Influence factors on fertilization rate in laboratory hybridization between Haliotis diversicolor and H.discus discus

To overcome the gametic incompatibility of interspecific hybridization between Haliotis diversicolor(S) and H.discus discus(J),the effects of gametic age,insemination sperm concentrations,Trypsin,Ca~(2+),pH and temperatures on the fertilization rate were investigated.The results showed that the age of egg and insemination sperm concentration are two important factors influencing the fertilization rate.In comparinson with the pure cross,the fertilization rate was low and declined much sharply for the heterospecific cross.At 21.5℃,the fertilization rate was 100% and did not declined significantly in 1 h post egg spawned for the pure cross,while it was 55.9%±8.1% at 2 min and declined by 50% at 4.7 min post spawned for the SJ cross,and it was 31.5%±9.7% at 4 min and declined by 70.9% at 10 min post spawn for the JS cross.The concentrations of sperms yielded maximum fertilization with the least abnormality in subsequent development was 6.0×10~(6)-2.4×10~(7)mL~(-1) for the SJ cross,and 3.8×10~(7)-7.5×10~(7)mL~(-1) for the reciprocal cross,which were about 100-fold higher than that in homologous cross.Higher temperature accelerated the egg losing the ability of being activated by the heterospecific sperm.For the eggs spawned for less than 10 min,the optimal temperature for hybridization is 26-(29℃).The other tested factors,including the addition of Trypsin or Ca~(2+) into the fertilization system and alteration of pH,led to decline of fertilization rate.