细鳞鲑早期发育过程中免疫器官发生

应用连续切片技术和显微观察法,对胚胎末期至仔鱼期的细鳞鲑(Brachymystax lenok)免疫器官(头肾、胸腺及脾组织)早期发育进行了系统研究。研究表明,在实验水温为10.0～16.2℃时,细鳞鲑的免疫器官原基发生及其淋巴化的先后顺序均为胸腺、头肾和脾。仔鱼出膜前5 d胸腺原基形成,出膜前1 d胸腺即出现少量淋巴细胞,仔鱼19日龄后,结缔组织和毛细血管渗入胸腺实质而形成小梁,仔鱼35日龄左右,胸腺己经分化出模糊的内区和外区;仔鱼出膜前2 d,出现头肾原基,由未分化的造血干细胞组成,仔鱼3日龄后,头肾由肾小管构成,10日龄后,组织开始淋巴化,仔鱼35～45日龄,肾小管上皮细胞开始退化,头肾内出现血窦,并进一步淋巴化,50日龄后,肾小管退化完毕,头肾主要由淋巴组织和大量血窦构成;5日龄细鳞鲑仔鱼,脾原基出现,16日龄后,脾开始淋巴化,35～50日龄,脾内建立起发达的微血管系统以及血窦结构。细鳞鲑的免疫器官分化较早,其发育速度较其他淡水硬骨鱼类相对滞后,但组织淋巴化速度较快。本研究旨在揭示细鳞鲑早期死亡率高的根本原因,为实现细鳞鲑的规模化养殖提供科学基础。

Ontogeny of immune organs during early developmental stages of Brachymystax lenok

The early development of the head kidney,thymus and spleen of Brachymystax lenok between late em-bryo and larval stages was studied by microscopic observation of serial sections.At a water temperature of 10.0–16.2°C,the order of appearance of lymphoid organ primordia was thymus,head kidney and spleen.The pri-mordium of the thymus formed 5 d before hatching and small lymphocytes appeared 1 d before hatching.Nineteen days after hatching,connective tissue and blood capillaries penetrated into the parenchyma of the thymus and the trabeculae appeared.Differentiation into indistinct inner and outer zones occurred after 35 d.The head kidney primordium,which consisted of undifferentiated hemopoietic stem cells,appeared 2 d before hatching.Kidney tubules were formed 3 d after hatching and lymphoid organs after 10 d.Between 35 d and 40 d after hatching,the epithelium of the renal tubules began to degrade and blood sinuses appeared in the head kidney.When the renal tubules had degenerated completely 50 d after hatching,the head kidney was composed principally of lymphoid tissue and a large number of blood sinuses.The spleen primordium appeared 5 d after hatching and the organ be-came lymphoid on the 16th day.Capillaries and blood sinuses were formed in the spleen between 35 d and 50 d.We conclude that the immune organs are differentiated earlier in Brachymystax lenok than in other fishes.Al-though the overall development rate was relatively slow in Brachymystax lenok,the lymphoid tissues developed earlier than in other teleosts.