A COMPARISON OF THE GROSS MORPHOLOGY AND MICRO-ANATOMY OF THE FOOT PADS IN 2 FOSSORIAL AND 2 CLIMBING RODENTS (MAMMALIA)

The foot pads of five rodents were studied by means of gross morpholog y and histology. The secretory portions of the glands are placed cauda d to the openings of the ducts in species that mostly walk on the grou nd. This way the secretions are pressed out during walking by rolling on the foot pads craniad. In climbing species, the secretory portions are placed underneath the openings of the ducts and lead to secretion delivery during climbing by grasping. With their small and flat pads w ith few glands, digging species have a rather smooth and dry volar asp ect to work in a shovel-like way. In contrast, climbing species have l arge and soft foot pads with a lot of glands. The thickness of the cor nified layer is positively correlated with the density of glands and i ncreases strikingly from digging to climbing species. Although scent p roduction is possible for these glands, this points to a function of t he secretions in connection with the cornified layer. In climbing spec ies, the secretions of glands can moisten the skin and thereby heighte n the friction between volar and climbing surface to prevent the anima l from slipping. The density of glands per unit of surface is doubled in the ridged skin of Muscardinus avellanarius in comparison with the coned skin in Micromys minutus. While M. minutus mainly climbs by gras ping stalks of reed and can tighten the grip by increasing the graspin g force, M. avellanarius often climbs by pressing the volar aspect on to the bark, whereby friction is increased by the moistened skin.