| Spirulina is a blue-green algae widely distributed in freshwater or saline lakes in tropical and subtropical regions.It is considered to be one of the richest sources of organic nutrients in the world.It can be used in various industries such as the production of health products,aquaculture feed,food and cosmetics.The protein content of spirulina powder is 60%-70%,which is far higher than the current edible protein content of animals and plants,and it is an ideal source of high protein.Algal cells are also rich in carbohydrates,algal polysaccharides and unsaturated fatty acids,high content of phycocyanin and gamma linolenic acid have good health care and pharmacological effects.However,with the gradual expansion of the scale of cultivation,the emergence of filter-feeding micro-animals(especially rotifers)in the process of cultivation has seriously restricted the development of Spirulina breeding industry and affected the yield and product quality of Spirulina.However,some of the known physical and chemical control methods have failed to achieve good results,and even have side effects such as harming algae.Some studies have shown that the nucleic acid inhibitor5-Fluoro-2'-Deoxyuridine(FDU)can prevent the reproduction of rotifers.Therefore,this study will start from the reproductive development of rotifers to the population growth,to explore its mechanism of action and the feasibility of controlling rotifer contamination.In addition,in order to ensure that the normal harvest of Spirulina as a commercial product will not be affected,the growth and nutritional components of Spirulina were evaluated.In order to provide an effective guidance for the production reduction and harm caused by rotifer population outbreak in the large-scale production process of Spirulina.The research contents and results of this paper include the following three aspects:1.Effects of temperature and FDU concentration on the reproductive and developmental toxicity of Brachionus plicatilis.As a kind of reproduction inhibitor,we setted three temperatures(20,25,30?)and six concentrations of FDU(0,60,110,160,210,260 ?g/L)in order to explore its influence on the reproductive development of rotifers.The whole life cycle of rotifer was observed and recorded.The results showed that FDU significantly prolonged the embryonic development time and pre-reproductive time.In the three temperature treatment groups,the embryonic development time and pre-reproductive time were prolonged by 13.95%?32.18%?55.63% and 26.36%?32.83%?41.91% respectively.While FDU had no significant effect on the reproduction period and post reproductive time of rotifers.In addition,FDU significantly reduced the number of eggs,but with the increase in temperature,the number of eggs has a tendency to increase.Compared with 20?,the number of rotifer eggs increased by 65.91% and 97.73% at 25? and30? respectively;treatment group(260 ?g/L)increased by 7.41% and 40.74%.At the same time,the inhibition rate of rotifer eggs increased linearly with the increase of FDU concentration,and the inhibition rate of 260 ?g/L FDU could reach 100%.In addition,an interesting phenomenon was observed in the experiment: A certain dose of FDU would have different effects on the morphology of rotifers,such as body wall transparented,body surface shrinked,swim slowly and so on.Secondly,some of the dropped eggs could not hatch successfully or the rotifer will die if they did not hatch successfully.These results show that FDU has a good egg suppression effect.2.The population growth of Brachionus plicatilis in response to FDU stress.The results of the experiment show that FDU can significantly inhibit the growth of rotifer population,and greatly reduce the maximum density and the time to reach the maximum density.At the same time,FDU has wide temperature effect,and each temperature group can inhibit the growth of rotifer population.At the same time,the population density of rotifers in the 30? treatment group has the most significant difference compared with the control group.In addition,the results of the life table experiment showed that the increase in temperature accelerated the time and speed of death of the rotifers,but there is no significant difference in the survival rate between the drug treatment groups at the same temperature.The temperature had a significant effect on the reproduction rate.The low temperature group has a lower reproduction rate and longer reproduction time;on the contrary,the higher the temperature,the higher the reproduction rate and the shorter the reproduction time.And in all temperature treatment groups,the reproduction rate of rotifers under FDU treatment was lower than that of the control group.At 20? 160,210 ?g/L,25? 210,260 ?g/L,and 30? 160,210,260 ?g/L,rotifers hardly produced offspring.In this study,the smaller reproduction rate and reproduction time also means a better insect effect.In addition,the effects of different concentrations of FDU on the net reproductive rate of rotifer at three temperatures showed that the net reproduction rate and intrinsic growth rate decreased with the increase of concentration in FDU treatment group,and the net reproduction rate of rotifer was basically 0 at high FDU concentration.The generation time and life expectancy increased with the increase of FDU concentration.3.The growth and nutrition of Spirulina under different FDU concentrations.Previous studies have proved that FDU has a positive effect on inhibiting rotifer population growth.So this study carried out a 16-day spirulina culture to comprehensively evaluate its safety and feasibility from the two aspects of spirulina growth and nutrient composition.The results showed that Spirulina was not stressed by FDU,and there were no significant differences in biomass and chlorophyll fluorescence parameters between the two groups.At the same time,the nutrient composition of Spirulina under FDU has the same amino acid and fatty acid composition as compared with the control group;even after FDU treatment,the content of essential amino acid,fatty acids and gamma linolenic acids are better than that of the control group.The results showed that FDU had no negative effect on the growth and nutrients of Spirulina.To sum up,FDU can be used as a safe and effective drug to control rotifers.The essence of FDU is to act on the early stage of development,blocking the synthesis of DNA of rotifer offspring.It prolongs the embryonic development period and prereproductive period,increasing the time of offspring production to reduce the number of eggs.At the same time,it can produce unhealthy offspring or directly inhibit the hatching of eggs at a higher concentration.In the subsequent population growth experiment,FDU also showed a good effect on inhibiting population density.There was almost no growth trend of rotifers at 260 ?g/L FDU,and the inhibitory effect was more obvious at high temperature(30?).At the same time,The dosage used in this study did not affect the growth of Spirulina at all,and there was no significant difference in the nutritional composition compared with the control group at the highest concentration(260 ? g / L FDU). |
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