Ecomorphology reveals Euler spiral of mammalian whiskers
G. Dougill, E.L. Starostin, A.O. Milne,
G.H.M. van der Heijden, V.G.A. Goss, R.A. Grant
Whiskers are present in many species of mammals. They are specialised
vibrotactile sensors that sit within strongly innervated follicles. Whisker
size and shape will affect the mechanical signals that reach the follicle,
and hence the information that reaches the brain. However, whisker size and
shape have not been quantified across mammals before. Using a novel method
for describing whisker curvature, this study quantifies whisker size and
shape across 19 mammalian species. We find that gross two-dimensional
whisker shape is relatively conserved across mammals. Indeed, whiskers are
all curved, tapered rods that can be summarised by Euler spiral models of
curvature and linear models of taper, which has implications for whisker
growth and function. We also observe that aquatic and semi-aquatic mammals
have relatively thicker, stiffer, and more highly tapered whiskers than
arboreal and terrestrial species. In addition, smaller mammals tend to have
relatively long, slender, flexible whiskers compared to larger species.
Therefore, we propose that whisker morphology varies between larger aquatic
species, and smaller scansorial species. These two whisker morphotypes are
likely to induce quite different mechanical signals in the follicle, which
has implications for follicle anatomy as well as whisker function.
keywords: curvature, mechanoreception, morphology, touch, vibrissae
Journal of Morphology 281, 1271-1279 (2020)
[https://doi.org/10.1002/jmor.21246]