Study On The Way Of Interdicting Ctenopharyngodon Idellus Artificial Infection Of Saprolegnia Parasitica

1Reasarch of zoospore invading fishSaprolegnia parasitica is a severe fish pathogen that causes important economiclosses worldwide. This research used the method of Saprolegnia artificial infectionfish to infect grass carp by ATCC200013(Saprolegnia parasitica). Using paraffinsection and HE staining to research on fish skin tissue pathological damage, alsousing scanning electron microscope to observe grass carp skin that have been infectedby Saprolegnia. And then discusses the method and process of Saprolegnia invadingthe fish body. The research results show that the zoospores can be in the form ofsingle or clustered to invade the fish body and cause varying degrees damage to fish.The spores sprout hypha after they attach to the fish body, absorb nutrition of the fish,and then germinate external hyphae in vitro.2The efficacy of Chitosan in controlling infection of S. parasiticaChitosan has the effect of promoting wound healing that is widely used in peopleand livestock medicine areas. About the effect of chitosan on the fish, such as thestudy of fish disease prevention, treatment effect is rare. Whether promote fish woundhealing or prevent Saprolegniasis has no reference. Therefore, soaking wound grasscarp with different concentrations of chitosan to verify the effect of chitosan onpromoting fish wound healing. It is found that chitosan concentration≥25mg/Lwound healing effect is remarkable for grass carp and the wound surface is withmucus; Two infection:1. Artificial infection of Saprolegnia on grass carp in25mg/Lchitosan;2. Artificial infection of Saprolegnia on grass carp after soaking in25mg/Lchitosan for72h. The results show that the grass carp artificial infected with Saprolegnia infection rates are down. Contracted artificial infection of Saprolegnia ongrass carp in25mg/L chitosan to artificial infection of Saprolegnia on grass carp aftersoaking in25mg/L chitosan for72h, the later one infection rate is relatively lower.This experiment confirmed that healing the wound of fish can block Saprolegniainfection in fish body and provided theoretical basis for control of fish Saprolegniasis.3Research of the effect of copper sulfate to hypha and zoosporeDifferent metal ions have different influence to spores, Cu2+toxicity is thestrongest, which has effect when it’s0.1mg/L. Therefore choosing copper sulfate asthe study drug, scanning electron microscopy was used to study the effect of differentconcentrations of copper sulfate on hypha and spores morphological structure. Inferthe mechanism of the inhibition. After copper sulfate treatment, the hypha began toirregular branch, the hypha appear swelling, dry at the top, eventually lead to stop thegrowth; Spores burst, shrivel, unable to form mycelium germination.4The efficacy of copper sulfate in controlling infection of S. parasiticaCopper is an important additive in the aquaculture industry for control of algalgrowth, ecto-parasites and fungi disease. However, at present no data is available onthe specific interaction of copper sulfate with oomycete. In our study, the efficacy ofcopper sulfate on the mycelium and zoospore of S. parasitica was assessed in vitro,and S. parasitica infection experiment was conducted to assess its performance invivo. The results indicated that copper sulfate at≥0.5mg/L inhibited the growth ofmycelium, no primary zoospores were released at≥1.0mg/L. Additionally,0.5mg/Lcopper sulfate could reduce the infection rate of S. parasitica in the grass carp,Ctenopharyngodon idellus. This study demonstrates that the good efficacy of coppersulfate on the control of S. parasitica infection in grass carps, and suggests thatinhibiting spores could be one way to control the S. parasitica infection in theaquaculture industry.