Developmental trajectories in laryngeal anatomy of California mice (Peromyscus californicus)

The mammalian larynx is a complex structure of mixed embryological origin, with its evolutionary diversification and its form-function relationship of interest to biologists and clinicians. This study compared the size and shape of the laryngeal cartilaginous framework and airway in two phylogenetically distant mouse species, the California mouse and House mouse, with distinct vocal behaviours. Using three-dimensional imaging and geometric morphometrics, we analysed ontogenetic shape changes from birth to old age to assess species differences, developmental trajectories and integration of cartilage shape. While statistically significant species-specific differences were found, they were minor, and neither species exhibited sexual dimorphism in laryngeal shape or size. A pronounced ontogenetic change in the relative size of the ventral pouch was observed in California mice but not in House mice. Shape changes from neonatal to adult stages were largely conserved across species, with the notable exception of the arytenoid cartilage, which exhibited divergent postnatal trajectories and integration patterns. Despite differences in vocal behaviour and phylogenetic distance, overall laryngeal morphology was remarkably similar. These findings highlight the need to consider additional selective pressures beyond vocal function in shaping laryngeal anatomy across rodents.