凡纳滨对虾鳃组织对高温和氨氮胁迫的生理响应

Physiological responses in gills of Litopenaeus vannamei exposed to the combined stress of temperature and ammonia

【目的】明确高温和氨氮单因素胁迫及二者复合胁迫对凡纳滨对虾(Litopenaeus vannamei)鳃组织的毒性效应,为开展凡纳滨对虾健康养殖提供理论依据。【方法】将体质健康的凡纳滨对虾随机分成4组,即对照(正常海水)组、高温(33℃)胁迫组、氨氮(15 mg/L)胁迫组、高温与氨氮复合胁迫(氨氮浓度15 mg/L,水温33℃)组。胁迫72 h后,从每个平行中随机挑取凡纳滨对虾鳃组织制作石蜡切片观察其病理变化,并采用试剂盒测定鳃组织生理功能指标的变化情况。【结果】经高温和氨氮单因素胁迫或二者复合胁迫后均致使凡纳滨对虾鳃组织发生病理性结构变化,表现为角皮层变薄或消失,上皮细胞逐渐分解,入鳃和出鳃血管变形或裂解,鳃丝连接松散,腔内出现液泡等。凡纳滨对虾鳃组织超氧阴离子自由基(O2-·)和过氧化氢(H2O2)含量均在氨氮胁迫后显著降低(P<0.05,下同),但经高温胁迫和高温与氨氮复合胁迫后无显著变化(P>0.05,下同);总抗氧化能力(T-AOC)和总超氧化物歧化酶(T-SOD)活性在高温或氨氮胁迫后均显著升高;谷氨酸脱氢酶(GDH)活性在高温和氨氮单因素胁迫及二者复合胁迫后均显著升高;谷氨酰胺酶(GLS)活性经氨氮胁迫后显著升高,经高温胁迫和高温与氨氮复合胁迫后则显著降低;己糖激酶(HK)活性在高温胁迫后显著降低,经氨氮胁迫后显著升高;乳酸脱氢酶(LDH)活性仅在氨氮胁迫后显著升高;酸性磷酸酶(ACP)活性经氨氮胁迫后显著升高,而在高温胁迫和高温与氨氮复合胁迫后均显著降低。【结论】经高温和氨氮单因素胁迫或二者复合胁迫后,凡纳滨对虾鳃组织出现明显的病理性变化,其氧化应激、氨氮代谢和能量代谢相关生理指标均发生显著变化。氨氮胁迫造成对虾鳃组织生理紊乱,且高温胁迫加重氨氮毒性,而降低对虾鳃组织生理功能。因此,对虾健康养殖特别是工厂化高密度养殖过程中因避免高温环境下氨氮胁迫对凡纳滨对虾的毒性效应。

【Objective】This study was to clarify the toxic effects of high temperature and ammonia single factor stress and their combined stress on the gills of Litopenaeus vannamei.Then,it could provide theoretical basis for healthy breeding of L.vannamei.【Method】The healthy L.vannamei were divided into four groups:the control(seawater)group,the high temperature(33℃)stress group,the ammonia(15 mg/L)stress group,and the combined of high temperature and ammonia stress(15 mg/L ammonia and 33℃water)group.After stress for 72 h,the gill tissues of L.vannamei were randomly selected from each parallel to make paraffin sections to observe the pathological changes.And changes of physiological function indexes of the L.vannamei were determined by kit.【Result】The single factor of high temperature and ammonia and the combined stress all caused pathological structural changes in the gill tissue,which was manifested as the thinning or disappearance of the cuticle layer,the gradual decomposition of epithelium,and the deformation and lysis of the afferent and efferent vessels of the gills.The gill filaments were loosely connected,and vacuoles appeared in the cavity.Oxidative damage indexes including superoxide anion radical(O2-·)and hydrogen peroxide(H2O2)levels were significantly decreased in gill tissue in the ammonia stress group(P<0.05,the same below),but no significant changes in the high temperature stress group and the combined stress group(P>0.05,the same below).The total antioxidant capacity(T-AOC)and total superoxide dismutase(T-SOD)activities were significantly increased in high temperature stress group and the ammonia stress group.The glutamate dehydrogenase(GDH)activity was significantly increased in all the stress groups,glutaminase(GLS)activity was significantly increased in the ammonia stress group,but significantly decreased in the high temperature stress group and the combined stress group.Hexokinase(HK)activity was significantly decreased in the high temperature stress group,but increased in the ammonia stress group;lactate dehydrogenase(LDH)activity was only significantly increased in the ammonia stress group;acid phosphatase(ACP)activity was significantly increased in the ammonia stress group,but significantly decreased in the high temperature stress group and the combined stress group.【Conclusion】The results show that high temperature and ammonia single factor and their combined stress all have significant effects on the physiological functions of the gill of L.vannamei,the gill tissue shows obvious pathological changes,oxidative stress,and ammonia nitrogen metabolism and energy metabolism-related physiological indicators all change significantly.The ammonia stress can induce the physiological disorder of gill tissue,while the high temperature stress aggravates the ammonia toxicity and reduces the physiological function of the shrimp.Therefore,the process of healthy shrimp farming should pay attention to the toxic effect caused by ammonia stress in high temperature environment,especially in high-density factory farming.