Ontogenetic studies of peripheral and central connections of fish taste system

对海鲶（Plotosus lineatus）、鲤鱼（Cyprinus carpio）、河豚（Fugu rubripes）、比目鱼（parichthys olivaceus）和红鲷鱼（Pagrus major）的幼虫进行了不同阶段的组织学检查，以揭示孵化后味蕾首次出现的时间和位置。鲤鱼、鲽鱼、河豚、比目鱼和红鲷鱼分别在第1天、第5天、第10天、第12天和第15天出现TBs。鲤和鱼的TBs首先同时出现在唇区和鳃腔中，而其他种类的TBs只出现在口腔中。用电镜观察了龙舌兰倒钩TBs的发育过程。TB的前体细胞在孵化后第2天出现，在表皮层真皮突起的顶端呈圆形或椭圆形的细胞团（小胡子的起源）。第4天，细胞数量增加，顶部有所伸长。第5天，在倒刺的尖端发现TBs向表面打开，形成一个味觉孔。神经纤维进入基底部，基底神经丛结构简单。t细胞、f细胞和基底细胞的形态、位置和精细结构可以明显识别出3种细胞类型。第6天之后，由于细胞的延长和数量的增加，T细胞本身变大了。研究了鲤和鲤鱼面叶的个体发育情况。使用NEC PC-9801VM，使用COSMOZONE 2SA（Nikon）进行面叶的三维重建。孵化后第12天，5个小叶首先出现在面叶的前端。它们仅位于肺叶的前三分之一。此后，小叶向前发展，直到它们占据面叶的前三分之二。鲤鱼面叶在早期呈一对结构，然后开始相互融合。本研究提示硬骨鱼初级面部味觉中枢的分化途径。最原始的味觉中枢是一对立柱，其前部与面叶相对应。鲶鱼型面叶是由前侧的刺小叶和前侧背侧的干小叶发育而成的。倒刺小叶的组织与倒刺的数量和相对长度有关。鲤鱼型面叶是由一对面叶向内侧旋转并相互融合而成。在这种类型中，唇和口腔上皮不成比例地扩大，而不是倒刺和躯干。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