不同盐度和驯养时间中华鲟子二代幼鱼鳃的显微结构变化

Microstructure Changes in the Gill Epithelia of Second Filial Acipenser sinensis Juvenile Acclimated to Various Salinities for Different Time

采用光学显微镜和组织切片方法,研究了不同盐度和驯养时间中华鲟幼鱼鳃及鳃中泌氯细胞的结构变化特征。试验用鱼为1+龄中华鲟子二代,平均全长50.7 cm,平均体重约441.9 g。试验前在养殖池中暂养1周。试验设2个盐度梯度(10、15)组和1个对照组(淡水)。盐度驯养为将中华鲟子二代从暂养池转入盐度10海水中驯养,分别取驯养1、3、6、9、12、24、48、72、96、120、144、168、192、216、240和264 h的幼鱼各1尾用于试验;将剩下的鱼再转入盐度15海水中驯养,分别取驯养24、48、72 h的幼鱼各1尾用于试验。结果显示,在淡水组中,中华鲟子二代幼鱼鳃丝发达,细胞饱满,鳃小片宽且长。鳃丝上皮的泌氯细胞数量较少,通常靠近鳃小片基部,呈近椭圆状。与淡水组相比,盐度10组的幼鱼鳃丝主干部明显变窄,鳃小片基部区域及鳃小片上泌氯细胞的数量略有增加,胞体变大,且随驯养时间的延长,出现了明显的细胞膜间隙。幼鱼在盐度15组中鳃丝主干明显变窄变短,鳃小片也显著缩短,鳃泌氯细胞数量显著增加,主要分布在鳃小片基部,有明显的分泌腔。中华鲟子二代幼鱼能够快速适应外界水体盐度的变化,这与鳃及鳃上皮中调节渗透压功能细胞的数量和结构变化相适应。

Acipenser sinensis, a typical migratory fish, can acclimate to the very different osmotic environments of fresh water and seawater. The gills play an important role in osmotic and ionic regulation. Morphological and physi- ological changes in the organs that respond to osmotic pressure changes of Acipenseridae under different salinities have been reported and include Russian sturgeon （Acipenser gueldenstaedti）, lake sturgeon （Acipenser fulvescens）, white sturgeon （Acipenser transmontanus） and Amur sturgeon （Acipenser schrenckii）. However, only a few studies have examined the physiological changes of the first filial generation of Acipenser sinensis during seawater acclimation and no relevant research on the second filial generation. Microstrueture modifications in the chloride cells of the gill epithelia of juvenile second filial Chinese sturgeon acclimated under different salinities and different time periods were examined by light microscopy and histological photomicrography. Twenty second filial Chinese sturgeon juven- iles with mean full length of 50.7 cm and mean body weight of 441.9 g were used in the investigation. The test fish were divided into 3 groups and assigned to three circular fiberglass tanks with salinities of 0, 10 and 15 g/kg, One juvenile Chinese sturgeon was selected to sample the second gill arch at times of 1, 3, 6, 9, 12, 24, 48, 72, 96, 120, 144, 168, 192, 216, 240 and 264 h for the 10 g/kg salinity group and at 24, 48 and 72 h for salinity 15 g/kg salinity group. The microstructure of the gill as well as the distribution and structural changes in chloride cells were examined after treatment. Results show that the gill filaments were developed with plump cells in the freshwater group and the gill lamella became wider and longer. A few chloride cells of elliptical shape were ob- served on the base of lamella. In contrast to the freshwater group, gill filaments were narrower in the 10 g/kg salin- ity group. Moreover, there was a little increase in the number and size of chloride cells on the base of gill lamella, and Chinese sturgeon juvenile showed a remarkable cell gap as the transfer time increased. At salinity of 15 g/kg, the gill filaments and lamella were narrower and significantly shorter. The number and size of chloride cells in the filaments increased remarkably. Chloride cells were generally centered at the base of lamella and had obvious secre- tory cavities. Juvenile Chinese sturgeon adapted quickly to the changes in salinity and is ascribed to structural chan- ges of the functional cells in gill filament epithelia.