光照周期对褐牙鲆幼鱼生长、能量分配及生化指标的影响

在循环水实验系统中,设置1 L∶23 D、9 L∶15 D、12 L∶12 D、15 L∶9 D、24 L∶0 D(光L∶暗D)共5个光照周期处理组,研究其对褐牙鲆幼鱼生长及部分生化指标的影响。实验结束时褐牙鲆幼鱼的体质量为41.10~43.98 g,不同处理组间无显著差异,体质量未表现出与日光照周期长短的相关性。日生长系数只在21~30 d阶段内出现显著差异,整个实验期间的平均日生长系数为1.86~2.02,不同处理组间不存在显著差异,日生长系数随日光照周期的延长略呈下降趋势。不同阶段的摄食率在31~40 d阶段出现显著差异,12 L∶12 D处理组摄食率显著高于9 L∶15 D处理组。在整个实验期间,1 L∶23 D的褐牙鲆幼鱼摄食率为1.64,显著低于12 L∶12 D的褐牙鲆幼鱼的摄食率(1.79)。整个实验期间,1 L∶23 D的褐牙鲆幼鱼平均饲料转化效率为113.49,显著高于12 L∶12 D、15 L∶9 D、24 L∶0 D的褐牙鲆幼鱼,并略高于9 L∶15 D的褐牙鲆幼鱼,饲料转化效率随光照时间的延长呈下降趋势。实验期间摄食能的分配比例仅在排泄能上出现显著差异,15 L∶9 D最高,12 L∶12 D最低,其他各项能量分配均无显著差异。不同光照周期对耗氧率影响显著,15 L∶9 D最高,为0.252 mg/(g·h),24 L∶0 D最低,为0.173 mg/(g·h)。耗氧率随着光照时间的延长呈先上升后下降的趋势。血浆生长激素和类胰岛素生长因子I含量在不同处理组间也不存在显著差异,随光照时间延长也未表现出明显变动趋势。血浆褪黑素含量随光照时间的增加呈先下降后上升的趋势,12 L∶12 D处理组MT含量最低,但与其他处理组差异不显著。实验结束时肌肉RNA/DNA比值随光照周期延长呈先上升后下降变动趋势,其中15 L∶9 D和24 L∶0 D处理组的肌肉RNA/DNA比值显著高于1 L∶23 D处理。肝脏RNA/DNA比值以12 L∶12 D最高,15 L∶9 D最低。实验结果表明光照周期对褐牙鲆幼鱼摄食量和饲料转化效率产生显著影响,但摄食量减少的处理组由于耗氧率降低因而饲料转化效率得到提高,因此光照周期对生长没有显著影响。光照周期明显影响血浆褪黑素、肌肉和肝脏RNA/DNA比值,但生化指标的差异与生长无明显相关性。

Effects of photoperiod on the growth, energy allocation,and biochemical parameters in juvenile brown flounder (Paralichthys olivaceus)

Photoperiod regimes(hours of light:hours of dark)were designed as 1L:23D,9L:15D,12L:12D,15L:9D,and 24L:0D to investigate the effects of photoperiods on the growth and biochemical parameters of juvenile brown flounder(Paralichthys olivaceus).At the end of the experiment,the average weight of the fish varied from 41.10 g to 43.98 g and no significant difference appeared in the average body weight through the experimental period.The average body weight did not show significant correlation to the photoperiods.The average DGC of the whole experimental period varied from 1.86 to 2.02 and no significant difference existed.Significant difference of daily growth coefficient(DGC)appeared only in period 21-30 d.A slightly decending trend of DGC along with the extending of light period was observed.The feeding rate of 12L:12D was significantly higher than 9L:15D in period 31-40 d.or the whole experimental period,and feeding rate of 1L:23D(1.64)was significantly lower than that of 12L:12D(1.79).The feed conversion efficiency showed a decending trends along with the extending of light period.Feed conversion efficiency of 1L:23D(113.49)was significantly higher than those of 12L:12D,15L:9D,and 24L:0D and it was also slightly higher than that of 9L:15D.Difference of the proportion allocation of ingested energy through whole experimental periods appeared only in excretion energy.The highest and lowest excretion energy appeared in 15L:9D and 12L:12D respectively.Photoperiods showed significant effects on the 24 h oxygen consumption rate of fish and the highest and lowest oxygen consumption rates appeared in 15L:9D and 24L:0D respectively.The oxygen consumption rate ascended along with the light period extending from 1 h to 15 h and then descended along with the light period extending from 15 h to 24 h.The content of growth hormone and insulin-like growth factor I in plasma showed no significant difference among different treatments and showed no obviously fluctuating trend along with the extending of light period. The content of melatonin in plasma ascended along with the light period extending from 1 h to 12 h and then descended along with the light period extending from 12 h to 24 h.The content of melatonin of 12L:12D was the lowest.But it was not significantly different from other treatments.The RNA/DNA ratio in muscle ascended along with the light period extending and the RNA/DNA ratios in 15L:9D and 24L:0D were significantly higher than that in 1L:23D.The highest and lowest RNA/DNA ratios in liver appeared in 12L:12D and 15L:9D respectively.The results of the experiment indicated that photoperiod has significant effects on the feeding rate and feed conversion efficiency of the whole experimental period.But the feed conversion efficiency of the feeding declined treatment was increased because the oxygen consumption rate was decreased.Thus the photoperiods did not have significant effects on the growth of fish.Photoperiods have significant effects on the content of melatonin in plasma,and RNA/DNA ratio in muscle and liver,but the differences of these parameters show no significant correlation to the growth of fish.