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New mechanism uncovered for the reduction of emu wings

.Researchers have uncovered a novel mechanism underlying the skeletal reduction and asymmetry of emu wings. Their research reveals that the absence of distal muscle formation results in a lack of mechanostress during development, leading to the observed bone abnormalities.

This study suggests that variations in embryonic and fetal movement could play a significant role in shaping body parts throughout evolution.

These findings are in Nature Communications.

The emu is a flightless bird with wings that have undergone significant reduction. Despite this, the precise mechanisms behind the morphological changes in their wings have remained largely unknown. In this study, the research team demonstrated that the skeletal reduction in emu wings is not only characterized by shortening but also by an asymmetric fusion of bones.

They identified that these skeletal abnormalities are caused by a lack of muscle formation in the distal wings, which results in insufficient movement during development—which is required for the shaping the embryonic and fetal skeleton.

Additionally, the study discovered the presence of muscle progenitor cells in emu wings that exhibit a dual identity, combining features of both somite-derived muscle progenitor cells and lateral plate mesoderm cells. These cells undergo cell death during the differentiation into muscle fibers, leading to a failure in muscle formation. The findings suggest that differences in embryonic and fetal movement can significantly influence morphological evolution.

The research team confirmed that the bones of emu wings are not only shortened but also show significant variation in pattern and length between individuals, and even between the left and right wings of the same individual. This distinctive skeletal pattern is linked to the lack of muscle formation at the distal region of their wings, which leads to inadequate mechanical stress during bone development.

This study highlights the crucial role that embryonic and fetal movement plays not only in the elongation of skeletal elements but also in the symmetrical patterning of bones. The findings underscore the significant impact that insufficient embryonic movement, particularly in cases of muscle formation defects like those observed in emus, can have on skeletal evolution. The research suggests that environmental factors influencing embryonic and fetal movement could have far-reaching effects on morphological evolution and diversification.

This research has demonstrated the profound impact that embryonic and fetal movement can have on the evolution of skeletal morphology. Moving forward, the team plans to investigate how variations in embryonic and fetal movement might influence skeletal evolution across vertebrates. This study opens new avenues for understanding the role of environmental factors in shaping the evolution of morphology through their effects on embryonic and fetal movement.