This study was conducted to characterise the muscle-specific gene expression, energy metabolism level and growth rates of Atlantic salmon Salmo salar L. reared under different photoperiod regimes. The effects of two photoperiod regimes - LD 16:8 (16 h light:8 h dark) and LD 24:0 (24 h light:0 h dark) over a period of 3 months (August to October) on growth, energy metabolism enzyme activities (cytochrome c oxidase, COX; lactate dehydrogenase, LDH; and aldolase) and the gene expression levels of myogenic regulatory factors (MRFs - MyoD1 paralogues (MyoD1a, MyoD1b, MyoD1c), Myf5, MyoG), myostatin paralogues (MSTN-1a, MSTN-1b, MSTN-2a) and the fast skeletal myosin heavy chain (MyHC) in the muscles of Atlantic salmon underyearling fry (0+) were investigated. The experiment was conducted in a fish hatchery with natural variations in water temperature. The results were compared with those obtained in salmon reared under the lighting conditions of a fish hatchery (HL, hatchery lighting). The results revealed that the fry reared under constant light (LD 24:0) grew faster and were bigger at the end of the experiment. Fishes reared within the photoperiod regime LD 16:8 had a lower growth rate. COX activity was lower in fish under the LD 16:8 regime compared with the LD 24:0 group. The LDH and aldolase enzyme activities were higher in the group with constant light in comparison to control in the beginning of September. The expression level for all of the genes studied variated during the duration of the experiment, and MyHC, MyoG, MyoD1a and Myf5 expression depended on the light regime as well. The more noticeable changes in gene expression occurred in October. The MyHC and MyoG mRNA levels increased, accompanied by MyD1c gene expression, in both groups that had additional lighting (LD 16:8 and LD24:0) at the beginning of October and were higher than the HL group. In the HL group, the elevation of MyHC and MyoG mRNA was gradual during October, but there was a sharp increase in Myf5 expression at the beginning of October. MyoD1 paralogues differently expressed during the experiment. The MyoD1a mRNA level was elevated at the end of October along with MyHC and MyoG expression, but MyoD1b and MyoD1c mRNA levels decreased along with Myf5 gene expression. The expression of MSTN paralogues were elevated with increases in MyHC and MRFs transcripts. These findings show that constant light has a positive effect on the growth rate of salmon, affecting the aerobic and anaerobic capacity in their muscles. The alterations in muscle-specific gene expression between the groups with different light indicated that the mechanisms for regulating muscle growth processes in fish depend on photoperiod duration.

中文翻译：

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在不同光周期条件下饲养的大西洋鲑鱼Salmo salar L.fry的肌肉特异性基因表达和代谢酶活性。

进行这项研究来表征在不同光周期条件下饲养的大西洋鲑鱼Salmo salar L.的肌肉特异性基因表达，能量代谢水平和生长速率。三种光周期方案-LD 16：8（16小时光照：8小时黑暗）和LD 24：0（24小时光照：0小时黑暗）在3个月（八月至十月）期间对生长，能量代谢的影响酶活性（细胞色素C氧化酶，COX；乳酸脱氢酶，LDH和醛缩酶）和肌调节因子（MRFs-MyoD1旁系同源物（MyoD1a，MyoD1b，MyoD1c），Myf5，MyoG），Myostatin旁系同源物（MSTN-1a）的基因表达水平（MSTN-1b，MSTN-2a）和大西洋鲑一岁鱼苗（0+）肌肉中的快速骨骼肌肌球蛋白重链（MyHC）进行了研究。该实验是在水温自然变化的鱼孵化场进行的。将结果与在鱼孵化场（HL，孵化场照明）的光照条件下饲养的鲑鱼中获得的结果进行了比较。结果表明，在恒定光照（LD 24：0）下饲养的鱼苗生长更快，并且在实验结束时更大。在LD 16：8的光周期条件下饲养的鱼的生长速度较低。与LD 24：0组相比，LD 16：8方案下鱼类的COX活性较低。与9月初的对照组相比，光照恒定的组的LDH和醛缩酶活性更高。在实验期间，所有研究基因的表达水平均发生变化，而MyHC，MyoG，MyoD1a和Myf5的表达也取决于光照条件。基因表达方面更明显的变化发生在十月。两组在10月初都有额外照明（LD 16：8和LD24：0）的MyHC和MyoG mRNA水平增加，并伴有MyD1c基因表达，并且高于HL组。在HL组中，MyHC和MyoG mRNA的升高在10月期间逐渐升高，但Myf5表达在10月初急剧增加。在实验过程中，MyoD1旁系同源物表达不同。MyoD1a mRNA水平与MyHC和MyoG表达一起在10月底升高，但MyoD1b和MyoD1c mRNA水平与Myf5基因表达一起下降。MSTN旁系同源物的表达随MyHC和MRFs转录物的增加而升高。这些发现表明，持续光照对鲑鱼的生长速度有积极影响，影响其肌肉的有氧和厌氧能力。