海湾扇贝类衣原体寄生及人工感染试验

Natural infection and artificial transmission of Chlamydia-like organism in Argopecten irridians Lamarck

于1999年10月至2001年3月海湾扇贝(Argopectenirridians)大量死亡期间,对不同生长阶段的海湾扇贝进行了组织学及超微结构观察,在贝消化腺上皮细胞内发现嗜碱性的类衣原体包涵体,该包涵体为圆形及不规则形状,大小约9μm×7μm,HE染色呈兰色。包涵体发育至晚期破裂,宿主细胞崩解,类衣原体逸出。超微结构观察显示,包涵体内部含有大小不同的3种个体形态,即网状体、原体和中间体。网状体大而疏松,呈圆形或不规则形,大小为(890.5±164.6)nm×(623.6±129.3)nm(n=20);原体个体小而致密,呈较为整齐的短棒状或纺锤形,大小为(317.5±40.1)nm×(180.3±40.0)nm(n=18);中间体数量较少,大小介于上述2种个体之间,可能处于二者的过渡阶段。将类衣原体分离后对海湾扇贝的幼体、稚贝和成贝进行了人工感染,结果表明,类衣原体可以感染海湾扇贝不同发育阶段(幼贝、稚贝、成贝)的个体,受感染个体生长缓慢,内脏干瘪,易从附着基上脱落。但不同阶段的贝体感染率与死亡率差异较大,幼体组感染率和死亡率分别达80%和90%以上;稚贝组分别达50%和70%左右;成贝组的感染率达50%以上,但死亡率与空白组及对照组无显著差异。说明类衣原体在一定条件下可造成对幼体和稚体扇贝的危害,但对成贝影响不大,不能导致成贝宿主的大量死亡。

The samples of bay scallop Argopecten irridians were collected at different stages during Oct.1999 to Mar.2001 when the outbreak of death happened to the bay scallop. The observation was conducted under light microscope and transmission electron microscope and the inclusions of Chlamydialike organisms (CLO) were found in the epithelial cells of digestive gland, which showed basophilic. The inclusions have round shape and some irregular shapes with the size of about 9 μm×7μm and show blue under HE staining. At the late development stage of the CLO, the inclusions break down and CLOs release. The ultrastructure results show that the inclusions have three types in shape, which are ①elementary body: small and electron dense with shortrod or spindle shape, sized (317.5±40.1) nm×(180.3±40.0) nm (n=18); ②reticular body: large and electron dispersal with round shape or irregular shapes, sized(890.5±164.6)nm ×(623.6±129.3) nm (n=20); ③intermediate body: at middle size between the above two with fewer numbers, maybe at the transitional stage between the elementary body and the reticular body.The CLO artificial transmission experiment was carried out in larval, postmetamorphic and adult individuals. The results show that CLO can infect bay scallop at different stages at the infecting rate of 50%-80% and lead to high mortality in larval and postmetamorphic individuals, but can do little harm to the adults. The conclusion is that CLOs may have great harmful effects on larval and postmetamorphic bay scallop under certain conditions, but can not lead to the large scale of death in adult bay scallop.