Directional Asymmetry of Morphological Traits During Postnatal Ontogeny in Root Vole Microtus oeconomus Pall. (Rodentia, Cricetidae)

Abstract

Directional asymmetry (DA) was demonstrated for teeth morphotypes, adrenal and kidney weights, and for length of the hind paw as well. DA may be formed both at early and later development stages and is not dependent on environmental factors and population density dynamics. Although each trait has its own dynamics DA in ontogeny, usually DA increases in the period of sexual maturation. Uncoordinated development of the sides in this period seems to associate with an increase in intensity of developmental processes. Our study argues that sexual dimorphism of continuous traits appears at the later developmental stages. This finding is consistent with Geodakian's evolutionary theory of sex. Evolutionary significance of the DA is to increase both short-term individual fitness and long-term population adaptive capacity. Developmental approach to the study of morphological and functional asymmetries in animals opens new possibilities for the study of evolutionary processes.