有机磷农药对缢蛏[Sinonovacula constricta （Lamarck）]

在实验室模拟缢蛏的生长环境，研究乐果和三唑磷对缢蛏的毒性效应，以气相色谱法测定缢蛏体内有机磷农药的含量，并通过光镜观察有机磷农药对缢蛏鳃和消化腺显微结构的影响，结果表明：缢蛏体内乐果和三唑磷的含量随着水体中有机磷农药的增加而增加，有很好的剂量一效应关系，但是无线性相关性，乐果和三唑磷对缢蛏鳃显微结构的影响是：鳃丝变短，鳃丝间隔和基底膜结缔组织增生，鳃孔、血管腔堵塞；不同的是：在乐果胁迫下，E皮细胞纤毛脱落严重，而三唑磷胁迫下，上皮细胞纤毛增生，乐果和三唑磷对缢蛏消化腺显微结构的影响主要表现为腺细胞界限模糊，腺泡水肿变形、部分坏死；结缔组织增生，细胞问质疏松，出现许多空泡；有机磷农药的浓度高时消化腺细胞变性、坏死，细胞质囊泡化，     

全氟辛烷磺酸（PFOS）急性暴露对斑马鱼鳃显微结构的影响

采用光镜和电镜的方法,探讨了高浓度全氟辛烷磺酸(PFOS)急性暴露对斑马鱼(Danio rerio)鳃显微结构的影响.暴露组PFOS浓度分别为0.5、1、2mg·L-1,同时设对照组,连续暴露7d,取鳃制备石蜡切片,进行光镜和扫描电镜观察.结果表明,7d后PFOS暴露组斑马鱼鳃部均有不同程度的损伤,石蜡切片上可观察到暴露组鱼鳃上皮细胞坏死脱落,鳃小片断裂或融合,并伴有鳃丝充血,且病变程度随PFOS浓度的升高而加重;扫描电镜下可观察到暴露组鱼鳃鳃丝表面分泌物增多,鳃丝细胞脱落或水肿,鳃小片前端细胞破损.高浓度PFOS急性暴露可在短期内对斑马鱼鳃组织造成严重损伤,且损伤程度存在剂量依赖效应.     

乐果降解菌LGX1的筛选及其降解特性研究

通过富集培养,从连续施用农药乐果的土壤中分离得到一株具有较强降解有机磷农药乐果能力的细菌菌株LGX1,通过菌落形态观察及细菌的16SrDNA测序,对其进行了鉴定,同时初步研究了其降解性能。结果表明：该菌株为蜡状芽孢杆菌（Bacillus cereus）,在接种量为20%,乐果初始质量浓度为100mg·L-1,外加碳源葡萄糖质量分数为2%,温度为35℃,初始pH值为4时该菌株对乐果的降解能力最强;并且能在以辛硫磷、毒死蜱和三唑磷为唯一碳源的基础盐培养基中生长,且均比在以乐果为唯一碳源的基础盐培养基中生长的OD600值要高,初步推断菌株LGX1对有机磷农药的降解有一定的广谱性。     

镉和铅对菲律宾蛤仔脂质过氧化及抗氧化酶活性的影响

为了研究亚致死浓度的重金属对海洋贝类的毒性效应,探讨其可能的作用机理,在实验生态条件下以菲律宾蛤仔(Ru-ditapes philip pinarum)为目标生物,采用半静态毒性实验方法,研究了不同浓度Cd2+(0.0948、0.237和0.474mg·L-1)和Pb2+(0.276、0.690和1.380mg·L-1)对菲律宾蛤仔鳃和消化腺组织中超氧化物歧化酶(SOD)、过氧化氢酶(CAT)活性以及丙二醛(MDA)含量的影响。结果显示:(1)鳃和消化腺中的抗氧化酶及MDA的变化呈现出类似的趋势,在胁迫初期,各浓度处理组菲律宾蛤仔鳃和消化腺组织SOD和CAT与对照组相比活性都显著升高(P<0.01),呈现出明显的诱导效应,而MDA含量与对照组相比差异不显著(P>0.05);随着胁迫时间的延长,高浓度Cd2+(0.474mg·L-1)和Pb2+(1.380mg·L-1)处理组中SOD、CAT活性快速下降,与对照组相比差异显著;低浓度处理组中的抗氧化活性虽然也较对照组有所下降,但总体下降幅度不如高浓度组明显,并且所历暴露时间较长。各浓度处理组中MDA含量变化一致,均呈现出先升高后降低的趋势,且含量均高于对照组。(2)通过相关性分析,菲律宾蛤仔消化腺组织中的SOD活性与Cd2+浓度的相关性大于鳃组织,与Pb2+浓度的相关性则小于鳃组织;消化腺组织中的CAT活性与Cd2+、Pb2+浓度呈抛物线型相关,与鳃组织CAT活性相关性不十分显著。这说明消化腺组织中SOD活性对Cd2+的敏感性大于鳃组织,消化腺组织中CAT活性对Cd2+、Pb2+的敏感性大于鳃组织。因此,菲律宾蛤仔消化腺中SOD、CAT对水环境中的重金属反应敏感,且存在一定的剂量-效应关系,消化腺组织中SOD和CAT活性与其他敏感性指标一起可以作为指示早期海洋重金属污染的生物标志物。     

有机磷农药二元混合物联合效应评价新方法的研究

以敌敌畏、乐果联合作用于线虫的毒理学实验为基础,基于FH插值法理论,通过较少的实验数据建立有机磷农药二元混合物联合效应模型,求解作用效应表达式并绘制联合效应三维曲面图;基于合并用药分析公式,计算联合作用评价q值并绘制农药浓度与q值的联合作用评价三维曲面图,结果表明敌敌畏与乐果混合物联合作用不仅表现为相加作用,而且还在局部低浓度表现为拮抗作用,与多元统计分析结果一致。上述研究表明FH插值法理论可作为二元有机磷农药联合效应分析及评价的一种新方法。     

溴氰菊酯对菲律宾蛤仔体内酶活性和组织损伤的初步探索

采用不同质量浓度的溴氰菊酯(0.0070 mg·L~(-1)、0.014 mg·L~(-1)、0.020 mg·L~(-1)、0.027 mg·L~(-1))对菲律宾蛤仔进行20 d半静置染毒,测定不同时间淋巴液中乙酰胆碱酯酶(ACh E)和钠离子-钾离子-三磷酸腺苷酶(Na~+-K~+-ATPase)活性、鳃和肝脏中谷胱甘肽转硫酶(GST)活性的变化,并观察染毒20 d后鳃丝组织和消化盲囊组织的损伤情况。酶活性分析结果显示,与对照组相比,低浓度组(0.0070 mg·L~(-1))试验期间酶活性均无显著差异(P0.05);中浓度组(0.014 mg·L~(-1)、0.020 mg·L~(-1))淋巴液中ACh E和Na~+-K~+-ATPase均呈先激活后抑制的变化规律(P0.05),鳃和肝脏中GST活性均呈上升趋势(P0.05);高浓度组(0.027mg·L~(-1))淋巴液中ACh E和Na~+-K~+-ATPase、肝脏中GST活性在试验期间持续下降(P0.01),而鳃中GST活性呈先抑制后升高的趋势(P0.05)。研究表明,低中浓度的溴氰菊酯对菲律宾蛤仔体内的酶活性表现为先诱导后抑制,具有明显的时间、剂量效应;高浓度的溴氰菊酯对菲律宾蛤仔体内酶活持续抑制,且染毒浓度越高,组织细胞变异越显著,表现为鳃丝上皮细胞纤毛层萎缩、纤毛脱落,消化盲囊上皮细胞膨胀,出现包涵体样结构。     

煤矸石对鲫鱼体内微量元素含量及组织结构的影响

来自煤矸石中的微量元素进入水体后,会对水生生物产生影响。通过水池养殖试验,采用单因子水质标识(Pi)、ICP-MS和组织学石蜡切片技术,探讨不同水/煤矸石质量比率(300?1和300?7)条件下,煤矸石对鲫鱼(Carassius auratus)肌肉、鳃中微量元素含量及组织结构的影响。结果表明,试验持续一年后,(1)煤矸石未对上覆水产生营养盐污染,水质整体可达到地表水Ⅲ类标准,符合水产养殖渔业水域的标准。(2)随着水/煤矸石质量比率由300?1增至300?7时,鲫鱼肌肉和鳃中Zn、Cu、Cd、Pb的质量分数显著增加(P0.05);鳃对微量元素的富集能力大于肌肉;不同微量元素在肌肉和鳃中的质量分数分别表现为ZnCuAsPbCd和ZnCuPbAsCd。(3)水/煤矸石质量比率为300?1和300?7的试验组中,肌肉与鳃均出现组织学病变。肌肉组织中,肌纤维细胞核数目不断减少、分布离散程度加深,肌纤维出现坏死、结缔组织出现增生情况。鳃组织中,鳃丝间距增大,鳃丝软骨逐渐变薄,末端鳃小片出现脱落,鳃小片弯曲程度加深,呈无规则排列。肌肉和鳃的组织学病变程度随组织中微量元素的含量、煤矸石污染程度的加深而加重。研究结论可为采煤沉陷区湿地生物保护及周边居民的健康提供科学依据。     

重金属Cu2+,Pb2+和Zn2+胁迫对近江牡蛎(Crassostrea rivularis) SOD活性影响研究

为探讨将近江牡蛎(Crassostrea rivularis)抗氧化酶防御体系参数作为海洋重金属污染生物监测指标可行性,文章在实验室条件下,研究这三种重金属暴露对近江牡蛎(C.rivularis)鳃和消化腺组织SOD活性的诱导作用;实验结果表明:Cu2 ,Pb2 和Zn2 能诱导近江牡蛎(C.rivularis)腮和消化腺SOD的产生,但由于近江牡蛎(C.rivularis)腮和消化腺的结构和功能的不同,在重金属的诱导下,消化腺内的SOD活性要比腮的大;Pb2 和Zn2 诱导近江牡蛎(C.rivularis)鳃和消化腺组织SOD活性变化的剂量-效应均为抛物线型;Cu2 对近江牡蛎(C.rivularis)鳃组织SOD活性诱导曲线不呈抛物线型,而对消化腺组织SOD活性诱导的剂量-效应呈抛物线型;根据对SOD活性影响的强弱,三种重金属对近江牡蛎(C.rivularis)的毒性强弱顺序为Cu2 >Pb2 >Zn2 。在实验室条件下,近江牡蛎(C.rivularis)消化腺组织中的SOD活性可作为养殖水体重金属污染程度监测指标,但应用到实际养殖水体尚须进一步研究。     

全氟辛烷磺酸对真鲷鳃抗氧化酶和组织损伤的影响

为了探讨全氟辛烷磺酸(PFOS)对真鲷(Pagrosomus major)的毒性及致毒机理,采用半静态毒性试验方法研究PFOS对真鲷的96 h急性毒性,并分析低浓度(0.1 mg.L-1)、中浓度(1.0 mg.L-1)和高浓度(2.0 mg.L-1)PFOS胁迫对真鲷鳃组织超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)活性,脂质过氧化物(MDA)含量以及组织损伤的影响。结果表明,PFOS对真鲷的96 h半致死浓度〔ρ(LC50)〕为22.56 mg.L-1。在PFOS胁迫阶段,低浓度组真鲷鳃组织SOD活性呈现先受诱导后受抑制的趋势,而中、高浓度组受到显著抑制(P<0.05),胁迫15 d时高浓度组抑制率为14.86%;各浓度组CAT活性的变化趋势呈"U"型,7和15 d时高浓度组诱导率分别为40.53%和62.32%;低浓度组POD活性在胁迫1 d时呈受诱导效应,之后下降至对照组水平(P>0.05),中、高浓度组则呈现先受抑制后受诱导的趋势,胁迫15 d时高浓度组诱导率为63.05%;MDA含量变化没有表现出明显的规律性。在净水恢复结束时,各浓度组真鲷鳃组织SOD活性恢复到对照组水平,而CAT、POD活性和MDA含量与对照组相比仍有显著差异(P<0.05)。在PFOS胁迫下真鲷鳃组织出现鳃丝上皮脱落与鳃丝融合现象,病变程度随着暴露浓度的增加和暴露时间的延长而加深。可见,PFOS可对真鲷鳃组织产生多个层面的毒性效应。     

虾夷扇贝毒素(yessotoxin)诱导的栉孔扇贝(Chlamys farreri)体内P糖蛋白转运活性及其分布研究

大量研究表明P-糖蛋白(P-glycoprotein,P-gp)介导的多型异源物质抗性机制(multi-xentiobiotic resistance,MXR)在贝类耐受或抵抗污染水域中有毒有害物质的毒害中具有重要作用,但是该机制在贝类抵抗或耐受食源性毒素方面作用的研究却很少。本研究以栉孔扇贝(Chlamys farreri)为实验动物,向其投喂产虾夷扇贝毒素(yessotoxins,YTXs)的网状原角藻(Protoceratium reticulatum),通过检测栉孔扇贝鳃和消化腺组织中YTX毒素含量随时间的变化情况,结合2种组织中P-gp介导的MXR活性变化及P-gp在组织中的表达和分布,探讨P-gp在扇贝耐受YTX毒素中可能的作用。研究结果表明,随着毒藻暴露时间的延长,栉孔扇贝鳃和消化腺中YTX含量逐渐增加,且具有明显的时间依赖关系。YTX的大量累积虽未导致扇贝死亡,但是仍然对扇贝组织产生不同程度的毒性。苏木精-伊红(hematoxylin-eosin,HE)染色发现,染毒12 h后,栉孔扇贝鳃组织前端出现明显黑化,消化腺组织导管上皮细胞部分脱落入管腔中,腺管内细胞界限模糊,部分腺管崩解。罗丹明B(rhodamine B,Rho B)外排实验表明YTX毒素暴露能显著增强栉孔扇贝鳃和消化腺组织中P-gp的转运活性,暴露12 h后鳃和消化腺Rho B的排出速率就已分别达到对照组的3.8倍和1.4倍,随着暴露时间的延长,P-gp活性略有增强,72 h后开始下降;P-gp的功能性抑制剂维拉帕米(verapamil,VRP)在实验设定的浓度下没有抑制反而增强了Rho B的外排;免疫定位显示,毒素暴露后栉孔扇贝鳃丝前端纤毛柱状细胞及消化腺导管上皮柱状细胞和腺管消化细胞P-gp免疫阳性信号增强,说明YTX毒素暴露提高了P-gp的表达量。综上推断,YTX毒素可能是P-gp的底物,它能够诱导P-gp转运活性增强,并增加P-gp的表达量来参与扇贝对YTX毒素的耐受或抗性;设定浓度的VRP不能抑制P-gp的活性,这可能是由于种属差异造成的,关于VRP对栉孔扇贝Pgp的作用还有待进一步的研究。     

Acid and alkaline phosphatase activities in the clam Ruditapes philippinarum

Acid and alkaline phosphatase activities have been partially characterized in Ruditapes philippinarum (Adams and Reeve, 1850). Two activity peaks at pH=4.5 and pH 10.5 were detected in the gill, digestive gland, mantle, siphon and foot. Acid phosphatase activity was higher than that of alkaline phosphatase. The highest activity for both enzymes was observed in the digestive gland and, in decreasing order, the gill, foot, siphon and mantle. Alkaline phosphatase activity was similar in the mantle, siphon and foot. K _m values were determined for both enzymes in the gill and digestive gland. Hill coefficients were near 1, indicating no allosteric behaviour for either enzyme in the two organs. The optimum temperature was the same for acid phosphatase in both gill and digestive gland (50 °C), while for alkaline phosphatase it differed for these two organs (gill, 40 °C; digestive gland, 35 °C). The apparent activation energy was obtained from Arrhenius plots, and ranged from 8.61 kcal/mol for alkaline phosphatase in the gill, to 10.84 kcal/mol for acid phosphatase in the digestive gland. The effects of metals (1 mM conc) on both enzyme activities were assayed in vitro. Hg strongly inhibited the enzyme activities in the gill and digestive gland, probably because of its affinity for the sulphydryl group. Histochemically, acid phosphatase in the gill was located in a granular form throughout the gill cells, but was undetectable in the ciliate epithelium of the gill filaments. Alkaline phosphatase was located in the gill skeleton. Clam size and phosphatase activities were inversely related, probably reflecting a decrease in shell deposition with inereasing size. As a function of season, both enzymes were present in lowest amounts in winter, when undifferentiated sex cells were predominant in the germinative epithelium, and highest in summer, when ripe individuals of both sexes were more frequent.     

Tissue and sub-cellular distribution of Fe,Cu, Zn and 210Po in the abalone Haliotis rubra

The tissue and sub-cellular distribution of Fe, Cu, Zn and the naturally occurring radionuclide polonium-210 was determined in the gastropod mollusc Haliotis rubra collected from Western Port Bay, Australia, between March and July 1988. The highest concentrations of the metals, with the exception of Cu, were found in the digestive gland. Copper was more uniformly distributed, with tissues that are more vasculated having higher concentrations. Ultrastructural examination of the digestive gland, gill and kidney showed dense membrane-bound granules within the cytoplasm. Elemental analysis of the granules by electron probe x-ray microanalysis indicated that the granules in the digestive gland and gill contained high concentrations of iron, with small amounts of copper and zinc. In contrast, the metal-containing granules in the kidney were predominantly composed of iron, copper and phosphorus, with variable contributions of sodium potassium, and calcium. Homogenisation and fractionation of the digestive gland by differential centrifugation confirmed that approximately 80, 10, 90 and 50% of the total homogenate Fe, Cu, Zn and ²¹⁰Po, respectively, sedimented at 1200xg. In the haemolymph, all the elements studied were associated with the soluble high molecular weight component of the serum, not with the amoebocytes. ²¹⁰Po was present in the mucus-secreting hypobranchial glands at about half the concentration found in gill tissue.     

The effect of copper and zinc on the metabolism of the mussel Mytilus edulis

The effects of copper and zinc on the metabolism of the mussel Mytilus edulis (L.) and its component tissues were studied. 500 ppm copper sodium citrate inhibited oxygen consumption of the whole animal and gill tissue, but no similar effect was observed on digestive gland tissue. 500 ppm zinc sodium citrate exerted no effect upon gill or digestive gland respiration, and neither metal salt affected the respiration of homogenates of gill, digestive gland or gonad. Direct observation of gill tissues during exposure to the metals revealed that 500 ppm copper sodium citrate caused inhibition of ciliary activity; exposure of tissues to 2 ppm Cu for 24 h resulted in only partial inhibition of the cilía. It is suggested that metabolic suppression noted in whole animals and gill tissues is due to the inhibition of an energy-consuming process such as ciliary activity rather than interference with respiratory enzyme systems.     

Characterisation and expression of four mRNA sequences encoding glutathione S-transferases pi,mu, omega and sigma classes in the Pacific oyster<Emphasis Type="Italic"> Crassostrea gigas</Emphasis> exposed to hydrocarbons and pesticides

Hydrocarbon and pesticide pollution in coastal ecosystems can disturb marine bivalve metabolism. In this study, we characterised four full-length cDNA sequences encoding glutathione S-transferases (GSTs) in the Pacific oyster Crassostrea gigas. A BLAST X search showed that these four sequences encode GSTs from four different classes: GST pi, sigma, mu and omega. A phylogenetic analysis of GST was made to determine the position of oyster GST compared to invertebrate and vertebrate sequences. We developed a semi-quantitative, multiplex RT-PCR to follow the expression of these four GSTs in tissues of oysters exposed to hydrocarbons and two pesticide treatments (glyphosate and a mixture composed of atrazine, diuron and isoproturon) under experimental conditions. Our results showed strong differential expression of these four GSTs that was both tissue specific as well as time and treatment dependent. We observed that expression levels were higher in digestive gland than in gill tissues in pesticide-exposed oysters. Furthermore, omega and mu class GST mRNA expression in the digestive gland might be useful as a possible marker of hydrocarbon exposure, while pi and sigma class GST mRNA expression in the digestive gland may be similarly useful as a marker of pesticide exposure in monitoring programmes.Communicated by S.A. Poulet, Roscoff     

Effects to perfluorooctane sulfonate (PFOS) on the mollusk Unio ravoisieri under laboratory exposure

To understand acute toxicity and oxidative stress of perfluorinated compounds in the freshwater ecosystems, we exposed freshwater mussels (Unio ravoisieri) to perfluorooctane sulfonate (PFOS), over a range of concentrations from 10 to 100?mg/L, in a laboratory experiment. Lethal concentration (LC50) was of about 65.9?mg/L after 96?h of exposure. The oxidative stress was assessed in gill and digestive gland of the freshwater mussels after 7 days of exposure to different nominal PFOS concentrations (C1=?2?mg/L, C2?=?6?mg/L and C3=?10?mg/L). C1 and C2 increased significantly (p?<?.05) the superoxide dismutase activity in both tissues compared, while the highest C3 decreased the enzyme activity. This implements an unfavourable response that highlights the excess of reactive oxygen species produced after contamination. The Catalase activity was also increased by about 40.05% and 66.63%, respectively, in gill and digestive gland after exposure to C3. The Malondialdehyde (MDA) level was increased in both gill and digestive gland in a concentration-dependent pattern. In contrast, the contamination of U. ravoisieri by PFOS did not affect the acetylcholinesterase activity in both organs (p?>?.005). These results provided information on potential biomarkers that could be effectively applied for the monitoring of freshwater ecosystem using indicator species such as U. ravoisieri.     

Metal Content in Selected Tissues and Shell of Pern A Virwis (L) From Pondicherry, East Coast of India

Mussels are good bioaccumulators of metals and have been used as indicators for environmental monitoring. in this study on P. viridis from Pondicherry coast, metal content (aluminium, lead, cadmium, copper and zinc) were analysed in selected tissues and shell nacre for a period of one year. the metal content shows that digestive gland accumulates higher concentrations of metal ions followed by gill, mantle and shell. of the different components (digestive gland, gill, mantle and shell nacre) of the organism, only shell nacre exhibited a significant relationship with ambient levels and therefore can be applied to temporal monitoring of metal contamination.     

Petroleum hydrocarbons in the marine bivalve Venus verrucosa: accumulation and cellular responses

Cellular and subcellular responses of the marine burrowing bivalve Venus verrucosa collected from the north-eastern coastline of Malta from January to June 1985, after exposure to petroleum hydrocarbons (PHC) were investigated. After long-term exposure to 100 gl^-1 of water-accomodated fractions (WAF) of crude oil, PHC were found to accumulate most rapidly in the digestive gland and then in the gills, with saturation levels being reached within 100 d of exposure in both cases. PHC accumulation, both in the mantle and muscle tissues, was more gradual and consistent throughout the whole exposure period. After 150 d of exposure, the digestive cells of the digestive gland were significantly reduced in height (atrophy) and exhibited reduced lysosomal membrane stability. After 144 h of exposure to higher concentration of PHC (820 and 420 gl^-1), several cytological effects were recorded, including an increase in cell volume and activity of gill mucocytes as well as in the number of haemocytes in gill blood sinuses. There was also evidence of damage to the epithelial lining of the foot, stomach and style sac and marked atrophy of the digestive cells of the digestive gland. The significance of such responses is discussed.     

Depuration of twelve trace metals in tissues of the oysters Crassostrea gigas and C. virginica

The depuration of 12 trace metals in the mantle, gill, digestive gland, and kidney of Crassostrea gigas and C. virginica was investigated under natural field conditions; oysters from a relatively contaminated environment (Redwood Creek in south San Francisco Bay) were transplanted to a relatively clean environment (Tomales Bay). In the transplanted oysters, the digestive gland and kidney depurated Cd, Cu, Hg, Ag, and Zn more readily than the mantle and gill. Other trace metals As, Fe, Mn, Ni and Se showed varying depuration patterns. The results for Cr and Pb were inconclusive, since initial concentrations were too low to follow any losses. Interspecific differences in trace metal depuration were observed. Biological half-lives for most trace metals were on the order of 23 to 60 d for C. gigas and on the order of 70 to 180 d for C. virginica.     

Accumulation,tissue distribution and elimination of 203HgCl2 and CH3 203HgCl in the tissues of the American oyster Crassostrea virginica

Oysters (Crassostrea virginica) were exposed for 3 days to mercury-203 labeled HgCl₂ or CH₃HgCl added directly to artificial seawater or added preconcentrated on the marine diatom Phaeodactylum tricornutum. The concentration of mercury in 5 tissues was measured for 45 days after mercury was removed from the ambient water. At the beginning of the depuration period, the highest concentrations of mercury in tissues were attained in: gill>digestive system>mantle>gonad>muscle in oysters exposed to water containing mercury; and in digestive system>gill>mantle> gonad>muscle in oysters fed labeled algae. This same distribution pattern is seen for both chemical forms of mercury. Although the initial pattern of accumulation was identical for both mercury compounds within each exposure group, the fate of the accumulated mercury was very different after 45-days depuration. In oysters accumulating mercury directly from seawater, inorganic mercury residues rapidly declined in gill and digestive tissue, but were slowly reduced in mantle, gonadal, and muscle tissue. This pattern was duplicated by oysters exposed to methyl mercuric chloride in seawater except that gonadal and muscle residues greatly increased during depuration. In oysters ingesting labeled P. tricornutum cells, mercuric chloride and methyl mercuric chloride residues rapidly declined in gill and digestive tissue, remained constant in the mantle, but sharply increased in gonadal and muscle tissue during depuration.