Effect Of Dietary Rhodotorula Benthica On Growth And Immunity In Juvetile Sea Cucumber Apostichopus Japonicus

In recent years,the rapid development of sea cucumber farming has lead to a series of problem,such as the low survive rate,growth retardation and the weakened immunity.It has caused serious economic losses and limited the sustainable development of this industry.The Rhodotorula benthica is appropriate for sea cucumber and it can improve the survival rate and immunity of the aquatic animals,which makes it a promising green feed additive.In this paper,the juvenile sea cucumbers Apostichopus japonicus were studied and they were fed with diets containing R.benthica 0,105,106 and 107 CFU/g for 30 days.The main contents are as follows:An analysis of specific growth rates,survival rate and digestive enzyme activities of sea cucumber A.japonicus had shown that R.benthica had significant effect on the specific growth rates of sea cucumbers(p<0.05).In this study,with the level of dietary R.benthica rising,the digestive enzyme activities increased.The amylase activity,cellulase activity and alginase activity were significantly higher than those of control group(p<0.05).But the R.benthica had not significant effect on protease activity and lipase activity(p>0.05).A feeding experiment was conducted to determine the influences of R.benthica on immunity and disease resistance in sea cucumber A.japonicus.Lysozyme activity,phagocytic activity and total nitric oxide synthase activity were significantly improved for the sea cucumber fed with R.benthica at 107CFU/g diet(p<0.05).The highest values of the phenoloxidase activity and alkaline phosphatase activity were found in sea cucumber fed with Rhodotorula benthica at 106CFU/g diet(p<0.05).But the R.benthica had not significant effect on the total coelomocytes counts and acid phosphatase activity(p>0.05).The cumulative mortality of sea cucumber fed with R.benthica after Vibrio.Splendidus challenge was found lower than those of control group.The present study showed that a diet supplemented with R.benthica could stimulate the immune system of sea cumber thus enhancing their disease resistance.