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

单系孵化幼虫（oncomiracidia）在识别鱼体表面的某种特殊物质后，在鱼宿主表面定居下来。然而，它没有任何特征。下面的实验阐明了诱导幼虫沉降的物质。净化它们。本文建立了一种新的方法来体外测定鱼体表上皮提取物的沉降诱导活性，该方法使用低宿主特异性的girellae neobenenia和seriolae特异性的Benedenia seriolae。在这种测定方法中，被测鱼类之间的活性几乎没有差异，并且活性是耐热的。天然寄主虎鲀黏液对冈氏异病菌的抑菌活性高于非天然寄主黏液。结果表明，WGA和Con A两种凝集素均能抑制该酶的活性。提示引起肿瘤的主要物质是糖相关物质，如糖蛋白或多糖。在定居在老虎河豚的鳃上后，h.o okamotoi oncomiracidia立即开始吸血，而它们几乎没有或根本没有能力吸收和/或消化来自草河豚、日本比目鱼或红鲷等非自然宿主的血液，并最终从它们身上脱落。采用体外实验方法，对从牙鲆体表上皮中提取的嗜酸乳杆菌沉降诱导物质进行了纯化。在0.2 ~ 0.3 m NaCl的阴离子交换树脂中溶解，经凝胶过滤，其分子量均在排除限以上。单系寄主特异性的表现包括寄主沉降后通过孵化幼虫识别寄主的能力、从寄主处吸收营养的能力、对寄主防御机制的耐受能力等。提示贝尼门和多蛇子叶单系动物在这些能力上有不同程度的差异，并且宿主特异性在不同的单系动物群体中表现为不同的因素。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