Nonylphenol polyethoxylate adjuvant mitigates the reproductive toxicity of fomesafen on the freshwater snail Lymnaea stagnalis in outdoor experimental ponds
✍ Scribed by Audrey Jumel; Marie-Agnes Coutellec; Jean-Pierre Cravedi; Laurent Lagadic
- Publisher
- John Wiley and Sons
- Year
- 2002
- Tongue
- English
- Weight
- 168 KB
- Volume
- 21
- Category
- Article
- ISSN
- 0730-7268
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✦ Synopsis
Abstract
The influence of nonylphenol polyethoxylates (NPEO), formulated astheadjuvant Agral® 90, on the effects of the diphenyl ether herbicide fomesafen in the pond snail Lymnaea stagnalis was investigated, with particular attention to the reproductive performances and underlying energetic and hormonal processes. Separate short‐term exposures to low concentrations of fomesafen and fomesafen‐Agral mixture were performed in the laboratory. Outdoor experimental ponds (mesocosms) were used for long‐term exposures to higher chemical concentrations. At the concentrations used in the studies, NPEO were known as nontoxic in L. stagnalis. Fomesafen was mixed with the adjuvant in the 3:7 ratio recommended for agricultural uses (nominal herbicide concentrations of 22 and 40 μg/L in laboratory and mesocosm, respectively). In mesocosms, multiple application of fomesafen, leading to maximal herbicide concentrations of 60.33 ± 2.68 μg/L in water, resulted in reduced number of egg masses and altered glycogen metabolism in contaminated snails. These changes, as well as affected steroid‐like levels in fomesafen‐exposed snails, support the hypothesis of impaired neuroendocrine functions. When Agral 90 was added to the herbicide, results obtained in mesocosms showed that the adjuvant softened the impact of fomesafen. In mesocosms treated with the fomesafen‐Agral mixture, significantly lower herbicide levels were found in the water (30.33 ± 14.91 μg/L at the end of the contamination period). Consequently, internal exposure of the snails to fomesafen was reduced when the herbicide was mixed with the adjuvant. Mitigation of the effects of fomesafen by the adjuvant may therefore result from nonionic surfactant activity of NPEO that prevented fomesafen from reaching the snails.