养殖锯缘青蟹呼肠孤样病毒粒子的电镜观察

Visualization of reo-like virus infection of cultivated Scylla serrata by electron microscope

经过对患病青蟹Scylla serrata的组织进行了超薄切片电镜观察,在病蟹的鳃上皮细胞、心肌细胞、胃和肠道上皮细胞中发现了大量的呼肠孤样病毒粒子。该病毒粒子的大小为60 nm左右,二十面体对称,无囊膜,在感染组织细胞浆中呈晶格状排列。根据病毒的形态特征和组织分布形态,初步认为该病毒为水生呼肠孤病毒,暂将其命名为青蟹呼肠孤病毒(Scylla serratareo-like virus,Ss-REO)。

Mud crab, Scylla serrata, is a major economic marine species cultured in China. With the development of intensive culture, various diseases have frequently appeared and severely affected the production. Since 2004 summer,one serious epidemic disease has prevailed in Zhejiang coastal breeding farms, causing high mortality of cultured Scylla serrata. The infected crab was sluggish, infirm, loss of appetite. The most prominent features of infected moribund crab were emaciated body, feet and viscera full of transparent fluid, atrophied hepatopancreas, iaphanous hydroperitoneum in the shield, empty stomach and slow blood coagulation speed. Ultrathin sections of the tissues of the diseased crabs were investigated with electron microscope. The results showed that cytoplasm of gut and gill cells were filled with considerable virus particles, including flaky viroplast, virus capsid and mature virus particles. Moreover, some mature virus particles had arranged in the crystalline inclusion body, and other virus particles were in the transition state forming crystalline inclusion body. However, viral inclusion body was not observed in the intestinal cells. The viral particles were in a crystalline arrangement within the infected stomach cells, which were 60 nm in diameter, in icosahedral symmetry and with visible surface spike. Some of the immature viral particles lacked of cores. The viruses which arranged like crystalline inclusion body caused the degradation of the infected heart tissues, apparently. According to the morphological characteristics and tissue distribution, the virus is assumed to be a aquareovirus and named Scylla serrata reo-like virus（SsREOV） temporally. Using PCR method, the white spot syndrome virus （WSSV） viral particles of crab from the farms with epidemic disease were detected. The results show that 16% detected crabs were affected by WSSV. But there was no conspicuous correlation between the WSSV infection and the epidemic disease.