Abstract Bloodfeeding leeches have powerful anticoagulants that allow them to feed for extended periods. However, many leech species are predatory rather than bloodfeeding. It is not known whether they express these proteins and whether the proteins are co-opted for other purposes. Little is known about salivary secretions of the sister groups of leeches, where blood is not part of the diet. We screened the transcriptomes of four non-bloodfeeding leeches and four leech relatives to identify major lineages of anticoagulant genes, helping to determine their evolutionary origin and maintenance. We estimated selection regimes that are expected after a change in feeding behaviour. We found widespread presence of putative anticoagulants, although our results also indicate that several of these are members of multicopy gene families. Our analyses suggest that homologues to leech anticoagulants were already present before the origin of bloodfeeding in leeches and that negative selection is the major driver of evolutionary rates even in non-bloodfeeding taxa. These results point to the retention of the original function by these molecules in non-bloodfeeding species. Ultimately, the proteins might not be involved in bloodfeeding or it seems likely that their putative pleiotropic effects are of great importance.

中文翻译：

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水蛭抗凝剂是祖传的，可能是多功能的

摘要 吸血水蛭具有强大的抗凝剂，可以让它们长时间进食。然而，许多水蛭物种是掠食性的，而不是吸血的。目前尚不清楚它们是否表达这些蛋白质，以及这些蛋白质是否被用于其他目的。关于水蛭姐妹群的唾液分泌知之甚少，血液不是饮食的一部分。我们筛选了四种非吸血水蛭和四种水蛭亲属的转录组，以确定抗凝基因的主要谱系，帮助确定它们的进化起源和维持。我们估计了进食行为改变后预期的选择机制。我们发现普遍存在推定的抗凝剂，尽管我们的结果也表明其中一些是多拷贝基因家族的成员。我们的分析表明，水蛭抗凝剂的同系物在水蛭吸血起源之前就已经存在，即使在非吸血类群中，负选择也是进化速度的主要驱动力。这些结果表明这些分子在非吸血物种中保留了原始功能。最终，这些蛋白质可能不参与血液喂养，或者它们推定的多效性似乎非常重要。