Leigh Marine Laboratory, Institute of Marine Science, University of Auckland, 160 Goat Island Road, Leigh, 0985, New Zealand.
Department of Biology and Marine Biology and the Center for Marine Science, University of North Carolina Wilmington, 5600 Marvin K Moss Lane, Wilmington, NC 28409, USA.
Hear Res. 2022 Oct;424:108600. doi: 10.1016/j.heares.2022.108600. Epub 2022 Aug 30.
Studies on the auditory system of fishes can provide fundamental information about the early evolution of vertebrate hearing. While there are limited data available on the auditory system of bony fishes, comparatively far less is known about auditory structures in elasmobranchs, despite their critical basal position within vertebrate evolution. Specifically, while there is a high degree of plasticity in the nervous system, little is known about how the different sensory epithelia within the inner ear vary throughout life in elasmobranchs. Using a combination of immunohistochemistry and fluorescence microscopy, we quantified macular area, number of sensory hair cells, hair cell density, and hair cell orientations in the saccule, lagena, utricle, and macula neglecta of school sharks (Galeorhinus galeus) of varying body size. In all maculae, macular area and the number of hair cells increased significantly throughout ontogeny, while hair cell density displayed a concurrent ontogenetic decrease (excluding the utricle). There were also significant differences in macular area, hair cell number, and hair cell density between the four maculae. However, hair cell orientation patterns did not vary between individuals and did not change with body growth. These findings represent one of the first comprehensive characterisations of the inner ear sensory epithelia in an elasmobranch, and reveal changes in morphology that may have implications for auditory capabilities through ontogeny.
鱼类听觉系统的研究可为脊椎动物听觉的早期演化提供基础信息。尽管软骨鱼类的听觉结构相对了解较少，但硬骨鱼类的听觉系统数据也很有限，尽管它们在脊椎动物演化中处于基础地位。具体而言，尽管神经系统具有高度的可塑性，但对于软骨鱼类内耳内不同感觉上皮在整个生命周期中的变化，我们知之甚少。本研究采用免疫组织化学和荧光显微镜相结合的方法，对不同体型的 schooling 姥鲨（Galeorhinus galeus）的囊斑、瓶状囊、椭圆囊和 macula neglecta 中的斑面积、毛细胞数量、毛细胞密度和毛细胞方向进行了量化。在所有斑中，斑面积和毛细胞数量在整个个体发育过程中显著增加，而毛细胞密度则呈协同性个体发育下降（不包括椭圆囊）。四个斑之间也存在显著的斑面积、毛细胞数量和毛细胞密度差异。然而，毛细胞方向模式在个体之间没有差异，也不会随身体生长而改变。这些发现代表了对软骨鱼类内耳感觉上皮的首次全面描述之一，并揭示了形态变化，这些变化可能对个体发育过程中的听觉能力产生影响。
