PDF(Pubmed)
Abstract：
We show that the globally invasive, human-infectious flatworm, Haplorchis pumilio, possesses the most physically specialized soldier caste yet documented in trematodes. Soldiers occur in colonies infecting the first intermediate host, the freshwater snail Melanoides tuberculata, and are readily distinguishable from immature and mature reproductive worms. Soldiers possess a pharynx five times absolutely larger than those of immature and mature reproductives, lack a germinal mass, and have a different developmental trajectory than reproductives, indicating that H. pumilio soldiers constitute a reproductively sterile physical caste. Neither immature nor mature reproductives showed aggression in in vitro trials, but soldiers readily attacked heterospecific trematodes that coinfect their host. Ecologically, we calculate that H. pumilio caused ~94% of the competitive deaths in the guild of trematodes infecting its host snail in its invasive range in southern California. Despite being a dominant competitor, H. pumilio soldiers did not attack conspecifics from other colonies. All prior reports documenting division of labor and a trematode soldier caste have involved soldiers that may be able to metamorphose to the reproductive stage and have been from nonhuman-infectious marine species; this study provides clear evidence for an obligately sterile trematode soldier, while extending the phenomenon of a trematode soldier caste to freshwater and to an invasive species of global public health concern.
摘要：
我们证明了全球入侵，人类感染的扁虫，Haplorchispumilio,拥有迄今为止在吸虫中记录的最专业的士兵种姓。士兵出现在感染第一个中间宿主的菌落中，淡水蜗牛Melanoidestuberculata,很容易区别于未成熟和成熟的生殖蠕虫。士兵的咽部绝对比未成熟和成熟的生殖者大五倍，缺乏生发团，并且具有与繁殖体不同的发育轨迹，表明H.pumilio士兵构成了生殖不育的身体种姓。在体外试验中，未成熟和成熟的生殖都没有表现出攻击性，但是士兵们很容易攻击共感染宿主的异源吸虫。生态学上,我们计算出，H.pumilio在吸虫行会中引起了约94％的竞争性死亡，这些感染在南加州的入侵范围内感染了其宿主蜗牛。尽管是一个主要的竞争对手，H.pumilio士兵没有攻击其他殖民地的物种。以前所有记录劳动分工和吸虫士兵种姓的报告都涉及可能变质到生殖阶段的士兵，并且来自非人类感染的海洋物种；这项研究为一个完全不育的吸虫士兵提供了明确的证据，同时将吸虫士兵种姓的现象扩展到淡水和全球公共卫生关注的入侵物种。
