Orbital shape in goat and sheep: Symmetric analysis

Area of Science:

• Comparative anatomy
• Geometric morphometry
• Skull morphology

Background:

• Orbital symmetry is crucial for visual function and skull development.
• Understanding asymmetry in animal skulls can provide insights into evolutionary pressures and developmental stability.
• Previous studies have explored skull asymmetry, but detailed orbital symmetry analysis in goats and sheep is limited.

Purpose of the Study:

• To quantitatively assess orbital symmetry in goat (Capra aegagrus hircus) and sheep (Ovis aries) skulls.
• To identify and compare patterns of fluctuating and directional asymmetry in the orbits of these species.
• To investigate the potential of orbital shape for species discrimination.

Main Methods:

• Geometric morphometry was employed on 83 goat and sheep skulls (33 goats, 50 sheep).
• 36 landmarks defined the orbital boundaries, with mirror images created for symmetry analysis.
• Statistical analyses included principal component analysis (PCA) and discriminant function analysis (DFA).

Main Results:

• Statistically significant fluctuating and directional asymmetry were detected in the orbital shape of both goats and sheep (p < 0.0001).
• Principal component analysis revealed significant shape variation attributable to both symmetric and asymmetric components.
• Discriminant function analysis showed high accuracy in grouping orbits by species, particularly the right orbit in goats (100%) and the left orbit in sheep (96.5%).

Conclusions:

• Goat and sheep skulls exhibit significant orbital asymmetry, indicating developmental or environmental influences.
• Orbital shape possesses discriminatory characteristics useful for species identification.
• The findings contribute to the understanding of craniofacial development and asymmetry in small ruminants.