Lethal and Sublethal Effects of the Herbicide Atrazine in the Early Stages of Development of Physalaemus gracilis (Anura: Leptodactylidae)

Abstract

Water sources used as reproductive sites by crying frog, Physalaemus gracilis, are extensively associated with agroecosystems in which the herbicide atrazine is employed. To evaluate the lethal and sublethal effects of atrazine commercial formulation, acute and chronic toxicity tests were performed in the embryonic phase and the beginning of the larval phase of P. gracilis. Tests were started on stage 19 of Gosner (Herpetologica 16:183-190, 1960) and performed in 24-well cell culture plates. Acute tests had a duration of 96 h with embryo mortality monitoring every 24 h. Chronic assays contemplated the transition from the embryonic to larval stages and lasted 168 h. Every 24 h the embryos/larvae were observed for mortality, mobility, and malformations. The LC50 of atrazine determined for P. gracilis embryos was 229.34 mg L. The sublethal concentrations did not affect the development of the larvae but were observed effects on mobility and malformations, such as spasmodic contractions, reduced mobility, malformations in mouth and intestine, and edema arising. From 1 mg L atrazine, the exposed larvae began to have changes in mobility and malformations. The atrazine commercial formulation has caused early life effects of P. gracilis that may compromise the survival of this species but at higher concentrations than recorded in the environment, so P. gracilis can be considered tolerant to this herbicide at environmentally relevant concentrations.

Effects of environmentally relevant sub-chronic atrazine concentrations on African clawed frog (Xenopus laevis) survival, growth and male gonad development

“…Studies on different frog species exposed to atrazine concentrations up to 20 μg L −1 (exposure periods from 2 to 75 days) have indicated that there are no significant effects on embryo hatchability and tadpole growth i.e length and mass endpoints (Allran and Karasov, 2001;Diana et al, 2000;Morgan, 1996) and exposures up to 100 μg L −1 for 75 days do not significantly affect sexual differentiation and survival (Kloas et al, 2009). Studies by Brodeur et al (2009) and Rutkoski et al (2018) have indicated that pre-and prometamorphosis tadpoles are more sensitive to atrazine than embryos. Design flaws and contamination of controls in some studies have led to questionable results and pronouncement of controversial conclusions (Hayes, 2004;Rohr and McCoy, 2010).…”

Toxicity and genotoxicity of imidacloprid in the tadpoles of Leptodactylus luctator and Physalaemus cuvieri (Anura: Leptodactylidae)

“…The total length (mm; snout to tail) and body mass (g) of these tadpoles were measured using digital calipers and a precision balance, respectively. Malformations of the oral structures (denticles or general morphology) and the intestine (edemas or general morphology) were evaluated according to Rutkoski et al 70 , 97 . Digital images of the oral and intestine structures were obtained using a digital camera (P510, Nikon, Tokyo, Japan) and analyzed in comparison with the control, using a stereomicroscope (SZ51, Olympus, Tokyo, Japan).…”

Effects of atrazine on fish, amphibians, and reptiles: update of the analysis based on quantitative weight of evidence

“…There were several new studies that included mortality as part of their assessment for fish and amphibians ( Figure 5). The frog Physalaemus gracilis was exposed to atrazine as the formulated product under laboratory conditions for 96 h with a reported LC50 of 229,430 mg/L (score for quality of methods was 2) (Rutkoski et al 2018). As the response was observed at >100 lg/L, the score for relevance was reduced to 0.…”

“…No significant differences in overall survival at study termination, survival to metamorphosis, or survival to tail re-absorption were reported. Rutkoski et al (2018) exposed the larvae of Physalaemus gracilis to atrazine as the formulated product for 7 d (score for quality of methods was 2). Stages-19 to -25 were exposed to 16 concentrations (450, 1000, 1700, 8500, 10,000, 25,000, 50,000, 60,000, 70,000, 80,000, 115,000, 125,000, 135,000, 145,000, 155,000, and 165,000 mg/L).…”

“…The frog Physalaemus gracilis was exposed to atrazine as the formulated product under laboratory conditions for 7 d (168 h) (score for quality of methods was 2) (Rutkoski et al 2018) and were assessed for malformations. The NOEC for the number of larvae with malformations (mouthparts) was 1000 mg/L and the LOEC was 1700 mg/L.…”