Journal
ECOTOXICOLOGY
Volume 22, Issue 1, Pages 148-155Publisher
SPRINGER
DOI: 10.1007/s10646-012-1011-3
Keywords
Nematodes; Ivermectin; Life history; Life-cycle traits; Population; Population growth rate
Categories
Funding
- Federal Ministry of Transport, Building and Urban Development, Berlin and Bonn, Germany
- National Institutes of Health-National Center for Research Resources (USA)
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The pharmaceutical ivermectin is used to treat parasitic infections, such as those caused by nematodes. While several studies have demonstrated the severe effects of ivermectin on non-target organisms, little is known about the drug's impact on free-living nematodes. In the present work, a full life-cycle experiment was conducted to estimate how an ivermectin lowest observed effect concentration derived from a Caenorhabditis elegans bioassay (endpoint reproduction) might translate into effects at the population level of this free-living nematode. The results showed that fecundity decreased to levels similar to those determined in the bioassay after a time of corresponding duration (18.6 % inhibition compared to the control), but the impact then rather weakened until the end of the experiment, at which point the net reproductive rate (R-0) was still, but not significantly, reduced by 12.4 %. Moreover, the average lifespan, length of the reproductive period, maximum daily reproduction rate, and intrinsic rate of increase (r(m)) were significantly reduced by 30.0, 25.9, 11.2, and 3.5 %, respectively. The experiment revealed that a 4-day bioassay is protective enough for C. elegans with respect to ivermectin's effects on fecundity. However, the pronounced effects of a low drug concentration on survival, a highly elastic trait, may better account for the observed population-level response, i.e., a decrease of r(m), than the effects on fecundity. These results emphasize that full life-cycle experiments are valuable for assessment of pollutants, because the effects on several life-cycle traits can be simultaneously measured and integrated into an ecologically relevant parameter, the population growth rate, that reflects a population's response to a specific pollutant.
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