急性氨氮胁迫对虎斑乌贼肝脏、鳃和脑组织结构的影响

为了探讨氨氮对虎斑乌贼器官组织结构的影响,以体质量为(13.80±0.65)g的幼虎斑乌贼为对象,研究了氨氮胁迫对其肝脏、鳃和脑组织结构的影响。根据96 h的LC50实验结果设计5个梯度(0、1、3、6和12 mg/L)进行96 h的氨氮胁迫后,利用光学显微镜和透射电子显微镜观察其肝脏、鳃和脑组织结构。结果显示,在相同浓度的氨氮胁迫下,虎斑乌贼不同组织器官之间损伤程度存在差异,其中肝脏损伤的程度最大,对氨氮胁迫表现最敏感,其次是鳃组织和脑组织,组织器官损伤程度与氨氮浓度呈现正相关。氨氮胁迫浓度越大或胁迫时间越长,肉眼观察发现肝脏颜色越鲜红,肿胀和易糜烂程度越明显,可通过肉眼观察肝脏颜色和肿胀程度初步判断机体氨中毒程度;氨氮胁迫后,对肝脏和鳃组织造成较为严重的损伤,可能是虎斑乌贼氨中毒致死的原因。当氨氮高于或等于6 mg/L时胁迫96 h后,通过显微观察发现肝小叶轮廓模糊不完整、排列不紧密和胞浆疏松透明,大量的细胞核溶解,细胞出现空泡化,肝血窦扩张;通过电镜观察发现细胞核皱缩变形、核仁消失、线粒体嵴紊乱、线粒体空泡化、线粒体外室肿胀,高尔基体数量减少;显微观察发现鳃组织的泌氯细胞和上皮细胞核溶解,细胞出现空泡化、排列紊乱,鳃丝肿胀淤血、轮廓模糊不完整,并出现坏死脱落和缺损;通过透射电镜观察,发现细胞核皱缩、核膜破损和细胞核裂解,线粒体出现了皱缩变形、空泡化和不完整破损现象;观察脑组织的神经团和视叶,未发现脑组织的细胞有显著损伤。

Effects of acute ammonia exposure on histopathology of liver, gill and brain in juvenile cuttlefish (Sepia pharaonis)

The aim of this study is to investigate the toxic effects of ammonia-N stress on the histopathological changes of liver, gill and brain in juvenile cuttlefish (Sepia pharaonis). The S. pharaonis, whose initial average weight was (13.80±0.65) g, were first exposed to ammonia-N for 96 hours and then the 96 hours median lethal concentration was obtained. In this study, we established a control group (0 mg/L) and four different ammonia nitrogen concentrations of 1, 3, 6, and 12 mg/L for the acute ammonia toxicity experiment according to preliminary experimental results, and each ammonia-N level was respectively sampled at 96 h. The liver, gill and brain tissues were observed by optical microscope and transmission electron microscope. The results showed that the severity of lesions clearly differed among organs with the liver showing the most extensive damages, followed in order by the gill and brain. And there was no damage to the brain tissue. The damages of liver and gill increased with increasing exposure concentration and time. It is found that the liver is bright red, swollen, and easily eroding from the 96 h after exposure to no less than 6 mg/L ammonia. Microscopical observation showed that the liver displayed hypertrophy of hepatocytes, nuclear hypertrophy, cellular peripheral nucleus, hepato cellular vacuolation, hydropic degeneration, necrosis, dilatation in sinusoids, cellular outline indistinguishable and cytolysis. The transmission electron microscope observation showed the hepatocyte nuclear crinkle deformation, the nucleolus disappearance, the mitochondrial crista disorder, the vacuolation and the outer chamber swelling, and the number of Golgi bodies decreased. Microscopical observation showed shedding epithelial cells from gill lamella, irregular array and some necrosis phenomenon, vessel of gill filaments was pycnosis or even became cavum, and branchial swelling and congestion. The transmission electron microscope observation showed gill epithelium and chloride nuclear membrane breakage, and nuclear cleavage, mitochondrion has crinkle deformation, vacuolization and incomplete breakage. While the brain tissue and the optic lobes were observed, there was no cell damage in the brain tissue.