Chromosome set manipulations and hybridization experiments in gilthead seabream (Sparus aurata). I. Induced gynogenesis and intergeneric hybridization using males of the red seabream (Pagrus major)

The parameters for the production of triploid and gynogenetic progenies of the gilthead seabream, Sparus aurata, have been established. To induce dipl oidization of the maternal genome the optimal heat shock temperature used w as 36.5-37.3 degrees C. Time after fertilization for shock treatment and du ration of shock were 3 and 2.5 min, respectively. Triploidization efficienc y in embryos was positively associated with shock temperature, reaching a m aximum of 100% at 37 degrees C. Gynogenetic diploid progenies of S. aurata were produced using the same conditions established for triploidization, ex cept that fertilization was carried out with UV-inactivated heterologous sp erm of red seabream, Pagrus major. The efficiency of the sperm inactivation was estimated to be 100%. Diploid and triploid hybrids between S. aurata f emales and P. major males were produced. The chromosome "markers" useful in interspecific hybridization experiments are discussed.