Analysis of intraindividual and intraspecific variation in semicircular canal dimensions using high-resolution x-ray computed tomography

Abstract

The semicircular canal system tracks head rotation and provides sensory input for the reflexive stabilization of gaze and posture. The purpose of this study was to investigate the intraspecific and intraindividual variation in the size of the three semicircular canals. The right and left temporal bones were extracted from 31 individuals of the short-tailed shrew (Blarina brevicauda) and scanned on a high-resolution x-ray computed tomography system. The radius of curvature was calculated for each of the three semicircular canals for each side. Paired t-tests and independent sample t-tests indicated no significant differences in canal size between the right and left canals of the same individuals or between those of males and females of the same species. Pearson product moment correlation analyses demonstrated that there was no significant correlation between canal size and body mass in this sample.

Fig. 1

Three-dimensional reconstruction of the bony labyrinth of Blarina brevicauda showing the shape of each canal.

Fig. 2

Boxplots of semicircular canal radius for each canal showing female vs male for left (top) and right (middle) as well as left vs right sides (bottom).

Fig. 3

Bivariate plot of canal radius against body mass for each semicircular canal (anterior, posterior and lateral) and the mean canal. Closed circles, left side; open circles, right side.