| With the continuous reduction of marine fisheries resources,marine fishing has been unable to meet people's demand for aquatic protein food sources,and aquaculture has become the most important means of supplying aquatic protein sources.In the breeding and breeding of economic animals such as fish and shrimp,whether the appropriate and sufficient open bait is one of the most important factors affecting the success or failure of aquaculture,the species,quality and nutrient composition of the open bait play an important role in the feeding demand and survival of the biological larvae.Studies have shown that the effect of feeding live feed at opening stage is significantly better than that of feeding fresh ice food and pellet feed.At present,in aquaculture,rotifer and Artemia are widely used as open bait for aquatic animals.Some living baits,such as cladoides and copepods,have also been used in the opening period and late nutrition fortification of the fish and shrimp.However,many research results show that the components of rotifer and Artemia lack the essential unsaturated fatty acids that are necessary for the growth and development of fish and shrimp,and there are some deficiencies in their nutritional value.Compared to rotifer and Artemia,copepods need to have 12 developmental stages,rich in amino acids,and can meet the nutritional requirements of different fish and shrimp aquatic animals.It is an open living bait with great potential.Copepods feed mainly on algae,and the species of algae have an important influence on the survival,spawning and metabolism of copepods.Therefore,it is of great significance and value to screen suitable algal bait for artificial cultivation and scale breeding of copepods.In this study,five species of unicellular algae food Phaeodactylum tricornutum,Platymonas subcordiformis,Skeletonema costatum,Isochrysis galbana,and Chlorella.sp were fed to the Eurytemora Pacifica.Organic carbon content(1.0mgC / L)was used to regulate the density of unicellular algae food.The results of the experimental data analysis showed that the feeding effect of five kinds of unicellular algae food had obvious difference.The survival rate of P.tricornutum,P.subcordiformis and S.costatum was higher than that of I.galbana and C.sp of the feeding bait.In the fecal pellet production,the number of feces produced by S.costatum was the most,and was statistically higher than that of the other 4 species of unicellular algae food(P<0.05).The amount of egg production on the surface of the E.Pacifica was lowest after the feeding of C.sp.(P<0.05).Based on the above experimental results,we concluded that P.subcordiformis and S.costatum are relatively suitable feed for E.Pacifica.The effects of bait concentration on the biology of the E.Pacifica were analyzed,and 5 bait concentrations of 1,2,4,8 and 16.0mgC/L were selected.The results showed that there was no significant change in the egg production of the E.Pacifica(P>0.05)after feeding with different concentrations of P.subcordiformis.The difference of survival rate,fecal pellet production and egg production was significant in different concentrations of S.costatum,and the survival rate,fecal pellet production and egg production gradually decreased with the increase of concentration(P<0.05).The results showed that the feeding effect of 2 mgC/L P.subcordiformis and S.costatum was the best(P<0.05),and there was no significant difference between them(P>0.05).The relative bait and feeding concentration of E.Pacifica were obtained through the study,which provided a basis for large-scale artificial culture of E.Pacifica.Through the above studies,we found that different unicellular algae food had significant effects on the survival,fecal pellet production and egg production of E.Pacifica.In order to further the study the mechanism of the effects of bait on the biological characteristics of the E.Pacifica,a preliminary study on the transcriptional group of the E.Pacifica was carried out in order to explore the possible mechanism of action from the molecular level,and to dig out the functional genes related to the bait.A preliminary study of the E.Pacifica transcriptional group showed that the total data of the E.Pacifica were 6.73 Gb.After assembly and further redundancy,50024 Unigene were obtained,the total length was 42162526 bp,the average length was 842 bp,the GC content was 43.50%,and N50 was 1397 bp.Then the Unigene was compared and annotated to the seven functional databases,and finally 8578(NT:17.15%),24812(NR:49.60%),20074(SwissProt:40.13%),19503(KOG:38.99%),20128(KEGG:40.24%),4269(GO:8.53%),and 18598(InterPro: 37.18%)Unigene,respectively.Get the functional annotations.This study provides a basic basis for further the study of the effects of feed nutrition and metabolic levels on the biological characteristics of copepods,and also provides an important reference for other copepods. |
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