Geometric morphometrics of the mandible in the Iberian desman, Galemys pyrenaicus (Mammalia: Soricomorpha): Is there a significant variation in form during post-weaning life?

Abstract

Geometric morphometrics was applied on the mandible of the Iberian desman, Galemys pyrenaicus, to determine for the first time possible sexual and post-weaning shape variation of this structure in a talpid species. Analyses were complemented by evaluating the effect of sex and age on size. The sample consisted of collection specimens from locations in the Cantabrian Mountains (northern Spain). Desmans were grouped into four relative age classes according to tooth wear. The shape of the internal side of the mandible was represented by 15 two-dimensional landmarks. Once young desmans leave the nest there is no significant variation in the form (size and shape) of the mandible. Thus, possible osseous changes and tooth abrasion derived from ageing do not produce obvious variation in mandible form. Mandible shape was significantly correlated with mandible size, resulting in a range of shapes that varies from a slender to a robust morphology. This variation was independent of geographic factors. Since the effect of non-heritable environmental influences on mandible size and shape was negligible, it can be considered that the mandible form of post-weaned desmans is the direct product of interactions between different developmental processes.

Post-weaning ontogeny of the mandible in fossorial water voles: ecological and evolutionary implications

“…Consequently, considering that in fossorial water voles the mandible is a basic tool in digging mechanics, we can expect that environmental factors also play a substantial role in mandible growth. Additionally, as reported in other small mammal species, the effect of size adjustment of the mandible itself (Cardini and Tongiorgi 2003; Ventura and López‐Fuster 2009) and the diet changes after weaning (Emerson and Bramble 1993; Cardini and Tongiorgi 2003) are probably also involved in the shape modifications of the water vole mandible during its growth. But, when and to what extent do all these factors remodel the mandible form in these voles?…”

“…2004) valuing its effectiveness in separating size and shape components of morphological variation and its usefulness in analysing the ontogeny of the rodent mandible (see e.g. Cardini and Tongiorgi 2003; Cardini and O’Higgins 2005; Ventura and López‐Fuster 2009). Additionally, as the water vole mandible is a nearly flat structure, the two‐dimensional approach implies a very limited loss of information and it allows graphical descriptors of shape variation to be obtained.…”