Effects Of Two Phospholipids On The Growth,Gonadal Development,Nutritional Quality And Lipid Metabolism Of Sea Urchin(Strongylocentrotus Intermedius)

Strongylocentrotus intermedius is one of the important mariculture species in the northern coastal areas and its gonads have very high economic and nutritional value.Phospholipids are a class of polar lipids containing phosphate groups.They are one of the important nutrients in aquatic animal feed,and have important significance for the survival,growth,development,immunity,and reproduction of aquatic animals.Many scholars have conducted research on the nutrition of phospholipids in various aquatic animals,but there is no report on the nutrition of phospholipids source from sea urchins.Therefore,this study aims to explore the effects of two phospholipid on the growth,gonadal development,nutritional quality of adult sea urchin.And the effects of two phospholipid on the growth,gonadal development,lipid composition and metabolism related gene expression of juvenile sea urchins.The main results and conclusions were summarized as follows:（1）Effects of two phospholipids on growth,gonad development and nutritional quality of adult sea urchin（Strongylocentrotus intermedius）This experiment was conducted to investigate the effects of two phospholipids on the growth,gonad development,and nutritional quality of adult sea urchin Strongylocentrotus intermedius.The casein and soya meal were included as the main protein sources,the soya lecithin was added to fish oil diet as the control group diet,and soya lecithin（PO+SL group）and krill oil（PO+KO group）were added to palm oil diet as the experimental group diet,respectively.Forty-five Strongylocentrotus intermedius with initial body weight of（18.86±0.55）g were randomly allocated to 3 groups,deed the above three diets,respectively,each groups contained15 sea urchins,and individually held in cages.The experience lasted for 42 days.The results showed as follows:1)There was no significant difference in final body weight,weight gain rate and gonad wet weigh among all groups（P>0.05）.The gonadosomatic index of PO+SL group was significantly lower than that of the control group（P<0.05）.2)The gonad moisture content of PO+SL group significantly higher than that of PO+KO group and control group（P<0.05）,the gonad crude protein content of PO+SL group was significantly lower than that of the control group（P<0.05）.3)There were no significant differences in gonad brightness and redness values among all groups（P>0.05）.The gonad yellowness value of PO+SL group was significantly lower than that of PO+KO group and control group（P<0.05）.4)The gonad issue section shows that the gonad development rate of PO+SL group was the slowest,with both male and female individuals developed to phase II.The male individual gonad of PO+KO group and control group developed quickly,all developed to have III;while female individual gonad developed to phase II.5)The contents of total amino acids（TAA）,essential amino acids（EAA）,sweet amino acids,delicious amino acids and bitter amino acids in gonad of PO+SL group were significant higher than those of PO+KO group and control group（P<0.05）.6)The contents of eicosapentaenoic acid（EPA）and docosahexenoic acid（DHA）in gonad of PO+KO group and control group were significantly higher than those of PO+SL group（P<0.05）.In conclusion,the soya lecithin or krill oil did not significantly affect the weight gain rate of sea urchins.Compared with the soya lecithin,the krill oil can increase the gonadosomatic index,development rate,and essential fatty acid content of Strongylocentrotus intermedius.This study suggests that feeding formulated feeds containing soya lecithin first,and then enhancing it by feeding formulated feeds containing krill oil before marketing could not only reduce raw material costs but also improve the fatty acid nutrition of the gonads of sea urchins.（2）Effects of two phospholipids on the growth,gonad development,lipid composition and metabolism related gene expression of juvenile sea urchin（Strongylocentrotus intermedius）This experiment was conducted to investigate the effects of two phospholipids on the growth,gonad development,lipid composition and metabolism related gene expression of juvenile sea urchin Strongylocentrotus intermedius.Casein and soybean meal were included as the main protein sources.Two palm oil-based feeds were formulated to contain different phospholipids（soya lecithin and krill oil）,which were named PO+SL and PO+KO,respectively.And the fish oil-based feed was added with soya lecithin and fresh kelp were used as the control diets,which were named FO+SL and Kelp.Each feed was randomly fed to three parallel groups of juvenile S.intermedius（initial weight:1.11±0.21 g）for a trial period of 60 days.The results showed that:1)The addition of two phospholipids did not significantly affect the weight gain rate and gonadosomatic index of sea urchins,and there was no significant difference compared to FO+SL（P>0.05）.2)The histological images showed that the gonads of the sea urchin males of the three formula feed have entered phase II,while the gonads of the female individuals remain in phase I.3)A total of 7257 lipids were collected using LC-MS technology.The relative contents of PC,PE,PS,PI,and PG of the gonads of sea urchins fed PO+KO were significantly higher than those of PO+SL and FO+SL（P<0.05）.4)The relative contents of C20:4n-6 and C20:5n-3 in the sn-2 position of the gonads of sea urchins fed FO+SL were significantly higher than those of PO+SL and PO+KO（P<0.05）;The relative contents of C20:4n-6,C20:5n-3,and C22:6n-3 in the sn-2 position of the gonads of sea urchins fed PO+KO were significantly higher than those of PO+SL and FO+SL（P<0.05）.5)The expression of Fatp4 in the digestive tract and gonads of sea urchins fed PO+KO and FO+SL were higher than those of PO+SL,while the expression of Pla₂ and Lpcat in the gonads of sea urchins fed PO+KO were higher than those of PO+SL and FO+SL.6)The expression of Elovl4,Fad1,and Fad2 in the digestive tract of sea urchins fed PO+KO were higher than those of PO+SL,while the expression of Elovl5,Fad1,and Fad2 in the gonads of sea urchins fed PO+KO were higher than those of PO+SL.In conclusion,soya lecithin or krill oil did not significantly affect the weight gain rate,gonadosomatic index,and gonadal development of juvenile S.intermedius.Compared to soya lecithin,krill oil can significantly affect the composition of lipid molecules in the gonads of juvenile S.intermedius,thereby increasing the content of PL-LC-PUFA in the gonads,which may be achieved by promoting phospholipid remodeling,transportation,and the expression of genes related to fatty acid synthesis.