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Phylogeny of the family Eunicidae (polychaete, Annelida) based on molecular and morphological data Open Access

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The bristle worm family Eunicidae (~326 spp. and 9 genera) is distributed worldwide, but most commonly in shallow tropical waters. Its monophyly is controversial and it has no apomorphic morphological features as traditionally recognized. Nevertheless, eunicid anterior end is characteristic and distinct from the other families in the order Eunicida. This inability to define clear characters is due to inconsistent hypotheses of homology between the different parts of the anterior end in the order Eunicida and poor understanding of morphological variability in the family Eunicidae. We used immunostaining and confocal Laser Scanning Microscope to examine the anterior nervous system of five families of Eunicida, thus improving information about morphological and innervation similarities and hypotheses of homology among features such as buccal lips, pharyngeal fold, dorsolateral fold and anterior extension of the dorsolateral fold of these families. Light microscopy and SEM examination of characters along the body further improved our knowledge of traditional characters and of their variation. These new approaches of morphological analysis improved character definition, increased the number of morphological characters and improved the morphological phylogenetic signal. Furthermore, 16S, COI and 18S nucleotide sequences added phylogenetically informative data at all levels of the tree, essential in recovering more stable and better supported relationships. Eunicidae is monophyletic, supported by at least two unique synapomorphies (dorsal buccal lip fused to the dorsal side of the prostomium and the anterior extensions of the dorsolateral fold medially connected) with Onuphidae as its sister group. Eunice sensu lato is polyphyletic. However, Eunice sensu stricto cannot be defined. The genera Leodice and Nicidion are resurrected. Nematonereis is included in Lysidice, making the latter monophyletic. Marphysa is emended to include only the species in the Marphysa sensu stricto clade, including Nauphanta mossambica. Nauphanta is valid but it has no diagnostic features at this point. Aciculomarphysa, Euniphysa, Fauchaldius, and Palola are valid genera and no changes are made to their traditional diagnostic characters. The integrative approach including different method of analyses of the morphology and molecular data, used here was essential to produce well resolved relationships and to identify morphological apomorphies used to redefine monophyletic taxa.

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