腐殖酸可降低纳米银的水生生物毒性

本文作者主要研究了腐殖酸对聚乙烯吡咯烷酮包覆的纳米银颗粒(polyvinylpyrrolidone-coated AgNPs)毒性的影响，受试生物涵盖了水生系统不同的营养级别，包括藻类(Raphidocelis subcapitata)、水蚤类(Chydorus sphaericus)以及淡水鱼类(Danio rerio)。结果显示，腐殖酸可降低AgNPs对本研究中所有水生生物的毒性，并具有明显的剂量效应关系。原因为：1）腐殖酸使AgNPs表面带有更多负电荷，这阻碍了AgNPs与藻细胞的接触，使毒性降低；2）腐殖酸抑制了AgNPs中Ag⁺的溶出，而本研究显示自由Ag⁺的毒性高于团聚的纳米银颗粒。
精选自Zhuang Wang, Joris T.K. Quik, Lan Song, Evert-Jan Van Den Brandhof, Marja Wouterse and Willie J.G.M. Peijnenburg. Humic substances alleviate the aquatic toxicity of polyvinylpyrrolidone-coated silver nanoparticles to organisms of different trophic levels. Environmental Toxicology and Chemistry: Volume 34, Issue 6, pages 1239–1245, June 2015. DOI: 10.1002/etc.2936
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.2936/full
     

腐殖酸可降低纳米银的水生生物毒性

本文作者主要研究了腐殖酸对聚乙烯吡咯烷酮包覆的纳米银颗粒(polyvinylpyrrolidone-coated AgNPs)毒性的影响,受试生物涵盖了水生系统不同的营养级别,包括藻类(Raphidocelis subcapitata)、水蚤类(Chydorus sphaericus)以及淡水鱼类(Danio rerio)。结果显示,腐殖酸可降低AgNPs对本研究中所有水生生物的毒性,并具有明显的剂量效应关系。原因为：1）腐殖酸使AgNPs表面带有更多负电荷,这阻碍了AgNPs与藻细胞的接触,使毒性降低;2）腐殖酸抑制了AgNPs中Ag⁺的溶出,而本研究显示自由Ag⁺的毒性高于团聚的纳米银颗粒。
精选自Zhuang Wang, Joris T.K. Quik, Lan Song, Evert-Jan Van Den Brandhof, Marja Wouterse and Willie J.G.M. Peijnenburg. Humic substances alleviate the aquatic toxicity of polyvinylpyrrolidone-coated silver nanoparticles to organisms of different trophic levels. Environmental Toxicology and Chemistry: Volume 34, Issue 6, pages 1239–1245, June 2015. DOI: 10.1002/etc.2936
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.2936/full
     

用于水中多环芳烃被动采样的聚合物厚度和材料的选择：哪个更有力地影响采样器性能？

本文使用3种单相聚合物制作用于多环芳烃被动采样的装置,这3种聚合物分别为聚甲醛(POM)、硅橡胶(SR)和聚乙烯(PE),通过室内试验测定了它们的分配系数和POM的扩散系数以及验证了动态积累模型。此外,在野外现场对每种装置的性能进行了评估。基于已开发模型的支持,讨论了使用不同材料和聚合物厚度的装置性能。结果表明,采样器性能,比如浓度平均周期的长短和多环芳烃的采集容量,都广受所选材料的影响。采样器的厚度也会对装置的性能造成影响,但程度很小。选择合适的聚合物和/或厚度可以使采样器更有适用于快速平衡或动态积累,以及促进膜或水边界层对动态积累的控制。此外,利用膜技术控制或平衡的化合物能够更精确的被量化,因为它们不需要利用参比法(PRC)来校正。然而,当富集浓度达到平衡后,采样器中的平均浓度就不能准备测量化合物浓度,而由膜控制的采样装置通过动态累积的方式能够提供不需要PRC校正的平均浓度;随着膜传质阻力的提高,采样器的检测限也得到提高。
精选自Angel Belles, Claire Alary, Yannick Mamindy-Pajany.Thickness and material selection of polymeric passive samplers for polycyclic aromatic hydrocarbons in water: which more strongly affects sampler properties?. Environmental Toxicology and Chemistry: Volume 35, Issue 7, pages 1708–1717, July 2016. DOI: 10.1002/etc.3326
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.3326/full
     

多种聚氧乙烯牛脂胺混合物MON 0818的水生环境危害评估：实验室急性暴露实验基础上的物种敏感度分布

本实验利用标准短期(48- 96 h)实验室测试测定了包括初级生产者，底栖无脊椎动物，水蚤类动物，软体动物和鱼类在内的15种水生生物对于MON 0818的敏感性。MON 0818是一种商业表面活性剂，由多种聚氧乙烯牛脂胺混合而成。此外本实验使用模糊网纹蚤(Ceriodaphnia dubia)潜在的长期(8 d)毒性，确定了暴露浓度。长期毒性测试中未在任何终端指标中发现显著效果。利用得出的数据和文献记载得到物种敏感度在4种暴露条件下的分布，通过对比物种敏感度分布进行了tier-1危害评估。评估显示在本研究规划下(以综述为原型，研究林业除草剂；12 L标准每公顷，等于4.27 kg每公顷) 最差的情况(无意中以最大标签使用速率直接过量喷洒到15 cm深的水体中)会造成中等危害(43.1%的物种处于暴露中，高于中位有效浓度水平)。在更多以最大使用速率使用的典型情况下，受到损害的物种降至20.9%(6 L标准每公顷，相当于2.14 kg每公顷)，在更频繁的雇佣施用速率(2.5 L标准每公顷，相当于0.89 kg每公顷)下，受损物种比例降至6.9%。通过草甘膦在环境中的最大测定浓度计算得到MON 0818的浓度，最终受损物种比例(3.8%)则小于此浓度下受损物种比例(5%)。
精选自Jose L. Rodriguez-Gil, Ryan Prosser, David Poirier, Linda Lissemore, Dean Thompson, Mark Hanson, Keith R. Solomon. Aquatic hazard assessment of MON 0818, a commercial mixture of alkylamine ethoxylates commonly used in glyphosate-containing herbicide formulations. Part 1: Species sensitivity distribution from laboratory acute exposures. Environmental Toxicology and Chemistry: Volume 36, Issue 2, pages 501–511, July 2017. DOI: 10.1002/etc.3559
详情请见http://onlinelibrary.wiley.com/wol1/doi/10.1002/etc.3559/full
     

蛋白组学分析揭示出阿特拉津对非洲爪蟾的生殖毒性源于其诱导生殖细胞凋亡并干扰紧密连接蛋白和代谢相关信号通路

阿特拉津可对雄性脊椎动物生殖系统造成不良影响,但其中分子机制尚不明了。本文作者将非洲爪蟾(Xenopus laevis)暴露于100 ppb的阿特拉津120 d,利用同位素标记相对和绝对定量(iTRAQ)技术检测了非洲爪蟾睾丸和卵巢中蛋白图谱的变化,结果显示100 ppb阿特拉津可影响爪蟾发育,延迟和阻碍雄性细精管的形成。组学分析显示,睾丸中143种以及卵巢中121种蛋白均表达异常,这些蛋白与细胞凋亡、细胞间紧密连接以及代谢途径相关。
精选自Xiuping Chen, Jiamei Wang, Haojun Zhu, Jiatong Ding and Yufa Peng. Proteomics analysis of Xenopus laevis gonad tissue following chronic exposure to atrazine. Environmental Toxicology and Chemistry: Volume 34, Issue 8, pages 1744–1750, August 2015. DOI: 10.1002/etc.2980
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.2980/full     

没有找到微塑料对黑头软口鲦(Pimephales promelas)幼鱼摄食量和生长影响的证据

微塑料是水环境中一种含量丰富的污染物。但关于其对幼鱼的影响情况知之甚少。我们考察了塑料微珠的密度增大对黑头软口鲦(Pimephales promelas)幼鱼觅食和生长的影响。我们发现微塑料对幼鱼摄食幼虫卤虫无节幼体(Artemia nauplii)的摄食量影响很小，对30天体长也基本无影响。 精选自Timothy David Malinich, Nathan Chou, Maria S. Sepúlveda, Tomas O. H??k. No evidence of microplastic impacts on consumption or growth of larval Pimephales promelas. Environmental Toxicology and Chemistry,2018,37:2912-2918.
详情请见 https://doi.org/10.1002/etc.4257
     

针对优选药物的水质指南导引

药物会进入淡水系统并影响水生态系统的健康。即使广泛应用的药物已经过毒性检测,以证据为基础的水质标准依然没有制定出。将BurrIII型分布应用于慢性毒性数据的物种敏感度分布(SSD),我们得到了卡马西平、双氯芬酸、氟西汀和美托洛尔4种药物在淡水中高度可靠的水质标准指引值(GV)。数据经过质检并且符合慢性无观察效应浓度(NOEC)或是10%有效浓度(即影响到10%的物种)要求,其终点与种群相关,效应指标为发育、生长、生殖与存活状况。由于生物标记物的回应(例如生化、组织及分子回应)与野生种群相关的影响并不存在直接的联系,故得出的相关数据并未考虑在内。在保护95%物种的范围内,得出卡马西平、双氯芬酸、氟西汀和美托洛尔4种药物的GV分别为4.3,770,1.6和14 μg?L^L-1。广泛应用在欧盟委员会、瑞士与德国的GV则是基于有限数据库中最敏感的实验终点 (可能包括生化、组织及分子生物标记物的回应)。本实验得出的GV显著高于这些可靠性未知的GV。
精选自Anupama Kumar, Graeme E. Batley, Bhanu Nidumolu, Thomas H. Hutchinson. Derivation of water quality guidelines for priority pharmaceuticals. Environmental Toxicology and Chemistry: Volume 35, Issue 7, pages 1815–1824, July 2016. DOI: 10.1002/etc.3336
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.3336/full
     

腐殖酸可降低纳米银的水生生物毒性

本文作者主要研究了腐殖酸对聚乙烯吡咯烷酮包覆的纳米银颗粒(polyvinylpyrrolidone-coated AgNPs)毒性的影响,受试生物涵盖了水生系统不同的营养级别,包括藻类(Raphidocelis subcapitata)、水蚤类(Chydorus sphaericus)以及淡水鱼类(Danio rerio)。结果显示,腐殖酸可降低AgNPs对本研究中所有水生生物的毒性,并具有明显的剂量效应关系。原因为：1）腐殖酸使AgNPs表面带有更多负电荷,这阻碍了AgNPs与藻细胞的接触,使毒性降低;2）腐殖酸抑制了AgNPs中Ag⁺的溶出,而本研究显示自由Ag⁺的毒性高于团聚的纳米银颗粒。
精选自Zhuang Wang, Joris T.K. Quik, Lan Song, Evert-Jan Van Den Brandhof, Marja Wouterse and Willie J.G.M. Peijnenburg. Humic substances alleviate the aquatic toxicity of polyvinylpyrrolidone-coated silver nanoparticles to organisms of different trophic levels. Environmental Toxicology and Chemistry: Volume 34, Issue 6, pages 1239–1245, June 2015. DOI: 10.1002/etc.2936
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.2936/full
     

蛋白组学分析揭示出阿特拉津对非洲爪蟾的生殖毒性源于其诱导生殖细胞凋亡并干扰紧密连接蛋白和代谢相关信号通路

阿特拉津可对雄性脊椎动物生殖系统造成不良影响，但其中分子机制尚不明了。本文作者将非洲爪蟾(Xenopus laevis)暴露于100 ppb的阿特拉津120 d，利用同位素标记相对和绝对定量(iTRAQ)技术检测了非洲爪蟾睾丸和卵巢中蛋白图谱的变化，结果显示100 ppb阿特拉津可影响爪蟾发育，延迟和阻碍雄性细精管的形成。组学分析显示，睾丸中143种以及卵巢中121种蛋白均表达异常，这些蛋白与细胞凋亡、细胞间紧密连接以及代谢途径相关。
精选自Xiuping Chen, Jiamei Wang, Haojun Zhu, Jiatong Ding and Yufa Peng. Proteomics analysis of Xenopus laevis gonad tissue following chronic exposure to atrazine. Environmental Toxicology and Chemistry: Volume 34, Issue 8, pages 1744–1750, August 2015. DOI: 10.1002/etc.2980
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.2980/full     

蛋白组学分析揭示出阿特拉津对非洲爪蟾的生殖毒性源于其诱导生殖细胞凋亡并干扰紧密连接蛋白和代谢相关信号通路

阿特拉津可对雄性脊椎动物生殖系统造成不良影响,但其中分子机制尚不明了。本文作者将非洲爪蟾(Xenopus laevis)暴露于100 ppb的阿特拉津120 d,利用同位素标记相对和绝对定量(iTRAQ)技术检测了非洲爪蟾睾丸和卵巢中蛋白图谱的变化,结果显示100 ppb阿特拉津可影响爪蟾发育,延迟和阻碍雄性细精管的形成。组学分析显示,睾丸中143种以及卵巢中121种蛋白均表达异常,这些蛋白与细胞凋亡、细胞间紧密连接以及代谢途径相关。
精选自Xiuping Chen, Jiamei Wang, Haojun Zhu, Jiatong Ding and Yufa Peng. Proteomics analysis of Xenopus laevis gonad tissue following chronic exposure to atrazine. Environmental Toxicology and Chemistry: Volume 34, Issue 8, pages 1744–1750, August 2015. DOI: 10.1002/etc.2980
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.2980/full     

建立组织外植体的共培养模型(in vitro)用于预测内分泌干扰效应(in vivo)：以黑头软口鲦(Pimephales promelas)的下丘脑-垂体-性腺（HPG）轴内分泌干扰作用为例

内分泌干扰物 （Endocrine Disrupting Compounds, EDCs）可以通过干扰下丘脑-垂体-性腺（HPG）轴来影响生殖系统。虽然目前已有筛选内分泌干扰物的体外检测方法,但这些方法在用于体内实验时却有着不稳定的准确性。本文记录了以黑头呆鱼（Pimephales promelas）的下丘脑-垂体-性腺轴与肝（HPG-L）的共培养组织作为组织外植体来模拟体内反应的结果。我们对成年鱼的大脑（下丘脑）,垂体,性腺和肝进行了单独和共同培养的检测来确定可以在体内重复的情况与组合。只有共培养体表现出去甲雄三烯醇酮对于雌二醇,睾酮和卵黄生成素生成趋势的影响。较低的暴露剂量会抑制激素生成,而较高的暴露剂量则会促进激素生成,形成U型作用曲线。这些数据表明下丘脑-垂体-性腺-肝轴的全部组织的共同培养可以作为体内实验与体外实验的连接,从而预测在完整生物体内内分泌系统的扰乱。本实验中以组织为基础的下丘脑-垂体-性腺-肝系统作为一个灵活的体内系统的解构版本得到了更好的实验控制。通过分离、审查和重组需要的组织,我们能够检测到生物系统功能与对于内分泌干扰物反应中的微小变化。
精选自Theresa K. Johnston, Edward Perkins, Duncan C. Ferguson, Donald M. Cropek. Tissue explant co-culture model of the hypothalamic-pituitary-gonadal-liver axis of the fathead minnow (Pimephales promelas) as a predictive tool for endocrine disruption. Environmental Toxicology and Chemistry: Volume 35, Issue 10, pages 2530–2541, October 2016. DOI: 10.1002/etc.3415
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.3415/full
     

Biotransformation rates of xenobiotic compounds in relation to enzymes activities: A critical review

Many biotransformation reactions and many activities of enzymes involved in the biotransformation of xenobiotics in fish have been described. Therefore, the prediction of biotransformation of (other) xenobiotics through literature data seems to be possible. However, very few data allow correlation of in vitro enzyme activities with in vivo biotransformation rates. This is mainly due to a lack of quantitative data. Suggestions are made for future research, which may help to relate enzyme activities and biotransformation in fish.     

Effects of the Ellagic acid on the N‐Acetyltransferase activity and Acetylation of 2‐aminofluorene in the rat

The effects of the ellagic acid on the in vitro and in vivo acetylation of 2‐aminofluorene were investigated in male Sprague‐Dawley rats. For in vitro examination, cytosols with or without ellagic acid co‐treatment showed different percentage of 2‐aminofluorene acetylation. For in vivo examination, pre‐treatment of male rats with ellagic acid (10 mg/kg) 24h prior to the administration of 2‐aminofluorene (50 mg/kg) resulted in a 26% and 29%, respectively, decrease in the urinary and fecal recovery of N‐acetyl‐2‐aminofluorene, and a 37% decrease in the metabolic clearance of 2‐aminofluorene to N‐acetyl‐2‐aminofluorene. This is the first demonstration that ellagic acid decrease the N‐acetylation of carcinogens in vitro and in vivo.     

Structure of and energy reserves in the liver of wild and cultured yellowtail flounder,<Emphasis Type="Italic"> Limanda ferruginea</Emphasis>

Knowledge of the structure and energy reserves, in the liver of commercially important fish species, is important in understanding metabolic processes and in assessing the impact of potential environmental physical and chemical stressors in both wild and cultured stocks. The present study investigated the microscopic morphology and histochemistry (total and neutral lipids, glycogen) of liver tissue of wild (3 ⁺) and cultured (1 ⁺) sexually immature female and male yellowtail flounder ( Limanda ferruginea Storer), sampled in late April 2001. Hepatosomatic indices [HSI: (liver weight/body weight-liver weight)×100] of cultured fish were significantly higher than those of wild fish. Females in the cultured group had significantly lower HSIs than males. The liver of both wild and cultured L. ferruginea was interspersed with pancreatic tissue. The main components of the liver tissue were irregular cords of hepatocytes arranged in tubules which surrounded vascular sinusoids. The hepatocytes contained an abundance of lipid, much of which appeared to be neutral lipids, in both sexes of the cultured fish. Total and neutral lipid droplets were larger, and the area occupied by these droplets was significantly greater in both cultured females and males compared to the wild fish, suggesting lipidosis in the cultured fish. In the cultured fish these differences were sex-dependent, the females having significantly more total and neutral lipids in hepatocytes than the males. This suggests a potentially greater storage capacity in females and/or a higher lipid metabolism in males. There were no statistically significant differences in glycogen content between the cultured and wild fish, or between the sexes in both sampling groups.     

Linear alkylbenzene sulphonates (LAS) and bioaccumulation of heavy metals (Cu and Pb) in Ruditapes philippinarum

The effect of linear alkylbenzene sulphonate (LAS) on copper and lead bioaccumulation in Ruditapes philippinarum was studied. The in vitro and in vivo effect of LAS on acid and alkaline phosphatase activities was also examined. For lead, significant differences (P<0.01) were observed between organisms exposed to lead and to the mixture of LAS and lead. In the case of copper, these differences were only significant in the digestive gland (P<0.05). In vitro acid phosphatase was inhibited by LAS and the mixture of LAS with copper showed the effect of decreasing the enzymatic activity. Nevertheless, in vivo no significant differences in the digestive gland and gills (P < 0.05) were observed.     

Concentrations of Cd,Ni, Pb,and Cr in the two edible fish species Liza klunzingeri and Sillago sihama collected from Hara biosphere in Iran

The concentrations of four metals (Cd, Ni, Pb, and Cr) were determined in the muscles, gills, and livers of two edible fish species (Liza klunzingeri and Sillago sihama) caught from the Hara biosphere of Southern Iran. In both fish species, metal concentrations and bioaccumulation factors were in the sequence liver?>?gill?>?muscle. Bioaccumulation factors were found to be highest in S. sihama. The metal concentrations were descending in the order of Ni?>?Cr?>?Pb?>?Cd, except for muscle samples from S. sihama showing an inversion of Pb and Cr. There is a significant negative correlation between the concentrations of the metals in each tissue with length, weight, and age, except for muscle in L. klunzingeri. Some metal levels in the muscle exceeded the limits recommended by FAO, WHO, and FEPA.     

三唑醇杀菌剂在雄性丽斑麻蜥体内的对映选择性降解、蓄积和肝毒性研究

三唑醇(triadimenol, TN)是一种广泛使用的手性三唑类杀菌剂,它含有2个手性中心,4个手性对映体,包括对映体A(A1(R,S)和A2(S,R))以及对映体B(B1(R,R)和B2(S,S))。为了研究三唑醇在爬行动物体内的对映选择性行为和潜在的肝毒性,将雄性丽斑麻蜥分别一次经口暴露和28 d长期暴露于三唑醇(100 mg·kg~(-1) body weight),一次经口暴露结果显示,三唑醇进入大脑和肾中的浓度低于肝、性腺、皮肤和尾,B2(S,S)和B1(R,R)对映体具有相似的代谢速率。代谢过程中A1(R,S)的浓度明显高于A2(S,R),并且在暴露后12 h出现二次上升,这可能是A2(S,R)在体内手性转换为A1(R,S)导致。丽斑麻蜥长期(28 d)暴露于三唑醇后,性腺和肾中无明显蓄积现象,皮和尾中浓度显著高于其他组织,各个组织中三唑醇趋向于保持外消旋状态。三唑醇暴露后肝中主要的代谢基因cyp1a1c、yp3a4c、yp2b1和cyp2d3的表达量都出现明显上升,组织病理学分析进一步显示,三唑醇暴露后的肝组织出现组织空泡、血窦阻塞的症状,说明三唑醇对肝组织具有一定的毒性作用。上述结果为手性农药对爬行动物的生态毒理学评价提供了重要依据。     

氧化石墨烯遗传毒性的实验研究

研究氧化石墨烯(GO)的遗传毒性,考察其致突变作用,为GO在生物领域的安全应用提供依据。采用Ames试验、体外CHL细胞染色体畸变试验和小鼠体内染色体畸变试验,分别在细菌水平、细胞水平及整体动物水平研究GO的遗传毒性。GO各剂量组的Ames试验结果为阴性。CHL试验中,CHL细胞染色体畸变率随GO浓度的增加而升高,其中1.000 mg·mL~(-1)剂量组(+S_9)和0.500 mg·mL~(-1)剂量组(-S_9)畸变率显著升高(P 0.05)。小鼠骨髓细胞染色体畸变试验中,骨髓细胞染色体畸变率同样随GO浓度的增加而升高,1.000和0.500 mg·kg~(-1)剂量组的畸变率显著提高(P 0.05)。虽然Ames试验结果没有反映出GO的遗传毒性,但在体外及体内染色体畸变试验中,GO均表现出对哺乳动物细胞染色体有潜在的遗传毒性。     

Toxicity and bioaccumulation of heavy metals in mullet fish Liza klunzingeri (Mugilidae: Perciformes)

The mullet fish, Liza klunzingeri, commercially important and widely relished by Kuwaiti residents, and the stressed ecosystem in Kuwait Bay instigated us to conduct toxicity and bioaccumulation tests on heavy metals (Pb, Ni, V, Cu and Fe). Among five metals, Pb had the lowest observed effect concentration (LOEC) at 1 μg?l ^?1. Using multi-factor Probit analysis, toxicity tests (72 h) on L. klunzingeri reared in filtered sea water in the laboratory showed Pb with maximum effect at median lethal concentration (LC₅₀) followed by V, Ni, Cu and Fe. Their bioaccumulation factor (BAF) was in the sequence Pb>V>Fe>Cu and Ni. For fish exposed for 30 d, bioaccumulation exhibited increasing metal levels in liver followed by gills and muscles. These results suggest the potential use of L. klunzingeri as a bioindicator of metal pollution in the future.     

Effects of organochlorines on the ultrastructure of the liver of the damselfish Parma microlepis from reefs in New South Wales, Australia

  Parma microlepis (Günther) were collected from Malabar, an urban location close to the centre of Sydney, Australia, and from Jervis Bay, a reference location 170 km south of the city centre. At each location, fish were collected from two sites separated by 100 to 200 m. The ultrastructure of normal liver tissue is described based on 20 female fish collected from Jervis Bay, where fish are known to be exposed to low levels of organochlorine contaminants. Alterations in the endoplasmic reticulum, mitochondria, lysosomes and nuclei of hepatocytes were identified and quantified in the liver tissue of fish from this location and compared to alterations in 20 female fish collected from Malabar, where fish are exposed to higher concentrations of organochlorine pesticides such as DDT compounds. There were significant differences in the percentage of hepatocytes with swollen mitochondria (F = 124.025, df = 2, 2, P = 0.008) and atypical nuclei (F = 22.198, df = 2, 2, P = 0.043) between sites (100 to 200 m apart), but there were no clear differences between the percentage of structural alterations in the hepatocytes of P. microlepis from Jervis Bay and Malabar. Associations between liver morphology and the organochlorines aldrin, dieldrin, DDE and chlordane were examined using a Pearson correlation matrix. Significant correlations were detected between the percentage of hepatocytes with dilated endoplasmic reticulum and the concentrations of the pesticide aldrin (r = 0.600, df = 11, r _{crit(α = 0.05)} = 0.553). Significant associations were also detected between the percentage of hepatocytes with disorganised endoplasmic reticulum and the concentrations of dieldrin and DDE residues in fish (r = 0.576, r = 0.567, respectively, df = 13, r _{crit (α = 0.05)} = 0.514). However, there was little evidence that ultrastructural alterations in fish responded to increasing concentrations of these pesticides in a consistent dose-response manner. Received: 20 October 1998 / Accepted: 24 November 1999