Abstract
Neonicotinoids are insecticides widely used as seed treatments that appear to have multiple negative effects on birds at a diversity of biological scales. Adult birds exposed to a low dose of imidacloprid, one of the most commonly used neonicotinoids, presented reduced fat stores, delayed migration and potentially altered orientation. However, little is known on the effect of imidacloprid on birds growth rate despite studies that have documented disruptive effects of low imidacloprid doses on thyroid gland communication. We performed a 2 times 2 factorial design experiment in Zebra finches, in which nestling birds were exposed to a very low dose (0.205 mg kg body hbox {mass}^{-1}) of imidacloprid combined with food restriction during posthatch development. During the early developmental period, imidacloprid exposure resulted in an improvement of body condition index in treated nestlings relative to controls. Imidacloprid also led to compensatory growth in food restricted nestlings. This early life neonicotinoid exposure also carried over to adult age, with exposed birds showing higher lean mass and basal metabolic rate than controls at ages of 90–800 days. This study presents the first evidence that very low-dose neonicotinoid exposure during early life can permanently alter adult phenotype in birds.
Highlights
Neonicotinoids are insecticides widely used as seed treatments that appear to have multiple negative effects on birds at a diversity of biological scales
We first validated that the ingested pesticide was present in nestlings’ blood by measuring imidacloprid concentration in plasma
We have shown that short-term exposure to a very low dose of imidacloprid, one of the most commonly-used neonicotinoid pesticides in the world, can positively impact body condition index during growth and body composition of adult birds
Summary
Neonicotinoids are insecticides widely used as seed treatments that appear to have multiple negative effects on birds at a diversity of biological scales. Imidacloprid led to compensatory growth in food restricted nestlings This early life neonicotinoid exposure carried over to adult age, with exposed birds showing higher lean mass and basal metabolic rate than controls at ages of 90–800 days. Zebra finches were exposed daily to a low dose of imidacloprid [0.205 mg kg body mass−1, 0.5% of the LD50 of House sparrow (Passer domesticus) 41 mg kg−1 ] and/or to food restriction during posthatch growth This dose was comparable to the one used in a passerine, the Red munia (Amandava amandava) where the administration of 0.155 mg kg−1 of imidacloprid in adults induced thyrotoxicity with potential damaging effects on thyroid c ells[11]. The current experiment was conducted on 129 nestlings over 3 months (See “Appendix A” for a visualisation of the birds used over time)
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