Effects And Mechanism Of Light On The Breeding Of Sea Cucumber, Apostichopus Japonicus

A detailed literature review of the technique of artificial breeding andecophysiological effect of light on sea cucumber Apostichopus japonicus wasundertaken. And then, a series of indoor experiments are conducted to investigate theeffects of light intensity and period on the growth, development, survival andmetabolism of larvae and juvenile sea cucumbers. At last, the reason caused the effectof light on the growth of juvenile sea cucumber is discussed with evidence from stableisotopes. The main results are detailed as follows:1. The effects of light intensity and photoperiod on the growth, survival, developmentand metamorphosis of sea cucumber （Apostichopus japonicus） larvaeThe effects of different light intensities （0Lux,50lux,500lux and2000lux） andphotoperiods （24L:0D,14L:10D,10L:14D and0L:24D） on larvae growth, survivalrate, development and metamorphosis of Apostichopus japonicus were studied. Theresults showed:（1） The larvae growth was significantly affected by light intensitiesand photoperiods （P<0.05）. The growth rates （GR） under different light intensities andphotoperiods were as followed:500lux>50lux>2000lux>0lux,14L:10D>10L:14D>24L:0D>0L:24D, respectively.（2） The larvae survival rate （SR） increasedwith the increase of light intensity. The larvae SR in0L:24D treatment was the lowestamong all the photoperiod treatments （P<0.05）.（3） In the9thday, the percentage ofdoliolaria larvae in500lux treatment was30.9%, while the percentage in0luxtreatment was5.2%, and the0lux treatment also had the highest abnormality rate（17.7%）. The percentage of doliolaria larvae in10L:14D treatment was34.8%, whichwas significantly higher than those in other photoperiod treatments （P<0.05）.（4） Themetamorphosis rate under different light intensities and photoperiods was as followed:50lux>500lux>2000lux>0lux，10L:14D>14L:10D>24L:0D>0L:24D, respectively. The larvae metamorphosis was affected significantly by light intensitiesand photoperiods （P<0.05）. Accordingly, appropriate light is more favorable to thegrowth and development of the of Apostichopus japonicus larvae.2. The effect of light on growth and metabolism of juvenile sea cucumberApostichopus japonicusThe effects of different light intensities （0Lux,100lux,1000lux and2500lux） andphotoperiods （24L:0D,14L:10D,10L:14D and0L:24D under1000lux） on growthrate and metabolism of juvenile sea cucumber Apostichopus japonicus were studiedover60days. The main results were as follows:（1） The specific growth rate （SGR） ofjuvenile sea cucumber increased with the increase of light intensity and it peaked atlight intensity of1000lux with1.48±0.04%, then decreased; SGR under different lightintensities was as followed:1000lux>2500lux>100lux>0lux.（2） The regressiveequation between the SGR of juvenile sea cucumber and light intensity can bedescribed as SGR=﹣2.6801×10^﹣7Lx2+7.798×10^﹣4Lx+0.9746（R²=0.9822）. Beingcalculated according to the formula of SGR, the optimum light intensity of juvenilesea cucumber is1454lux.（3） Among all the photoperiod treatments, juvenile seacucumbers in14L:10D had the highest SGR （1.43±0.67%）, which was significantlyhigher than24L:0D and0L:24D treatments （P<0.05）.（4） Light intensity hadsignificant effect on the oxygen consumption rate （OCR） and ammonia-N excretionrate （AER） of juvenile sea cucumbers （P<0.05）. Both OCR and AER had similarchanging trend:2500lux>100lux>0lux>1000lux. The O: N ratios indicated thatjuvenile sea cucumbers mainly utilized protein as its energy source in theexperimental condition.3. The contribution of fresh diatom in diets under different light intensities to thegrowth of juvenile sea cucumber Apostichopus japonicusContribution of fresh diatom in diets to the growth of juvenile Apostichopusjaponicus under different light intensity groups （0lux,1000lux and2500lux） wasstudied with evidence of carbon and nitrogen stable isotopes. The juvenile sea cucumbers in each light intensity group were fed with three kinds of diets: thesediment of natural pond （Diet A）, fresh Cylindrotheca fusiformis suspension mixedwith sea mud （Diet B） and formulated feed （Diet C）. After80d cultivation, the mainresults were as follows:（1） The specific growth rate （SGR） of juvenile sea cucumberswas significantly affected by light intensity and diet and the interaction between themwas significant （P<0.05）.（2） Juvenile sea cucumbers in2500lux treatment showedthe significantly highest specific growth rate （SGR） among three light treatments（P<0.05）.（3） The survival rates （SR） of juvenile sea cucumbers in diet B treatmentswere significantly higher than those in diet A treatments （P<0.05） and the SR of theB-1000lux was the highest （89.2±2.8%）.（4） Calculation with carbon and nitrogentable isotope model revealed that the contribution of algae in diet A and diet Bincreased with the increase of light intensity. The contribution of benthic diatom indiet A increased from13.36%to62.10%and the contribution of diatom in diet B alsoincreased from83.62%to97.54%, but the contribution rates of formulated feed werenot significantly affected by light intensity （P>0.05）. Accordingly, freshCylindrotheca fusiformis was a substitute for Sargassum thunbergii in formulated feedfor sea cucumbers, and the feed efficiency could be enhanced by appropriate lightwhen feed the sea cucumbers with fresh Cylindrotheca fusiformis suspension.