ADAPTIVE DIFFERENTIATIONS OF THE SKIN OF THE HEAD IN A SUBTERRANEAN RODENT, SPALAX-EHRENBERGI

The skin of macroscopically distinct regions (hairy skin, vibrissal fi elds, buccal ridge, and rhinarium) of the head of the blind mole-rat, Spalax ehrenbergi, was studied by routine histological methods. Few gu ard and several soft vellus hairs are organized into tufts that grow f rom a group of hair follicles localized in an invaginated compound cav ity. We suggest that this hair arrangement may be a burrowing adaptati on to match frictional resistance. The follicles and the compound cavi ty possess either well developed complex striated musculature or errec tor pill muscles. There are no structural specializations (sweat gland s, glomus bodies) to enhance thermoregulatory (heat dissipative) capac ities in the hairy skin of the head. Vibrissae penetrate the epidermal surface as single hairs. They are microscopically normally developed and arranged in vibrissal fields according to a basal mammalian patter n. Most of them are, however, relatively short and inconspicuous. The mystacial vibrissal field is horizontally divided by a prominent bucca l ridge which is probably involved in bulldozing. The hairs in the rid ge leave the compound cavity singularly. The follicles of guard hairs and bristles are equipped with well developed pilo-Ruffini complexes i ndicating that the buccal ridge may serve also as a tactile organ. The glabrous skin of the rhinarium has a highly interdigitated dermal-epi dermal interface. The dermal papillae possess simple lamellated and/or simple Meissner's corpuscles and few Merkel cell-axon-complexes indic ating that the skin of the rhinarium may be particularly sensitive to perception of vibrations. (C) 1997 Wiley-Liss, Inc.