The Prevention And Control Drug Screening On Pseudovorticella Jiangi Parasiting On Eriocheir Sinensis And The Toxicity Of The Drug On Several Fresh Water Organisms

Pseudovorticella jiangi is a kind of ciliates which can cause disease ofEriocheir sinensis, it belongs to Ciliophora, Oligohymenophora,Peritrichida, Sessilina. Pseudovorticella jiangi can propagate on the bodysurface of Eriocheir sinensis abundantly, it can cause the crab die becauseof affecting its activity, ingestion and ecdysis, so farmers maybe have afinancial loss, so it is necessary to screen a kind of drug to prevention andcure the disease on crabs. Of cause, the drug must be sure security, highefficiency, economic and conveniency. We hope that this work can have acontribution to the production of Eriocheir sinensis.In order to screen a effective drug to prevention and cure the diseasecaused by Pseudovorticella jiangi, we decided to screen the drug from10kind of drugs, and static aquatic toxicity experiment method was adopted toimprove the experiment, the result showed that the24h LC50of eight kindsof drug on Pseudovorticella jiangi. and the sensitivity on the tested drugs inorder were crystal violet0.18mg/L, benzalkonium bromide0.26mg/L,capric methyl bromide0.93mg/L, potassium permanganate1.53mg/L,benzyl chloride1.81mg/L, zinc sulfate2.31mg/L, methylene blue3.53mg/L, sulfamonomethoxine sodium5.96mg/L, formaldehyde23.04mg/L,respectively, the drug screening was based on the principle of security, high efficiency, economic and conveniency, because of crystal violet wasinsecurity, so we choose benzalkonium bromide as the drug for theprevention and control of the disease caused by Pseudovorticella jiangi.After we decided choose benzalkonium bromide as the drug for theprevention and cure of the disease caused by Pseudovorticella jiangi, inorder to be sure whether benzalkonium bromide had a side effect on crabs,experiments of acute toxicity test had been carried out to crabs of fourperiod of crab. The result showd that he24h LC50of crabs of four periodwere5.5mg/L,14.7mg/L,18.07mg/L and17.99mg/L，safe concentrationwere0.48mg/L,0.65mg/L,1.15mg/L and1.74mg/L. Because of the24hLC50of benzalkonium bromide on Pseudovorticella jiangi was0.26mg/L，which was lower than the SC of benzalkonium bromide to every growingperiod of Eriocheir sinensis, so benzalkonium bromide could be used inproduction of the culture of chinese mitten crab. Bath experiment had beenconducted and the result showed that the2h LC50of benzalkonium bromideon Pseudovorticella jiangi was6.57mg/L,10mg/L of benzalkoniumbromide wasn’t harmful to megalopa in3hours. So the conclusion was thatbenzalkonium bromide was suit to be the drug to prevention and cure thedisease caused by Pseudovorticella jiangi under the selection principle ofsure security, high efficiency, economic and conveniency. At the period ofmegalopa and P1, we adviced that the dosage of splashing concentrationwas0.35mg/L and the dosage of bath therapy was8.0mg/L in2hours.We could abtain good results to use benzalkonium bromide for theprevention and cure the disease caused by Pseudovorticella jiangi, but theinfluence of benzalkonium bromide to other aquatic organism wasunknown, so we choosed four kinds of aquatic organism for the study ofthe influence of benzalkonium bromide to aquatic organism. The result showed that the24h EC50of benzalkonium bromide on Chlorella vulgariswas0.36mg/L, the24h LC50of benzalkonium bromide on Stentor,Daphnia magna, Cipangopaludina cahayensis were0.54mg/L,0.55mg/Land24.4mg/L, respectively, SC were0.037mg/L,0.039mg/L and1.008mg/L, respectively. The toxicity of benzalkonium bromide toChlorella vulgaris, Stentor and Daphnia magna was larger than the toxicityto Cipangopaludina cahayensis.Bath experiment of benzalkonium bromide to Eriocheir sinensis offirst period(P1) had been conducted and the histopathologic changes hadbeen observed. The result showed that the gills was changed obviouslycaused by benzalkonium bromide, and this change aggravated with theincrease of benzalkonium bromide concentration in water body. The gilltissue appeared gill coarsen dice, distortions, and part of the gill mergingdice, end enlargement, the phenomenon such as hyperplasia of gill filamentends. The normal live of P1was threatened by benzalkonium bromide; Andwith the increase of benzalkonium bromide concentration and growth ofaction time, the liver cell obviously increased, small pipe wall R wallthickening, F cells cavitation, make liver small lumen size smaller, so Inthe process of drug use, we should control the quantity of benzalkoniumbromide and change water in time after drug use.