Abnormal Swimming Behavior Under Physical Stimulation In Zebrafish(Danio Rerio) And Control Measures

In recent years, sudden water pollution accidents occur frequently all over thecountry. Traditional chemical testing methods have been unable to monitor the watertoxicity real-timely and accurately, which makes the biological monitoring come intobeing. Zebrafish has been one of the most popular biological indicator species. Thisfreshwater fish offers a number of advantages in biological monitoring including smallsize, low husbandry costs, easy maintenance and a high genetic homology with humanbeing. The behavioral research of zebrafish establishes the foundation for using them inbiological early warning system.The Real-time Toxicity Biomonitor (RTB) is a typical biological monitoring systemwith zebrafish as an indicator, invented by Shenzhen Water Group CO., LTD. However,in the operation we find that noise and abrupt change of light intensity in theenvironment will affect the swimming behavior of zebrafish and cause false alarm. Inaddition, sometimes swimming activity decrease caused by non-toxic factors will alsolead to false alarm, which is bad for stability.In order to formulate criteria of light and noise in the installation environment,effects of light and noise stimulation on swimming behavior in zebrafish is studied inthis paper. The differences of behavioral response to a certain intensity of light, noiseand electricity after being exposed to pollutants have been researched for feasibilityanalysis of alarm verification. The main conclusion include as follows:Zebrafish response to the sound press level (SPL) which is high than80dB withthe frequency range from20Hz to2000Hz and light intensity within2000lx in thisresearch. The short-term light and sound stimulus will cause abrupt change ofswimming speed, turns and height in zebrafish. Specifically, the maximum speed duringsound stimulation has a15mm/s increase at least than the average speed before thestimulus appears. In light stimulation experiment, the maximum increase is more than20mm/s in speed and10turns/t in turns.Zebrafish in a long-term noisy environment of80dB and90dB present a decreasein swimming speed and turns, while it’s not obvious in70dB. When exposed in naturalphotoperiod, zebrafish present an obvious circadian rhythm. The circadian rhythm willfade away in dark environment with a background light on. We found that the circadianrhythm will generally disappear in the first day when the background light intensity ismore than100lx.The short-term light and noise stimulation cause abrupt change in parameterswhich will return to normal level in30minutes in most stimulation experiments. This would cause false alarm. In a conclusion, the magnitude of noise in the installationenvironment should be lower than80dB. Proper measures should be taken if the noiseis too loud. RTB should be settled in dark environment without a photoperiod as muchas possible. And an anti-glare film should be posted on the glass door. The door must betightly closed during running.200lx is advised to be a proper intensity of backgroundlight.The swimming behavioral response of zebrafish to physical stimulation decreasedafter exposed to Cd2+, Cr6+, deltamethrin and DDVP (Dimethyl dichloroviny phosphate)in a certain concentration and exposure time. According to the statistical result, we setthe threshold of alarm verification with a500lx light as maximum speed difference of25mm/s, average speed difference of10mm/s; the threshold of alarm verification witha50Hz,90dB sound as maximum speed difference of20mm/s, average speeddifference of15mm/s; the threshold of alarm verification with a10V direct current asmaximum speed of80mm/s, average speed of60mm/s, maximum turns of20turns/t,average turns of15turns/t. When RTB alarms, alarm verification system send a stimuliand the compute collects relevant data to calculate response intensity of zebrafish. Thenby comparing to the verification threshold, system can determine whether it is a correctalarm. The verification system also can be used to test whether the chosen fish areactive enough for use in RTB. Among the three alarm verification methods, soundverification has the best testing effect and light verification is most feasible.By this research, we formulate the criteria of light intensity and noise magnitude ininstallation environment and optimize the background light intensity. We have alsoundertaken the feasibility analysis of alarm verification with light, sound and electricitystimulation. At last, the stability of RTB will get improved.