A comparison of the Eimer's organs of three North American moles: the hairy-tailed mole (Parascalops breweri), the star-nosed mole (Condylura cristata), and the eastern mole (Scalopus aquaticus).

Eimer's organ is a tactile sensory structure found predominantly on the snouts of moles. It consists of a raised papilla of epidermis containing a column of cells associated with sensory receptors. This study compares the Eimer's organs of the hairy-tailed mole, Parascalops breweri, the star-nosed mole, Condylura cristata, and the eastern mole, Scalopus aquaticus, by using scanning electron microscopy and light microscopy. Eimer's organs are visible on the snout of the hairy-tailed and the star-nosed moles, but not the eastern mole. The Eimer's organs of the hairy-tailed mole are similar in external appearance, distribution, and internal structure to those found in most species examined. The Eimer's organs of the star-nosed mole and the eastern mole diverge from this basic form in seemingly opposite directions. The Eimer's organs of the star-nosed mole are more numerous, smaller, and highly organized units with a consistent pattern of neuronal terminal swellings within a cell column, below a thin keratinized epidermis. By contrast, the Eimer's organs of the eastern mole lie below a thick keratinized epidermis, are less organized in structure, and have no central cell column. The extreme differences between the Eimer's organs of the star-nosed mole and thos of the eastern mole may be the result of the habitat of each species, saturated mud allowing a more elaborate and delicate sensory apparatus in the star-nosed mole and drier soil requiring a thick keratinized epidermis over the organ in the eastern mole.