小瓜虫在澳洲龙纹斑鳃器官上的分布及其影响

【目的】小瓜虫病是澳洲龙纹斑苗种阶段危害巨大的寄生虫病。探究小瓜虫在澳洲龙纹斑鳃器官上的分布及其影响可以丰富小瓜虫的致病性及病理学方面的研究内容,也可以为渔业生产中小瓜虫病的防治提供参考。【方法】采用光镜及扫描电镜技术确定病原,并观察小瓜虫在澳洲龙纹斑鳃丝、鳃小片及鳃盖上的分布情况及这些器官的变化情况。【结果】小瓜虫侵染澳洲龙纹斑的鳃器官后,分布在鳃丝、鳃小片及鳃盖的表面,上皮细胞之下及鳃小片之间,或是包裹在黏液细胞里,但侵染后期在鳃丝及鳃小片上的数量明显少于鳃盖。侵染后期,鳃丝、鳃小片及鳃盖出现一定程度的膨胀变形,黏液细胞分泌增多,鳃小片末端膨大变形甚至黏连融合,顶端充血呈球状或棒状。【结论】对于鳃部而言,侵染后期小瓜虫主要分布在澳洲龙纹斑的鳃盖上。小瓜虫主要通过侵染引发澳洲龙纹斑鳃部器官的变形膨大,使其丧失正常的功能,造成血液循环受阻、渗透压调节失衡,最终导致鱼体缺氧死亡。

Distribution and effect of the parasite Ichthyophthirius multifiliis on the gill organs of the Murray cod, Maccullochella peelii

Aim] The white spot disease, caused by the parasite Ichthyophthirius multifiliis is harmful to the Murray cod, Maccullochella peelii. The distribution and influence of I. multifiliis on the gills of M. peelii were investigated to better understand its pathogenicity and pathology and provide reference for the control of this disease in fish production.Method] Light microscope and scanning electron microscope were used to identify the pathogen and describe its distribution on the gill-filaments, gill-lamella and the operculum of M. peelii.Result] In infected M. peelii, I. multifiliis was distributed on the surface of gill-filaments, gill-lamella, operculum, under epithelial cells, between the gill-lamella or wrapped in mucus cells. The numbers of I. multifiliis on gill-filaments and gill-lamella were significantly fewer than on the operculum during the later period. In the late stage of infection, there was a certain degree of expansion and deformation of the gill-filaments, gill-lamella and operculum. Secretion by mucus cells increased, and the ends of the gills expanded and became deformed, even adhered and fused, and the top was globular or rod-shaped.Conclusion] For the gills organs, I. multifiliis was mainly distributed on the operculum of M. peelii during the later period of infection. I. multifiliis caused the deformation of gill organs of M. peelii, which lost its normal function, blocking blood circulation and leading to unbalanced osmotic pressure, eventually causing death from hypoxia.