Saprolegniasis,caused by Saprolegnia infection,is one of the most common diseases in freshwater fish.Our study aimed to determine the epidemiological characteristics of saprolegniasis in Chinese regions of high incidence.Saprolegnia were isolated and identified by morphological and molecular methods targeting the internal transcribed spacer(ITS)ribosomal DNA(rDNA)and building neighbor-joining(NJ)and maximum parsimony(MP)phylogenetic trees.The ITS sequences of eight isolated strains were compared with GenBank sequences and all strains fell into three clades:CLADE1(02,LP,04 and 14),CLADE2(S1),and CLADE3(CP,S2,L5 and the reference ATCC200013).Isolates 02 and LP shared 80%sequence similarity with S.diclina,S.longicaulis,S.ferax,S.mixta,and S.anomalies.Further,isolates 04 and 14 shared 80%similarity with S.bulbosa and S.oliviae.Finally,extremely high ITS sequence similarities were identified between isolates S1 and S.australis(100%);CP and S.hypogyna(96%);and S2,L5,ATCC200013 and S.salmonis(98%).This research provides insights into the identification,prevention and control of saprolegniasis pathogens and the potential development of effective drugs.
Siya LiuPengpeng SongRenjian OuWenhong FangMao LinJiming RuanXianle YangKun Hu
The effect of the main-panel angle of a single-slotted cambered otter-board was investigated using engineering models in a wind tunnel.Three different angles(0,6,and 12)were evaluated at a wind speed of 28 m/s.Parameters measured included:drag coefficient Cx,lift coefficient Cy,pitch moment coefficient Cm,center of pressure coefficient Cp,and the liftedrag ratio Cy/Cx,over a range of angle of attack(0e70).These coefficients were used in analyzing the differences in the performance among the three otter-board models.Results showed that the maximum lift coefficient Cy of the otter-board model with a main-panel angle of 0was highest(1.875 at a¼25).However,when the angle of attack was smaller(0
Lei WangLumin WangChunlei FengAizhong ZhouWenwen YuYu ZhangXun Zhang
In the present work,the hydrodynamic performance of the double deflector rectangular cambered otter board was studied using wind tunnel experiment,flume tank experiment and numerical simulation.Results showed that the otter board had a good hydrodynamic performance with the maximum lift-to-drag ratio(K_(MAX) = 3.70).The flow separation occurred when the angle of attack(AOA) was at 45?,which revealed that the double deflector structure of the otter board can delay the flow separation.Numerical simulation results showed a good agreement with experiment ones,and could predict the critical AOA,which showed that it can be used to study the hydrodynamic performance of the otter board with the advantage of flow visualization.However,the drag coefficient in flume tank was much higher than that in wind tunnel,which resulted in a lower lift-to-drag ratio.These may be due to different fluid media between flume tank and wind tunnel,which result in the big difference of the vortexes around the otter board.Given the otter boards are operated in water,it was suggested to apply both flume tank experiment and numerical simulation to study the hydrodynamic performance of otter board.
