中华鲟免疫器官的早期发育

为了解中华鲟(Acipenser sinensis)免疫器官早期发育的形态和组织学特征,实验以1~300 dph中华鲟子二代的仔鱼、稚鱼和幼鱼为研究对象,使用连续石蜡切片技术和显微观察方法对免疫器官(头肾、胸腺和脾脏)的发育过程进行观察和记录。结果显示,培育水温为12.9~22.6℃时,中华鲟免疫器官原基出现的先后顺序为头肾(3 dph)、胸腺(7 dph)和脾脏(9 dph);免疫器官淋巴化先后顺序为胸腺(12 dph)、头肾(15 dph)和脾脏(33 dph)。仔鱼发育至15 dph可见头肾和胸腺间有淋巴细胞“桥”连接现象, 180 dph胸腺内可见哈氏小体结构,头肾、胸腺和脾脏内含有黑色素细胞或黑色素巨噬细胞中心(MMCs)。总体而言,中华鲟免疫器官发育具有原基出现时间早、发育速度慢和发育周期长的特点。由于仔稚幼鱼免疫系统发育不完善,建议在其培育过程中加强病害防治和早期疫苗的开发。

Ontogeny of immune organs during early developmental stages of Chinese sturgeon (Acipenser sinensis)

The wild populations of Chinese sturgeon (Acipenser sinensis) have decreased dramatically since the 1970s because of environmental degradation, overfishing, and construction of the Gezhouba Dam in the Yangtze River. In 1989, A. sinensis was listed as a first-protected animal in China, also it has been on the IUCN Red List as a Critically Endangered species since 2009. The artificial propagation technology of A. sinensis was realized in 2012, and large-scale hatching of larvae is possible. However, the larval to juvenile stage is the main period of disease occurrence, especially when larvae start feeding and juveniles convert bait; there is often high mortality. This has seriously restricted the protection and utilization of the germplasm resources of A. sinensis. Thus, it is critical to understand the development of the immune system. The goals of this research were to understand the early developmental process and characteristics of the immune organs of A. sinensis by anatomical and histological methods. This provides morphological and histological data for the early development of the lymphoid organs of A. sinensis, and also accumulates basic data for the large-scale cultivation of fry. The healthy larvae and juveniles of F₂ A. sinensis with 1-300 dph were regarded as appropriate species for this test. The occurrence of immune organs (head kidney, thymus, and spleen) was observed and recorded by means of continuous paraffin section and microscopic observation. The results showed that the primordia of immune organs from A. sinensis appeared in the order of the head kidney (3 dph), thymus (7 dph), and spleen (9 dph), and small lymphocytes appeared in the order of the thymus (12 dph), head kidney (15 dph), and spleen (33 dph). At 15 dph, lymphocyte bridges were observed between the head kidney and thymus. At 180 dph, Hassall''s corpuscles were observed in the thymus, and Melanocyte or Melano-macrophage centers (MMCs) were found in the head kidney, thymus, and spleen. In conclusion, the immune organs of A. sinensis have the characteristics of early primordial differentiation, a slow developmental rate, and a long developmental cycle. Because the structure of the immune system is not fully developed from larval to juveniles, it is suggested that disease prevention and vaccine development should be strengthened in the early cultivation process.