Lanford P J, Popper A N
Department of Zoology, University of Maryland, College Park, USA.
J Comp Neurol. 1996 Mar 18;366(4):572-9. doi: 10.1002/(SICI)1096-9861(19960318)366:4<572::AID-CNE2>3.0.CO;2-1.
Using transmission electron microscopy, we have identified a new type of afferent terminal structure in the crista ampullaris of the goldfish Carassius auratus. In addition to the bouton-type afferent terminals previously described in the ear of this species, the crista also contained enlarged afferent terminals that enveloped a portion of the basolateral hair cell membrane. The hair cell membrane was evaginated and protruded into the afferent terminal in a glove-and-finger configuration. The membranes of the two cells were regularly aligned in the protruded region of the contact and had a distinct symmetrical electron density. The electron-dense profiles of these contacts were easily identified and were present in every crista sampled. In some cases, efferent terminals synapsed onto the afferents at a point where the hair cell protruded into the terminal. The ultrastructural similarities of the goldfish crista afferents to calyx afferents found in amniotes (birds, reptiles, and mammals) are discussed. The results of the study support the hypothesis that structural variation in the vertebrate inner ear may have evolved much earlier in evolution than previously supposed.
利用透射电子显微镜，我们在金鱼（Carassius auratus）的壶腹嵴中鉴定出一种新型传入终末结构。除了此前在该物种内耳中描述过的纽扣型传入终末外，嵴中还含有扩大的传入终末，其包裹着部分基底外侧毛细胞膜。毛细胞膜形成内陷，并以手套与手指的形态突入传入终末。在接触的突出区域，两个细胞的膜呈规则排列，且具有明显的对称电子密度。这些接触的电子致密轮廓易于识别，且存在于所采集的每个嵴中。在某些情况下，传出终末在毛细胞突入终末的部位与传入终末形成突触。本文讨论了金鱼嵴传入终末与羊膜动物（鸟类、爬行动物和哺乳动物）中发现的花萼传入终末的超微结构相似性。该研究结果支持了这样一种假说，即脊椎动物内耳的结构变异在进化过程中出现的时间可能比之前认为的要早得多。
