Research On Causative Aetiology For The Abnormal Mortality Of Scallop Chlamys Farreri

The pathologic and histopathologic changes of the scallop Chlamys farreri and the morphology of the virus particles were observed under optic and electronic microscope. The results showed that there were spherical virus-like particles in the digestive gland, kidney, and the intestine of moribund scallop Chlamys farreri. The virion are approximately 130 to 170 nm in diameter and has a bilaminal envelope, while the nucleo capsids are 90-140 nm. The virus occurs and distributes in the cytoplasmic vesicles of infected cells, and forms occluding protein. The tissue infected with the virus showed distinct pathologic changes. The ultrastructure section show that damnifications exist in karyon, endoplasmic reticulum and chondriosome of the infected cell.Artificial infection experiment of healthy scallop was conducted by injection or dipping with sick scallop tissue homogenate. The Artificially infected scallops showed the same symptom as the natural scallop and the same virion was found in the infected scallops' tissue , which proved that the virus is the causative aetiology for the abnormal mortality , according to the Koch's principle.The virions were isolated from moribund scallop (Chlamys farreri) through differential centrifugation and discontinuous sucrose gradient centrifugation. The viral particles are consistent in size and morphology in preparations derived from the isolation and also from ultrastructure sections. The spikes of envelope are clearly observed with negative staining. Three methods , Proteinase K digestion based approach , acid-guanidium-phenol-chloroform (AGPC) and TRIZOL method ,were used to extract nucleic acid from the virions. The nucleic acid extracted from the virions could be degraded only by RNase-A ,which indicated the virion is a RNA-virus particle. To build up a detective approach , the cloning system of the virus gene was setup.and the methods to detect the clone were discussed.