INCREASE OF FERTILITY IN TETRAPLOID MALE SILKWORMS BY STARVATION

Tetraploid male silkworms are sterile in nature. However, occasionally , fertile tetraploid males have appeared. After many trials to increas e the fertility of tetraploid males, starvation at the Fifth larval in star was found to be the most effective stimulus. The. tetraploid male s were starved for 48 h at various stages (0 h, 24 h, 48 h, 54 h, 60 h , 72 h, and 96 h) of the fifth larval instar, in the fall and summer s easons of 1993 and in the summer season of 1994. Fertility of the tetr aploid males increased as the stage of the starvation was delayed and became highest at 60 h of the fifth instar. Since the male meiosis in the tetraploids started after 48 h of the fifth instar, in contrast to 0 h in the diploid, our data suggest that a factor promoting normal s permiogenesis is produced by starvation at the specific stage of the f ifth instar.