BOLIN, Greta M.*; BURGGREN, Warren W.; University of North Texas; University of North Texas: Effects of Incubation Humidity on Kidney Development in Chicken Embryos

Embryological development in birds is influenced by ambient humidity during incubation. Indeed, high (HH) and low (LH) humidity incubation increase mortality rates in chicken embryos, due to the osmotic stresses of inadequate water availability or excessive water loss from the egg. The chorioallantoic membrane and developing urinary system of the embryo work in unison to regulate water and ions of body fluids. Yet, the effects of varying humidity levels specifically on kidney development remain unclear. White leghorn chicken eggs were incubated at 37.5°C±0.5°C and either 40%, 70% or 90% relative humidity. Embryo and egg mass, hematology and kidney structure were examined in embryos from each population on incubation days (d) 10, 14 and 18. Embryonic wet mass as a % of egg weight on d10 was 5.6% LH (n=2), 5.7% NH (n=2), and 6.2% HH (n=2) (Kruskal-Wallis; not significant, NS): d14 values were 18% LH (n=3), 22% NH (n=4) and 17.5% HH (n=2) (NS). On d18, there were significant differences between groups: 43.6% LH (n=5), 50.4% NH (n=7) and 38.8% HH (n=5) (p<0.002). Kidney wet mass as a % of embryo wet mass d14 was 0.19% LH (n=3), 0.29% NH (n=4) and 0.22% HH (n=2) (p<0.05). HH and LH masses were significantly lower than NH. Humidity affected kidney dry mass at d18: 11.6mg LH (n=5), 13.7mg NH (n=7) and 10.8mg HH (n=5) (p<0.01). D10 hematocrit and [Hb] values reflected relative water accumulation (HH) or water loss (LH) as expected. Preliminary histological examination shows renal morphological changes associated with humidity at d10-d18 (e.g. d10 LH nephrons have enlarged Bowmanís space). Collectively, these data show developmental phenotypic plasticity of the urinary system produced by humidity extremes during incubation in the chicken.