Highly efficient induction of triploid Pacific abalone Haliotis discus hahnai by caffeine treatment

In order to develop a highly efficient method for mass production of triploid Pacific abalone Haliotis discus hannai, caffeine treatment that is safe and inexpensive was optimized. To suppress the first meiotic division, fertilized eggs were exposed to either a 10- or 15-mM caffeine solution for 24 min beginning at 12 min after fertilization. In most treated batches, the rates of cleaved eggs showed no significant difference from the control batches. However, in most treated batches, the rates of occurrence of normal larvae and the survival rates of the early juveniles were significantly lower than those of the controls. The triploid rates at 6 days to 11 months after settlement in all the treated batches were extremely high (91-100%). There was no significant difference in the mean triploid rates between 10- and 15-mM caffeine treatments. These results suggest that both treatment conditions were conducive to triploid abalone production. One live 2n/3n mosaic specimen was found in the treated batches. However, since the frequency of mosaic was extremely low, the mosaicism would probably not have an adverse effect on the stable production of triploid abalones.