Effects of developmental and functional interactions on mouse cranial variability through late ontogeny

Area of Science:

• Developmental biology
• Comparative anatomy
• Mammalian skull morphology

Background:

• Cranial growth and development are complex, yet patterns of skull variation and covariation during postnatal development remain understudied.
• Understanding dynamic changes in skull morphology is crucial for comprehending functional influences on development.

Purpose of the Study:

• To investigate the dynamic changes in cranial covariation and variation throughout postnatal growth in mice.
• To assess how patterns of morphological integration, canalization, and developmental stability evolve with age.

Main Methods:

• Analysis of random-bred mouse skulls at three postnatal ages (35, 90, and 150 days).
• Utilized Procrustes coordinate and Euclidean distance-based methods to quantify mean shape, canalization, developmental stability, and morphological integration.
• Applied the functional matrix model to assess facial region integration.

Main Results:

• Contrary to predictions, canalization, developmental stability, and morphological integration stabilized before 35 days of age.
• Significant changes in mean skull shape were observed throughout postnatal development.
• Only the facial region exhibited significant integration, aligning with the functional matrix model.

Conclusions:

• Mammalian skull phenotypic integration patterns are established early and may not dynamically change as predicted by functional influences like mastication.
• Observed integration patterns in mice differ from those typically found in primates, highlighting the need for caution in interspecies comparisons.
• Cranial shape evolves post-35 days, but the underlying integration structure appears largely predetermined earlier in development.