Fischer F P
Institut für Zoologie, Technische Universität München, Germany.
Scanning Microsc. 1994;8(2):351-63; discussion 363-4.
In different bird species, there is a common pattern in the hair-cell morphology and innervation of the basilar papilla; the absolute values, however, are species-specific. In the barn-owl papilla, an extreme being case, the basal high-frequency part of the papilla is greatly expanded. In this behaviorally most important frequency range of the barn owl, the number of afferent nerve terminals to neural hair cells is extensively increased. Instead of about 2 afferent terminals as in other species, up to 20 afferents are present. In the bird species studied (chicken, starling, emu, barn owl), the area of the afferent nerve terminals correlates well with the best hearing range. There is a continuous transition from neural to abneural, and from apical to basal in the morphological hair-cell parameters. Thus, the only precise and functionally relevant classification of avian hair-cell types (tall hair cells versus short hair cells) must be based on whether the hair cells have an afferent innervation or not. The differentiation of the evolutionarily-new short-hair-cell type is apparently essential in the high-frequency area of the papilla. This probably functionally supportive type has lost its afferent innervation; its function must therefore be within the papilla itself.
在不同鸟类中，基底乳头的毛细胞形态和神经支配存在一种共同模式；然而，绝对值具有物种特异性。在仓鸮的乳头中，这是一个极端例子，乳头的基部高频部分大幅扩展。在仓鸮这个行为上最重要的频率范围内，神经毛细胞的传入神经末梢数量大幅增加。与其他物种约2个传入末梢不同，这里存在多达20个传入末梢。在所研究的鸟类物种（鸡、椋鸟、鸸鹋、仓鸮）中，传入神经末梢的面积与最佳听力范围密切相关。在形态学毛细胞参数方面，从神经到非神经、从顶端到基部存在连续过渡。因此，鸟类毛细胞类型（高毛细胞与短毛细胞）唯一精确且与功能相关的分类必须基于毛细胞是否有传入神经支配。进化上新出现的短毛细胞类型的分化在乳头的高频区域显然至关重要。这种可能具有功能支持作用的类型已经失去了传入神经支配；因此其功能必定在乳头自身内部。
