Abstract: The survival,growth performance[specific growth rate(SGR)and coefficient of variation(CV)]and phenotypic characteristics(count of chromatophore cells and ossicle shape on tube feet,and spine length and color)were compared in sea urchin hybrid juveniles of Strongylocentrotus intermedius(♀)×S.nudus(♂)and the two purebred sea urchin offsprings to evaluate the heterosis.The 90 d feeding trial showed that both S.intermedius and S.nudus had survival rate of 100%,and the hybrids 97%at the end of the experiment,without significant difference(P＞0.05).However,there was significantly higher SGR(4.00%/d)in the hybrids than that in the parents(2.91%/d in S.intermedius and 3.15%/d in S.nudus)(P＜0.05),without significant difference between the two parental species(P＞0.05).From 60 days to 90 days,therewas no significant difference among the three sea urchins(P＞0.05).The hybrids had significantly higher coefficient of variation for body weight of (76.12%)than the S.intermedius(52.05%)and S.nudus(63.81%)at the end of the experiment(P＜0.05), indicating that interspecific hybridization significantly led to increase in genetic variation in hybrid offsprings.The maximal chromatophore cellswere observed on the tube feet in S.nudus while theminimal oneswere found in S.intermedius.The hybrids showed themoderate number of chromatophore cells on tube feet.The hybrids had spines with a light purple color,between S.intermedius(white)and S.nudus(deep purple),and thinner and shorter spines compared to the parental sea urchins.Unlike the colors of spines and tube feet,a new variation was observed at the ends of the ossicles on tube feet.The findings indicate that the hybrid juveniles has an obviously different phenotype from that of the parents,and are characterized by good growth rate and higher level of variation, as a high breeding potential.
2015, Vol. 30 
