亚硝酸氮对中华小长臂虾的急性毒性及非特异性免疫指标的影响

采用生物毒性实验方法研究了亚硝酸氮(NO_2~--N)对体重为(0.28±0.05)g的中华小长臂虾(Palaemonetes sinensis)的急性毒性作用。结果表明:在温度为18±1℃、pH 7.3±0.1条件下,NO_2~--N对中华小长臂虾24、48、72和96 h的半致死浓度(LC50)分别为37.9、27.3、24.9和23.2 mg·L~(-1),安全浓度为2.32 mg·L~(-1);根据96 h LC50和安全浓度按照等差数列设置5个NO_2~--N浓度梯度,分别为6.0、9.5、13.0、16.5和20 mg·L~(-1),研究了NO_2~--N胁迫对中华小长臂虾非特异性免疫指标的影响;在24 h时,除20 mg·L~(-1)处理组肌肉的超氧化物歧化酶(SOD)活性外,各NO_2~--N处理组的中华小长臂虾肝胰腺和肌肉SOD活性与对照组均无显著性差异(P0.05);到96 h时,13、16.5和20 mg·L~(-1)处理组肝胰腺SOD活性下降,显著低于对照组(P0.05),但肌肉组织则未出现显著性下降,而6和9.5 mg·L~(-1)处理组显著性高于对照组;24 h时,只有最高浓度20 mg·L~(-1)组的肝胰腺酸性磷酸酶(ACP)活性以及6 mg·L~(-1)组的碱性磷酸酶(AKP)活性显著高于对照组,其他处理组与对照组均无显著性差异;随着处理时间的延长,到达96 h时,出现了与SOD相同的趋势,即13、16.5和20 mg·L~(-1)处理组酶活性显著低于对照组(P0.05);与肝胰腺不同的是,24 h时肌肉组织ACP和AKP活性出现了明显的"毒物兴奋效应",除了13和20 mg·L~(-1)的AKP外,其他处理组均出现了显著性升高(P0.05);到96 h时,除9.5 mg·L~(-1)处理组外,其他处理组的ACP和AKP活性均与对照组无显著性差异(P0.05)。本研究发现,中华小长臂虾可耐受较高浓度NO_2~--N,而长时间的NO_2~--N胁迫则对中华小长臂虾的免疫酶活性存在抑制作用,研究结果可为中华小长臂虾健康养殖提供科学依据。     

镉对长江华溪蟹免疫相关酶活性的影响

采用浸浴法研究了镉(Cd2+)对长江华溪蟹Sinopotamon yangtsekiense免疫系统相关酶的影响.Cd2+处理组浓度分别为7.25 mg/L、14.5 mg/L、29mg/L、58 mg/L和116 mg/L,同时设对照组.分别在Cd2+处理24 h、48h、72 h和96 h取血清进行酚氧化酶(PO)、超氧化物歧化酶(SOD)、酸性磷酸酶(ACP)和碱性磷酸酶(AKP)活力测定.结果显示,在相同处理时间,随着cd2+浓度增加,PO和SOD活力均呈现先升后降的趋势,且分别于24 h、7.25 mg/L和96 h、14.5 mg/L时达到最大值.当处理浓度相同、作用时间延长时,ACP活力先升后降,且在48 h、58 mg/L时升至最高,AKP活力则持续上升.表明Cd2+对长江华溪蟹免疫相关酶活力具有不同程度的影响,且其作用和效果具有浓度及时间效应.PO和SOD活力变化能够灵敏反映Cd2+对水生动物的胁迫程度,可作为指示镉污染的生物学指标.     

氨对褶纹冠蚌钩介幼虫及稚蚌的急性毒性

为探究氨对蚌类早期生活史阶段的毒性效应,研究分别以褶纹冠蚌(Cristaria plicata)的钩介幼虫及稚蚌为实验对象开展了24h和48h的急性毒性实验。结果表明:氨对褶纹冠蚌钩介幼虫的24h半致死浓度(LC₅₀)为0.63 mg NH₃-N/L (NH₃,分子氨)和78 mg TAN_7.0,20℃/L (TAN_7.0,20℃,pH 7.0水温20℃时即标准化的总氨氮);氨对褶纹冠蚌稚蚌的48h LC₅₀为0.60 mg NH₃-N/L和104 mg TAN_7.0,20℃/L;上述阈值高于已有研究中氨对其他淡水蚌类的毒性阈值;褶纹冠蚌钩介幼虫对氨氮的耐受性低于稚蚌,二者均低于幼蚌,因此褶纹冠蚌更早期生活史阶段对氨的耐受性更低。相关研究结果可完善氨对蚌类毒性的理解,为水体氮管理策略的制定和蚌类保护提供一定科学依据。     

pH对中华小长臂虾存活及呼吸代谢的影响

为研究中华小长臂虾(Palaemonetes sinensis)对pH的耐受性,采用静水毒性实验方法确定了中华小长臂虾的半致死pH。实验设置酸性条件下的pH为3.0、3.2、3.4、3.6、3.8和4.0,碱性条件下的pH为10.4、10.6、10.8、11.0、11.2和11.4,统计中华小长臂虾在24、48、72和96 h的死亡率。中华小长臂虾24、48、72和96 h的酸性半致死pH(LpH50)分别为3.416、3.426、3.463和3.463,碱性半致死pH(LpH50)分别为10.813、10.609、10.516和10.516,酸性条件下和碱性条件下的安全pH分别为4.463和9.516。在半致死pH(LpH50)基础上以静水密闭式方法研究了pH对中华小长臂虾耗氧率、排氨率和窒息点的影响,pH设置为4、5、6、7、8、9、10,以pH 7为对照组。与对照组相比,只有pH为9和10时的耗氧率显著升高(P0.05),其他pH则未发生显著性变化(P0.05);排氨率则只有pH为5和6时显著高于对照组(P0.05),其他pH组与对照组没有显著性变化(P0.05);在pH为4~9时,中华小长臂虾氧氮比(O/N)的变化范围为4.14~10.95,此时以蛋白质为主要供能物质,随着pH继续上升到10时,中华小长臂虾的氧氮比(O/N)突然增加至29.62,此时供能物质则变成以脂肪为主;在各pH条件下窒息点没有发生显著性变化(P0.05)。本实验结果表明,中华小长臂虾对pH有很强的耐受性,但不同的pH会影响到中华小长臂虾的呼吸代谢以及能量供给方式。     

重金属镉对鲫鱼碱性磷酸酶和酸性磷酸酶活性的影响

研究了重金属镉对鲫鱼肠、肝胰脏、鳃组织碱性磷酸酶和酸性磷酸酶活性的影响。结果表明,在0.2、0.4、0.8mg/L镉浓度条件下静态染毒12h、24h、48h、96h后,鲫鱼肠、鳃组织中碱性磷酸酶(AKP)和酸性磷酸酶(ACP)的活性降低,肝和胰脏的碱性磷酸酶活性没有明显变化,其酸性磷酸酶活性则升高。     

五种重金属离子对克氏原螯虾（Procambarus clarkiai）的急性毒性作用研究

采用静水生物法、充气和恒温法研究了5种重金属离子对克氏原螯虾的急性毒性作用,并以直线内插法得出了24 h、48 h、72 h和96 h的半致死量（LD50）.研究结果表明：重金属离子的毒性顺序由大到小依次为：Hg2＋、Cd2＋、Cu2＋、Pb2＋和Zn2＋.根据毒性分级标准,5种重金属离子对克氏原螫虾均为高毒物,其安全质量浓度依次为：0.0143 mg/L、0.0322 mg/L、0.0401 mg/L、0.1995 ms/L和0.2795 mg/L.以浓度对数和死亡率进行回归分析,分别得出了5种重金属离子对螯虾24 h、48 h和96 h的回归方程.     

副溶血弧菌高效消毒剂的筛选及PHMG防治对虾AHPNS的应用研究

为寻找凡纳滨对虾急性肝胰腺坏死综合症(AHPNS)重要致病菌——副溶血弧菌的高效低毒消毒剂, 选取了包括苯扎溴铵、聚六亚甲基胍盐酸盐(PHMG)等22种水产或医学上常用的消毒剂, 比较分析其对副溶血弧菌的杀灭效果。悬液定量杀菌试验发现, 22种消毒剂中PHMG对副溶血弧菌的杀灭效果最好。接着, 进一步分析PHMG的有效杀菌浓度, 结果显示, PHMG浓度达到0.2 mg/L时作用48h即能100%地杀死副溶血弧菌。对7种常见病原菌和凝结芽孢杆菌的杀灭试验显示, PHMG对弧菌的杀灭效果最好, 0.5 mg/L PHMG能100%地杀灭四种弧菌, 对迟钝爱德华菌、嗜水气单胞菌和海豚链球菌的杀灭效果较差, 对凝结芽孢杆菌的杀灭效果最差。急性毒性试验得出PHMG 24h的LC₅₀=80.28 mg/L; 48h的LC₅₀=23.32 mg/L, 安全浓度SC=0.59 mg/L。对攻毒副溶血弧菌凡纳滨对虾的保护试验显示, PHMG浓度达到0.5 mg/L时, 24h对对虾的相对保护率达(77.78±5.01)%左右, 且与三个高浓度组相对保护率差异不显著。随着PHMG浓度的升高, 凡纳滨对虾肝胰腺所含副溶血弧菌数量明显减少, 48h后1.1及1.4 mg/L组副溶血弧菌数量降为0。降解试验结果显示: 0.5 mg/L的PHMG在第5、第6天浓度有所下降, 1 mg/L的PHMG在试验7d中基本保持稳定。研究证明了PHMG具有高效、低毒、低降解的特性, 是防治凡纳滨对虾AHPNS的理想消毒剂。     

不同浓度噻虫嗪对点蜂缘蝽种群的跨代效应

【目的】为探明不同浓度噻虫嗪对点蜂缘蝽Riptortus pedestris种群的跨代效应。【方法】点蜂缘蝽3龄若虫用不同浓度[LC₁₀(5.2 mg/L), LC₂₀(11.2 mg/L), LC₃₀(19.6 mg/L), LC₄₀(31.6 mg/L)和LC₅₀(49.4 mg/L)]噻虫嗪药液浸渍处理的大豆籽粒喂食24 h,存活若虫继续饲养至成虫羽化,继续繁殖建立其F₁代种群,并系统记录其F₁代种群的生长发育和繁殖情况,采用年龄-龄期两性生命表分析F₁代种群生物学参数。【结果】点蜂缘蝽3龄若虫取食不同浓度噻虫嗪处理的大豆籽粒后,其F₁代种群的发育历期和产卵前期均有所延长,其中LC₅₀噻虫嗪处理卵历期和若虫历期最长,较对照(清水)的分别延长了1.01和8.39 d; LC₂₀噻虫嗪处理成虫产卵前期最长,较对照的延长了3.54 d。噻虫嗪处理不...     

氰虫酰胺对小菜蛾生物学特性及相关酶活性的影响(英文）

【目的】小菜蛾Plutella xylostella（L.)是全球十字花科植物上最重要的害虫。氰虫酰胺作为一种新型的邻甲酰胺基苯甲酰胺类杀虫剂有着独特的作用方式,而关于氰虫酰胺对小菜蛾的影响的报道几乎没有。【方法】本研究采用叶片药膜法研究室内条件下氰虫酰胺对小菜蛾生理生化的影响,饲喂小菜蛾含有氰虫酰胺药液(0, LC₂₀和LC₅₀)的甘蓝叶片48 h后,观察小菜蛾的生物学特性及其相关酶活性的变化。【结果】氰虫酰胺对小菜蛾3龄幼虫的LC₂₀和LC₅₀分别为0.03和0.08 mg/L。使用LC20和LC50浓度的氰虫酰胺处理小菜蛾3龄幼虫48 h后,对其影响表现为显著降低小菜蛾的蛹重、化蛹率和羽化率;明显延长4龄幼虫期和蛹期。采用这两个浓度氰虫酰胺处理小菜蛾48 h,其保护酶（CAT和POD）活性在处理24 h内持续升高并且高于对照组;随后,活性继续升高但是与对照组没有差异(CAT: P=0.58; POD: P=0.13)。而其解毒酶(CarE, GST和ODM)活性在处理12 h内与对照组没有差异(CarE: P=0.43; GST: P=0.54; ODM: P=0.25),但是随着取食时间的延长,其活性明显高于对照组。【结论】LC₂₀和LC₅₀浓度氰虫酰胺能够显著抑制小菜蛾的生长发育,对降低害虫虫口密度有一定的作用。同时这两个浓度氰虫酰胺还能够诱导小菜蛾体内解毒酶活性的升高,这将为田间合理施药,延缓害虫抗药性的产生提供理论依据。     

高CO2浓度下西花蓟马和花蓟马对虫螨腈和唑虫酰胺的响应比较

【目的】比较不同CO2浓度下虫螨腈和唑虫酰胺对西花蓟马Frankliniella occidentalis和花蓟马F. intonsa成虫的毒力以及体内保护酶和解毒酶等酶活性的影响,对未来高CO₂浓度下进一步研究蓟马对虫螨腈和唑虫酰胺的抗性管理具有一定的指导意义,以便及时做出害虫管理策略的调整。【方法】采用浸渍法测定正常CO₂浓度(400 μL/L)和高CO₂浓度(800 μL/L)环境下虫螨腈和唑虫酰胺对两种蓟马成虫的毒力［致死中浓度(LC₅₀值)和亚致死浓度(LC₂₅值)］;通过酶活性分析测定这两种CO₂浓度下LC₂₅浓度虫螨腈和唑虫酰胺处理48 h后这两种蓟马成虫体内保护酶［超氧化物歧化酶(superoxide dismutase,SOD)、过氧化物酶(peroxidase, POD)和过氧化氢酶(catalase, CAT)］,解毒酶［羧酸酯酶(carboxylesterase, CarE)、谷胱甘肽S-转移酶(glutathione S-transferase, GST)和细胞色素P450(cytochrome P450 enzyme system, CYP450)］以及乙酰胆碱酯酶(AChE)的活性。【结果】800 μL/LCO₂下虫螨腈在48 h内对西花蓟马和花蓟马成虫的LC50值分别为1.33和0.37 mg/L,分别是400 μL/LCO₂下的0.68和0.66倍; LC₂₅值分别为0.60和0.24 mg/L, 分别为400 μL/L CO₂下的0.61和0.83倍。800 μL/L CO₂下唑虫酰胺在48 h内对西花蓟马和花蓟马成虫的LC₅₀值分别为1 002.64和247.66 mg/L,分别是400 μL/L CO₂下的0.98和0.78倍; LC₂₅值分别为368.77和146.10 mg/L, 分别是400 μL/LCO₂下的2.44和1.21倍。在800 μL/L CO₂下,LC₂₅浓度虫螨腈和唑虫酰胺处理48 h后两种蓟马成虫体内测试的各种酶活性(CYP450除外)均高于400 μL/L CO₂下的;两个CO₂浓度下西花蓟马成虫体内SOD, POD,CAT以及AChE活性均显著高于花蓟马成虫体内的相应酶活性。两个CO₂浓度下,经LC₂₅浓度唑虫酰胺处理后,两种蓟马成虫体内的3种保护酶活性(400 μL/L CO2下花蓟马SOD活性除外)均显著高于对照(含0.1%吐温-80的蒸馏水处理),且800 μL/L CO₂下西花蓟马成虫体内SOD和CAT活性均最高,分别为39.74±1.59和37.93±1.31 U/mg pro。两个CO₂浓度下,LC₂₅浓度虫螨腈和唑虫酰胺处理48 h后,西花蓟马成虫体内CarE活性较对照显著降低,而花蓟马成虫体内CarE活性高于对照,其中,经唑虫酰胺处理后达到显著差异;同时两种蓟马成虫体内AChE活性较对照均显著提高。【结论】高CO₂浓度增强了杀虫剂对西花蓟马和花蓟马的毒杀效果,花蓟马对这两种杀虫剂的敏感性强于西花蓟马,且西花蓟马对这两种杀虫剂的适应能力强于花蓟马。     

Acute toxicity of ammonia on Litopenaeus vannamei Boone juveniles at different salinity levels

Litopenaeus vannamei juveniles (total length 22+/-2.4 mm) were exposed to different concentrations of ammonia-N (un-ionized plus ionized ammonia as nitrogen), using the static renewal method at different salinity levels of 15 per thousand, 25 per thousand and 35 per thousand at pH 8.05 and 23 degrees C. The 24, 48, 72, 96 h LC50 values of ammonia-N on L. vannamei juveniles were 59.72, 40.58, 32.15, 24.39 mg l(-1) at 15 per thousand; 66.38, 48.83, 43.17, 35.4 mg l(-1) at 25 per thousand; 68.75, 53.84, 44.93, 39.54 mg l(-1) at 35 per thousand, respectively. The 24, 48, 72, 96 h LC50 values of NH(3)-N (un-ionized ammonia as nitrogen) were 2.95, 2.00, 1.59, 1.20 mg l(-1) at 15 per thousand; 2.93, 2.16, 1.91, 1.57 mg l(-1) at 25 per thousand; 2.78, 2.18, 1.82, 1.60 mg l(-1) at 35 per thousand, respectively. As the salinity decreased from 35 per thousand to 15 per thousand, susceptibility of ammonia-N increased by 115%, 132%, 140% and 162% after 24, 48, 72 and 96 h exposure, respectively. The "safety level" for rearing L. vannamei juveniles was estimated to be 2.44, 3.55, 3.95 mg l(-1) for ammonia-N and 0.12, 0.16, 0.16 mg l(-1) for NH(3)-N in 15 per thousand, 25 per thousand and 35 per thousand, respectively.     

Acute toxicity of ammonia and its effects on the haemolymph osmolality, ammonia-N, pH and ionic composition of early juvenile mud crabs, Scylla serrata (Forskål)

The current study was conducted to determine the LC(50) value of ammonia-N as well as the effects of acute exposure to elevated ammonia on the haemolymph osmolality, ionic composition, ammonia-N and pH levels of early juvenile mud crabs, Scylla serrata. The results show that early S. serrata juveniles have a high 96-h LC(50) value of 95.35 mg/L ammonia-N (6.81 mg/L NH(3)-N) or 6.80 mmol/L total ammonia-N (0.486 mmol/L NH(3)-N). Following a 96-h exposure, the haemolymph osmolality and K(+) levels of the surviving crabs remained unaltered (p>0.05) at all ammonia-N concentrations, while the haemolymph Na(+) and Ca(2+) were significantly lower (p<0.05) for the crabs exposed to 5.710 and 7.138 mmol/L ammonia-N. While the haemolymph ammonia-N levels of the crabs significantly increased (p<0.01) with increasing external ammonia-N concentrations, the haemolymph ammonia-N of the crabs remained below the external ammonia-N concentrations. The haemolymph pH of the crabs significantly increased between 0.714 and 4.283 mmol/L total ammonia-N. However, at 5.710 mmol/L total ammonia-N the haemolymph pH dropped and was not significantly different (p>0.05) from that of the control crabs which coincided with significantly lower (p<0.05) haemolymph Na(+) and Ca(2+) levels. These physiological responses may explain the high ammonia tolerance of early S. serrata juveniles.     

嗜水气单胞菌感染对背角无齿蚌5种免疫相关酶活力的影响

本研究以背角无齿蚌为材料,利用嗜水气单胞菌为诱导刺激物,对背角无齿蚌进行注射感染,在注射后3、6、12 、24、48h分别取血淋巴、肝胰腺,测定其超氧化物歧化酶（SOD）、酚氧化酶 (PO)、酸性磷酸酶 (ACP)、碱性磷酸酶 (AKP) 及过氧化氢酶 (CAT) 的活力,并研究各项酶活力的变化规律。结果表明：除3h肝胰腺外,实验组的SOD活力均不同程度地高于对照组;血清实验组的PO活力开始显著高于对照组,然后降低,而肝胰腺实验组的PO活力持续高于对照组;另外,与对照组相比,实验组中血淋巴与肝胰腺的ACP、AKP和CAT活力在不同的时间段虽然有所增强,但两者之间无显著差异。因此,认为SOD、PO活性可以作为背角无齿蚌免疫抗病功能指标参数,而ACP、AKP及CAT活性能否作为该参数还有待于进一步研究。     

Effect of ammonia on the immune response of white shrimp Litopenaeus vannamei and its susceptibility to Vibrio alginolyticus

Growth of Vibrio alginolyticus was not affected by TSB medium containing ammonia-N concentration in the range of 0-20 mg l(-1). White shrimp Litopenaeus vannamei (7-12 g in the intermolt stage) were challenged with V. alginolyticus, which had been incubated for 24 h in the TSB medium containing different concentrations of ammonia-N (0, 1, 5. 10 and 20 mg l(-1)). There was no significant difference in cumulative mortality for shrimp incubated in the TSB medium containing 0, 1, 5, 10 and 20 mg l(-1)ammonia-N after 120 h of challenge. The shrimps were challenged with V. alginolyticus previously incubated in the TSB medium for 24 h, then placed in water containing concentrations of ammonia-N at 0.01 mg l(-1)(control), 1.10, 5.24, 11.10 and 21.60 mg l(-1). Mortality of shrimp in 5.24, 11.10 and 21.60 mg l(-1)was significantly higher than those in the control solution (0.01 mg l(-1)) after 48-168 h. Shrimps which had been exposed to control, 1.10, 5.24, 11.10 and 21.60 mg l(-1)ammonia-N for 7 days were examined for THC (total haemocyte count), granular cells, hyaline cells, phenoloxidase activity, release of superoxide anion, superoxide dismutase (SOD) activity, phagocytic activity and clearance efficiency to V. alginolyticus. No significant difference in THC, hyaline cells and granular cells were observed among shrimps at different ammonia-N concentrations. Phenoloxidase activity however, decreased when the shrimps were exposed to 5.24 mg l(-1)ammonia-N and greater after 7 days. The release of superoxide anion increased significantly, whereas SOD activity decreased significantly at 21.60 mg l(-1)ammonia-N. With shrimps exposed to 11.21 and 21.22 mg l(-1)ammonia-N for 7 days, phagocytic activity and clearance efficiency to V. alginolyticus significantly decreased. It is therefore suggested that ammonia in water caused a depression in the immune response and an increase in mortality of L. vannamei from the V. alginolyticus infection.     

Metabolic responses of the white shrimp, Penaeus vannamei, to ambient ammonia

Juvenile shrimp were individually exposed during 24 h to 0.007 (control), 0.36, 1.07, and 2.14 mmol/l total ammonia-N at 28 degrees C and 39 ppt salinity. After 22 h of ammonia-N exposure, oxygen consumption was measured for 2 h, and then hemolymph, hepatopancreas, and muscle tissues were sampled. Oxygen consumption, and levels of lactate and glycogen in the hepatopancreas increased significantly at the highest ammonia-N concentration. Concentration of oxyhemocyanin, acylglycerol, and cholesterol in hemolymph, and lactate in muscle decreased significantly in the group exposed to the highest ammonia levels. The changes observed in hemolymph and tissue metabolic fuels suggest a reduced use of carbohydrate through anaerobic metabolism and an increase in the use of lipids to satisfy the metabolic demand.     

Metabolic responses of the white shrimp, Penaeus vannamei, to ambient ammonia

Juvenile shrimp were individually exposed during 24 h to 0.007 (control), 0.36, 1.07, and 2.14 mmol/l total ammonia-N at 28°C and 39 ppt salinity. After 22 h of ammonia-N exposure, oxygen consumption was measured for 2 h, and then hemolymph, hepatopancreas, and muscle tissues were sampled. Oxygen consumption, and levels of lactate and glycogen in the hepatopancreas increased significantly at the highest ammonia-N concentration. Concentration of oxyhemocyanin, acylglycerol, and cholesterol in hemolymph, and lactate in muscle decreased significantly in the group exposed to the highest ammonia levels. The changes observed in hemolymph and tissue metabolic fuels suggest a reduced use of carbohydrate through anaerobic metabolism and an increase in the use of lipids to satisfy the metabolic demand.     

氨氮对脊尾白虾幼体存活生长及体内RNA/DNA比值的影响

以脊尾白虾(Exopalaemon carinicauda)糠虾幼体为实验材料,用氯化铵模拟水体中氨氮进行毒性试验.结果表明,氨氮对糠虾幼体24、48、72和96 h的半致死浓度(LC50)分别为27.51、23.15、19.46和10.28 mg/L.糠虾幼体体内毒性蓄积程度随实验时间逐步增强.在6 d的糠虾幼体蜕壳...     

Natural cytotoxic activity in seabream (Sparus aurata L.) and its modulation by vitamin C

Growth of pathogen bacterium. Enterococcus was not affected in tryptic soy broth (TSB) medium containing ammonia-N concentration in the range of 0-5.14 mg l(-1). Giant freshwater prawn Macrobrachium rosenbergii (8-12 g) were challenged with Enterococcus which had been incubated for 24 h in TSB medium containing different concentrations of ammonia-N at 0-5.14 mg l(-1) Cumulative mortality of M. rosenbergii was higher for the bacteria incubated in TSB medium having ammonia-N at 0 and 0.26 mg l(-1), than those incubated in TSB medium having 1.28, 2.57 and 5.14 mg l(-1) ammonia-N after 24 h of challenge. However, cumulative mortality of prawn was significantly higher for the bacteria incubated in TSB medium with no ammonia added after 120 h of challenge. The prawns (8-12 g) were challenged with Enterococcus previously incubated in TSB medium for 24 h, then placed in water having concentrations of ammonia-N at control (0.06 mg l(-1)), 0.55, 1.01, 1.68 and 3.18 mg l(-1). Mortality of prawns increased directly with ammonia-N concentrations after 72 h challenge. The pranws (20-30 g) which had been exposed to control, 0.55, 1.68 and 3.18 mg (-1) ammonia-N for 7 days were examined for the total haemocyte count (THC), differential haemocyte count (DHC), phenoloxidase activity and respiratory burst of haemocytes. Phenoloxidase activity decreased when the prawns were exposed to ammonia-N greater than 0.55 mg l(-1). The respiratory burst increased significantly at 0.55 mg l(-1) but decreased significantly at 1.68 and 3.18mg (-1) ammonia-N. No significant difference in haemocyte count was observed among the prawns at different ammonia-N concentrations. It is suggested that ammonia in water decreases the virulence of Enterococcus, and reduces the immune resistance of M. rosenbergii.     

溶解氧对线纹海马幼鱼氨氮耐受性的影响及氨氮胁迫下鳃、肝脏组织结构的变化

为了解氨氮对线纹海马(Hippocampus erectus)幼鱼的毒理影响,本实验探讨了在正常溶解氧(4.32~5.12 mg·L-1)和高溶解氧(8.22~9.46 mg·L-1)条件下,线纹海马幼鱼的氨氮半致死浓度,以及6、9、12 mg·L-1的氨氮溶液胁迫下线纹海马幼鱼的鳃、肝脏组织结构的变化。结果表明:正常溶解氧条件下,氨氮对线纹海马幼鱼96 h半致死浓度(96 h LC50)为10.22 mg·L-1,安全浓度(SC)为1.02 mg·L-1;非离子氨的半致死浓度(96 h LC50)为0.16 mg·L-1,安全浓度(SC)为0.016 mg·L-1;高溶解氧条件下,氨氮对幼鱼的96 h LC50为12.68 mg·L-1,SC为1.27 mg·L-1;非离子氨96 h LC50为0.2 mg·L-1,SC为0.02mg·L-1。氨氮胁迫造成线纹海马幼鱼鳃组织在不同时间出现鳃丝血管扩张、泌氯细胞增生,鳃小片基部毛细血管破裂、红细胞溢出、鳃组织充血变性、卷曲变短、呼吸上皮细胞变性脱落等现象,并使肝脏肝细胞出现肿胀、细胞核肿大,肝血窦扩张、细胞轮廓模糊等组织变化;随着胁迫物浓度和胁迫时间增加,肝组织出现水样变性、空泡化、溶解,导致肝组织变得松散无序。综上,适当提高溶解氧能有效减轻氨氮对线纹海马幼鱼的毒性,超过阈值的氨氮胁迫会损害线纹海马幼鱼的鳃和肝脏组织结构。