Researches On The Biological Characteristics Of Miamiensis Avidus

Objective:An investigation had been carried out to find out how serious Paralichthys olivaceus were suffered from a pathogen called Miamiensis avidus, how to culture the parasites in the laboratory, how the environmental factors influence the population density, the rate of natural increase and the generation time. The molecular phylogenetic trees were custructed to reveal the relationship of Miamiensis avidus to all species of ciliatese analyzed.Methods:(1)During April to August in 2008, the routine methods were applied for investigation of the prevalence of the ciliatesis in Fuzhou. For example, the pathogens were picked up from the focus of fishes and observed the feature of morphology under microscopy. (2)The Miamiensis avidus were cultured in lab with the routine methods of marine ciliates. The influences of environmental factors to the Miamiensis avidus were showed by the study of experimental ecology. (3)The ITS-5.8S gene fragment of Miamiensis avidus was sequenced, and the phylogenetic tree was constructed with the PHYLIP 3.66 and MEGA 3.1.Results:(1)The pathogen was determined as Miamiensis avidus after morphological identification. It was the first report in Fujian. The disease caused by Miamiensis avidus in Fuzhou was serious, which may cause Paralichthys olivaceus to die at last with the mortality rate was 60%-70%.(2)the rice ectra and the yeast extract medium were better for Miamiensis avidus's living than the other two. And the best environments for Miamiensis avidus were temperature of 25℃, the salinity of 40‰, the pH of 6.0, respectively. And we can prevent the disease by changing the environment according to the above data. (3)The ITS-5.8S gene fragment of Miamiensis avidus was first time to be sequenced, which has enriched the information in the GenBank. The phylogenetic trees revealed that the relationship of Miamiensis avidus was most closed to Parauronema longum in all species of ciliatese analyzed.