Programmed cell death or apoptosis was observed in both female and male gonads of Z. asper by TUNEL and immunohistological methods. In ovary, apoptosis occurred only in the postovulatory follicles, to eliminate the hypertrophied follicular cells after spawning. In regressed testis, after sperm release, Leydig cells, Sertoli cells and a few type A spermatogonia were apoptotic.