• 検索結果がありません。

淡水二枚貝を用いた銅の生態毒性学的研究

N/A
N/A
Protected

Academic year: 2022

シェア "淡水二枚貝を用いた銅の生態毒性学的研究"

Copied!
3
0
0

読み込み中.... (全文を見る)

全文

(1)

九州大学学術情報リポジトリ

Kyushu University Institutional Repository

淡水二枚貝を用いた銅の生態毒性学的研究

劉, 洪波

http://hdl.handle.net/2324/1807154

出版情報:Kyushu University, 2016, 博士(農学), 論文博士 バージョン:

権利関係:Public access to the fulltext file is restricted for unavoidable reason (3)

(2)

氏 名 :劉 洪波

論文題名 :

An ecotoxicological study of copper in freshwater mussels (淡水二枚貝を用いた銅の生態毒性学的研究)

区 分 :乙

論 文 内 容 の 要 旨

Mussels easily accumulate heavy metals from the environment, and significant relationships have been found between heavy metal concentrations in aquatic habitats and the soft tissues of the mussels living in those habitats. In this study, freshwater mussel species were used as sentinel organisms, by their bioaccumulation (indicated by the heavy metal concentrations in mussel tissues), survival, biochemical responses (multi-parameter antioxidant enzyme and DNA damage responses), and behavioral responses (valve movement responses), to assess heavy metal contamination in the environment, and to evaluate whether water chemical condition and phases of the mussel life cycle affect water borne Cu toxicity.

The bioaccumulative status of 13 trace elements (Ag, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Se, and Zn) were investigated by 38 freshwater mussels (Anodonta woodiana) from four sites (Dapu, Huzhou, Manshan, and Sanshandao) around Taihu Lake in China. It was found that A. woodiana was able to bioaccumulate essential metal Mn and toxic metal Cd to the extremely high level, and the highest Mn and Cd concentrations found in the tissue samples were 19240, and 53 mg kg−1 dry weight, respectively. The concentrations of each trace element except As and Pb were generally significantly different in samples from different sampling sites, and the trace metal concentrations were higher in the mussels from the Sanshandao site than in the mussels from the other sites. The Cd concentrations were higher than the Cu and Se concentrations in A.

woodiana from the Sanshandao and Manshan sites, and the Cd concentrations in these samples were higher than the Chinese maximum residue limits. These results suggest that A. woodiana might be a suitable bioindicator to provide the information of contamination of heavy metal in freshwater environment.

The effects of calcium (Ca2+) and magnesium (Mg2+) ions and dissolved organic carbon (DOC) on the toxicity of Cu to glochidia, newly transformed juvenile A. woodiana (aged 1–2 days), and juvenile A.

woodiana (aged 2 months) were then evaluated. Acute Cu toxicity tests were first performed using glochidia (for 24 h) and newly transformed juvenile A. woodiana (for 96 h) using measured Ca2+ concentrations of 1.1, 14, 26, 51, and 99 mg L−1 or measured Mg2+ concentrations of 2.6, 11, 21, and 39 mg L−1. No significant effect of Ca2+ and Mg2+ on the Cu toxicity was observed. The 24 h EC50 for Cu for glochidia was 0.082 mg L−1, and, in contrast, the 96 h EC50 for Cu for newly transformed juvenile A. woodiana was 0.012 mg L−1, indicating that juvenile A. woodiana are more vulnerable than glochidia to Cu contamination at concentrations close to currently accepted levels. Acute Cu toxicity tests were performed using 2-month-old juvenile A. woodiana (for 96 h) using five nominal DOC concentrations (0, 0.8, 1.5, 3, and 6 mg L−1 as carbon, i.e., [C]). The EC50 values for Cu were 0.866–0.707 mg L−1 at different DOC concentrations, and the 95% confidence intervals for the EC50 values at different DOC concentrations overlapped. This indicated that DOC did not protect 2-month-old juvenile A. woodiana against Cu toxicity under the test conditions that were used.

(3)

Genotoxic and biochemical responses in juvenile and adult A. woodiana to exposure to Cu were then evaluated. Juveniles were exposed to Cu at 0, 0.125, and 0.25 mg L−1 for 48 h and 96 h, while adults were exposed at 0, 0.75, 1.5, and 3 mg L−1 also for 48 h and 96 h. Comet assays with olive tail moments were then performed on gill cells from the exposed A. woodiana to evaluate DNA damage. Significant dose-related DNA damage occurred in the adult test groups after 48 h and 96 h of exposure of Cu. Time-related changes in the olive tail moments were observed in the juveniles at a Cu concentration of 0.25 mg L−1 and in the adults at a Cu concentration of 1.5 mg L−1. The activities of the antioxidant enzymes superoxide dismutase and catalase, the levels of the non-enzymatic antioxidant glutathione, and the levels of the lipid peroxidation product malondialdehyde in the adductor muscles, feet, gills, mantles, and visceral masses of A. woodiana exposed to Cu for 48 h and 96 h were also measured. The biochemical responses were generally higher in the feet and mantles of the juveniles and in the adductor muscles of the adults than in the controls. The biochemical responses of the different tissues to redox-active Cu were different, and no significant relationships were found between the Cu concentration and the responses of the biochemical parameters (P>0.05). However, low levels of DNA damage were found in the control group gill cells and significant dose-related DNA lesions were found in the adult test group gill cells after 48 h and 96 h of exposure to Cu (48 h r2 = 0.988, P = 0.006; 96 h r2 = 0.965, P = 0.018). The changes in the levels of the oxidative stress biomarkers and DNA damage indicated that the comet assay using bivalve gill cells should be the preferred method for monitoring trace metal pollutants in freshwater environments.

In the final study, the Hall element sensor system was used to investigate exposure–response relationships for valve movements in freshwater 3 kinds of mussels A. woodiana, Corbicula fluminea, and Hyriopsis cumingii exposed to Cu at concentrations of 0, 0.01, 0.1, 1, and 10 mg L−1. Two behavioral parameters, the valve opening amplitude and the valve adduction frequency, were measured. The mean valve opening amplitude was significantly lower in C. fluminea exposed to Cu at concentrations of 0.1 and 1 mg L−1 than in the control C. fluminea, and the valve opening amplitude was lower in H. cumingii and A. woodiana exposed to Cu at a concentration of 10 mg L−1 than in the control H. cumingii and A. woodiana. The mean valve adduction frequency was significantly lower in H. cumingii exposed to Cu at concentrations of 1 and 10 mg L−1 than in the controls. The mean valve adduction frequency was lower in A. woodiana exposed to Cu at a concentration of 10 mg L−1 than in the controls. Inherent valve movement rhythms and dose-dependent responses occurred in all three species when exposed to Cu.

In summary, freshwater mussel including, A. woodiana are suitable surrogates for monitoring the bioavailabilities of pollutants and for pollution-sensitive and pollution-tolerant species. The comet assay can be used to assess inter-cell variability in responses to pollutants, and interspecies variations in valve movements can be determined over time using the Hall element sensor system. It is essential that basic ecotoxicological research into A. woodiana continues, and further research is required to improve our ability to use A. woodiana as an indicator of ecological integrity. Unionid ecotoxicological research, particularly heavy metal-specific toxicity tests, will continue to be important research to protect aquatic ecosystems from metal contamination.

参照

関連したドキュメント

Volatile aromatic hydrocarbon concentrations in heavy fuel oil and the atmosphere collected from seashores affected by an oil spill.

イシガイ UワiO吻祝glαSiαεn砲ρOnθnSiS 29.5 4.9 4.9 ニセマツカサガイ  加Vε75i祝nioアonα9卿θnsis 13.0 1.3 1.7 マツカサガィ P70no4擢α7iαノ4ραnθnsis

[r]

The emotional behavior in wild and KO male mice was evaluated at 9e10 weeks of age by the elevated plus-maze test, open field test, social interaction test, and sucrose preference

The paper assesses the environmental policy that sets the thresholds of concentration levels that the operating companies should apply to avoid toxicological harm around

そこで, 本研究ではこれ らの二枚月の PSPの消長 に関う る 知見を手 等るため,帝化の指標 となるムラサキイガイ とともに チ 2 Eウセンハマグ

GCDFP-15: Gross cystic disease fluid protein-15.... AR:

Each week students were given readings based on the topics listed on the syllabus, but their homework assignments were related to academic research methods and paper writing, and