淡水和半咸水条件下中华鲟幼鱼鳃上皮泌氯细胞的形态特征与数量分布

为了探讨中华鲟幼鱼进入长江口半咸水环境后,渗透压适应调节过程中鳃上皮泌氯细胞的适应性变化,将幼鱼在淡水(盐度0)和半咸水(盐度15)两种条件下驯养60 d,利用光镜和扫描电镜技术对比分析鳃上皮泌氯细胞的形态、分布与数量特征。结果表明:幼鱼鳃上皮泌氯细胞主要集中分布于鳃小片基部和鳃小片之间的鳃丝上,细胞略呈椭圆形。半咸水条件下,幼鱼鳃丝上皮泌氯细胞数量和大小显著增加,鳃小片上皮泌氯细胞数量则未发生改变,但细胞大小显著增加;而鳃丝和鳃小片上皮泌氯细胞的形态在淡水和半咸水中均未发生显著变化。扫描电镜观察发现,鳃丝上皮泌氯细胞顶膜开口的形态分为3种类型:Ⅰ型,突起型;Ⅱ型,凹陷型;Ⅲ型,深洞型。淡水条件下,顶膜开口形态多为Ⅰ型和Ⅱ型,未发现Ⅲ型存在;而半咸水条件下,顶膜开口形态以Ⅲ型为主,Ⅰ型与Ⅱ型也有少量分布。

Characters of morphology,distribution and quantity of branchial chloride cells of juvenile Acipenser sinensis acclimated in freshwater and brackish water

To understand the adaptive changes of branchial chloride cells (CCs)in juvenile Chinese sturgeon Acipenser sinensis in the Yangtze Estuary,juveniles were acclimated to 0 (freshwater,FW)and brackish water (salinity 15,BW)for 60 days.Histological and ultrastructural observation on branchial CCs were comparatively studied in juveniles adapted either in FW or BW.Results showed that:CCs were slightly oval, and mainly distributed in the base of lamellae and interlamellar regions of filaments.When juveniles were adapted in BW,the number and size of branchial CCs on filaments increased significantly.However,there was no change on number of CCs,and there was a significant increase on size of CCs on lamellae.The morphology of CCs on filaments and lamellae did not change in fish adapted to FW or BW.Apical opening of CCs was largely classified into the following three types:Ⅰ,convex type;Ⅱ,concave type;Ⅲ,deep-hole type.In FW,apical opening of CCs on juvenile Chinese surgeon gills presented as type Ⅰ and Ⅱ,and no type Ⅲ was found.After the fish was adapted in BW,apical opening of CCs on juvenile gills was mainly type Ⅲ, and a small amount of type Ⅰ and Ⅱ apical opening appeared.The increase of number and size of branchial CCs on filaments and the morphological changes of apical opening of CCs is the adapting adjustment of juvenile Acipenser sinensis for osmoregulation and maintaining osmotic balance.