Siddall Mark E, Brugler Mercer R, Kvist Sebastian
Sackler Institute for Comparative Genomics, and Division of Invertebrate Zoology, American Museum of Natural History, Central Park West at 79th Street, New York, New York 10024.
J Parasitol. 2016 Feb;102(1):143-50. doi: 10.1645/15-802. Epub 2015 Nov 4.
One of the recalcitrant questions regarding the evolutionary history of clitellate annelids involves the feeding preference of the common ancestor of extant rhynchobdellid (proboscis bearing) and arhynchobdellid (jaw bearing) leeches. Whereas early evidence, based on morphological data, pointed towards independent acquisitions of blood feeding in the 2 orders, molecular-based phylogenetic data suggest that the ancestor of modern leeches was a sanguivore. Here, we use a comparative transcriptomic approach in order to increase our understanding of the diversity of anticoagulation factors for 3 species of the genus Placobdella, for which comparative data have been lacking, and inspect these in light of archetypal anticoagulant data for both arhynchobdellid and other rhynchobdellid species. Notwithstanding the varying levels of host specificity displayed by the 3 different species of Placobdella, transcriptomic profiles with respect to anticoagulation factors were largely similar -this despite the fact that Placobdella kwetlumye only retains a single pair of salivary glands, as opposed to the 2 pairs more common in the genus. Results show that 9 different anticoagulant proteins and an additional 5 putative antihemostasis proteins are expressed in salivary secretions of the 3 species. In particular, an ortholog of the archetypal, single-copy, anticoagulant hirudin (not previously available as comparative data for rhynchobdellids) is present in at least 2 of 3 species examined, corroborating the notion of a single origin of blood feeding in the ancestral leech.
关于寡毛纲环节动物进化史的一个棘手问题涉及现存吻蛭目（有吻）和无吻蛭目（有颚）水蛭共同祖先的摄食偏好。早期基于形态学数据的证据表明这两个目独立演化出了吸血习性，而基于分子的系统发育数据则表明现代水蛭的祖先为吸血动物。在此，我们采用比较转录组学方法，以增进对三种蛭属物种抗凝因子多样性的理解，此前针对这三种物种缺乏比较数据，并结合无吻蛭目和其他吻蛭目物种的典型抗凝数据进行考察。尽管三种不同的蛭属物种表现出不同程度的宿主特异性，但它们在抗凝因子方面的转录组图谱大体相似——尽管克氏蛭仅保留了一对唾液腺，而该属中更常见的是两对唾液腺。结果显示，这三种物种的唾液分泌物中表达了9种不同的抗凝蛋白和另外5种假定的抗止血蛋白。特别是，典型的单拷贝抗凝蛋白水蛭素的一个直系同源物（此前没有作为吻蛭目的比较数据）在至少2种被检测的物种中存在，证实了吸血习性在水蛭祖先中单次起源的观点。
