑鱼脑中 AsLRa1 和 AsMR 转录本的表达。AsLRa1 的表达模式与下丘脑中 AsMR 的表达模式相似。具有较低 AsLRa1 转录水平的鱼的食物摄入量较高。这表明光周期通过改变下丘脑和 SV 中 AsLRa1 的表达影响食欲来影响体细胞生长。此外，我们发现 SV 似乎充当季节性传感器，以类似于下丘脑的方式调节繁殖。