Martínez Alejandro, Di Domenico Maikon, Rouse Greg W, Worsaae Katrine
Marine Biology Section, University of Copenhagen, Strandpromenaden 5, 3000, Helsingør, Denmark.
Biological Institute, University of Campinas (UNICAMP), Zoological Museum "Prof. Dr. Adão José Cardoso", Biological Institute, University of Campinas (UNICAMP), R Charles Darwin s/n, Bloco N, P.O. Box 6109 13083-863, Campinas, SP, Brazil.
Cladistics. 2015 Jun;31(3):250-276. doi: 10.1111/cla.12089. Epub 2014 Jul 16.
Protodrilidae is a group of small, superficially simple-looking annelids, lacking chaetae and appendages, except for two prostomial palps. Originally considered to be one of the primitive "archiannelid" families, its affinity within Annelida is still highly debated. Protodrilids are found worldwide in the interstices of intertidal and subtidal marine sediments. Despite their simple appearance they constitute one of the most species-rich interstitial families, with 36 described species in two genera, Protodrilus and the gutless Astomus. Here we present the first phylogenetic study of Protodrilidae employing five gene fragments, 55 morphological characters and 73 terminals (including seven outgroups) analysed under direct optimization and parsimony as well as model-based methods. The large data set includes all 36 described species of Protodrilidae (17 of which are represented only by the morphological partition) as well as 30 undescribed or uncertain species (represented by both morphology and molecules). This comprehensive, inclusive and combined analysis revealed a new perspective on the phylogeny of Protodrilidae: the family is shown to contain six cosmopolitan subclades, each supported by several morphological apomorphies, and with the genus Astomus consistently nested among the other five clades rather than next to these. Consequently, the diagnosis of Protodrilus is emended, Astomus remains unchanged and the four remaining lineages are diagnosed and named Megadrilus n. gen, Meiodrilus gen. nov., Claudrilus n. gen and Lindrilus gen. nov. Character transformations showed that large size and presence of pigmentation, oviducts and eyes are plesiomorphies of the family, retained in Protodrilus, Megadrilus gen. nov. and Lindrilus gen. nov. These features are secondarily lost in the gutless Astomus with epidermal uptake of nutrients, as well as in Meiodrilus gen. nov. and some species of Claudrilus n. gen, with smaller size correlated to life in interstices of finer sediments.
原钻蚓科是一类小型的环节动物，外观看似简单，除了两个口前触须外，没有刚毛和附肢。原钻蚓科最初被认为是原始的“古环节动物”家族之一，其在环节动物门中的亲缘关系仍存在激烈争议。原钻蚓在全球潮间带和潮下带海洋沉积物的间隙中均有发现。尽管它们外观简单，但却是物种最为丰富的间隙动物家族之一，在原钻蚓属和无肠的无口蚓属这两个属中，已描述的物种有36种。在此，我们首次对原钻蚓科进行系统发育研究，采用了五个基因片段、55个形态学特征以及73个分类单元（包括七个外类群），并运用直接优化、简约法以及基于模型的方法进行分析。这个庞大的数据集涵盖了原钻蚓科所有36个已描述的物种（其中17个仅由形态学部分代表）以及30个未描述或不确定的物种（由形态学和分子数据共同代表）。这种全面、包容且综合的分析揭示了原钻蚓科系统发育的新视角：该科包含六个世界性的亚分支，每个亚分支都有几个形态学上的近裔性状支持，并且无口蚓属始终嵌套在其他五个分支之中，而非与它们相邻。因此，原钻蚓属的诊断得以修订，无口蚓属保持不变，其余四个谱系被诊断并命名为巨钻蚓属（Megadrilus）、小钻蚓属（Meiodrilus）、克劳德钻蚓属（Claudrilus）和林德钻蚓属（Lindrilus）。性状转变表明，体型较大、存在色素沉着、输卵管和眼睛是该科的祖征，在原钻蚓属、巨钻蚓属和林德钻蚓属中得以保留。这些特征在通过表皮吸收营养的无肠的无口蚓属中，以及在小钻蚓属和克劳德钻蚓属的一些物种中次生丢失，这些物种体型较小，与生活在更细沉积物的间隙中有关。
