Animals regulate a variety of aspects of physiology according to environmental light conditions via nonvisual opsins such as melanopsin. In order to study photic regulation of fish physiology, expression changes of the genes for melanopsin (opn4xa and opn4xb) and effects of light on them were examined in juvenile grass puffer Takifugu alboplumbeus using quantitative real-time PCR. In the brain of juvenile fish, no significant diurnal nor circadian changes were observed in opn4x mRNA levels. On the other hand, in the eyes, the mRNA level of opn4xa showed a significant diurnal rhythm with a peak at Zeitgeber time (ZT) 4, while no apparent circadian changes were observed. The mRNA level of opn4xb in the eyes showed a diurnal change similar to that of opn4xa, while it showed a significant circadian change. Furthermore, continuous exposure to light during a subjective night significantly increased the mRNA levels of opn4xa in the eyes at ZT24, suggesting that light induces gene expression of opn4xa in the eyes and that the induction occurs only during the night-day transition period. These results suggest that Opn4xa and Opn4xb play differential roles in the eyes of juvenile grass puffer to mediate the physiological effects of environmental light information.

动物通过非视觉视蛋白（例如黑视蛋白）根据环境光照条件调节生理的各个方面。为了研究鱼类生理的光调节作用，使用定量实时荧光定量PCR在幼草缓冲液Takifugu alboplumbeus中检测了黑素蛋白基因（opn4xa和opn4xb）的表达变化以及光对其的影响。在幼鱼的大脑中，opn4x mRNA水平未见明显的昼夜变化或昼夜节律变化。另一方面，在眼睛中，opn4xa的mRNA水平显示出明显的昼夜节律，并在Zeitgeber时间（ZT）4达到峰值，而未观察到明显的昼夜节律变化。opn4xb的mRNA水平眼睛的昼夜变化与opn4xa相似，而昼夜节律则明显变化。此外，连续暴露于光时的主观夜间显著增加的mRNA水平opn4xa在ZT24在眼睛上，这表明的光诱导基因表达opn4xa在眼睛和只在夜间天过渡期间发生的诱导。这些结果表明，Opn4xa和Opn4xb在幼草缓冲液的眼睛中起着不同的作用，以介导环境光信息的生理作用。