Meeting Abstract
Maternal investments in eggs affect offspring growth & development, but mechanisms of these effects are not always clear. Melatonin is a hormone with wide ranging effects on phenotypes, & is found in egg yolks. In order to understand melatonin’s role in development, we conducted two experiments using chicken embryos (Gallus gallus): 1)We dosed eggs with melatonin to understand effects of variation in yolk-derived melatonin on development; 2)We administered agonists & antagonists of the melatonin receptors (Mel1a, Mel1b, & Mel1c) to evaluate their role in early development. We assigned approximately 300 eggs to one of eight treatments: one of four concentrations of melatonin (600,000 pg, 100,000 pg, 1,000 pg, or 100 pg per gram of yolk), Luzindole (Mel1a/1b antagonist), Prazosine Hydrochloride (Mel1c antagonist), 5-MCA-NAT (Mel1c agonist)/Luzindole mix, or saline vehicle. Eggs were injected with 100 ul of their respective treatment before incubation. After approximately two days of incubation we opened eggs, measured embryonic heart rate, staged embryos, & recorded images of embryos for morphological measurements. Melatonin concentration influenced progression of development, but did not follow simple linear response. Heart rate was unaffected by melatonin concentration. Conversely, receptor treatments did not have effect on stage, but blocking of any melatonin receptors decreased overall heart rate. Furthermore, adding a Mel1c agonist restored heart rate to almost normal (vehicle control). We hypothesize embryos possess a minimum & maximum concentration threshold for which significant effects in development can be measured. These results suggest maternal melatonin may influence embryonic developmental trajectories, & may ultimately affect offspring survival & fitness.
