P. Galbusera et al., Gynogenesis in the African catfish Clarias gariepinus (Burchell, 1822) III. Induction of endomitosis and the presence of residual genetic variation, AQUACULTURE, 185(1-2), 2000, pp. 25-42
Gynogenesis is thought to be a useful method to generate fully inbred lines
in teleost fish. Endomitosis, which refers to the inhibition of first mito
sis, should lead to fully homozygous offspring. In this study, the optimal
conditions to induce mitogynogenesis (endomitosis) by heat shocking of the
eggs were determined in the African catfish Clarias gariepinus. Comparable
survival rates were obtained with a shock of 40 degrees C applied for 1 min
and a shock of 39 degrees C applied for 1.5-2 min. Applying the shock arou
nd 20 or 37 min after activation resulted in the highest survival rates (ca
. 5% relative to the positive control). The amount of inbreeding (homozygos
ity) and paternal contamination were assayed by using polymorphic microsate
llite DNA markers. In less than 1% of the offspring paternal alleles were p
resent, indicating a true gynogenic background for most of the progeny. Mei
ogynogenetic and mitogynogenetic C. gariepinus showed a fair amount of resi
dual heterozygosity (respectively 86% and 75% for one of the markers). Hete
rozygous catfish obtained through mitogynogenesis were attributed to the (s
imultaneous) presence of meiogynogens. In addition, we prove that the sex d
etermining system of African catfish C, gariepinus is heterogametic in the
male (XY/XX). (C) 2000 Elsevier Science B.V. All rights reserved.