Chronic Toxicities of Neonicotinoids to Nymphs of the Common New Zealand Mayfly Deleatidium spp.
Neonicotinoid insecticides have been shown to have high chronic toxicity relative to acute toxicity, and therefore short-term toxicity tests ≤96 h in duration may underestimate their environmental risks. Among nontarget aquatic invertebrates, insects of the orders Diptera and Ephemeroptera have been found to be the most sensitive to neonicotinoids. To undertake a more accurate assessment of the risks posed by neonicotinoids to freshwater ecosystems, more data are needed from long-term tests employing the most sensitive taxa. Using nymphs of the common New Zealand mayfly genus Deleatidium spp., we performed 28-d static-renewal exposures with the widely used neonicotinoids imidacloprid, clothianidin, and thiamethoxam. We monitored survival, immobility, impairment, and mayfly moulting propensity at varying time points throughout the experiment. Imidacloprid and clothianidin exerted strong chronic toxicity effects on Deleatidium nymphs, with 28-d median lethal concentrations (LC50s) of 0.28 and 1.36 µg/L, respectively, whereas thiamethoxam was the least toxic, with a 28-d LC50 > 4 µg/L (highest concentration tested). Mayfly moulting propensity was also negatively affected by clothianidin (during 3 of 4 wk), imidacloprid (2 of 4 wk), and thiamethoxam (1 of 4 wk). Comparisons with published neonicotinoid chronic toxicity data for other mayfly taxa and larvae of the midge genus Chironomus showed similar sensitivities for mayflies and midges, suggesting that experiments using these taxa provide reliable assessments of the threats of neonicotinoids to the most vulnerable freshwater species. Environ Toxicol Chem 2019;38:2459-2471. © 2019 SETAC.
['Macaulay|Samuel J|SJ|', 'Hageman|Kimberly J|KJ|', 'Alumbaugh|Robert E|RE|', 'Lyons|Sean M|SM|', 'Piggott|Jeremy J|JJ|', 'Matthaei|Christoph D|CD|']
D000818:Animals D004781:Environmental Exposure D065133:Ephemeroptera D006146:Guanidines D007306:Insecticides D016014:Linear Models D018978:Molting D000073943:Neonicotinoids D009520:New Zealand D009574:Nitro Compounds D009758:Nymph D016019:Survival Analysis D000077922:Thiamethoxam D013844:Thiazoles D036401:Toxicity Tests, Chronic D014874:Water Pollutants, Chemical
Aquatic invertebrates Imidacloprid Clothianidin Thiamethoxam Freshwater toxicology Pesticides