| The nutritional value of initial feeding determines the quality and survival rate of larvae.At present,artificial diets such as soybean oil,soybean milk and egg yolk are mainly used as the initial feeding in the breeding of freshwater larvae,but the feeding rate is low and a large number of larvae die during the breeding process.Rotifers are an important component of freshwater zooplankton,with high nutritional value,palatable size and high availability,they are the ideal opening bait for freshwater larvae.Currently,the yield of rotifer cultivation is low and the technology is not perfect in China,making it often difficult to meet the demand in production.Hydrodynamic disturbance is commonly present in natural water bodies,and research has reported that water disturbance has a significant impact on the feeding,growth,and reproduction of planktonic animals.However,there are few reports on the impact of water disturbance methods and intensity on the reproduction of rotifer populations.Rotifers have a wide range of feeding habits,Among them,the cultured rotifers mainly consisted of Chlorella proteinae and yeast..In this study,the Brachionus calyciflorus was taken as the research object,Chlorella pyrenoidosa and baker’s yeast were used as the diets for rotifers,the large-scale cultivation of rotifers was studied with different disturbance methods(aeration disturbance and flow disturbance)and different disturbance intensity.The main research findings are as follows:(1)The effects of different disturbance modes and intensities on the feeding rate of B.calyciflorus were studied after they had fed on C.pyrenoidosa,at concentrations of 1×10~6cells/m L,5×10~6 cells/m L and 10×10~6 cells/m L.The experimental results showed that at three algal densities,the feeding rate of rotifers increased first and then decreased with the increases of disturbance intensity.In the aeration treatment group,the feeding rate of rotifer was higher at the aeration rate of 12 L/min,while the feeding rate of rotifer was higher at the flow rate of8000 L/H and 13000 L/H in the flow treatment group.Under the same disturbance mode,the feeding rate of rotifers increases with the increase of algal density,reaching 10×10~6 cells/m L,the feeding rate of rotifers in each experimental group reached its maximum,with the resting group reaching 3.89×10~3 cells/ind.·h;The maximum feeding rate of the inflatable groups is6.70×10~3 cells/ind.·h,significantly higher than the stationary group(P<0.05);The maximum feeding rate of the flow making groups is 8.57×10~3 cells/ind.·h,significantly higher than the stationary and inflatable groups(P<0.05).The experimental results indicate that water disturbance can significantly increase the feeding intensity of rotifers,and under the disturbance of flow making,rotifers can consume more food.(2)Using C.pyrenoidosa as bait,the effects of different disturbance modes and intensities on the culture of rotifer B.calyciflorus were studied by means of population accumulation culture.The experimental results showed that compared with static culture and aerated culture,flow culture can significantly improve the reproductive speed of rotifers.The 13000 L/H flow making group has a good reproductive effect of rotifers,and the population density can reach107 ind./m L within 7 days;However,the highest inflation culture was only 56 ind./m L,while static culture was only 23 ind./m L,both of which were significantly lower than flow culture(P<0.05).This experiment shows that when C.pyrenoidosa is used as bait,water disturbance can improve the cultivation effect of rotifers,and flow disturbance is the best disturbance mode for rotifer large-scale culture.(3)The culture effects of different disturbance modes and intensity on B.calyciflorus were studied by population accumulation culture method with baker’s yeast as bait.The experimental results found that in the inflatable treatment group,the highest population density of rotifers was 162 ind./m L at a 12 L/min inflation rate,while the population density of rotifers in all the flow making treatment groups exceeded 200 ind./m L,among them,the population density of rotifers reached 297 ind./m L at a flow intensity of 8000 L/H,which was significantly different from the inflatable treatment group(P<0.01).The results of this experimental study indicate that when using bread yeast as bait,the flow disturbance is beneficial to achieve high yield of rotifers.(4)Using C.pyrenoidosa as bait,the effects of different disturbances modes on the nutritional value of B.calyciflorus were studied.The experimental results showed that in static cultivation,the total amount of 17 amino acids in rotifers is 29.94%(dry weight),and the necessary amino acid content is 15.37%(dry weight).Compared to this,the total amino acid content of rotifers was reduced by 18%and 14%,and the essential amino acid content was reduced by 22%and 15%respectively under 12 L/min inflatable culture and 13000 L/H flow culture.Twenty fatty acids were detected in all three groups,among which 13 fatty acids had significant differences(P<0.05).In terms of the essential fatty acids linoleic acid,α-linolenic acid andγ-linolenic acid of freshwater larvae.The content ofα-linolenic acid in static group accounted for 19.37%of total fatty acids,which was significantly higher than that in the 13000L/H group(P<0.05),while the content of linoleic acid accounts for 3.36%of the total fatty acids,which was significantly lower than that of 12 L/min group and 13000 L/H group(P<0.05).There was no significant difference inγ-linolenic acid content among the three groups(P>0.05).Overall,the nutrient levels of static cultured rotifers are higher than those of disturbed cultured rotifers. |
