Tessler Michael, Marancik David, Champagne Donald, Dove Alistair, Camus Alvin, Siddall Mark E, Kvist Sebastian
1 Richard Gilder Graduate School, American Museum of Natural History, Central Park West at 79th Street, New York, New York 10024.
2 Sackler Institute for Comparative Genomics, American Museum of Natural History, Central Park West at 79th Street, New York, New York 10024.
J Parasitol. 2018 Jun;104(3):210-220. doi: 10.1645/17-64. Epub 2018 Mar 16.
Leeches (Annelida: Hirudinea) possess powerful salivary anticoagulants and, accordingly, are frequently employed in modern, authoritative medicine. Members of the almost exclusively marine family Piscicolidae account for 20% of leech species diversity, and they feed on host groups (e.g., sharks) not encountered by their freshwater and terrestrial counterparts. Moreover, some species of Ozobranchidae feed on endangered marine turtles and have been implicated as potential vectors for the tumor-associated turtle herpesvirus. In spite of their ecological importance and unique host associations, there is a distinct paucity of data regarding the salivary transcriptomes of either of these families. Using next-generation sequencing, we profiled transcribed, putative anticoagulants and other salivary bioactive compounds that have previously been linked to blood feeding from 7 piscicolid species (3 elasmobranch feeders; 4 non-cartilaginous fish feeders) and 1 ozobranchid species (2 samples). In total, 149 putative anticoagulants and bioactive loci were discovered in varying constellations throughout the different samples. The putative anticoagulants showed a broad spectrum of described antagonistic pathways, such as inhibition of factor Xa and platelet aggregation, which likely have similar bioactive roles in marine fish and turtles. A transcript with homology to ohanin, originally isolated from king cobras, was found in Cystobranchus vividus but is otherwise unknown from leeches. Estimation of selection pressures for the putative anticoagulants recovered evidence for both positive and purifying selection along several isolated branches in the gene trees, and positive selection was also estimated for a few select codons in a variety of marine species. Similarly, phylogenetic analyses of the amino acid sequences for several anticoagulants indicated divergent evolution.
水蛭（环节动物门：蛭纲）拥有强大的唾液抗凝剂，因此，它们经常被应用于现代权威医学中。几乎完全生活在海洋中的鱼蛭科成员占水蛭物种多样性的20%，它们以淡水和陆生水蛭所未遇到的宿主群体（如鲨鱼）为食。此外，某些舌蛭科物种以濒危海龟为食，并被认为是肿瘤相关海龟疱疹病毒的潜在传播媒介。尽管它们具有生态重要性和独特的宿主关联，但关于这两个科中任何一科的唾液转录组的数据都明显匮乏。我们使用下一代测序技术，对转录的、假定的抗凝剂和其他唾液生物活性化合物进行了分析，这些化合物先前已与7种鱼蛭科物种（3种以软骨鱼为食；4种以非软骨鱼为食）和1种舌蛭科物种（2个样本）的吸血行为相关联。在不同样本中，总共发现了149个假定的抗凝剂和生物活性位点。这些假定的抗凝剂显示出广泛描述的拮抗途径，如对Xa因子的抑制和血小板聚集，它们在海洋鱼类和海龟中可能具有类似的生物活性作用。在鲜艳囊蛭中发现了一种与最初从眼镜王蛇中分离出的ohanin具有同源性的转录本，但在水蛭中其他地方尚未发现。对假定抗凝剂的选择压力估计在基因树的几个孤立分支上恢复了正选择和纯化选择的证据，并且在各种海洋物种的一些选定密码子上也估计有正选择。同样，对几种抗凝剂的氨基酸序列进行的系统发育分析表明存在趋异进化。
