松浦镜鲤越冬期的形态、组织结构及生化组成变化

Changes in morphology, histological structure, and biochemical composition during overwintering in Songpu mirror carp, Cyprinus carpio var. songpu morror

利用电子标记跟踪同期孵化、同条件养殖的松浦镜鲤（Cyprinus carpio var.songpu mirror）在越冬前后的生长过程,比较实验鱼在125 d（越冬前）、170 d（结冰初期）及325 d（越冬后）的形态、组织结构及生化组成变化,并探讨越冬后鱼体主要供能物质含量与越冬体重损失的关系。结果显示,鲤325 d的体重（BW）、肥满度（CF）、脏体指数（VSI）、肝体指数（HSI）和肠体指数（ISI）均显著低于125 d（P〈0.05）;与125 d相比,325 d时的肝和前肠组织结构变化明显,主要表现在肝细胞体积变小,细胞界限模糊,糖原和脂滴丢失。前肠直径、绒毛高度和肌层厚度均显著下降（P〈0.05）,柱状上皮杯状细胞减少,纹状缘萎缩;鲤内脏脂肪和肝糖原含量在越冬期各测定时段均显著下降（P〈0.05）,肌肉和全鱼蛋白质含量仅在冰下阶段（170～325 d）下降明显（P〈0.05）。越冬后肌肉蛋白质含量与体重损失率呈显著的负相关（P〈0.05）,但内脏脂肪含量与越冬体重损失率无相关（P〉0.05）。以上结果表明,越冬导致鲤体重相关的形体指标显著变化;越冬长期饥饿引起了肝和前肠组织退化;越冬期间鲤贮能物质的消耗存在阶段性,在结冰前阶段（125～170 d）,能量来源以肝糖原和脂肪为主。在冰下阶段（170～325 d）,肝糖原、脂肪和蛋白质共同参与能量代谢。越冬后肌肉蛋白质含量可作为衡量越冬期体重损失程度的参考指标。

Common carp（Cyprinus carpio） is the main fish species cultured in ponds at high latitudes in northern China, where there are long and cold winters. Common carp reaches market size after a 5-month overwintering period in northeast China. Thus, it is critical to understand the effects of overwintering on the survival and growth of cultured fish. In this study, the growth of Songpu mirror carp （Cyprinus carpio var. songpu mirror） was monitored using passive in- tegrated transponders before and after overwintering. All fish were hatched at the same time and cultured under the same conditions. Morphological indices, liver and foregut histological structure, and biochemical composition of the viscera, muscle, and whole body were analyzed at 125 d （before overwintering）, 170 d （beginning of freezing）, and 325 d （after overwintering）. Furthermore, the correlation between major energetic material at 325 d and overwintering body weight loss rate （WRL） was evaluated. The results showed that body weight （BW）, condition factor （CF）, visceral-somatic index （VSI）, hepatosomatic index （HIS）, and intestine-somatic index （ISI） decreased significantly over the entire overwintering period （125-325 d） （P〈0.05）. Significant degeneration of histological structures for the hepatic and foregut was observed during 125-325 d. Hepatic cells shrank, and the boundaries between hepatic cells were blurred. The abundant hepatic glycogen and lipid stores present before winter disappeared after winter. Foregnt diame- ter, villus height, and muscle layer thickness decreased significantly after winter compared with those before winter （P〈0.05）, and the striated borders of the foregut were clearly atrophied. Visceral fat and hepatic glycogen contents were significantly attenuated at each sampling period （P〈0.05）. However, whole-body and muscle protein contents only de- creased significantly during 170-325 d （P〈0.05）. In addition, a significant negative correlation was detected between muscle protein content at 325 d and WRL （P〈0.05）, but no association was found between visceral fat at 325 d and WRL（P〉0.05）. Taken together, these results suggest that overwintering led to significant changes in the morphological indices based on common carp BW. Degeneration of the hepatic and foregut histological structures resulted from chronic hunger during the winter. The stages of consuming endogenous energy during the winter varied. Hepatic gly- cogen and fat were used initially during 125-170 d, whereas hepatic glycogen, fat, and protein were used for energy ex- penditure during 170-325 d. Muscle protein content after the winter could be useful as a reference indicator for WRL.