DEVELOPMENT AND REPLACEMENT OF PHARYNGEAL TEETH IN THE CYPRINID FISH, DISTOECHODON COMPRESSUS

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.