Gynogenesis in the African catfish Clarias gariepinus (Burchell, 1822) III. Induction of endomitosis and the presence of residual genetic variation.

摘要

The optimal conditions to induce mitogynogenesis (endomitosis) by heat shocking of the eggs were determined in the African catfish. Comparable survival rates were obtained with a shock of 40deg C applied for 1 min and a shock of 39deg C applied for 1.5-2min. Applying the shock around 20 or 37 min after activation resulted in the highest survival rates (ca. 5% relative to the positive control). The amount of inbreeding (homozygosity) and paternal contamination were assayed by using polymorphic microsatellite DNA markers. Paternal alleles were present in less than 1% of the offspring, indicating a true gynogenic background for most of the progeny. Meiogynogenetic and mitogynogenetic C. gariepinus showed a fair amount of residual heterozygosity (respectively 86% and 75% for one of the markers). Heterozygous catfish obtained through mitogynogenesis were attributed to the (simultaneous) presence of meiogynogens. It was also shown that the sex determining system of African catfish was heterogametic in the male (XY/XX).