Host recognition and mechanism of settlement of monogenean hatching larvae infecting fish

单殖吸虫的孵化幼虫（oncomiracidia）在识别出鱼体表面的某些特殊物质后，在鱼体表面定居下来。然而，目前还没有对其进行任何表征。以下实验旨在阐明诱导幼虫定居和生长的物质。净化它们。建立了一种利用低宿主特异性的新登虫（Neobenedenia girellae）和seriola特异性的贝登虫（Benedenia seriolae）体外测定鱼体表面上皮提取物的沉降诱导活性的新方法。在该测定方法中，所测试的鱼类物种之间的活性几乎没有差异，并且该活性是耐热的。天然宿主虎河豚粘液对冈本异槽绦虫的毒力高于非天然宿主虎河豚粘液.结果表明，该活性被特异性凝集素抑制：WGA对N.girellae和Con A对B. seriolae。这表明，物质诱导oncomira ...更多信息 食蟹类定居点是糖相关的，如糖蛋白或多糖。冈本血吸虫在附着于河豚鳃后立即开始吸血，而对河豚、比目鱼、真鲷等非自然宿主的血液几乎没有吸收和消化能力，并最终从其鳃上脱落。利用体外试验，试图纯化从日本比目鱼体表上皮细胞中提取的N.girellae oncomiracidium沉降诱导物质。它们在0.2-0.3M NaCl下溶解在阴离子交换树脂中，并且通过凝胶过滤具有高于排阻极限的分子大小。单殖吸虫的寄主专一性表现为幼虫孵化后识别寄主的能力、吸收寄主营养的能力、耐受寄主防御机制的能力等，表明单殖吸虫在这些能力上存在着不同的水平，不同类群的单殖吸虫寄主专一性表现为不同的因子。少

Monogenean hatching larvae (oncomiracidia) settle down on the surface of fish host after they recognize some particular substance(s) present on fish body surface. However, nothing has been characterized about it. Following experiments were done to elucidate substances inducing larval settlement and. to purify them.1. A new method has been developed to assay in vitro the settlement-inducing activity in the fish body surface epithelium extracts, using low host-specific Neobenedenia girellae and Seriola-specific Benedenia seriolae. In this assay method, there were almost no differences in the activity among fish species tested, and the activity was heat tolerant. The activity against Heterobothrium okamotoi oncomiracidium was higher in mucus from tiger puffer, the natural host, than those in mucus from unnatural hosts.2. It was shown that the activity was inhibited by specific lectins : WGA against N.girellae and Con A against B.seriolae. It is suggested that substances to induce oncomira … More cidial settlement are sugar-related ones like glycoproteins or polysaccharides.3. H.okamotoi oncomiracidia started to feed blood immediately after settlement on the gills of tiger puffer, while they showed little or no ability to absorb and/or digest blood from unnatural hosts like grass puffer, Japanese flounder or red sea bream, and eventually came off from them.4. Using the in vitro assay an attempt was made to purify N.girellae oncomiracidium settlement-inducing substances extracted from body surface epithelium of Japanese flounder. They were solubilized in anion exchange resin at 0.2-0.3M NaCl, and had a molecular size above the exclusion limit by gel filtration.5. Manifestation of monogenean host specificity involves the ability to recognize host by hatching larvae upon settlement, ability to absorb nutrition from host, ability to be tolerant of host defense mechanisms, etc. It is suggested that benedeniid and polyopisthocotylean monogeneans have different levels in these abilities, and that host specificity is manifested by different factors in different groups of monogeneans. Less