Effects Of Protein Sources And Lipid Sources In Feed On Growth,Nutrition Composition And Transcription Of Fatty Acid Synthesis Related Genes In Strongylocentrotus Intermedius

The effects of protein sources and lipid sources on the growth of sea urchin,nutrient composition of gonadotropin and gene expression of fatty acid synthesis were investigated in the study of Strongylocentrotus intermedius,an important breed of mariculture in China.(1)This study was conducted to investigate the effects of different protein sources on the growth performance,digestive enzyme activities,gonadosomatic index and amino acid profile in juvenile sea urchin(Strongylocentrotus intermedius).Four formulated feeds were made to include fish meal,soybean meal,kelp meal or degummed kelp as the protein source in the diets,which were named as F-K,S-K,F-S-K and F-S-D,respectively.Juvenile sea urchins were randomly allocated to 12 floating cages and each cage was stocked with 20 individuals(initial weight: 0.75±0.02g).Results showed that weight gain rate(WGR)was highest in the sea urchins fed F-K,significantly higher than that in the other three treatments(p<0.05).Similarly,gonadosomatic index(GI)was highest in the sea urchins fed F-K,significantly higher than that fed F-S-K(p<0.05).No significance was observed in the digestive enzyme activities among different dietary treatments(p>0.05).Total essential amino acid was highest in F-K and F-S-D,significantly higher than that in F-S-K(p<0.05).Results above showed that the best protein source for sea urchins was F-K,followed by F-S-D,S-K,and F-S-K.Compared with the kelp,the degumming kelp powder is more beneficial to the growth of the sea urchin and the development of the gonadal gland.This may be because the degumming kelp powder containing less kelp glue is more beneficial to the improvement of the digestibility of the sea urchin.(2)This study was conducted to investigate the effects of different lipid sources on the growth performance,digestive enzyme activities,gonadosomatic index(GI)and fatty acid profile in juvenile sea urchin(Strongylocentrotus intermedius).Four formulated feeds were made to include linseed oil,fish oil,rapeseed oil,soybean oil as the lipid source in the diets,which were named LO,FO,RO and SO,respectively.Juvenile sea urchins were randomly allocated to 12 floating cages and each cage was stocked with 20 individuals(initial weight: 0.75±0.02g).Results showed that the weight gain rate(WGR)of the sea urchins fed kelp was significantly higher than that fed formulated feeds(p<0.05).Among the four lipid sources,WGR was highest in LO,which was comparable to that in FO and RO(p>0.05),but was significantly higher than that in SO(p<0.05).However,sea urchins fed the kelp had the lowest GI compared to the other four formulated feed groups(p<0.05).Among the four lipid sources,GI was lowest in SO,which was comparable to that in RO(p>0.05),but was significantly lower than that in LO and FO(p<0.05).The fatty acid composition of sea urchin could be significantly affected by different lipid sources.EPA in RO was slightly higher than that in FO(p>0.05).EPA was lowest in SO,which was significantly lower than that in other three lipid sources(p<0.05).DHA content was highest in FO,followed by RO,which were significantly higher than that in kelp,LO and SO(p<0.05).ARA in the gonads in RO was significantly higher than that in other three lipid sources(p<0.05).The above results show that the kelp is superior to formulated feeds in growth performance,but inferior to formulated feeds in gonad development.Based on growth performance,gonad development and fatty acid profile,rapeseed oil and linseed oil,rather than soybean oil,were recommended as potential lipid sources to replace fish oil.(3)In this study,the effects of different lipid sources on the expression of Elovl4 and Elovl5 and ?6Fad in sea urchin were studied.Four formulated feeds were made to include linseed oil,fish oil,rapeseed oil,bean oil as the lipid source in the diets.Juvenile sea urchins were randomly allocated to 12 floating cages and each cage was stocked with 20 individuals(initial weight: 0.75±0.02g).Results showed thatthe transcription of fatty acid synthesis related genes was significantly affected by different lipid sources.The expression of Elovl4 and Elovl5 and ?6Fad in the digestive tract of sea urchins fed fish oil was lowest,which was significantly lower than that fed rapeseed oil.Elovl5 in both digestive tract and gonad,as well as ?6Fad in digestive tract of sea urchins fed diets with soybean oil were significantly higher than that fed fish oil(p<0.05).The above results suggest that the high accumulation of essential fatty acids in the canola oil treatment group may be related to the increased expression of fatty acid synthesis related genes in the intestinal tract and gonads of sea urchins.