Ontogenetic studies of peripheral and central connections of fish taste system

通过对不同发育阶段的斑点叉尾鱼(Plotosus Lineatus)、鲤鱼(Cyprinus Carpio)、红鳍河豚(Fugu Rubripe)、牙鲆(Paralichthys Olivaceus)和真鳍金枪鱼(Pagrus Main)幼体的组织学观察，揭示了孵化后味蕾出现的时间和地点。鲤鱼、斑嘴鱼、河豚、比目鱼和红鱼分别在第1、5、10、12、15天出现TBS。鲤鱼和鲤鱼的触须最早同时出现在唇区和鳃腔内，而其他物种的触须只出现在口腔内。在孵化后第2天，结核前体细胞在真皮突起(触须的起源)顶端的表皮层中出现圆形或椭圆形细胞团。第4天，细胞数量增多，心尖稍有拉长。第5天，TBS发现触须尖端向表面张开，形成味孔。神经纤维进入…结节的基底部和基底神经丛较多，结构简单。三种细胞(t细胞、f细胞、基底细胞)的形态、位置和细微结构明显可识别。第6天后，由于细胞的延长和数量的增加，T本身变大。本文研究了Plotosus和鲤鱼面叶的个体发育。在NEC PC-9801VM上使用COSMOZONE 2SA(Nikon)进行面叶三维重建。在孵化后第12天，5个小叶首先出现在面叶的前端。它们仅位于叶的前1/3。此后，小叶向前发育，直到占据面叶的前2/3。鲤鱼的面叶在早期出现成对的结构，然后开始相互融合，这一研究表明硬骨鱼初级面部味觉中心的分化途径。最原始的味觉中心是一对柱子，它们的前部对应于面部的额叶。面叶是由触须小叶向前发育，主干小叶前背向外发育而成的。触须小叶的组织与触须的数量和相对长度有关。鲤鱼型面叶是通过向内旋转一对面叶并相互融合而得到的。在这种类型中，嘴唇和口腔上皮不成比例地扩大，而不是触须和躯干。较少

Various stages of the larvae of sea catfish(Plotosus lineatus), carp(Cyprinus carpio), puffer(Fugu rubripes), flounder(Paralichthys olivaceus) and red sea bream snapper(Pagrus major) were examined histologically to reveal when and where taste buds(TBs) first appear after hatching. The carp, plotosus, puffer, flounder and red snapper first possessed TBs at first, 5th, 10th, 12th, 15th day, respectively. TBs first appeared simultaneously in the lip region and gill cavity for the carp and Plotosus while they appeared only in the mouth cavity for the other species.The developing process of the barbel TBs of Plotosus was examined by electron microscopy. Precursor cells of TB appeared at 2nd day after hatching as round or oval cell mass in the epidermal layer at the tip of dermal protrusions(origin of the barbel). At 4th day, cells increased in number and somewhat elongated apicard. At 5th day, TBs found on the tip of barbel opened to the surface to make a taste pore. Nerve fibers entered in … More to basal part of TB and basal nerve plexus with simple structures appeared. Three types of cells(t-cell, f-cell, basal cell) were obviously recognized by their shape, position and fine structures. After 6th day, T itself became larger as a result of both an elongation and an increase in number of cells. The ontogenetic development of the facial lobe was examined in the Plotosus and carp. Three-dimensional reconstructions of the facial lobe were produced with a NEC PC-9801VM using COSMOZONE 2SA(Nikon). At 12th day after hatching, the five lobules first appeared in the anterior tip of the facial lobe. They were located only in the anterior one third of the lobe. Thereafter, the lobules developed anteriorly until they occupied the anterior two third of the facial lobe. The facial lobe of the carp appeared as a pair structure in the early stage, and then began to fuse each other.This study suggests the pathway of differentiation of the primary facial taste center in teleost fish. The most primitive taste center is a pair of column and their anterior portion corresponds to the facial lobe. The catfish type of facial lobe is obtained by developing the barbel lobules anteriorly and trunk lobule antero-dorsolaterally. The organization of barbel lobules is related to both the number and relative lengths of the barbels. The carp type of facial lobe is obtained by rotating a pair of the facial lobe medially and fusing each other. In this type, the lip and oral epithelium are disproportionally enlarged in stead of the barbels and trunk. Less