Trematode larvae must generally invade a molluscan intermediate host, usually a gastropod, before they can reach reproductive maturity in another definitive host. The research literature to date has focused almost exclusively on the documented specificity between particular trematode species and particular molluscan hosts; little attention has been paid to gastropod species that do not appear to serve as hosts. We sampled Rhode Island and Massachusetts populations of the marine gastropod Crepidula fornicata to determine whether this widespread species serves as a first intermediate host for trematodes. We also sampled from the same habitat populations of Littorina littorea and Ilyanassa obsoleta, gastropods known to serve as first intermediate hosts for several trematode species. All individuals were examined by dissection for the presence of sporocysts, rediae, or developing cercariae. Although 4-28% of L. littorea (N=112) and I. obsoleta (N=84) were infected by larvae of at least one trematode species, no individuals of C. fornicata sampled from the same locations were so infected (N=136). A survey of the Biological Abstracts computer database indicates that snails in only about 10% of marine gastropod families are known to serve as first intermediate hosts for trematodes. We suggest that more attention be paid to marine gastropods that appear not to be infected by trematode miracidia. Such species may productively serve as new models for understanding trematode host specificity and gastropod resistance to infection.

中文翻译：

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Crepidula fornicata 不是吸虫的第一中间宿主：谁是？

吸虫幼虫通常必须侵入软体动物中间宿主，通常是腹足动物，然后才能在另一个终宿主中达到生殖成熟。迄今为止的研究文献几乎完全集中在特定吸虫物种和特定软体动物宿主之间记录的特异性；很少有人注意到似乎不作为宿主的腹足动物物种。我们对海洋腹足动物 Crepidula fornicata 的罗德岛和马萨诸塞州种群进行了采样，以确定这种分布广泛的物种是否作为吸虫的第一中间宿主。我们还从 Littorina littorea 和 Ilyanassa obsoleta 的相同栖息地种群中取样，这些腹足动物已知是几种吸虫物种的第一中间宿主。通过解剖检查所有个体是否存在孢子囊、尾蚴或发育中的尾蚴。尽管 4-28% 的 L. littorea (N=112) 和 I. obsoleta (N=84) 被至少一种吸虫种类的幼虫感染，但从同一地点采样的 C. fornicata 个体没有受到如此感染（N =136）。对 Biological Abstracts 计算机数据库的一项调查表明，已知只有约 10% 的海洋腹足动物科中的蜗牛是吸虫的第一中间宿主。我们建议更多地关注似乎没有被吸虫感染的海洋腹足类动物。这些物种可以有效地用作了解吸虫宿主特异性和腹足动物对感染的抵抗力的新模型。obsoleta (N=84) 被至少一种吸虫种类的幼虫感染，没有从同一地点采样的 C. fornicata 个体被感染 (N=136)。对 Biological Abstracts 计算机数据库的一项调查表明，已知只有约 10% 的海洋腹足动物科中的蜗牛是吸虫的第一中间宿主。我们建议更多地关注似乎没有被吸虫感染的海洋腹足类动物。这些物种可以有效地用作了解吸虫宿主特异性和腹足动物对感染的抵抗力的新模型。obsoleta (N=84) 被至少一种吸虫种类的幼虫感染，没有从同一地点采样的 C. fornicata 个体被感染 (N=136)。对 Biological Abstracts 计算机数据库的一项调查表明，已知只有约 10% 的海洋腹足动物科中的蜗牛是吸虫的第一中间宿主。我们建议更多地关注似乎没有被吸虫感染的海洋腹足类动物。这些物种可以有效地用作了解吸虫宿主特异性和腹足动物对感染的抵抗力的新模型。对 Biological Abstracts 计算机数据库的一项调查表明，已知只有约 10% 的海洋腹足动物科中的蜗牛是吸虫的第一中间宿主。我们建议更多地关注似乎没有被吸虫感染的海洋腹足类动物。这些物种可以有效地用作了解吸虫宿主特异性和腹足动物对感染的抵抗力的新模型。对 Biological Abstracts 计算机数据库的一项调查表明，已知只有约 10% 的海洋腹足动物科中的蜗牛是吸虫的第一中间宿主。我们建议更多地关注似乎没有被吸虫感染的海洋腹足类动物。这些物种可以有效地用作了解吸虫宿主特异性和腹足动物对感染的抵抗力的新模型。