Study On The Motion Behavior And Foraging Mechanism Of Navicular Arenaria Var.Rostellata

Diatom is an important primary producer of aquatic ecosystems,contributing 25%of the global primary productivity and driving the global biogeochemical cycle of carbon and silicon.Diatom's physiological activities,production,metabolism and exchange of material affect the surrounding environment.At the same time,as a bottom rung of the food chain,diatomaffect the whole aquatic ecosystem from substances variation of trace elements.Pennatae Navicular arenaria var.rostellata is widely used in aquaculture,environmental monitoring and bioenergy production.However,the multiplication of diatom will lead to diatom blooms,marine biofouling and marine snow phenomenon,which does harm to economic loss in the aquatic and landscape industry.Navicular arenaria var.rostellata moves forward or backward through the excretion of extracellular polymeric substances from its raphe.Navicular arenaria var.rostellata,as a typical active matter,can independently generate motion by continuous consuming outside energy.Compared to the traditional systems driven by macroscopic gradients,active matter is more sensitive to environmental disturbance and response more complicated.In the complex systems,each individual affects its neighbors'individual motion behaviour andstate,that is,the spatial complexity can significantly affects the motion behavior of the active matter and finally show different long-term cluster behavior in the system.We use Navicular arenaria var.rostellata as the research object,and analyze Navicular arenaria var.rostellata's motion through fast,automatic,continuous image collection.We realized the analysis by high-speed microscopic tracking and modern data analysis technology.Based on the tracking analysis,the biodynamic data of Navicular arenaria var.rostellata are calculated,such as velocity,motion angle,and curvature etc.and describe the motion trajectory,so as to complete the comprehensive statistical analysis of Navicular arenaria var.rostellata motion behaviour.We have studied the chemotaxis,and effect of space complexity and different concentrations of dSi on the motion of Navicular arenaria var.rostellata and the following main conclusions are obtained:?1?Under the homogeneous environment and when the cell density and collisionis low,the trajectory of Navicular arenaria var.rostellata is circular arc,so the typical motion mode is“circular-reverse–circular”,that is,trajectory include a large number of non-constant circular arcs and a small amount of reverse behaviour.The reverse behavior can be divided into single reverse and double reverse,single reverse leads to the direction change and double reverse which doesn't.In addition,distributions of motion angles between consecutive steps display a significant bimodal pattern,the peak is near 3.14?circular arc motion?and 0?reverse?.Distribution of the consecutive step lengths is Poisson.?2?Navicular arenaria var.rostellata have chemotaxis to the spatial gradient of nutrient source.In the environment containing local DSi,Navicular arenaria var.rostellata has a chemotaxis motion towards the central DSi source,while in the homogeneous nutrient environment Navicular arenaria var.rostellata randomly walks and no directed movement.Physically,we analyzed of the biological dynamic data and found that the foraging mechanism relies on more frequent flipping adjustments,small angles and more directional movement of the tumbling frequency in the direction of the concentration gradient;Navicular arenaria var.rostellata accumulate to the center of DSi source leads to more cell collision and slower speed.With the combination the research of the bacteria chemotaxis,we clarify Navicular arenaria var.rostellata physics foraging mechanism through experiments and analysis.?3?The space complexity has a significant influence on the movement behavior of Navicular arenaria var.rostellata.In the experiment,we set up different spatial complexity?such as the different density of cell and the different density of obstacles?.We found that the motion behavior in different complex environments has three stages.In a short time,the motion shows a ballistic behavior due to cell along the long axis of the body the self-driven inertia.At intermediate time scales,cell is supper-diffusion because of the rotating deviation in the circular motion.In a long time scale and under low complex environment?low cell density??=0.03%?,intermediate cell density??=0.14%?,second high cell density??=0.71%?and low obstacles density??=1.76%??,cell showssub-diffusion behavior.In a long time scale and under high complex environment,?high cell density??=4.46%?,intermediate obstacles density??=7.82%?and high obstacles density??=23.75%??,cell shows normal-diffusion behavior.Navicular arenaria var.rostellata's walking length and the persistence time is power-law and shows Levy walk.The density of cell and the density of the obstacles had a significant effect on the velocity.When the density was low or high,the velocity was slower,while the density was intermediate,the velocity was faster.The velocity was gradually decreasing with the increase of the density of the obstacles.?4?The motion behaviors of Navicular arenaria var.rostellata significantly depend on the concentration of DSi.Trace concentrations?1 mg/L,Na₂SiO₃?and high concentrations?120 mg/L,Na₂SiO₃;240 mg/L,Na₂SiO₃?could inhibit the movement,and low concentration?15 mg/L,Na₂SiO₃?and intermediate concentration?30 mg/L,Na₂SiO₃;60 mg/L,Na₂SiO₃?would enhance the diffusion coefficient.Under different DSi concentrations,Navicular arenaria var.rostellata showed ballistic behavior at short-time scale,super diffusion behavior at intermediate-time scale and normal diffusion behavior at a long time scale.Based on the above studies,we explained the typical trajectories,the chemotaxis,the effect of spatial complexity and different concentrations of dSi on the movement of Navicular arenaria var.rostellata.The quantitative study on the motion behavior of Navicular arenaria var.rostellata can be carried out from the single-cell track and the quantitative characterization of each cell help understand the motion behavior,foraging strategy,evasion mechanism and aggregation behavior of Navicular arenaria var.rostellata.Revealing the physiological moving characteristicswithexploring the influence of different external environmental factors and different concentrations of nutrients on the movement of Navicular arenaria var.rostellata,is more accurate to evaluate the diffusion rate of diatom in liquid and helpful to find the causes of diatom blooms in complex environment,as well as,explore the rapid formation of biofilm,provide reference for marine biofouling and marine snow triggering,and provide a new understanding of the effective control of spring diatom blooms and understanding of its blooms mechanism,and reveal the stability of marine plankton diversity and the mechanism of determination and change.