Abstract

The germinal epithelium in fish gonads is defined herein. An active germinal epithelium in the ovaries of mature fish is the basis for indeterminate egg production-the ability to produce an unlimited number of eggs. In males, changes that occur in testicular germinal epithelia during annual reproductive cycles can be used to define five reproductive classes: regressed, early maturation, mid maturation, late maturation, and regression. It is proposed that gonadal function changes during annual reproductive cycles in male fish. Mitosis is the mode of germ cell division during the regressed class, and the mode by which diploid germ cells, the spermatogonia, repopulate testis lobules. Meiosis never occurs. When reproductive, meiosis is the predominate mode by which germ cells divide, and sperm are produced. Mitotic divisions of spermatogonia may occur. In the ovary of the group-synchronous fish studied, common snook, meiosis occurs throughout the year. Oocytes, arrested in the diplotene stage of meiosis, and follicles are continuously produced by the germinal epithelium. Vitellogenesis occurs only during the reproductive season. In contrast to male fish, changes in the stages of oocytes that are present within the ovarian lamellae, not changes in the germinal epithelium, are used to define reproductive classes in females

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