The structural changes of the chromosomes during meiosis of gynogenetic triploid female ginbuna Carassius auratus langsdorfii, and naturally produced or sex-reversed male ginbuna were studied cytologically. In triploid female ginbuna, at zygotene stage two homologue-like chromosomes out of three were sometimes adjacent each other in the neighbourhood. At pachytene stage almost all of the chromosomes were univalents, and at diplotene stage almost all of lampbrush chromosomes were also univalents. From these results it seems probable that the two homologue-like chromosomes undergo synapsis at zygotene stage, but they might be separated to univalents on and after pachytene stage. Thereafter, each univalent chromosome might be split to two chromatids and result in separation of one chromatids to one direction and the other to the opposite one. In this way, the egg may maintain the maternal chromosome number and karyotype throughout the oogenesis. On the other hand, in some specimens at diplotene stage at most two to three bivalent lampbrush chromosomes, connected with one chiasma, were observed. These facts seem to explain the hypervariabilities among the gynogenetic triploid ginbuna. On the other hand, male individuals were almost similar to the processes in meiosis, though in some chromosomes it observed a few bivalents and rod-shaped bi-, tri-, and multivalent chromosomes at metaphase.Article信州大学理学部紀要 19(1): 37-52(1984)departmental bulletin pape
