扁圆吻鲴下咽齿的个体发生及替换规律

扁圆吻鲴下咽齿的个体发生可分为三个阶段：初齿期、过渡齿期和成齿期。初步期符合鲤科鱼类的一般规律；过渡齿期相当延长，产生全部齿位，６或７枚齿，齿的发生存在两种类型；成齿与幼齿的替换规律完全不同，发育进入成齿阶段后，主行齿由奇数齿位与偶数齿位交错替换转变为相二枚齿进行替换，替换公式为１－４，２－５，３－６或１－４－７，２－５，３－６（主行齿６枚或７枚），全部替换一次分三列替换波完成，可将扁圆吻鲴下咽齿的发育模式视为新的类型，副行齿在过渡齿期出现，与主行齿的发展模式不同，替换形式始终为相令齿位交错进行，本文还探讨了咽骨的发育及其对下咽发生的影响。

DEVELOPMENT AND REPLACEMENT OF PHARYNGEAL TEETH IN THE CYPRINID FISH

Distoechodon compressus bears 2-row pharyngeal teeth, the major row teeth with 6—7 and the minor row 2—4. The development and replacement of pharyngeal teeth in this species was observed through successive stages of larvae and juvenile. The development process could be divided into three stages: initial dentition, interim dentition and mature dentition. The appearance of initial dentition accorded with the universality of cyprinids; the interim stage prolonged rather and produced all of tooth positions, the appearance of which was found to be two types; the replacement in mature dentition was different from that in larval dentition which was similar to other cyprinids, namely, adjoining teeth were replaced in alternation, but the teeth in mature dentition was replaced in order A1-A4, A2-A5, A3-A6 (the major row teeth 6), or A1-A4-A7, A2-A5, A3-A6 (the major row teeth 7), the major row consisted of teeth on three replacement waves. It was suggested that the early development of pharyngeal teeth be a new pattern. The minor row teeth formed during the interim stage, and their replacement progressed alternately among the adjoining teeth. It was observed that the grow rate of pharyngeal bone would affect the formation of tooth germs.