铜鱼和圆口铜鱼的早期发育

本文比较系统地观察了长江和汉江铜鱼和圆口铜鱼鱼卵、鱼苗的胚胎发育,记述了两种铜鱼胚胎发育的各个阶段的形态特征,比较两种铜鱼早期发育的相似性状和主要差别。这些差别主要是:雏形胚体出现的迟早、眼基和肌节出现的先后、眼睛大小、胸鳍长短以及颌须出现的迟早和长短等,依据这些差异,可以把两种铜鱼在早期发育阶段准确地区分开来。本文还对长江兴修水利枢纽与两种铜鱼资源的关系进行了调查和分析。  

THE EARLY DEVELOPMENT OF COREIUS HETERODON AND COREIUS GUICHENOTI

Coreius heterodon and C. guichenoti, the two of the total three species belonging to the genus Corcius, are most famous fishes of the upper and middle reaches of the Changjiang Valley. The most conspicuous external features comparing with those of other cyprinids of the Changjiang River are smaller eyes and rather longer maxillary barbels.The successive developmental stages of the early development of these two fishes were examined under natural water tempertures, ranging from 18.2 to 32.8℃. The newly cast eggs were collected during the summer seasons of the years 1961—1966, 1973, 1976—1978 and 1981 in the very spawning area of the main streams of the Changjiang River and one of its main tributaries, the Hanjiang. Although the rivers were obstructed at Danjiangkou and Gezhouba by the construction of dams, yet most of the spawning grounds are still functional and even extended both to the main reaches below the dams and to the upper part of the Danjiangkou reservoir.The morphological features of 49 stages of the embryonic and postembryonic development of these fishes are rather similar with each other. However, there are also some obvious differences in a few stages. The formation of proembryo of C. guichenoti during embryonic development occurs in middle gastrula, while it arises in late gastrula for C. heterodon. The first appearance of the muscle segments is prior to the formation of eye vesicle in C. guichenoti, but they come out in reverse order in the other species. Furthermore, the emergence of the barbel bud is earlier, the pectoral fin is shorter and the eye is a little larger in C. heterodon than that of C. guichenoti throughout the period of post-embryonic development.