Reproductive biology of the freshwater catfish, Tandanus tandanus Mitchell, in the Gwydir River, Australia. I. Structure of the gonads

Abstract

The gross morphology and histology of the gonads of T. tandanus were examined as a preliminary to describing the reproductive cycle of this species in the Gwydir River.

The macroscopic appearance of the gonads at different stages of maturity is described. The complicated structure of the testes made it difficult to classify them into well-defined stages of maturity. The relationship between the stage of maturity of the ovaries and the histological changes associated with oocyte maturation was clear cut.

Six spermatogenetic stages were recognized; primary germ cells, spermatogonia, primary spermatocytes, secondary spermatocytes, spermatids, and spermatozoa.

The sequence of oocyte maturation was divided into nine stages; chromatin nucleolus, early perinucleolus, late perinucleolus, yolk vesicle, primary yolk, secondary yolk, tertiary yolk, and ripe egg stage.

Atresia was observed in some oocytes from the primary yolk stage onwards. The sequence of yolk resorption in atretic oocytes is described.