Abstract:

In this study, amphibian tadpoles of Hypsiboas pulchellus were exposed to herbicide Liberty®, which contains glufosinate ammonium (GLA), for 48 h to the following concentrations: 0 (control), 3.55, 4.74, 6.32, 8.43, 11.25, 15, 20, 26.6, and 35.5 mg GLA L−1. Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities, as well as swimming capabilities (swimming speed and mean distance) were measured in tadpoles whose concentrations displayed survival rates >85 %. Our results reveal that sublethal concentrations of GLA significantly inhibited both AChE and BChE activities in tadpoles with respect to the control, showing a concentration-dependent inhibitory effect. The highest inhibition percentages of AChE (50.86 %) and BChE (53.02 %) were registered in tadpoles exposed to 15 mg GLA L−1. At this concentration, a significant increase of the swimming speed and mean distance were found in exposed tadpoles with respect to the control, as well as a negative and significant correlation between swimming speed and BChE activity, thus suggesting that this enzyme inhibition is related to an increase in swimming speed. Therefore, exposure of tadpoles to GLA in the wild at concentrations similar to those tested here may have adverse consequences at population level because neurotransmission and swimming performance are essential for tadpole performance and survival.

Author affiliation: Peltzer, Paola. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe; Argentina

Author affiliation: Junges, Celina Maria. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe; Argentina

Author affiliation: Attademo, Andres Maximiliano. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe; Argentina

Author affiliation: Bassó, Agustín. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentina

Author affiliation: Grenón, Paula. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentina

Author affiliation: Lajmanovich, Rafael Carlos. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe; Argentina

Abstract:

The neonicotinoid insecticide imidacloprid (IMI) affects the insect central nervous system and is successfully applied to control pests for a variety of agricultural crops. In the current study, acute toxicity and genotoxicity of the IMI-containing commercial formulation insecticide Glacoxan Imida (35 percent IMI) was evaluated on Hypsiboas pulchellus (Anura: Hylidae) tadpoles exposed under laboratory conditions. A lethal effect was evaluated as the end point for lethality, whereas micronucleus (MN) frequency and DNA single-strand breaks evaluated by the single cell gel electrophoresis (SCGE) assay were employed as end points for genotoxicity. Sublethal end points were assayed within the 12.5–37.5 mg/L IMI concentration range. Experiments were performed on tadpoles at stage 36 (range, 35–37) according to the classification proposed by Gosner. Lethality studies revealed an LC50 96 h value of 52.622 mg/L IMI. Increased frequency of MNs was only observed when 25.0 mg/L was assayed for 96 h, whereas no other nuclear abnormalities were induced. Increase of the genetic damage index was observed at 48 h of treatment within the 12.5–37.5 mg/L concentration range, whereas an increased frequency of DNA damage was observed only in tadpoles treated with 37.5 mg/L IMI for 96 h. This study represents the first evidence of the acute lethal and genotoxic effects exerted by IMI on tadpoles of an amphibian species native to Argentina under laboratory conditions.

Author affiliation: Pérez Iglesias, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Cátedra de Citología; Argentina

Author affiliation: Ruiz de Arcaute, Celeste. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Cátedra de Citología; Argentina

Author affiliation: Nikoloff, Noelia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Cátedra de Citología; Argentina

Author affiliation: Dury, Lucía. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Cátedra de Citología; Argentina

Author affiliation: Soloneski, Sonia Maria Elsa. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Cátedra de Citología; Argentina

Author affiliation: Natale, Guillermo Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas; Argentina

Author affiliation: Larramendy, Marcelo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Cátedra de Citología; Argentina