Habitat use and vestibular system's dimensions in lacertidlizards

Habitat use and vestibular system's dimensions in lacertid
lizards:

Abstract

The vestibular
system is crucial for movement control during locomotion. As the
dimensions of the vestibular system determine the fluid dynamics of
the endolymph and, as such, the system's function, we investigate
the interaction between vestibular system size, head size and
microhabitat use in lizards. We grouped 24 lacertid species in
three microhabitat types, we acquired three‐dimensional models of
the bony vestibular systems using micro‐computer tomography
scanning, and we performed linear and surface measurements. All
vestibular measurements scale with a negative allometry with head
size, suggesting that smaller heads house disproportionally large
ears. As the sensitivity of the vestibular system is positively
related to size, a sufficiently large vestibular system in
small‐headed animals may meet the sensitivity demands during
challenged locomotion. We also found that the microhabitat affects
the locomotor dynamics: lizards inhabiting open microhabitats run
at higher dimensionless speeds. On the other hand, no statistical
relationship exists between dimensionless speed and the vestibular
system dimensions. Hence, if the vestibular size would differ
between microhabitats, this would be a direct effect (i.e. imposed,
for instance, by requirements for manoeuvring, balance control,
etc.), rather than depending on the lizards’ intrinsic running
speed. However, we found no effect of the microhabitat on the
allometric relationship between head and vestibular system size.
The finding that microhabitat is not reflected in the vestibular
system size (hence sensitivity) of the lacertids in this study is
possibly due to spatial constraints of the
skull.