COMPARATIVE CYTOLOGICAL STUDIES ON THE OOCYTE MATURATION IN GYNOGENETIC CRUCIAN CARP AND AMPHIMICTIC RED CARP

The present study compared the oocyte maturation in gynogenetic crucian carp(Carassius auratus gibelio) and amphimictic red carp (Cyprinus carpio red variety). After GVBD,the GV materials in the most oocytes of crucian carp showed behavious dif- ferent from those in the red carp during meiosis I.The chromosomes in the most ooeytes of crucian carp were divided into three interrelated,but independent groups.The three groups of chromosomes finally developed into a tripolar spindle.Later,The tripolar spindle twisted, over laped and finally reunited into a normal spindle.In a few oocytes of crucian carp,ho- wever,there were common dipolar spindle similar to that in the red carp. In both types of oocyte maturation in the crucian carp,the extrusion of the first polar- body was not observed.Thus there was no reduction of the chromosomal number in this fish. It was concluded that the stability of chromosomal ploidy in the crucian carp was maintained through the unusual meiosis I during which there was no reduction in the chromosomal num- ber.We speculated that some cytoplasmic factors in the oocyte may play an important role in controlling the meiosis I in the oocyte maturation of crucian carp.