Document Detail


Maternal transfer efficiency and transgenerational toxicity of methylmercury in Daphnia magna.
MedLine Citation:
PMID:  15376536     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
We examined maternal transfer efficiency, retention by subsequent generations, and transgenerational toxicity of methylmercury (CH3Hg or MeHg) in a population of freshwater zooplankton (Daphnia magna). The effect of dietary MeHg residence time in the daphnids on the efflux system also was quantified. After ingesting a relatively high dosage of MeHg, D. magna exhibited a reduction of live neonates and an increase of undeveloped eggs (or embryos), which reflected the sublethal toxicity of MeHg. The daily maternal transfer efficiency of MeHg to both reproductive outputs ranged from 0.42 to 4.9% over different ages of the parental daphnids, which was dependent on the daily reproductive output. During the lifetime of D. magna, reproduction contributed to 10.8% +/- 1.74% (n = 3) SD of total MeHg loss from the parental daphnids. The percentage of MeHg retention by the second generation (F1) of D. magna (40-60%) was generally higher than that by the parental generation (F0; approximately 25%) after 20 d of depuration. Methylmercury imposed sublethal toxicity to the F0 and F1 generations, but a smaller effect was observed on the F2 generation. Because of the very low MeHg body burden in the subsequent generations, we hypothesized that factors other than MeHg, such as nutritional deficiency in the offspring contributed to the transgenerational toxicity. Different MeHg residence times did not significantly affect the efflux rate of MeHg but did significantly affect the relative importance of reproduction as the elimination pathway for MeHg. Based on the MeHg body burden of neonates, we estimated that MeHg took 2.5 to 3.0 d to be optimally transferred from assimilation (e.g., gut) to the site of egg development (e.g., brood chamber) in D. magna. Our study demonstrated that maternal transfer of MeHg in freshwater zooplankton is an important predictor of MeHg concentration in their offspring and is a time-dependent and highly dynamic process.
Authors:
Martin T K Tsui; Wen-Xiong Wang
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Environmental toxicology and chemistry / SETAC     Volume:  23     ISSN:  0730-7268     ISO Abbreviation:  Environ. Toxicol. Chem.     Publication Date:  2004 Jun 
Date Detail:
Created Date:  2004-09-20     Completed Date:  2004-10-05     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8308958     Medline TA:  Environ Toxicol Chem     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1504-11     Citation Subset:  IM    
Affiliation:
Department of Biology, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
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MeSH Terms
Descriptor/Qualifier:
Administration, Oral
Animals
Body Burden
Daphnia / genetics*,  physiology
Diet
Female
Maternal-Fetal Exchange*
Methylmercury Compounds / pharmacokinetics*,  toxicity*
Pregnancy
Tissue Distribution
Water Pollutants, Chemical / pharmacokinetics*,  toxicity*
Wills
Chemical
Reg. No./Substance:
0/Methylmercury Compounds; 0/Water Pollutants, Chemical

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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