A comparison of the gross morphology and micro-anatomy of the foot pads in two fossorial and two climbing rodents (Mammalia)

Abstract

The foot pads of ®ve rodents were studied by means of gross morphology and histology. The secretory portions of the glands are placed caudad to the openings of the ducts in species that mostly walk on the ground. 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¯at pads with few glands, digging species have a rather smooth and dry volar aspect to work in a shovel-like way. In contrast, climbing species have large and soft foot pads with a lot of glands. The thickness of the corni®ed layer is positively correlated with the density of glands and increases strikingly from digging to climbing species. Although scent production is possible for these glands, this points to a function of the secretions in connection with the corni®ed layer. In climbing species, the secretions of glands can moisten the skin and thereby heighten the friction between volar and climbing surface to prevent the animal 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 grasping stalks of reed and can tighten the grip by increasing the grasping force, M. avellanarius often climbs by pressing the volar aspect on to the bark, whereby friction is increased by the moistened skin.

Paw Morphology in the Domestic Guinea Pig (Cavia porcellus) and Brown Rat (Rattus norvegicus)

“…A–C). The thick epidermis is also associated with an increase in the number of glands which produce fluid to increase surface friction during climbing (Haffner, ), although we did not observe any fluid secreting glands in our preparation.…”

Mechanics of generating friction during locomotion on rough and smooth arboreal trackways

“…These longer digits probably allow the animals to grip branches more strongly than they can if their digits were shorter. Some arboreal rodents have pads with glands that secrete fluid so as to increase the friction between autopodia and substrate (Haffner, 1998). I predict that animals that are morphologically specialized to move in trees will have greater flexibility in terms of where and how they grip branches.…”

“…I predict that animals that are morphologically specialized to move in trees will have greater flexibility in terms of where and how they grip branches. An animal with long, opposable digits (or fluid-secreting glands, claws or microscopic setae that interact with the substrate at a molecular level) (Cartmill, 1985;Haffner, 1998;Autumn et al, 2006) should be able to grip the top of a branch, which means that much more of its body weight is applied normal to the branch. Thus, even when moving about on a relatively smooth or slippery branch, such a specialized animal will be able to avoid slowing its speed and adjusting its footfall patterns (as measured by duty factor and limb phase) as much as M. domestica.…”

“…The second way to generate adequate friction force is to increase μ s . It might be possible for an animal to increase the effective μ s by changing the shape or moisture content of its hand or foot (Haffner, 1998). Finally, the animal can decrease the need to generate friction force by decreasing the shear forces.…”

Rhipidomys (Rodentia, Cricetidae) from Paraguay: noteworthy new records and identity of the Paraguayan species

“…Fur length differs among species and varies with geographic locality. The feet of Rhipidomys specimens are short and broad, with relatively short metatarsals compared to the digits, and large, fleshy plantar pads characteristic of arboreal species (Hildebrand 1974, Haffner 1998, Rivas-Rodriguez et al 2010; the hind foot has six such pads closely packed together and covering most of the ventral surface of the foot ( Figure 3B). The tails are characterized by a terminal pencil or tuft of hairs extending 5 mm to 40 mm beyond the tip ( Figure 3A), which alone is sufficient to distinguish members of this genus from most other sigmodontines.…”