[Ultrastructure and peculiarities of the otolith lagena in pigeons]

Rosenhall reported the polarization of kinocilium of otolith organs in the avian inner ear by LM. However, the otolith lagena, which is called the third otolith organ, is not well known, especially in terms of the 3-dimensional relationship between each maculae (utricular maculae, saccular maculae, maculae of the otolith lagena), the details of the striola and otoconial layers, and so on. Therefore, the author conducted a study to clarify these points using 20 Columba Domestica pigeons (40 ears), under the rules for animal experiments established by Nihon University School of Medicine. The pigeons were divided into 4 groups, 1. observations of the membranous labyrinth with binocular microscopes, 2. histological examination of serial sections of inner ear, 3. observations of the otolith lagena by SEM, 4. computer-aided 3-dimensional reconstruction of the membranous labyrinth. The following results were obtained. 1. the mean angle between the utricular maculae and maculae of the otolith lagena was 31 degrees (n = 3), the mean angle between the saccular maculae and maculae of the otolith lagena was 45 degrees (n = 3). 2. striola of the otolith lagena demonstrated a C form and the kinocilium exhibited an orientation identical to that of the striola of the outer saccular maculae, 3. the otolithic membrane of the otolith lagena demonstrated a mesh form and the otoconial layer was observed to be thin above the striola. 4. the surface area of the maculae of the otolith lagena was 0.98mm2 (n = 3) and the number of sensory cells was 16,800 (n = 3). The author also considered the functions of the otolith lagena.