Glyphosate and Roundup® alter morphology and behavior in zebrafish

Abstract

Glyphosate has become the most widely used herbicide in the world, due to the wide scale adoption of transgenic glyphosate resistant crops after its introduction in 1996. Glyphosate may be used alone, but it is commonly applied as an active ingredient of the herbicide Roundup. This pesticide contains several adjuvants, which may promote an unknown toxicity. The indiscriminate application poses numerous problems, both for the health of the applicators and consumers, and for the environment, contaminating the soil, water and leading to the death of plants and animals. Zebrafish (Danio rerio) is quickly gaining popularity in behavioral research, because of physiological similarity to mammals, sensitivity to pharmacological factors, robust performance, low cost, short spawning intervals, external fertilization, transparency of embryos through larval stages, and rapid development. The aim of this study was evaluate the effects of glyphosate and Roundup on behavioral and morphological parameters in zebrafish larvae and adults. Zebrafish larvae at 3days post-fertilization and adults were exposed to glyphosate (0.01, 0.065, and 0.5mg/L) or Roundup (0.01, 0.065, and 0.5mg/L) for 96h. Immediately after the exposure, we performed the analysis of locomotor activity, aversive behavior, and morphology for the larvae and exploratory behavior, aggression and inhibitory avoidance memory for adult zebrafish. In zebrafish larvae, there were significant differences in the locomotor activity and aversive behavior after glyphosate or Roundup exposure when compared to the control group. Our findings demonstrated that exposure to glyphosate at the concentration of 0.5mg/L, Roundup at 0.065 or 0.5mg/L reduced the distance traveled, the mean speed and the line crossings in adult zebrafish. A decreased ocular distance was observed for larvae exposed at 0.5mg/L of glyphosate. We verified that at 0.5mg/L of Roundup-treated adult zebrafish demonstrated a significant impairment in memory. Both glyphosate and Roundup reduced aggressive behavior. Our data suggest that there are small differences between the effects induced by glyphosate and Roundup, altering morphological and behavioral parameters in zebrafish, suggesting common mechanisms of toxicity and cellular response.

Re-registration Challenges of Glyphosate in the European Union

“…Effects of glyphosate on somatic and ovarian growth, as well as of glyphosatebased formulations on ovarian growth and immune status of freshwater and estuarine crab species were reported (Hong et al, 2017;Avigliano et al, 2018;Canosa et al, 2018). Toxicities have extensively been reported for fish, including the zebrafish D. rerio, on which both glyphosate (Armiliato et al, 2014;Lopes et al, 2014;Uren Webster et al, 2014) and its formulated products (Bridi et al, 2017;Sulukan et al, 2017) were found to exert acute toxicity through inhibited carbonic anhydrase activity due to oxidative stress (production of reactive oxygen species), cellular apoptosis, effects on locomotor activity and aversive behavior, as well as reproduction disorders, deteriorating sperm quality, embryotoxicity malformations, and other endocrine disruption symptoms. Another study found carp (Cyprinus carpio) more sensitive to embryotoxicity of glyphosate at high concentrations (50 mg/l) than zebrafish (Fiorino et al, 2018).…”

Exposure to Sub-Acute Concentrations of Glyphosate Induce Clinico-Hematological, Serum Biochemical and Genotoxic Damage in Adult Cockerels

“…In published literature reports are available about the acute toxicity of glyphosate (Piola et al, 2013) but scanty information is available about its adverse effects on exposed organisms at very low concentrations. However, the toxic effects of glyphosate might be because of occurrence of sub lethal and complex changes like alteration in metabolic conditions, mitochondrial dysfunction, immunotoxicity, developmental toxicity, neurotoxicity and endocrine disruption (Bridi et al, 2017;Schimpf et al, 2017). Previously, in accessible published literature, no information is available regarding the adverse effects of glyphosate on male birds.…”

Spatial avoidance as a response to contamination by aquatic organisms in nonforced, multicompartmented exposure systems: A complementary approach to the behavioral response

“…The most common approach when one is assessing behavioral responses related to movement is to focus on displacement patterns such as swimming activities (orientation, posture, frequency, duration, and speed of movements), spontaneous activity, burst swimming, ability to capture prey and escape from predators, etc. (Nakamura ; Little et al ; Saglio et al ; Bridges ; Zhou and Weis ; Fleeger et al ; Ren et al ; Oliveira et al ; Bridi et al ; Jutfelt et al, ). Therefore, in behavioral ecotoxicology, the response considered as avoidance is, in reality, a predictive endpoint about what would be expected to occur if, under real field conditions, organisms were mandatorily and continuously exposed to contamination (Farr et al ).…”