Effects Of Temperature, Light Intensity And Nitrogen On The Reproduction Cycle Of Oocystis Borgei

Microalgae is an extremely important part of the shrimp culture ecosystem and great significance for the conversion of nitrogen pollutants in the culture system.Constructing a benign microalgae community,improving nitrogen absorption efficiency and improving the breeding environment are important technical measures for the healthy breeding of shrimp,and also reduce the pollution of farming to the environment.Oocystis borgei have the good ecological value of reducing the content of nitrogen and phosphorus in the aquaculture water,inhibiting the growth of Vibrio,and stabilizing the ecological microbial population in the water.However,there are few studies on the propagation.The cell division pattern of O.borgei was be observe,and the effects of nitrogen concentration,light intensity and temperature on the growth,cell volume and the time and number of commitment points in the cell cycle of Oocystis borgei be explored in thie paper.The experimental results are as follows:1.Cell division pattern of Oocystis borgeiThere are four Cell division patterns was found in Oocystis borgei,2-autospore type,3-autospore type,4-autospore type and 8-autospore type,usually it was 4-autospore type.in the absence of nitrogen and low light conditions,the frequency of 2-autospore types and 3-autospore types increased.The cells are not synchronized during the process of division,forming three daughter cells,which is particularly significant under nitrogen deficiency and low light intensity conditions.2.The cell cycle type of Oocysts borgeiThe Oocysts borgei can usually be split once or twice in one cell cycle.When the Oocysts borgei reaches the 1st CP,if the environmental conditions are poor(nitrogen deficiency,weak light),the growth rate of the cells is low,the cells will enter the division sequence,and form an amorphous population of 2 cells.However,if the environmental conditions are excellent and the growth rate is high enough,the cells will start a new G1 phase,the cell volume is increased by about 4 times compared with the daughter cells,and a few cells can reach the 3st CP,and the cells divide three times.an amorphous population of 8 cells was formed.3.The effect of temperature on the reproduction cycle Oocystis borgeithe temperature increased,and the growth rate of Oocystis borgei was increased.The average number of daughter cells per mother cell was not significantly different between the three temperature treatment groups.temperature did not only affect the cell cycle.The length of the previous commitment period,as the temperature increases,the length of the late stage of the commitment point is shortened from 20.2 h to 13.8 h,and the cell cycle length is shortened from 32 h to 20 h.4.Influence of light intensity on the reproduction cycle Oocystis borgeiAs the growth rate increased,the cell cycle length of Oocystis borgei was reduced from 30 hours to 22 hours,and the average number of daughter cells per mother cell increased from 3.224 to 3.982.There is a clear distinction between the early stage of the commitment point and the late stage of the commitment point and the response to the growth rate: the length of the previous stage of the commitment point is inversely proportional to the growth rate and is determined by the time required to reach the critical cell size.Conversely,the duration of the late point of the commitment point varies between 15.3 and 15.6 hours,independent of the growth rate.These findings indicate that the duration of the cell cycle of Oocystis borgei is regulated by the rate of cell growth under experimental light intensity.5.Effect of nitrogen concentration on the reproduction cycle Oocystis borgeiUnder the condition of nitrogen starvation,the cells stopped schizophrenia and the cell volume became larger.After nitrogen compensation,the cell division returned to normal level,and the number of cells reaching three promise points was much higher than the other two groups.(p <0.01);in the 0.25 mmol/L group of Oocystis borgei in a given 12L:12D photoperiod,the number of cells reaching the promise point gradually decreased and the cell cycle was disturbed.