Morphometric analysis of the superior vestibular nerve in ground and tree squirrels

Abstract

The fiber architecture of the superior vestibular nerve was compared in cross section of tree dwelling species (Sciurus carolinensis and S. niger) and ground dwelling species (Spermophilus tridecemlineatus, S. mexicanus, and S. variegatus) using light microscopy. In five adult males of each species, fiber number, internal minor diameter of the axon, and axon area were measured in 31,959 fibers.

No significant differences were found among species in comparisons of fiber number, internal minor diameter, or axon area. This suggests that climbing behaviors are not correlated with morphological structures in the superior vestibular nerve or that morphological differences exist elsewhere in the vestibular apparatus or related structures.