Nereididae comprises a diverse group of marine worms and is one of the most studied families in Annelida. However, phylogenetic relationships within the group are still poorly understood. Previous studies, based on morphological data, have disagreed on the membership of recognized subfamilies and, current taxonomy lacks sufficient phylogenetic underpinning. This study uses complete mitochondrial genome and transcriptome data to evaluate relationships within Nereididae and test currently employed subfamilies. Ancestral state reconstructions were performed to evaluate if morphological traits found in the pharynx, that is papillae and paragnaths, correspond with phylogenetic relationships based on mitochondrial data. Our results suggest that Nereidinae and Gymnonereidinae, as currently recognized, are not monophyletic groups. In general, molecular results suggest that morphological features used in nereidid taxonomy need re-evaluation as they may be more evolutionary plastic than recognized. Ancestral state reconstruction suggests that papillae and paragnaths may have evolved early in the family and their presence, as currently employed in taxonomy, does not allow accurate diagnose of groups within Nereididae. In contrast, unique mitochondrial gene order defines at least one higherlevel clade within Nereididae.
K E Y W O R D Sgene order, Gymnonereidinae, mtDNA, Namanereidinae, Nereidinae, ragworm | 367 ALVES Et AL.
The subfamily Namanereidinae represents one of the few groups of Polychaeta strongly adapted to low salinity and freshwater. Recently, some new species of the subfamily have been described, but no new phylogenetic analyses for the group have been undertaken since 1999. Here, we describe a new species of Namanereidinae, Namalycastis caetensis sp. nov., and provide a morphology-based phylogenetic analysis of the genus Namalycastis with the aim of assessing the evolutionary relationships for this new species. The designation of this new species is supported by the presence of elongated falcigers (also known as pseudospinigers, an unusual character in the genus), lack of an anterior cleft in the prostomium, slightly indistinct cirrophores, four pairs of tentacular cirri, and subconical acicular ligulae. Our results suggest that Namalycastis caetensis is closely related to N. geayi and N. fauveli. The existence of poorly-characterized species, from a morphological and molecular point of view, still limits our understanding of Namanereidinae relationships.
The polychaete fauna from the mangroves of the Amazon Coast in Maranhão state, Brazil, is reported in this study. Fourteen species are listed, namely Alitta
succinea (Leuckart, 1847); Arabella (Arabella) iricolor Montagu, 1804; Capitella
capitata (Fabricius, 1780) complex; Exogone (Exogone) breviantennata Hartmann-Schröder, 1959; Heteromastus
filiformis (Claparède, 1864); Isolda
pulchella Müller, 1858; Mediomastus
californiensis Hartman, 1944; Namalycastis
fauveli Nageswara Rao, 1981; Namalycastis
geayi (Gravier, 1901); Namalycastis
senegalensis (Saint-Joseph, 1901); Nephtys
simoni Perkins, 1980; Paraonis
amazonica
sp. n.; Sigambra
bassi (Hartman, 1945); and Sigambra
grubii Müller, 1858. Among them, Namalycastis
fauveli and Namalycastis
geayi are recorded for the first time in Brazil. Paraonis
amazonica
sp. n. is a new species for science, characterized by a rounded prostomium, 4–8 pairs of foliaceous branchiae, absent eyes, and two types of modified neurochaetae, acicular and hook-shaped.
The Namanereidinae are one of the most successful polychaete groups to colonize subterranean waters. Many species have evolved adaptations to underground life including elongation of appendages and reduction of eyes and pigmentation. However, the use of these troglomorphic characters in the group’s systematics is contentious. The present study conducts a series of tree searching and phylogeny reconstructions to evaluate the influence of these characters in the phylogeny of the group. Results show that troglomorphic characters cause no serious errors in the phylogenetic reconstruction of Namanereidinae, and support the two existing genera, which can be unequivocally distinguished by non-troglomorphic traits. As a consequence of this phylogenetic hypothesis the following taxonomic changes are required: Lycastoides becomes a junior synonym of Namanereis, and its only species becomes a new combination, N. alticola n. comb. and Namalycastis occulta is moved to Namanereis becoming Namanereis occulta n. comb.
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