网箱养殖密度对虹鳟甲状腺激素及血脂指标的影响

摘要

The aims of this study were to evaluate the effects of stocking density of Oncorhynchus mykiss that were reared in net cages on free triiodothyronine (FT3), free thyroxine (FT4), triglyceride (TG) and total cholesterin (TC) levels, and the expression of IGF-I and TR-α. The results showed that FT3 and FT4 levels decreased gradually as the stocking density increased, and they were positively associated with the culture time before November. TG levels de-creased as the stocking density increased while TC levels increased as the stocking density increased and both TG and TC levels were negatively associated with the culture temperature. Moreover, TG levels in the treatment group 3(GR3) were significantly lower than those in the treatment group 1(GR1) in November, and significant differences were ob-served among the three treatments in January of the following year (P < 0.05). Additionally, the expression levels of IGF-I and TR-αdecreased gradually as the stocking density increased. These results indicate that high stocking density could be a stressor for O. mykiss, that nd that may reduce FT3 and FT4 levels in the blood and then affect the growth and development of fish, which is supported by the trend of special growth rate (SGR). There was a relationship between thyroid hormone and the expression of IGF-I, The levels of thyroid hormone was related to the expression of IGF-I;however further investigation is needed to study whether thyroid hormone regulates the expression.%为研究网箱养殖密度对虹鳟甲状腺激素及血脂指标的影响，测定了血液中游离甲状腺激素 T3(FT3)、游离甲状腺激素 T4(FT4)、甘油三酯(TG)和总胆固醇(TC)含量，检测了高密度胁迫对肝脏和肠中 IGF-Ⅰ和肝脏、肾脏中 TR-α表达的影响。结果显示，随着养殖密度的升高 FT3和 FT4的含量逐渐降低，并且在11月份之前含量与养殖时间成正相关性；血清中TG含量随着密度的升高而降低， TC随着密度升高而升高，并且与温度存在负相关性，在11月份时密度处理组3(GR3)中的TG含量显著低于密度处理组1(GR1)，翌年1月份时3个密度处理组间都存在显著性差异(P<0.05)；而 IGF-Ⅰ和 TR-α也随着养殖密度的增加表达量逐渐降低。结果说明高密度网箱养殖作为一种环境胁迫因子使得血清中 FT3和 FT4含量降低，从而影响虹鳟鱼的生长发育，这一现象与特定生长率(SGR)的变化趋势一致。甲状腺激素含量的降低使得 TR-α表达量降低，实验中 IGF-Ⅰ的表达与甲状腺激素含量也存在相关性，甲状腺激素是否调控 IGF-Ⅰ的表达有待于进一步的研究。