| Sea urchin Strongylocentrotus intermedius belongs to echinoidea of echinodermata,which occurs around lithoherm,dinas and gravel in inter-tide and shallow seas.S.intermedius is a ecologically important marine invertebrate in intertidal zone and shallow sea tectonic marine benthic community.Previous studies,which studied the effect of short-term UV-B radiation on the behavior of S.intermedius,found that S.intermedius were sensitive to short-term UV-B radiation.In addition,S.intermedius have a number of fitness-related traits and photosensitivity-related genes that can be measured.Therefore,S.intermedius is an ideal model for studying the effects of short-term UV-B radiation on marine invertebrates.In this thesis,the effects of UV-B radiation on S.intermedius were studied from three aspects.The main results are summarized as follows:1)The effects of UV-B radiation on the fitness-related traits of S.intermediusThree groups（30 individuals in each group）were exposed to ultraviolet-B（UV-B）at 0,10 and20μw.cm-22 for 1 hour,respectively.Three groups of sea urchins were cultured under natural light for 8 weeks after the ultraviolet radiation.Fitness related traits of three groups of sea urchins were measured,including survival,behavior,food consumption,growth and so on.The results showed that the survival rate and food consumption of the S.intermedius exposed to UV-B at 20μw.cm-2were significantly less than those exposed to 0μw.cm-22 UV-B radiation.These results show that short-term UV-B radiation has a long negative retention effects on the survival and growth of S.intermedius（8 weeks）.The UV-B radiation had no obvious effect on righting behavior of S.intermedius.This indicates that the righting behavior can be recovered after 8 weeks of UV-B radiation.The test thickness and test pressure were not significantly affected by UV-B radiation,but the body size significantly decreased.The results extend the opinion that high temperature does not cause sea urchin test to become fragile after UV-B radiation.Although food consumption was significantly reduced,UV-B radiation had no significant effect on the length and weight of Aristotle’s lantern.The results show that Aristotle lantern had strong toughness to UV-B radiation.The gonad weight and gonadal crude protein decreased significantly in S.intermedius exposed to UV-B.However,the effects of UV-B radiation on intestinal weight and intestinal crude protein were not significant.Together with previous studies,it had been shown that the gonads of S.intermedius exposed to environmental pressure is more sensitive.2)Transgenerational effects of UV-B radiation on egg size,fertilization,hatching and larval size of S.intermediusS.intermedius exposed to 0μw.cm-22 and 20μw.cm-22 were fed artificially for 10 months in the laboratory.The three mating groups were set up as:A(♀0μw.cm-2×♂0μw.cm-2);Group B(♀20μw.cm-2×♂20μw.cm-2);Group C(♀20μw.cm-2×♂0μw.cm-2).There were 3 families in each group（N=3）.Egg diameter,fertilization rate,hatching rate and larval size（larval length,larval width,stomach length,stomach width,post-oral arm length,body rod length）were measured in each group.The results showed that short-term UV-B radiation had no significant effect on the fertilization rate.This suggests that although their parents faced adverse environments,larvae were not affected in the stability of fertilization.The hatching rate of S.intermedius significantly increased groups B and C.The increasing of hatching rate may be due to relatively short radiation time（1 hour）and long-term recovery（10 months）.The changing trend of hatching rate was consistent with that of egg diameter.Larger eggs contain more energy and beneficial biochemical components,which may contribute to the increasing hatching rate of sea urchins.The increased egg size and the subsequent increasing hatchability indicate the adaptation of marine invertebrates to UV-B radiation.When both parents were exposed to short-term UV-B radiation(20μw.cm-2),the larval length and width were significantly shortened（P<0.05）.These results suggest that UV-B radiation has a harmful transgenerational effect on the size of S.intermedius larvae.Interestingly,the larval length was not significantly shortened in group C,whoes female parent was exposed to UV-B radiation,while the male parent was not.In addition,the larval width in group C was the largest,indicating that the harmfulnesss of the male parent exposed to UV-B radiation to the offspring was greater than the exposure of the female parent.When both parents were exposed to short-term UV-B radiation(20μw.cm-2),the length and width of the stomach were significantly shortened.This result is consistent with the reduction of the larval size in the study,and also shows that the UV-B radiation has a detrimental transgenerational effect on the size of the stomach.There was no significant decrease in the stomach width of the group C,but the length of the stomach was affected.The results also confirm that the transgenerational effect of UV-B radiation on the S.intermedius mainly depends on the male parent.In this study,the post-oral arm length/body rod length of the parents exposed to UV-B increased significantly,indicating that short-term UV-B radiation had beneficial transgenerational effects on wrist length.This result indicates that post-oral arm length is probably an adaptation of the less food intake of their parents.3)The effects of UV-B radiation on the expression of light detectiongenesof S.intermediusWe selected three group sea urchins（CB:covering behavior group,SB:sheltering behavior group and NA:control group）to experience short-term UV-B radiation(0–2 h,20μw.cm-2)in S.intermedius.The expressions of light detection genes（Pax6,Opsin4 and Opsin5）in three groups of S.intermedius were determined by extracting RNA,reverse transcription and real-time RT-PCR.In the study,except at 0.5 h,the relative expression level in the covering group was the highest compared with the control group and the sheltering group at 1 h,1.5 h and 2 h.The results showed that the expressions of light detection genes in covering group of S.intermedius were more sensitive to UV-B radiation than that in sheltering group.Together with previous studies,the present results suggest that covering behavior has better effect on the protection of light than the sheltering behavior of S.intermedius.We guess that the relatively long-term UV-B radiation may destroy the light defense system of S.intermedius and lead to abnormal expression of related genes.The molecular mechanisms remain unknown.Further experimental studies are needed... |
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