Imazapyr herbicideformulation induced multiple abnormalities in gonadal development of Xenopus laevis at environmentally relevant concentrations

Abstract Mankind is now in the era of environmental contamination and pollution, where the environment has become a warehouse of its several toxicants. In fact, there are no longer any pristine area without these anthropogenic toxicants, with serious consequences on wildlife’s physiological processes including growth and reproduction. The widespread occurrence of pesticides for example, is being linked to numerous reproductive malformations in wildlife organisms, but the degree of association has not been characterised. Using the extended Xenopus Metamorphosis Assay (XEMA) protocol, the exposure impacts of imazapyr herbicide formulation (Arsenal), approved for aquatic environment was assessed on gonadal development of Xenopus laevis at environmentally relevant concentrations of 0.5, 2.0, and 3.5 mg/L. The formulation significantly reduced the mean body mass at premetamorphosis (NF-stage 55) at 3.5 mg/L concentration compared to the control. In sex ratio, the exposure only showed marginal fluctuations at all the exposure concentrations. For gonadal malformations, an abnormality index of 17.5%, 25%, and 35% was derived at 0.5 mg/L, 2.0, and 3.5 mg/L concentrations respectively, with malformations including tissues separation, segmented aplasia, aplasia, mixed sex, narrow hypoplasia, and angular deformity. This study showed that at relevant environmental concentrations, this formulation induced concentration dependent complex gonadal malformations, suggesting its potential capacities to induced serious reproductive disruptions that can negatively impacts fecundity, fertility, and general reproductive fitness of amphibians. In order to protect the wildlife from reproductive impacts, there is a serious need for cautions in application of this herbicide formulation