Morphometric effects of neonicotinoid and nicotine exposure in a chicken embryo assay

Nicotine is a known teratogen. Imidacloprid is a neonicotinoid designed to target the nicotinic acetylcholine receptors of invertebrate insects but may affect the development of vertebrates. We evaluated the developmental impact of environmental relevant imidacloprid (10 µg/mL) exposure on vertebrate development using a chicken embryo assay and compared that with the effects of saline or nicotine exposure (0, 10 and 100 µg/mL). Research grade, specific-pathogen-free (SPF) eggs were injected on day 0 and harvested on day 14 of development. Egg weight, embryo weight and body morphometrics were compared between the treatment groups. Eggs treated with nicotine had an overall (10 - 20%) lower survival rate (P < 0.05). Embryos exposed to 10 µg/mL nicotine that remained viable at 14 days did not differ significantly from controls. Embryos exposed to 100 µg/mL exhibited reductions in limb development (P < 0.01) and altered head circumference (P < 0.009). Reductions in limb length were also noted in imidacloprid exposed embryos (P = 0.054). Embryo weight was significantly reduced in the imidacloprid exposed embryos relative to controls (P = 0.034). Tissues were harvested to determine histological changes as a result of imidacloprid. Use of the chicken embryo assay highlights the potential effects of developmental neonicotinoid exposure in vertebrates. Avian species may also be of particular risk of exposure from environmental pesticides and ingestion of contaminated insects and freshwater species. Support provided through research grants from the College of Science and Health and the Office of Student Research at the University of Wisconsin La Crosse. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.