Study On The Major Bacterial Diseases Of Cultured Sea Cucumber (Apostichopus Japonicus) During Larval Stages

Mass mortalities of cultured sea cucumber Apostichopus japonicus had occurred frequently in the fishery farms of Shangdong peninsula in recent years. Due to the high stocking density,poor management and the susceptivity to disease during larval stages,diseases occurred frequently. They caused high mortalities and reduced the seed outputs of hatcheries. In order to find out the pathogens of these diseases and give effective countermeasures,we conducted an epidemiological and etiological study on the diseases of cultured sea cucumber along the coastal area of Shandong province and Dalian city from 2004 to 2005,in which two important bacterial diseases disease had been discovered. The preliminary studies revealed that bacteria are the major pathogens of these contagious diseases. In this paper,a primary work was done to ascertain the etiology of epidemic diseases.The infected sea cucumber samples including lavae,juvenile and adults were mainly collected from the affected farms of A. japonicus in Shandong province. The study on the pathogens followed the next steps: firstly,smears of the focus of the affected sea cucumbers were observed under a microscope to make a preliminary conclusion on the pathogens; Secondly,incubate the bacteria existing on the focus by using solid medium such as TSB,TCBS and respectively according to the pathogen observed; Thirdly,artificial infection experiments were carried out to confirm if the isolates were the right pathogens of the diseases. When the pathogens were decided,morphological study and identification on the pathogen were subsequently performed. The methods include negative-staining of bacteria before observing by electron microscope,Gram staining,biochemical testing,analyzing of gene homology of 16 SrRNA of bacteria.The identification results of the pathogenic bacteria revealed that the pathogens of Stomach ulcer disease,syndrome of off-plate,are Vibrio splendidus; Alteromonas sp,Pseudoalteromonas sp,Vibrio lentus respectively.and two Vibrio sp. Upon the...