Toxic Effects Of Cd And Hg Exposure On Phascolosoma Esculenta

With the rapid development of coastal industries, heavy metal pollution is becomingmore and more severe, Threatening the Survival and growth of benthos in Shoals,leading to recession of biological species resources, limiting the development ofsustainable aquaculture. The Wenzhou Ocean Environmental Quality Bulletin in2010shows that the content of heavy metals （Cr6+, Cu, Zn） from water in seven sea outfalls ismore than the standards, the contents of Cr, Zn and Cu in the sediments from localwaters were up to the first-class quality standard for marine sediments, and near-shoreaquatic also had a certain degree of pollution. So the problem of heavy metal pollutionin Wenzhou is ubiquitous. Phascolosoma esculenta was used as model animal, andcombining detection and analysis of the field samples with exposure test was used. toexplore heavy metal contents, the correlativity between P. esculenta and habitatsediments and the biological concentration factor （BCF）,reflecting the environmentalconditions of living area in the southeast coast of P.esculenta, as well as mentioning thetheoretical reference of other aquatic farming environment.. And then discuss acutetoxicity, survival, growth rate and moisture content, BCFs, the change rate of proteincontent, the change rate of fat content,and DNA damage to study drug manufacturingmechanism of Cd and Hg on P. esculenta under experimental ecological conditions, toprovide the basic data for fishery water quality testing and toxicological studies of otherbenthic organisms, and offer theoretical basis for pollution indicator organism,protection of the marine ecological environment, development rationally of P. esculentaresources, and healthy aquaculture, processing and consumption.The main findings are as follows:1. Heavy metal contents in P. esculenta and in their habitat sedimentsThe results showed a significant difference of heavy metal contents in P. esculentasfrom different sites （P<0.05）. Lead concentrations in P. esculentas from all the samplingsites and Cd from Xiamen were above the security standards. The heavy metals contentsin the sediments from Xiamen,Yueqing and culture area of Wenling were relatively high. The content of Cu in sediments from all the sampling sites and Zn from culture area ofWenling were up to the second-class quality standard for marine sediments, while theothers reached the first-class standard. The BCFs of Zn, Cu and Fe were less than one;whereas the BCFs of Mn, Cd, Pb, Hg and As were higher than one, the BCFs of Zn, Cu,Fe, Pb and As with no significant variation among most of sampling sites. A mostpositive correlation was observed for the Fe and As levels in muscle and that in thesediments, closely followed by Zn and Hg, while others elements presentedfaint-correlation or non-correlation. The contents of Zn, Mn, Fe, Pb and Hg were morethan in the visceral mass, there were much more contents of Cu, Cd and As in thevisceral mass.2. Single and joint acute toxicity test of Cd²⁺and Hg²⁺to P. esculentaThe24-h,48-h,72-h and96h LC50values（95%confidence interval estimation） ofCd²⁺、Hg²⁺and(Cd²⁺+Hg²⁺)were16.19（12.09～25.38）mg/L、4.17（3.27～5.81）mg/L、2.82（1.56～3.98）mg/L,8.75（605～13.04）mg/L、1.98（1.35～3.02）mg/L、1.31（0.98～2.41）mg/L,5.51（3.81～7.90）mg/L、1.33（0.88～2.03）mg/L and1.12（0.67～2.17）mg/L,5.46（3.35～8.47）mg/L、0.93（0.64～1.67）mg/L、0.74（0.34～1.56）mg/L. The safe concentrations of Cd²⁺、Hg²⁺and (Cd²⁺+Hg²⁺)for P. esculenta were0.27,0.0465,0.037mg/L, respectively. The toxicity sequence of the heavy metals was(Cd²⁺+Hg²⁺)＞Hg²⁺＞Cd²⁺at48and96h. Cd²⁺and Hg²⁺in the48h and96h aresynergies.3. Cd and Hg affecting on growth rate and moisture content, BCFs, the change rate ofprotein content, the change rate of fat contentThe growth rate of P. esculenta decreased with increasing concentrations of heavymetals. The highest concentration of Cd²⁺and (Cd²⁺+Hg²⁺) had less impact on thegrowth rate, but were significant differences with the control group（P＜0.05）, indicatingthat heavy metals can inhibit the P. esculenta growth, stopping growing when theconcentration reached a certain value.The P. esculenta were exposed in different claybed for120ds, the change rate of fat content:0.58～-20.53%,0.36～-17.35%,2.38～-29.08%.The overall trend were gradually reduced as the concentration increasing, thetreatment groups had significant differences with the control group（P＜0.05or P＜0.01）. The change rate of protein content:1.56%～16.19%、1.65～8.84%、-8.07～17.64%, the protein content firstly increased and then decreased as the content of heavymetals increased, even less than content of control group. the treatment groups had significant differences with the control group（P＜0.05or P＜0.01）, the differencebetween with part of concentration group was significantly（P＜0.05）.4. Changes in heavy metal content in muscle P. esculentaThe contents of Cd and Hg had not increased with the increasing of exposure timeand concentration until reaching balance, showing a certain degree ofconcentration-time-dose effect. The enrichment rate of the lower concentration waslower than the higher. The exposed time, concentration and the interaction between withthem had significant impact on contents of Cd and Hg（P＜0.01）.5. The interaction between Cd with Hg in muscle P. esculenta.In the rage of experimental concentration, the contents of Cd firstly increased andthen decreased with increasing of Hg, that was to say that adding Hg to promote theenrichment of Cd. But the content of Hg decreased with increasing of Cd, that was tosay that adding Cd to inhibit the enrichment of Hg.6. Cd and Hg affecting DNA damage of body fluid cellsDNA damage was indicated by taking comet tail length and tail moment（TM） asDNA damage evaluation, and the latter was more accurate. With the increase of heavymetal concentration and exposed time, DNA damage was more serious。...