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Title: Energy allocation in Daphnia magna exposed to xenobiotics: A biochemical approach

Abstract

A new approach to sublethal aquatic toxicity testing based on a biochemical assessment of the energy budget of Daphnia magna was developed and evaluated. With this method energy consumption (E{sub c}) is estimated by measuring the electron transport activity based on the calorimetric measurement of a tetrazolium salt reduction. Total available energy (E{sub a}) is assessed by measuring the lipid, protein and sugar content of the test organism using calorimetric methods. E{sub a} {minus} E{sup c} can subsequently be calculated and represents the ``surplus`` energy available for growth and reproduction. D. magna neonates were exposed to cadmium and 2,4-dichlorophenoxy acetic acid for 4 days after which the electron transport activity and the total lipid, protein and sugar content of the test organisms were determined. Using the enthalpy of combustion of the different macromolecular groups and converting the oxygen consumption into oxyenthalpic equivalents, an estimation of the total energy budget of the test organisms was made. Additionally, the age specific survival and reproduction and the growth of D. magna populations exposed to the same sublethal concentrations was assessed in 21 day life table experiments. Energy allocation patterns of stressed D. magna obtained with the new biochemical approach were similar to thosemore » obtained with the conventional Scope for Growth determinations. Although more research is needed, comparison between the suborganismal (biochemical) and supraorganismal (life table) endpoints indicate that the proposed short-term assay based on energy allocation could be used to predict long-term effects on the survival, growth and reproduction of daphnids.« less

Authors:
; ;  [1]
  1. Univ. of Ghent (Belgium). Lab. for Biological Research in Aquatic Pollution
Publication Date:
OSTI Identifier:
201200
Report Number(s):
CONF-9511137-
ISBN 1-880611-03-1; TRN: IM9613%%177
Resource Type:
Conference
Resource Relation:
Conference: 2. Society of Environmental Toxicology and Chemistry (SETAC) world conference, Vancouver (Canada), 5-9 Nov 1995; Other Information: PBD: 1995; Related Information: Is Part Of Second SETAC world congress (16. annual meeting): Abstract book. Global environmental protection: Science, politics, and common sense; PB: 378 p.
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 56 BIOLOGY AND MEDICINE, APPLIED STUDIES; WATER POLLUTION; BIOLOGICAL INDICATORS; DAPHNIA; BIOLOGICAL STRESS; CADMIUM; TOXICITY; ACETIC ACID; XENOBIOTICS; AGE DEPENDENCE; ANIMAL GROWTH; SURVIVAL TIME; BIOASSAY; CALORIMETRY

Citation Formats

Coen, W.M. De, Janssen, C.R., and Persoone, G. Energy allocation in Daphnia magna exposed to xenobiotics: A biochemical approach. United States: N. p., 1995. Web.
Coen, W.M. De, Janssen, C.R., & Persoone, G. Energy allocation in Daphnia magna exposed to xenobiotics: A biochemical approach. United States.
Coen, W.M. De, Janssen, C.R., and Persoone, G. Sun . "Energy allocation in Daphnia magna exposed to xenobiotics: A biochemical approach". United States. doi:.
@article{osti_201200,
title = {Energy allocation in Daphnia magna exposed to xenobiotics: A biochemical approach},
author = {Coen, W.M. De and Janssen, C.R. and Persoone, G.},
abstractNote = {A new approach to sublethal aquatic toxicity testing based on a biochemical assessment of the energy budget of Daphnia magna was developed and evaluated. With this method energy consumption (E{sub c}) is estimated by measuring the electron transport activity based on the calorimetric measurement of a tetrazolium salt reduction. Total available energy (E{sub a}) is assessed by measuring the lipid, protein and sugar content of the test organism using calorimetric methods. E{sub a} {minus} E{sup c} can subsequently be calculated and represents the ``surplus`` energy available for growth and reproduction. D. magna neonates were exposed to cadmium and 2,4-dichlorophenoxy acetic acid for 4 days after which the electron transport activity and the total lipid, protein and sugar content of the test organisms were determined. Using the enthalpy of combustion of the different macromolecular groups and converting the oxygen consumption into oxyenthalpic equivalents, an estimation of the total energy budget of the test organisms was made. Additionally, the age specific survival and reproduction and the growth of D. magna populations exposed to the same sublethal concentrations was assessed in 21 day life table experiments. Energy allocation patterns of stressed D. magna obtained with the new biochemical approach were similar to those obtained with the conventional Scope for Growth determinations. Although more research is needed, comparison between the suborganismal (biochemical) and supraorganismal (life table) endpoints indicate that the proposed short-term assay based on energy allocation could be used to predict long-term effects on the survival, growth and reproduction of daphnids.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Dec 31 00:00:00 EST 1995},
month = {Sun Dec 31 00:00:00 EST 1995}
}

Conference:
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  • Two new rapid toxicity tests, based on ingestion activity and digestive enzyme activity of D. magna, were developed and evaluated. The ingestion activity was measured using fluorescent latex micro-beads and an automated microplate fluorimeter allowing a sensitive quantification of the feeding activity of the organisms. The activity of the digestive enzymes, 6-galactosidase, esterase and trypsin, was determined in test organism homogenates using the following fluorogenic{sup 1} and chromogenic{sup 2} substrates: 4-methylumbelliferyl-{beta}-D galactoside{sup 1}, fluorescin diacetate{sup 1} and N-Benzoyl-L-arginine-4-nitroanilide{sup 2}. Both biomarker techniques were developed to allow rapid toxicity screening on a routine basis. The toxicity of the pore waters ofmore » eight contaminated samples was assessed with the aid of the developed biomarker assays. Comparison of the conventional 24h EC50 values with the EC50 values obtained with the 1.5h ingestion test and the threshold concentrations of the 2h digestive enzyme tests revealed a positive correlation between the different effect concentrations. A similar correlation (r{sup 2} = 0.87) between the conventional 24h EC50 values and 1.5h EC50 values was observed in toxicity tests with pure compounds. Correlation coefficients for the relationships between the 3 enzyme effect concentrations and the 24h EC50 values ranged from 0.95 to 0.98, The positive correlations between the conventional and biomarker effect criteria, observed for both environmental samples and pure compounds, demonstrate the potential use of the developed methods as rapid toxicity screening tools.« less
  • Steroid hydroxylase activities were characterized in Daphnia magna and evaluated for potential use as biomarkers of xenobiotic exposure. Microsomes prepared from Daphnia magna generated as single NADPH-dependent metabolite of [[sup 14]C] testosterone. However, intact daphnids excreted at least 10 polar metabolites of [[sup 14]C] testosterone into the test medium. Six of these metabolites were identified as 2[alpha]-, 16[beta]-, 6[beta]-, 6[alpha]-, 7[alpha]-, and 15[alpha]-[[sup 14]C]hydroxytestosterone. The unidentified metabolites are also presumed to be hydroxylated products of testosterone, based on their relative migrations during TLC. The inefficient metabolism of [[sup 14]C] testosterone during the in vitro microsomal incubations may have been duemore » to the release of P450 inhibitors during microsome preparation. Exposure of daphnids to the P450 modulators phenobarbital, [beta]-naphthoflavone, piperonyl butoxide, and malathion differentially inhibited the steroid hydroxylase activities. Results from this study indicate that Daphnia magna expresses several P450 enzymes and that these enzymes are differentially modulated by xenobiotic exposure. Steroid hydroxylase activities may serve not only as a biomarker of toxicant exposure, but also as a predictor of toxicant effects involving perturbations of steroid hormone homeostasis.« less
  • The estrogenic properties of many environmental contaminants, such as DDE and PCBs, have been associated with reproductive failure in a variety of vertebrate species. While estrogens have been measured in many invertebrate species, the function of this hormone in invertebrates is controversial. The objective of the present study was to identify possible physiological and biochemical target sites for the estrogenic effects of some xenobiotics on the freshwater crustacean Daphnia magna using the model environmental estrogen diethylstilbestrol (DES). Chronic exposure of daphnids to 0.50 mg/L DES reduced molting frequency among first-generation juveniles and decreased fecundity of second-generation daphnids. Adult first-generation daphnidsmore » chronically exposed to DES, as well as adult daphnids acutely exposed to DES for only 48 h, were examined for steroid hormone metabolic capabilities using testosterone as the model steroid. The rate of elimination of two major hydroxylated metabolites of testosterone was significantly reduced, and elimination of glucose conjugates of testosterone was significantly elevated from exposure to 0.50 mg/L DES. These results demonstrate that multigeneration exposure of daphnids to DES results in reduced fecundity and altered steroid metabolic capabilities. Thus, some arthropods, like vertebrates, are sensitive to the effects of endocrine-disrupting chemicals.« less
  • A method of DNA profiling using the random amplified polymorphic DNA (RAPD) was used to assess toxicant-induced DNA effects in laboratory populations of Daphnia magna exposed to varying concentrations of the genotoxic hydrocarbon benzo[a]pyrene. These effects, represented by changes in the RAPD profiles, were compared with a number of key ecological fitness parameters (age-specific survival, age-specific fecundity, net reproductive rate, and intrinsic rate of population increase). Not only was the RAPD profiling method shown to be a rapid and reproducible assay of toxicant-induced DNA effects, but the qualitative measure of genomic template stability compared favorably with the traditional indices ofmore » fitness. The RAPD profiles, however, exhibited higher sensitivity in detecting toxic effects. The significance of these findings for future ecotoxicological studies is discussed.« less
  • Concentrations causing inhibition of growth of Daphnia magna after 16 days of exposure were determined for nine chemicals that presumably act through different modes of action. The joint toxic effect of a mixture of these chemicals is found to be nonadditive.