Autotriploid and allotriploid abalone larvae (Haliotis discus hannai and H. discus hannai O x Haliotis fulgens ♂) produced by two chemical methods

Two types of abalone larvae, Haliotis discus hannai and H. discus hannai 9 x Haliotis fulgens male, were produced by inhibiting polar body II (PB2) via treatment with two chemicals: cytochalasin-B (CB) and 6-dimethylaminopurine (6-DMAP). After 70 % of the fertilized eggs released polar body I, the zygotes and hybrid zygotes were treated with four CB (1, 1.25, 1.5, and 1.75 mg L-1) or 6-DMAP concentrations (10, 20, 30, and 40 mg L-1) for 10, 15, and 20 min. The hatching indices of embryo, including cleavage and hatching of fertilized eggs, were evaluated, and composite ploidy was determined using flow cytometry at 24 h after fertilization. Our results showed that hatching rate and triploid rate of autotriploid and allotriploid larvae were significantly affected by the CB and 6DMAP concentration and treatment duration, respectively (P 0.05), except for the effect of 6-DMAP treatment duration on allotriploid and triploid rate of autotriploid larvae (P 0.05). Higher triploid rate induced a low hatching rate and vice versa. Combining both high rates of triploidy and reasonable hatching, the optimal treatment combination for triploid induction in autotriploid abalone was 1.75 mg L-1 CB for 15 min and 40 mg L-1 6-DMAP for 10 min, and optimization of triploidy induction in allotriploid abalone was achieved using CB (1.75 mg L-1) for 15 min and 6-DMAP (30 mg L-1) for 20 min. The hatching rate and triploid rate were 73.11-85.20 % and 91.66-100.00 %, respectively. This study confirmed the improvements in the effectiveness of 6-DMAP and CB in inducing autotriploid larvae in H. discus hannai and established an improved procedure for inducing triploidy in hybrid of H. discus hannai female and H. fulgens male using chemical methods. These methods will likely be useful for production of triploid strains in abalone aquaculture.