Prenatal incubation temperature affects neonatal precocial birds' locomotor behavior

Temperature during the prenatal period is an important factor for developing embryos. Extensive human and animal research indicate embryos are sensitive to small fluctuations in temperature which has profound effects on phenotype development. Much of this research has focused on survivability, morphology, and incubation duration, but comparatively less in known about how prenatal temperature influences the development of motor coordination. In this study, we experimentally tested whether exposure to naturally occurring cool (36.9 degrees C) or warm (38.1 degrees C) thermal conditions for a brief period (4 days) during early incubation can influence postnatal motor performance in neonatal bobwhite quail hatchlings. We compared gait spatiotemporal parameters, body kinematics, and locomotive behaviors of control chicks incubated in an optimal thermal environment (37.5 degrees C) with thermally manipulated chicks. Experimental temperature treatment began on embryonic day five (E5) and ended on E8. Chicks were tested 24-h after hatching. Cool thermal exposure during incubation delayed hatching, reduced body mass, and increased fall frequency, intertarsal joint angle and stride length variability during the gait task compared to optimally incubated chicks. Warm thermal exposure during incubation delayed bone growth and increased fall frequency relative to controls. We discuss the relationship between motor development and thermal regulatory processes and provide insight into how spatiotemporal parameters aid in elucidating subtle differences in coordinated movement which may contribute to atypical motor development and be associated with neural developmental disorders. We provide the first spatiotemporal evidence for the importance of optimal thermal microclimates for typical prenatal motor development.