We evaluated the chronic toxicity of zinc sulphate in the crayfish Procambarus clarkii. Mature P. Clarkii were exposed to 0, 0.40, 4.04, or 40.37 mg/L Zn2+ for 21 days. Each day, we randomly selected five crayfish in each group and collected samples of the hepatopancreas, gill, and muscle tissue from males and females and ovarian tissue from each female. The tissues were placed in Bouin's fixative for 24 h, sectioned in paraffin, and stained using H-E. We observed a number of brick red particles in the cytoplasm of cells from the hepatopancreas and antennal gland in animals exposed to Zn2+. The number of these particles was positively correlated with the concentration of Zn2+ and exposure time. There was no obvious histopathology in the group exposed to 0.40 mg/L Zn2+. We observed bleeding and necrosis in hepatopancreas, antennal gland, and gills in the group exposed to 4.04 mg/L after 7 d. The proportion of necrotic cells increased as the concentration of Zn2+ and time of exposure increased. We observed spermatocyte necrosis after 14 d in exposure to 40.37 mg/L Zn2+. After 21 d, we observed bleeding of the spermary and ovary and necrosis of the ootid and spermatocyte cells. A large number of hepato-cytes exhibited necrosis and had dropped from the hepatic ducts. The connective tissue exhibited hyperplasia, with large numbers of cells blocking the hepatic ducts, resulting in macroscopical bulky grains in the hapatopancreas of the group exposed to 40.37 mg/L. Our results suggest that exposure to 4.04 mg/L Zn2+ for 21 d causes pathological changes in the hepatopancreas, antennal gland, gills, and gonad tissue of P. Clarkii. Given that zinc sulphate interferes with the metabolic, respiratory, and reproductive systems, chronic exposure is likely to threaten the survival of P. Clarkii populations.%将克氏原螯虾(Procambarus clarkii)成虾在Zn2+质量浓度为0、0.40 mg/L、4.04 mg/L和40.37 mg/L的硫酸锌溶液中浸浴21 d,分别于第7、14和21天时每组随机抽取5只虾,采集肝胰腺、鳃、触角腺、性腺、肌肉及消化道组织,于Bouin's液中固定24 h.采用石蜡切片和HE染色的方法,观察其组织的病理变化,从组织学水平研究硫酸锌对克氏原螯虾的慢性毒性作用.结果显示,浸浴时各Zn2+浓度组肝胰腺、触角腺细胞质中出现被染成红棕色的颗粒,且颗粒的数量与浸浴浓度及时间成正相关.0.40 mg/L组在浸浴期间各组织均未出现其他明显病变；4.04mg/L组及40.37mg/L组从浸浴第7天开始肝胰腺、触角腺、鳃组织出现出血、细胞坏死等病变,随浸浴浓度增大和时间延长坏死细胞比例增大.40.37 mg/L组第14天时精母细胞开始出现坏死；第21天时精巢、卵巢严重出血,精、卵细胞出现大面积坏死,肝细胞大量坏死脱落,肝小管结缔组织增生,大量脱落的细胞塞满管腔使肝胰腺表面形成肉眼可见的红棕色颗粒状斑点.结果表明在Zn2+质量浓度高于4.04 mg/L的硫酸锌浸浴21 d后,克氏原螯虾肝胰腺、触角腺、鳃、性腺组织均出现不同程度的病变,表明其代谢系统、呼吸系统、生殖系统等受到较严重的损伤,因此长期暴露在Zn2+质量浓度高于4.04 mg/L的环境中会严重威胁克氏原螯虾的生存和繁殖.
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