Effects of 2,4-D-based herbicide (DMA® 806) on sensitivity, respiration rates, energy reserves and behavior of tadpoles.
Ecotoxicol Environ Saf
; 182: 109446, 2019 Oct 30.
Article
em En
| MEDLINE
| ID: mdl-31323523
ABSTRACT
Increased use of sugarcane pesticides and their destination to non-target environments in Brazil has generated concerns related to the conservation of more vulnerable groups, such as amphibians. Besides the high skin permeability, tadpoles are constantly restricted to small and ephemeral ponds, where exposure to high concentrations of pesticides in agricultural areas is inevitable. This study evaluated chronic effects caused by sub-lethal concentrations of 2,4-dichlorophenoxyacetic acid herbicide on energy storage, development, respiration rates, swimming performance and avoidance behavior of bullfrog tadpoles (Lithobates catesbeianus). Firstly, we conducted acute toxicity test (96â¯h) to estipulate sub-lethal concentrations of 2,4-D and evaluate the sensitivity of three tadpoles' species to this herbicide. Results showed that Leptodactylus fuscus presented the lowest LC50 96â¯h, 28.81â¯mg/L, followed by Physalaemus nattereri (143.08â¯mg/L) and L. catesbeianus (574.52â¯mg/L). Chronic exposure to 2,4-D (125, 250 and 500⯵g/L) delayed metamorphosis and inhibited the growth of tadpoles at concentrations of 125⯵g/L. Effects on biochemical reserves showed that 2,4-D increased total hepatic lipids in tadpoles, although some individual lipid classes (e.g. free fatty acids and triglycerides) were reduced. Protein and carbohydrates contents were also impaired by 2,4-D, suggesting a disruption on energy metabolism of amphibians by the herbicide. In addition to biochemical changes, respiration rates and swimming speed were also decreased after chronic exposure to 2,4-D, and these responses appeared to be correlated with the changes detected in the basic energy content. Avoidance test indicated that tadpoles of L. catesbeinus avoided the presence of 2,4-D, however they were unable to detect increasing gradients of the contaminant. Our data showed that chronic exposure to 2,4-D impaired biochemical, physiological and behavioral aspects of tadpoles, which may compromise their health and make them more vulnerable to environmental stressors in natural systems.
Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Aprendizagem da Esquiva
/
Poluentes Químicos da Água
/
Ácido 2,4-Diclorofenoxiacético
/
Metabolismo Energético
/
Taxa Respiratória
/
Herbicidas
/
Larva
Tipo de estudo:
Diagnostic_studies
Limite:
Animals
País/Região como assunto:
America do sul
/
Brasil
Idioma:
En
Ano de publicação:
2019
Tipo de documento:
Article