Hair cells of different shapes and their placement along the frog crista ampullaris

• Published in: Hearing research Vol. 73; no. 1; pp. 109 - 115
• Main Authors: Guth, P.S., Fermin, C.D., Pantoja, M., Edwards, R., Norris, C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.02.1994; Elsevier
• Subjects: Animals; Biological and medical sciences; Cell Count; Cell Size; Frog; Fundamental and applied biological sciences. Psychology; Hair cell; Hair Cells, Auditory - cytology; Hair Cells, Auditory - ultrastructure; Microscopy, Electron; Morphology; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Rana pipiens; Semicircular canal; Semicircular Canals - cytology; Shape; Space life sciences; Tissue Embedding; Vertebrates: nervous system and sense organs; Vestibular; Hair cell; Shape; Frog; Semicircular canal; Morphology; Vestibular; Vertebrata; Amphibia; Ciliated cell; Salientia; Crista ampullaris; Vestibular system; Anatomy; Inner ear
• ISSN: 0378-5955; 1878-5891
• DOI: 10.1016/0378-5955(94)90288-7

The list of distinguishing morphological features of hair cells includes: Type I and Type II afferent innervation, and length, shapes and arrangements of stereo- and kinocilia. We now add to this list the shapes of the hair cells themselves and their placement within the mechanosensory organ, in this case the semicircular canal. Although hair cells of the crista ampullaris of the frog are only of Type II they may now be further classified into three sub-groups according to shape: club-, cigar- and pear-shaped. The cigar- and club-shaped hair cells are each about 40% while the pear-shaped cells are about 20% of the total numbers of hair cells in the crista. The differently-shaped hair cells also distribute differently along the crista. The cigar- and club-shaped are more-or-less uniformly distributed with somewhat higher concentrations at the ends of the crista than in the center. The pear-shaped hair cells, on the other hand, are mostly concentrated toward the center of the crista. This distribution of the pear-shaped hair cells, and their shape is reminiscent of the distribution of calyceal endings (Type I hair cell) in the cristae of amniotes [Goldberg et al., Hear. Res. 49, 89–102 (1990) in Chinchilla; Fernandez et al., Soc. Neurosci. Abstr. 17, 312 (1991) in Monkey]. There are some quantitative differences between hair cells of the same shape but from different portions of the crista. For instance, pear-shaped hair cells of the center are generally of greater cross-sectional area than those of the ends. Also, club-shaped hair cells are taller in the slopes of the crista than they are in the center. Lastly, hair cells of all three shapes have smaller cross-sectional areas after isolation from the crista as, for example, in preparation for patch-clamping. The greatest of these areal differences is seen in the pear-shaped hair cells. Thus, the emerging picture of the hair cell of the semicircular canal when considering both morphology and physiology is one of diversity and complexity suggesting a role in signal processing of greater importance than previously appreciated.