Limits...
Juvenile food limitation in standardized tests: a warning to ecotoxicologists.

Zimmer EI, Jager T, Ducrot V, Lagadic L, Kooijman SA - Ecotoxicology (2012)

Bottom Line: In a simulation study with the DEB model, we compared the effects of three hypothetical toxicants in different feeding situations.The initial food limitation when fed with lettuce always intensified the effect of the toxicants.When fed with fish flakes, the predicted effect of the toxicants was less pronounced.

View Article: PubMed Central - PubMed

Affiliation: Department of Theoretical Biology, Faculty of Earth & Life Sciences, Vrije Universiteit, de Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands. elke.zimmer@vu.nl

ABSTRACT
Standard ecotoxicological tests are as simple as possible and food sources are mainly chosen for practical reasons. Since some organisms change their food preferences during the life-cycle, they might be food limited at some stage if we do not account for such a switch. As organisms tend to respond more sensitively to toxicant exposure under food limitation, the interpretation of test results may then be biased. Using a reformulation of the von Bertalanffy model to analyze growth data of the pond snail Lymnaea stagnalis, we detected food limitation in the early juvenile phase. The snails were held under conditions proposed for a standardized test protocol, which prescribes lettuce as food source. Additional experiments showed that juveniles grow considerably faster when fed with fish flakes. The model is based on Dynamic Energy Budget (DEB) theory, which allows for mechanistic interpretation of toxic effects in terms of changes in energy allocation. In a simulation study with the DEB model, we compared the effects of three hypothetical toxicants in different feeding situations. The initial food limitation when fed with lettuce always intensified the effect of the toxicants. When fed with fish flakes, the predicted effect of the toxicants was less pronounced. From this study, we conclude that (i) the proposed test conditions for L. stagnalis are not optimal, and require further investigation, (ii) fish flakes are a better food source for juvenile pond snails than lettuce, (iii) analyzing data with a mechanistic modeling approach such as DEB allows identifying deviations from constant conditions, (iv) being unaware of food limitation in the laboratory can lead to an overestimation of toxicity in ecotoxicological tests.

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The simulation of growth curves of snails exposed to the hypothetical toxicants. From left to right, the different mechanisms of effect are shown, while from top to bottom, the feeding scenarios are displayed. Scenarios: a–c without food limitation; d–f with the linear food limiting function, assumed to be fed on lettuce; g–i with the linear food limiting function, assumed to be fed with fish flakes. Top line: control conditions. Lines from top to bottom represent the scenarios were the respective parameters are changed
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Fig3: The simulation of growth curves of snails exposed to the hypothetical toxicants. From left to right, the different mechanisms of effect are shown, while from top to bottom, the feeding scenarios are displayed. Scenarios: a–c without food limitation; d–f with the linear food limiting function, assumed to be fed on lettuce; g–i with the linear food limiting function, assumed to be fed with fish flakes. Top line: control conditions. Lines from top to bottom represent the scenarios were the respective parameters are changed

Mentions: The simulated growth curves for the scenarios with the three hypothetical toxicants are shown in Fig. 3.


Juvenile food limitation in standardized tests: a warning to ecotoxicologists.

Zimmer EI, Jager T, Ducrot V, Lagadic L, Kooijman SA - Ecotoxicology (2012)

The simulation of growth curves of snails exposed to the hypothetical toxicants. From left to right, the different mechanisms of effect are shown, while from top to bottom, the feeding scenarios are displayed. Scenarios: a–c without food limitation; d–f with the linear food limiting function, assumed to be fed on lettuce; g–i with the linear food limiting function, assumed to be fed with fish flakes. Top line: control conditions. Lines from top to bottom represent the scenarios were the respective parameters are changed
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3475972&req=5

Fig3: The simulation of growth curves of snails exposed to the hypothetical toxicants. From left to right, the different mechanisms of effect are shown, while from top to bottom, the feeding scenarios are displayed. Scenarios: a–c without food limitation; d–f with the linear food limiting function, assumed to be fed on lettuce; g–i with the linear food limiting function, assumed to be fed with fish flakes. Top line: control conditions. Lines from top to bottom represent the scenarios were the respective parameters are changed
Mentions: The simulated growth curves for the scenarios with the three hypothetical toxicants are shown in Fig. 3.

Bottom Line: In a simulation study with the DEB model, we compared the effects of three hypothetical toxicants in different feeding situations.The initial food limitation when fed with lettuce always intensified the effect of the toxicants.When fed with fish flakes, the predicted effect of the toxicants was less pronounced.

View Article: PubMed Central - PubMed

Affiliation: Department of Theoretical Biology, Faculty of Earth & Life Sciences, Vrije Universiteit, de Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands. elke.zimmer@vu.nl

ABSTRACT
Standard ecotoxicological tests are as simple as possible and food sources are mainly chosen for practical reasons. Since some organisms change their food preferences during the life-cycle, they might be food limited at some stage if we do not account for such a switch. As organisms tend to respond more sensitively to toxicant exposure under food limitation, the interpretation of test results may then be biased. Using a reformulation of the von Bertalanffy model to analyze growth data of the pond snail Lymnaea stagnalis, we detected food limitation in the early juvenile phase. The snails were held under conditions proposed for a standardized test protocol, which prescribes lettuce as food source. Additional experiments showed that juveniles grow considerably faster when fed with fish flakes. The model is based on Dynamic Energy Budget (DEB) theory, which allows for mechanistic interpretation of toxic effects in terms of changes in energy allocation. In a simulation study with the DEB model, we compared the effects of three hypothetical toxicants in different feeding situations. The initial food limitation when fed with lettuce always intensified the effect of the toxicants. When fed with fish flakes, the predicted effect of the toxicants was less pronounced. From this study, we conclude that (i) the proposed test conditions for L. stagnalis are not optimal, and require further investigation, (ii) fish flakes are a better food source for juvenile pond snails than lettuce, (iii) analyzing data with a mechanistic modeling approach such as DEB allows identifying deviations from constant conditions, (iv) being unaware of food limitation in the laboratory can lead to an overestimation of toxicity in ecotoxicological tests.

Show MeSH
Related in: MedlinePlus