Phenotypic correlations of somatic and gonad traits of sea urchins Glyptocidaris crenularis in two sampled periods:first insight into its breeding and aquaculture

Prior knowledge of the correlations among commercially important traits in Glyptocidaris crenularis can be used to guide development of breeding and aquaculture programs for this species.We evaluated the phenotypic correlations between somatic and gonadal traits in G.crenularis during two sample periods(October 2010 and April 2011).The coeffi cients of variation(CV%)for body weight(BW),redness(a*),yellowness(b*),gonad wet weight(GW),and gonad index(GI)were>20% in both periods,while those of other traits were very low.GW was signifi cantly correlated with somatic traits(diameter,height,and body weight)in both periods,although the correlation coeffi cients ranged from 0.473 to 0.636(P<0.01).Gonad moisture content(GC),a*,and lightness(L*)were not signifi cantly correlated with somatic traits(P>0.05).The color trait b* was negatively correlated with somatic traits(test diameter,test height,and body weight)during the period when the gonads were well developed(April 2011,P<0.05).We observed little difference in the nature of the phenotypic correlations between the two sample periods.The high variation in the somatic and gonad weight traits in G.crenularis suggests there is considerable potential for selective breeding.However,our results suggest that gonad quality traits cannot be selected indirectly by selecting for body weight.Our study provides an insight into the method for improving the breeding and aquaculture of G.crenulari.

Effects of seawater acidification on the early development of sea urchin Glyptocidaris crenularis

In this study, we evaluated the effects of CO_2-induced seawater acidification on fertilization, embryogenesis and early larval development in the sea urchin Glyptocidaris crenularis, that inhabits subtidal coastal areas in northern China. The range in seawater p H used in experiments was based on the projections of the Intergovernmental Panel on Climate Change(IPCC), to the year 2100. A natural seawater treatment(p H_(nbs) =7.98±0.03) and three laboratory-controlled acidified treatments(OA_1, ΔpH_(nbs) =-0.3 units; OA_2, ΔpH_(nbs) =-0.4 units; OA_3, ΔpH_(nbs) =-0.5 units) were used in experiments. Results show that:(1) there was a negative effect of seawater acidification on fertilization and on the percentage of abnormal fertilized eggs;(2) the size of early cleavage stage embryos decreased in a dose-dependent manner with decreasing p H;(3) both the hatching rate of blastulae and the survival rate of four-armed pluteus larvae decreased as pH declined;(4) larval abnormalities including asymmetrical development, changes in the length of skeletal elements, and corroded spicules were observed in all seawater acidified-treatments compared with the control. These data indicate that seawater acidification has a negative impact on the early development of G. crenularis, and supports the hypothesis that the response of echinoderms to ocean acidification(OA) varies among species. Further research is required to clarify the specific cellular mechanisms involved.

Correlation analyses of covering and righting behaviors to fitness related traits of the sea urchin Glyptocidaris crenularis in different environmental conditions

Complex marine benthic environments shape a number of ecologically important behaviors in sea urchins, including covering and righting behaviors. The present study correlated covering and righting behaviors to a series of fi tness-related traits in sea urchins. Righting response time of Glyptocidaris crenularis was signifi cantly positively correlated with body size, but signifi cantly negatively correlated with food consumption. Covering behavior was not signifi cantly correlated with test diameter, test height or body weight, but covering response time was negatively correlated with body weight. A signifi cantly negative correlation was found between righting response time and covering response time. Glyptocidaris crenularis showed a signifi cantly positive correlation in covering response time with and without exposure to poured sand, but no signifi cance in covering ability(number of shells used to cover). The present study provides new insight into internal mechanisms and evolutionary drives of covering and righting behaviors of sea urchins.