EMBRYONIC AND EXTERNAL LARVAL DEVELOPMENT AND SEXUAL MATURITY OF THE AFRICAN CATFISH HETEROBRANCHUS-ISOPTERUS (SILUROIDEI, CLARIIDAE)

The embryonic and external larval development of the African catfish H eterobranchus isopterus (Clariidae) has been described chronologically up to 23 days of age. The ontogeny of this species is similar to that of H. longifilis. However, the growth rate of embryonic and larval de velopment in H. isopterus is slower. Also the adhesive pastille on the yolk sac of the post-hatching larvae is absent. At the age of 6 days, cannibalism was noted. The juvenile period starts after 23 days at 26 degrees C. Sexual maturity and the effect of temperature on the eggs have also been studied in H. isopterus. The study of oocyte diameter a nd influence of temperature on embryonic development enabled to conclu de that the species can be reproduced throughout the year. The optimal hatching rate and the highest ratio of normal larvae are obtained bet ween 24 degrees C and 26 degrees C.