Fine structure of Eimer's organ in the coast mole (Scapanus orarius)

Abstract

Eimer's organ is a small, densely innervated sensory structure found on the glabrous rhinarium of most talpid moles. This structure consists of an epidermal papilla containing a central circular column of cells associated with intraepidermal free nerve endings, Merkel cell neurite complexes, and lamellated corpuscles. The free nerve endings within the central cell column form a ring invested in the margins of the column, surrounding 1-2 fibers that pass through the center of the column. A group of small-diameter nociceptive free nerve endings that are immunoreactive for substance P surrounds this central ring of larger-diameter free nerve endings. Transmission electron microscopy revealed a high concentration of tonofibrils in the epidermal cells of the central column, suggesting they are more rigid than the surrounding keratinocytes and may play a mechanical role in transducing stimuli to the different receptor terminals. The intraepidermal free nerve endings within the central column begin to degrade 15 mm from the base of the stratum corneum and do not appear to be active within the keratinized outer layer. The peripheral free nerve endings are structurally distinct from their counterparts in the central column and immunocytochemical double labeling with myelin basic protein and substance P indicates these afferents are unmyelinated. Merkel cell-neurite complexes and lamellated corpuscles are similar in morphology to those found in a range of other mammalian skin. Anat Rec, 290:437-448, 2007Rec, 290:437-448, . 2007 Wiley-Liss, Inc.

A complex sensory organ in the nose skin of the prosimian primate Lemur catta

“…D). The arrangement is similar to the one described for the coast mole (Marasco et al, ). The nerve and especially the spines are filled with mitochondria.…”

“…These appear usually as separate entities in the mammalian skin. More complex mechanosensory structures in mammalians are found in the vibrissae (Andres, ; Gottschaldt et al, ; Tyrell et al, ) and Eimer's organ of moles, echindnas, and platypus (Eimer, ; Catania, ; Marasco et al, ). In birds, there are the mechanosensory bill tip organs (Gottschaldt and Lausmann, ; Berkhoudt, ; Gentle and Breward, ; Cunningham et al, ).…”

“…Eimer's organ was described originally in the rhinarium of moles (Eimer, ) and has later been extensively studied (Catania, ; Marasco et al, ) in the moles. Also, the monotreme species Tachyglossus aculeatus (Andres et al, ; Manger and Hughes, ), Zaglossus bruijnii (Manger et al, ), and Ornithorhyncus anatinus (Manger and Pettigrew, ) possess an Eimer's organ.…”

Fluorescent AM1-43 and FM1-43 probes for dental sensory nerves and cells: Their labeling mechanisms and applications

“…Interestingly, free nerve endings labeled with AM1-43 are often observed to reach the epidermis and to terminate at the stratum corneum, whereas similar nerve endings labeled with the antineurofilament protein NF-200 antibody terminate below the stratum corneum. The AM1-43-labeled nerve endings display ghostlike profiles in the stratum corneum when examined by electron microscopy, and appear to be degraded [42]. This observation suggests that remnants of degraded, but not living, nerve fibers can still be labeled by AM1-43, but not by anti-neurofilament proteins.…”

“…This organ is sensitive to mechanosensory stimuli and consists of free nerve endings, Merkel cells and laminated corpuscles, all of which can be labeled with AM1-43 [41,42]. In addition, since some groups of the free nerve endings are immunohistochemically positive for substance P, at least some of these nerve fibers may play a nociceptive role.…”