Induction of diploid gynogenesis using interspecific sperm and production of tetraploids in African catfish, Clarias gariepinus Burchell (1822)

Homozygous diploid gynogenetic and tetraploid progeny of African catfish (Clarias gariepinus) were produced by the suppression of the first mitotic division by applying thermal shock. The duration of one mitotic cycle during synchronous cell divisions ( tau(0)-value) was used as unit after fertilization for expression of the time of development. After determination of sensitive and non-sensitive periods, a temperature of 40.5 degrees C for 2 min was subsequently used. Diploid gynogenesis was obtained (6.34 +/- 2.35% survivors at swimming stage) when eggs were fertilized with genetically inactivated rosy barb (Barbus conchonius) sperm. We have not found any embryos using intact interspecific sperm. When African catfish sperm was used for fertilization a ratio of 9.2% tetraploids was obtained (mixed eggs from four females). The highest frequency of both gynogens and tetraploids was observed when the heat shock was initiated at 1.4 tau(0)-value. We used electrophoresis, chromosomes and nucleoli counting for identification of homozygosity and tetraploidy. (C) 1999 Elsevier Science B.V. All rights reserved.