Evaluation of cytochalasin B (CB) treatments for triploidy induction in the blacklip abalone, Haliotis rubra (Leach, 1814)

Abstract

The e¡ectiveness of cytochalasin B (CB) treatments for inducing triploidy was evaluated in the blacklip abalone Haliotis rubra (Leach, 1814) in two orthogonal design experiments. The ¢rst experiment employed three dosages (DSs) of 0.25, 0.5 and 1.0 mg CB L À 1 , three starting times (STs) of 5, 15 and 25 min post fertilization and three treatment durations (TDs) of 10, 20 and 40 min, for a total of 27 treatments. The second experiment comprised of two DSs of 0.25 and 0.5 mg CB L À 1 , ¢ve STs of 5, 15, 20, 25 and 30 min post fertilization, and three TDs of 10, 20 and 40 min, for a total of 30 treatments. Water temperature was held at 17.5^18.5 1C. Day 3 larvae were sampled for triploidy using £ow cytometry (FCM) and survival. Optimal inductions were treatments starting at 15 or 20 min post fertilization and continuing for 40 min, and those initiated 25 or 30 min post fertilization for 20 or 40 min, using 0.5 mg CB L À1 . These treatments were all targeted at inhibition of the second polar body (PB2) formation and yielded triploidy rates of 84.8^89.5% coupled with (relative) survival rates of 20.1^52.1% in the ¢rst experiment, and corresponding rates of 86.5^96.5% and 33.0^74.1%, respectively, in the second experiment. A common and essential feature of these optimal conditions is that treatment must fully span the period of time for most of the eggs to extrude PB2. Treatments that resulted in suppression of the ¢rst polar body (PB1) formation induced triploidy levels below 71.5% and 57.6% in experiments 1 and 2 respectively. Treatments that had overlapping e¡ects on both PB1 and PB2 extrusion led to triploidy rates above 80% but very low survival rates of 1.8% and 5.4% in experiments 1 and 2 respectively.