Electroantennography recordings showed that both IVM and MOX ingestion negatively but differently affected the antennal olfactory apparatus of S. For both tested odorants, LOECs obtained were 1.0 µg kg (fw) for both IVM and MOX, respectively (Table 1).Fitting the % inhibition of antennal response data to log (inhibitor) vs.
Fitting the data for time duration until ataxia to three parameter inhibitor vs.
response models allowed for the interpolation of the dose of both MLs that caused paralysis and subsequent death in S.
2, and lowest significant observed effect concentration (LOEC) reported from Dunnet’s tests performed in the ANOVA-GLM analyses.
Concentration response curves for inhibition of antennal response by ivermectin (IVM) and moxidectin (MOX), using trimethylamine (A) and ammonia (B) as test odorants. Shaded areas represent the 95% confidence intervals of each model.
Thus, from an environmental point of view, obtained LOEC values indicate that MOX, despite needing more time for its elimination in the faeces could be half as harmful to dung beetles as IVM.
Furthermore, a comparison of the toxic thresholds (IC, thus suggesting an increased environmental risk for dung beetles.Even though the effects of individual MLs on dung beetle species have been previously studied, their results are difficult to compare because of the lack of a standardised and common methodological procedure.Literature comparing IVM and MOX toxicological effects shows that test results reported in this study are approximately on the same order of magnitude as those determined by other studies.cicatricosus adults by 50% (p LC corresponds to the quantity of each ML ingested by beetles (µg of each ML/g of individual beetles) that provoked a response halfway between the minimum number of days and the maximum number of days that produced pre-lethal paralysis.Both sub-lethal and pre-lethal symptoms obtained in this study coincide in that IVM is six times more toxic than MOX for adults of S. This is the first study to examine the comparative effects of IVM and MOX on the physiology of adult dung beetles using electroantennography procedures.The substituents that differ from IVM and MOX are highlighted in orange and blue, respectively. Among the non-target organisms affected by these substances, dung beetles are particularly sensitive.Dung beetles are considered one of the most important groups within dung pat assemblages in terms of number of species, abundance, biomass and ecosystem services.Inhibition of antennal response and ataxia were tested as two intuitive and ecologically relevant parameters by obtaining the lowest observed effect concentration (LOEC) values and interpolating other relevant toxicity thresholds derived from concentration-response curves (IC, as the quantity of ingested ML where partial paralysis was observed by half of treated individuals) from concentration-response curves.Both sub-lethal and pre-lethal symptoms obtained in this study coincided in that IVM was six times more toxic than MOX for adult dung beetles.Values of LOEC, IC obtained for IVM and MOX evaluated in an environmental context indicate that MOX, despite needing more time for its elimination in the faeces, would be half as harmful to dung beetles as IVM.This approach will be valuable to clarify the real impact of MLs on dung beetle health and to avoid the subsequent environmental consequences.