Light accelerates morphogenesis and acquisition of interlimb stepping in chick embryos

Area of Science:

• Developmental biology
• Neuroscience
• Animal locomotion

Background:

• Chicks exhibit rapid development of bipedal locomotor skills post-hatching.
• Neural circuits for stepping are established late in chicken embryogenesis (embryonic days 18-20).
• Environmental factors like light exposure can alter hatching and walking onset times.

Purpose of the Study:

• To investigate the impact of light exposure during embryogenesis on interlimb coordination development.
• To determine if light conditions affect the maturation of locomotor circuits at embryonic day 19.
• To explore the relationship between light, hatching time, and the emergence of coordinated stepping patterns.

Main Methods:

• Chicken embryos were incubated under three different light conditions.
• Bilateral leg muscle activity was recorded in ovo at embryonic day 19.
• Burst analysis quantified interlimb coordination from spontaneous locomotor activity.

Main Results:

• The extent of interlimb coordination varied significantly with embryonic light exposure.
• Embryos incubated in constant bright light showed more reliable left-right alternating steps.
• Morphological development of the leg also differed based on light exposure conditions.

Conclusions:

• Light exposure during incubation can accelerate the development of interlimb coordination, aligning with earlier hatching.
• Alternating left-right stepping appears to be the default interlimb coordination pattern generated by embryonic locomotor circuits.
• Environmental light plays a crucial role in the precocious development of coordinated limb movements in chicks.