RESUMO
Nereidid polychaetes are well known from shallow marine habitats, but their diversity in the deep sea is poorly known. Here we describe an unusual new nereidid species found at methane seeps off the Pacific coast of Costa Rica. Specimens of Pectinereis strickrotti gen. nov., sp. nov. had been observed dating back to 2009 swimming just above the seafloor at ~1,000 m depth but were not successfully captured until 2018. Male epitokes were collected as well as a fragment of an infaunal female found in a pushcore sample. The specimens were all confirmed as the same species based on mitochondrial COI. Phylogenetic analyses, including one based on available whole mitochondrial genomes for nereidids, revealed no close relative, allowing for the placement of the new species in its own genus within the subfamily Nereidinae. This was supported by the unusual non-reproductive and epitokous morphology, including parapodial cirrostyles as pectinate gills, hooked aciculae, elfin-shoe-shaped ventral cirrophores, and elongate, fusiform dorsal ligules emerging sub-medially to enlarged cirrophores. Additionally, the gill-bearing subfamily Dendronereidinae, generally regarded as a junior synonym of Gymnonereidinae, is reviewed and it is here reinstated and as a monogeneric taxon.
Assuntos
Anelídeos , Apocynaceae , Poliquetos , Feminino , Masculino , Animais , Brânquias , Filogenia , Poliquetos/genéticaRESUMO
Alitta virens species complex encompasses elongate nereidids appreciated commercially both in the fishing and aquaculture industries. This complex has been well studied in biological and ecological terms. Nevertheless, detailed taxonomic analyses have scarcely been addressed, to the extent that only a few species in the complex have been recognized as valid but with some difficulties: Alitta brandti Malmgren, 1865 (Sea of Okhotsk), A. grandis (Stimpson, 1853) (northeastern USA) and A. virens (Sars, 1835) (Norway). Whereas, other several species have typically been regarded as synonyms, including those originally described from the North Pacific Ocean: Nereis (Alitta) virens plenidentata Moore, 1909 (California, USA), Nereis dyamusi Izuka, 1912 (Japan) and Nereis foliata Baird, 1863 (Vancouver, Canada). In this study, an examination of the immature and epitoke type and non-type material available for the A. virens species complex from the North Pacific was carried out. Herein, the status of A. brandti as a valid species is reinforced being clearly distinct from A. virens and related species. Alitta dyamusi n. comb., A. plenidentata n. comb. and A. williami nom. nov. are reinstated and transferred to Alitta, the specific epithet of the latter species is a replacement name for Nereis foliata Baird, 1863, which is a junior, primary homonym of Nereis foliata Dalyell, 1853. Lectotypes for A. plenidentata n. comb. and A. williami nom. nov. are designated. The North Pacific species of the A. virens complex, excluding A. plenidentata n. comb. which has several distinctive features that differ from all the Alitta species, are characterized by having homogomph spinigers in both supracicular and subacicular neurochaetae, oral ring with a larger number of rows and paragnaths, and epitoke males with unmetamorphosed pygidium and epitoke-modified chaetae in both neuropodial fascicles. The morphology of epitoke females in the A. virens complex is described for the first time. Identification keys to atoke and epitoke species of this complex are also provided.
Assuntos
Anelídeos , Poliquetos , Animais , California , Canadá , Feminino , Japão , Masculino , Noruega , Oceano PacíficoRESUMO
The nereidid worm Alitta succinea (Leuckart, 1847), described from Western Germany, has been considered by some authors as a widespread and alien invasive species, or else as a group of morphologically indistinguishable species. Neither idea has yet been supported by critical taxonomic revisions of relevant material. Most characterizations of A. succinea were based upon a mixture of morphological features from specimens from the type locality and from other regions. Moreover, four species described from America are considered junior synonyms of A. succinea, including Nereis acutifolia Ehlers, 1901, described from the eastern tropical Pacific. The type material of the latter species has not been reviewed since its description. We re-examined type and topotype materials of A. succinea and N. acutifolia including atokous and epitokous specimens. In addition, newly collected specimens were used to evaluate genetic divergence between both species using the mitochondrial gene COI. Alitta succinea is redescribed from type material and specimens from Germany. We rejected the recent placement of the species in Neanthes and we transferred it to Alitta. Further, we refuse the synonymy of N. acutifolia with A. succinea due to morphological and molecular differences. Consequently, we regard Alitta acutifolia n. comb. as a valid species, and the supposed introduction and the alien status of A. succinea along the Mexican and Central American Pacific shores are rejected.