João Miguel DE Matos Nogueira

During an oceanographic campaign led by the Museum National d’Histoire Naturelle and the Institut de Recherche pour le Développement to explore the biodiversity of Walters Shoal Seamount in the Indian Ocean, a new species of Morgana was discovered. Until now, this genus was monotypic with the only known species described from shallow waters off São Paulo, south-eastern Brazil: M. bisetosa Nogueira & Amaral, 2001. This new deep-sea species, M. waltershoalensis sp. nov., is characterised by the absence of branchiae, the notopodia beginning from segment 4 and the neuropodia from the 6th, a great number of segments with notopodia ( n = 53), and the presence of a pair of large nephridial papillae dorsally, on segment 3. This species differs from M. bisetosa by the absence of eyespots, the shape of both noto- and neurochaetae and by the presence of a large pair nephridial papillae on the third segment. Following this study, the boundaries of the genus have been modified, particularly with regard to the number of segments with notopodia, the presence of eyespots and the large papilla on segment 3.

Members of the genus Acromegalomma Gil & Nishi, 2017, of family Sabellidae, are characterized by the presence of subdistal compound eyes on the radioles. To date, 38 valid species of this genus have been recognized worldwide, including four species previously recorded in Brazil. In this study, we reviewed some of these records and identified four species new to science: A. josei sp. nov., A. omenae sp. nov., A. punctum sp. nov. and A. scutolenis sp. nov. These findings are based on material from various independent expeditions, conducted between 1999 and 2023, along the Brazilian coast. A discussion on the key diagnostic features of members of these species and a comparative table of the morphological characters are provided, together with their formal descriptions and comparisons with the most morphologically similar congeners. Finally, a key for the identification of members of all species of Acromegalomma described from the Atlantic Ocean and South America is provided.

Syllidae is one of the largest families of polychaete annelids, with more than 1,100 described species, comprehending relatively small-bodied, errant animals. Among these, specimens of Exogone can be relatively common in certain areas and substrates, figuring as an important component of the fauna in many locations. In Brazil, 13 species of this genus have been reported, but in some cases with records difficult to confirm/reject. Herein we present an overview of the known diversity of the genus for the country, with additional four new occurrences for the Brazilian coast that were previously only registered in the 'grey literature', and an identification key to the species currently identified along the Brazilian coast; also, we bring the description of Exogone paulolanai sp. nov., raising to 18 the number of Exogone species for the country.

This paper is the conclusion of the “Spaghetti Project” aiming to revise French species of Terebellidae sensu lato (s.l.) belonging to the five families: Polycirridae, Telothelepodidae, Terebellidae sensu stricto (s.s.), Thelepodidae and Trichobranchidae. During this project, 41 species were observed, 31 of them new for science: eight species of Polycirridae, eleven species of Terebellidae s.s., three species of Thelepodidae and nine species of Trichobranchidae. We provide a comprehensive key for all European species of terebellids with a focus on the important diagnostic characters for each family. Finally, we discuss issues on taxonomy, biodiversity and cryptic and pseudo-cryptic species of polychaetes in European waters, based on results obtained during this project.

We report herein three epibiotic associations between peritrich ciliate protozoans and polychaete worms, as observed in Tamilnadu, southeastern coast of India. Epibiont ciliates Epistylis sp.1 were found all over the integument of individuals of the terebellid polychaete Terebella sp., collected from Vellar estuary. Epistylis sp.2 ciliates were observed attached to Namalycastis abiuma polychaetes, on both sides of parapodia. Cothurnia sp. ciliates were found on anterior most paleae and hooks of Sabellaria sp. polychaetes, both latter associations from material from the Uppanar estuary. Those epibiont/basibiont associations are all new to science and discussed herein, together with a review on the previous reports of epibiont ciliate protozoans in Indian waters.

[This corrects the article DOI: 10.1371/journal.pone.0250472.].

Sabellida Levinsen, 1883 is a large morphologically uniform group of sedentary annelids commonly known as fanworms. These annelids live in tubes made either of calcareous carbonate or mucus with agglutinated sediment. They share the presence of an anterior crown consisting of radioles and the division of the body into thorax and abdomen marked by a chaetal and fecal groove inversion. This study synthesises the current state of knowledge about the diversity of fanworms in the broad sense (morphological, ecological, species richness), the species occurrences in the different biogeographic regions, highlights latest surveys, provides guidelines for identification of members of each group, and describe novel methodologies for species delimitation. As some members of this group are well-known introduced pests, we address information about these species and their current invasive status. In addition, an overview of the current evolutionary hypothesis and history of the classification of members of Sabellida is presented. The main aim of this review is to highlight the knowledge gaps to stimulate research in those directions.

Terebelliformia comprises a large group of sedentary polychaetes which live from the intertidal to the deep sea. The majority live in tubes and are selective deposit feeders. This study synthesises the current knowledge of this group, including their distribution, in the different biogeographic regions. We highlight the new methodologies being used to describe them and the resolution of species complexes occurring in the group. The main aim of this review is to highlight the knowledge gaps and to stimulate research in those directions, which will allow for knowledge of their distribution and abundances to be used by ecologists and managers.

Polycirrus changbunker sp. nov. is herein described, from specimens collected off the states of Paraná (type locality, southern Brazil), São Paulo (southeastern Brazil), and Pernambuco and Paraíba (northeastern Brazil). Members of Polycirrus changbunker sp. nov. present 31–43 pairs of notopodia, bearing pinnate and narrowly-winged chaetae, neuropodia beginning on segment 9, bearing type 1 uncini sensu Glasby & Glasby (2006) throughout, paired ventro-lateral glandular pads on segments 3–13, and nephridial and genital papillae on segments 3–8. A full description for members of Polycirrus changbunker sp. nov. is herein provided, together with a comparison with the individuals of the most similar congener species.

Two of the species of Pectinariidae previously reported from the Brazilian coast are herein described, together with a new species and also new record for the genus Petta Malmgren, 1866 for the southern Atlantic. Amphictene catharinensis (Grube, 1870) was described from material from off Santa Catarina, southern Brazil, but the most recent description for these animals comes from Nilsson (1928); a redescription for A. catharinensis is herein provided. Pectinaria nonatoi n. sp. was informally described as P. (Pectinaria) laelia nomen nudum in an unpublished thesis and a formal description has never been provided, although the species has been reported from several other localities off the Brazilian shoreline, mostly in ecological studies; the species is formally described herein and compared to the most similar congeners. Petta alissoni n. sp. is also described and compared to the most similar congeners and this is the first record for animals of this genus from southern Atlantic. There are also records for Pectinaria gouldii (Verrill, 1874) and P. regalis Verrill, 1901 from off the Brazilian coast, and a doubtful record for Lagis pseudokoreni (Day, 1955), but we did not find any material belonging to those taxa.