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The deleterious effects of fungicides and herbicides on Xenopus laevis embryos
Abstract:
Groups of 30 Xenopus laevis embryos, at "tail-bud" stage (Nieukoop-Faber stages 22-24) were exposed to 0.1-2 ppm concentrations of various pesticides for 1 to 10 days. The pesticides used were chloranil and dichlone (both are fungicidal and herbicidal); diquat (herbicide); and nabam (fungicide). The parameters examined were mortality, gross morphology, histology, and behavior. Chloranil (1.25 to 1.75 ppm) treated embryos showed abnormalities of the otolith, optic cup, and general pigmentation. Their movement was sporadically convulsive and they were unable to maintain proper balance. Dichlone (0.1 to 0.15 ppm) disrupted the development of the cephalic end of the embryo. Many of these embryos developed a slightly retarded trunk and tail only. These headless embryos lived for a time and were relatively lethargic. Diquat (0.75 to 2.0 ppm) administration reduced body size and pigmentation, and altered body shape. When embryos were treated with both 1.0 ppm of diquat and 2.0 ppm of nabam the integrity of myomeres and myocommata of the musculature was disrupted. The histological bases of these morphological and behavioral changes are discussed.
Insights
Pesticide exposure during early development caused significant abnormalities in Xenopus laevis embryos. These included morphological defects, behavioral changes, and disrupted muscle development, highlighting environmental risks.
Area of Science:
- Developmental toxicology
- Environmental science
- Comparative toxicology
Background:
- Pesticides pose risks to aquatic ecosystems.
- Understanding pesticide effects on early development is crucial for environmental risk assessment.
Purpose of the Study:
- To investigate the developmental toxicity of various pesticides on Xenopus laevis embryos.
- To characterize morphological, histological, and behavioral changes induced by pesticide exposure.
Main Methods:
- Xenopus laevis embryos (stages 22-24) were exposed to chloranil, dichlone, diquat, and nabam at concentrations ranging from 0.1-2 ppm for 1-10 days.
- Evaluated parameters included mortality, gross morphology, histology, and behavior.
- Specific abnormalities were documented for each pesticide and combination.
Main Results:
- Chlornail induced otolith, optic cup, and pigmentation abnormalities, with convulsive movements and balance issues.
- Dichlone caused cephalic developmental disruption, resulting in headless embryos with reduced activity.
- Diquat affected body size, pigmentation, and shape; combined diquat and nabam disrupted muscle integrity.
Conclusions:
- Pesticides like chloranil, dichlone, diquat, and nabam cause significant developmental abnormalities in Xenopus laevis.
- These findings underscore the potential ecological impact of pesticide pollution on amphibian development.
- Histological analysis provides insight into the mechanisms underlying observed morphological and behavioral deficits.