Takeuchi H, Ido S, Kaigawa Y, Nagai T
Department of Biology, Faculty of Science, Shizuoka University, Japan.
Chem Senses. 1997 Oct;22(5):535-45. doi: 10.1093/chemse/22.5.535.
Morphological changes of oral cavity during metamorphosis with special reference to the taste organ were examined in Ezo salamanders (Hynobius retardatus) and axolotis (Ambystoma mexicanum), and compared with those in bullfrogs (Rana catesbeiana). The non-distensible tongue of salamanders changed the structure progressively during metamorphosis: a small area of the rostrum protruded and developed caudally with recession of the flat area of the tongue. The protrusion that developed on the tongue had numerous papillae, as seen in the frog tongue. The apical region of the papillae occasionally had a cell mass similar to the taste disk of frogs (termed a taste disk-like cell mass). On the flat area of the tongue, the barrel-shaped taste buds of larval salamanders were transformed into taste buds with a wider receptor area. The barrel-shaped taste buds decreased progressively during metamorphosis, while taste disk-like cell masses increased. Neuronal labeling with an antibody to neuron-specific enolase and fluorescent carbocyanine dye showed that the taste disk-like cell masses in metamorphosed salamanders were innervated by the glossopharyngeal nerve (nerve IX). Nerve IX responded to taste stimulation as well as mechanical stimulation applied to the rostral tongue. During metamorphosis the salamanders undergo transformation and rearrangement of taste organs on the tongue possibly as an adaptation to the terrestrial environment.
研究了北海道蝾螈（Hynobius retardatus）和美西钝口螈（Ambystoma mexicanum）变态过程中口腔的形态变化，特别关注味觉器官，并与牛蛙（Rana catesbeiana）的口腔形态变化进行了比较。蝾螈不能伸展的舌头在变态过程中结构逐渐改变：吻部的一小部分区域突出并向尾部发育，同时舌头的平坦区域逐渐退缩。舌头上发育出的突出部分有许多乳头，类似于蛙舌。乳头的顶端区域偶尔会有一团细胞，类似于蛙的味盘（称为味盘样细胞团）。在舌头的平坦区域，幼体蝾螈的桶状味蕾转变为具有更宽感受器区域的味蕾。桶状味蕾在变态过程中逐渐减少，而味盘样细胞团增加。用神经元特异性烯醇化酶抗体和荧光碳菁染料进行的神经元标记显示，变态后的蝾螈中的味盘样细胞团由舌咽神经（第九对脑神经）支配。第九对脑神经对味觉刺激以及施加到吻部舌头的机械刺激都有反应。在变态过程中，蝾螈的舌头味觉器官可能会发生转变和重新排列，这可能是对陆地环境的一种适应。
