The basilar papillae of snakes have received little attention. No recognizable efferent terminals have been found in lizards. The ball and vesicle structures, similar to those reported within other receptor cells opposite sensory terminals ( Cohen, 1960 Smith and Sjöstrand, 1961a), are often found opposite nerve endings in the lizard, thus strengthening the assumption that they are afferent nerve terminals. Nerve endings in the lizards studied by Baird (1970a) have the ultrastructural features of sensory terminals. Possibly, the variations in the tectorial membrane as demonstrated by Wever (1967a, b) and the kinociliary arrangement may fit together in a functional pattern. This is an interesting situation, for unless the tectorial membrane is moving in different ways in different parts of the papilla, all hair cells on a given active segment of basilar membrane are not activated simultaneously. Anteriorly, uniformly oriented groups appose each other along two or three axes. Posteriorly, the directional polarization is divided by a longitudinal median so that two groups of cells on either side have opposite orientations. The directional polarization of the hair bundle by the kinocilium is not uniform throughout. Each hair bundle contains a single kinocilium. The sensory cells do not display any unusual specializations and seem to be rather similar from place to place. The supporting cells of Anolis carolinensis papilla rest on the basilar membrane and separate the sensory cells from each other. The most complete histological and ultrastructural description of a lizard's basilar papilla is to be found in Baird's (1970a) recent chapter on the anatomy of the reptilian ear. In some lizards, some of the hair cells on the papilla are covered only by a material whose nature and attachments are ill defined at present. Other tectorial membranes have more or less independent gelatinous masses, the “sallets,” covering only a few hair cells. The tectorial membrane in some lizards is in the form of a fibrous plate with thin terminal strands that lie over the hair cells. Wever (1967a, b) later studied variations in the tectorial membrane which is attached to the limbic lip. The marked variations in the limbic lip of different lizards have been pointed out by Schmidt (1964). Some of the longer receptor organs possess basilar membranes with properties that change in an orderly manner from one end to the other, whereas other receptor organs have regional widenings of the membrane and dimensional variations in other structures. The total number of hair cells ranges from 65 in the leopard lizard's papilla to 1600 in G. Wever (1965, 1967c Wever et al., 1965) counted hair cells and measured various components of the papillae in seven species of lizards. A slender connection between sallet and finger process of tectorial membrane is present. Shown is a “sallet” and its connections to some of the hair bundles and a finger process connecting to the others. Cross section of the papilla of Gekko gecko taken from the ventral region. He states, “The papilla varies from small ovoid aggregates of sustentacular and hair cells to elongated, fusiform or divided structures” (Miller, 1966a).įig. The shape of the papilla differs considerably as demonstrated by Miller's illustrations. This ratio ranges within Gekkonidae from 1.28 to 2.37. Miller also found that the size of the lagena (at the tip of the cochlear duct) has its own individual variations, so that not even the ratio of the length of the cochlear duct to the length of the basilar papilla is constant. For example, Sceloporus magister, whose snout–vent length is 90 mm, has a papilla with an area of 0.018 mm 2, whereas Gekko gecko, of similar size (100 mm snout–vent length), has a papilla almost ten times larger (0.150 mm 2). In the 205 species that he examined, Miller found that the sizes of the auditory papillae were not necessarily correlated with body sizes. salvator has a papilla 2.4 mm in length with an area of 0.19 mm 2. The largest papillae measured were those of the Varanidae of which V. Miller's measurements (1966a) on the auditory papillae of lizards include those of the chameleons which are 0.15 mm in length and no greater than 0.013 mm 2 in area and those of the Amphisbaenidae which are also quite small in size. The inner ear in common with external and middle parts likewise shows considerable variation in different species of reptiles. Smith, Tomonori Takasaka, in Contributions to Sensory Physiology, 1971 3 Inner Ear
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