Proxies to detect hotspots of invertebrate biodiversity on rhodolith beds across the Southwestern Atlantic.

Rhodolith beds are known worldwide to host high biodiversity to several taxa. Despite their importance, few ecological data explored the influence of rhodolith features and environmental variables on associated biodiversity, a gap that has been hampering the mapping of diversity hotspots and priority areas for conservation. In this study, we investigated large-scale spatial variations of rhodolith beds and their associated fauna, using annelid polychaetes as a biological model. We aimed to identify proxies, based on rhodolith features and environmental variables, to detect biodiversity hotspots across Southwestern Atlantic beds, laying the groundwork for mapping priority areas for conservation. With this goal, we sampled a total of 136 rhodolith nodules across seven sites with beds under distinct latitudes, depths, distances from the mainland coast of Brazil, and rhodolith densities. For each nodule sampled, we measured the volume, diameter, and mass of sediment trapped, as well as the attributes of the associated polychaetes (abundance, richness, diversity, and composition). Our results revealed a complex network of collinearities and synergisms between the rhodolith features and the majority of the polychaetes attributes (i.e., abundance, diversity, and composition). Polychaete richness, in contrast, can be explained by the combination of two proxies: (1) rhodolith nodule diameter and (2) distance of the rhodolith bed from the mainland coast. Nearshore rhodolith beds and larger nodules were associated with higher values of richness. Additionally, rhodoliths with a hollow morphology were also associated with higher values of polychaete richness. These results suggest that nearshore rhodolith beds with large and hollow nodules could be priority areas for conservation. However, further multi-taxa studies using our framework are still needed to explore other regions and scales, delineating more comprehensive proxies for predicting ecological patterns of the rhodoliths associated fauna and to identify priorities for conservation across Southwestern Atlantic beds.

Palatability and Physical and Chemical Defenses in Five Annelid Polychaetes from Tropical Brazilian Beaches.

AbstractAlthough researchers have examined numerous marine organisms' compensatory characteristics to minimize predation pressure, few have investigated the defensive mechanisms of polychaetes, despite their diversity. Thus, our study's aim was to evaluate the palatability and defensive strategies, both chemical and structural, in the polychaetes Branchiomma luctuosum, Perinereis anderssoni, Phragmatopoma caudata, Eurythoe complanata, and Timarete sp. Another twofold aim was to determine, by comparing our results with the literature, any latitudinal difference in the defensive strategies of E. complanata and to assess defensive mechanisms and palatability in relation to individuals' mobility, overtness, body regionalization, and color. Specimens were collected at Boa Viagem and Itaipu Beaches in Niterói, Rio de Janeiro, Brazil. In assays, a generalist consumer, the hermit crab Calcinus tibicen, was used to evaluate palatability and defenses. In palatability assays of live tissue of the polychaetes, consumers were offered a fresh piece of each polychaete to gauge their acceptance or rejection; in artificial food assays to test extracts of the polychaetes, artificial bait containing extracts of the polychaetes was offered to crabs to identify any chemical defense. Although the extracts of B. luctuosum, E. complanata, P. caudata (i.e., opercular crown), and Timarete sp. were not palatable to the consumers, extracts of P. anderssoni and P. caudata (i.e., body) were. Moreover, the opercular crown of P. caudata and the branchial crown of B. luctuosum showed evidence of structural and chemical defenses. The results corroborate past findings, suggesting no latitudinal variation in the defensive strategies of E. complanata. In general, less motile and more exposed species, aposematic or dark in color, exhibited greater investment in defensive strategies and unpalatability.

A Review of "Polychaeta" Chemicals and their Possible Ecological Role.

Despite the many publications concerning the isolation of substances and the many reviews of marine natural products, some groups of organisms remain poorly studied, including "Polychaeta". In response, this review covers articles published through December 2016 that address marine natural products produced from polychaetes, with a focus on antipredatory strategies, competitors, fouling, and pathogens. A total of 121 compounds were isolated from 1934 to 2016, which includes halogenated aromatics, proteins, amino acids and Lumazine derivatives most notably-with a defensive function were found in the literature, most frequently in the families Sabellidae, Terebellidae, Glyceridae, and Nereididae. The period of highest discovery of natural products in defensive actions for the group was the 2000s. Polychaetes were addressed in 26 revisions of the total 51 articles analyzed and are less reported than other marine invertebrates such as sponges, cnidarians, mollusks, and tunicates. In sum, the present review provides a basis for future research on the marine chemical ecology of polychaetes.

On the use of troglomorphic characters in Namanereidinae (Annelida; Nereididae) systematics.

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.

A new species of Pisionidens (Aiyar & Alikunhi, 1943) (Annelida: Sigalionidae) from Southeastern Brazil.

Herein we describe specimens found along the southeastern coast of Brazil which belong to a new species, P. caissara sp. nov. This species differs from the other species of the genus by the glabrous antennae and palps, proboscis extending up to the sixth segment, jaws with smooth cutting edge and a pair of lateral wing-like sheaths, two pairs of seriate male copulatory organs, first pair of testes on segment 19 and ovaries from segment 26 onward. Reproductive characters commonly used for characterizing species are also discussed.

Orbinia (Polychaeta: Orbiniidae) from the Brazilian coast: two new species and two new records.

Representatives of the Family Orbiniidae are very common in marine sediments and are found in both shallow and deep waters. Currently, 26 species and 10 genera have been recorded along the Brazilian coast. The specimens examined in this study were collected at depths ranging from 25 to 400 m in the Campos Basin (20-24ºS; 39-42ºW), Rio de Janeiro, in the summer and winter of 2008 and 2009. We describe two new species, Orbinia sagitta n. sp. and Orbinia camposiensis n. sp., and record the occurrences of Orbinia johnsoni (Moore, 1909), which was originally described in California, and Orbinia oligopapillata (López, Cladera & San Martin, 2006), which was previously described from the Pacific coasts of Panama. We provide a key for all the species of Orbinia recorded in the Campos Basin.

Description of a new species of Namalycastis (Annelida: Nereididae: Namanereidinae) from the Brazilian coast with a phylogeny of the genus.

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.

Three new species of Diplocirrus Haase, 1915 (Polychaeta: Flabelligeridae) from Campos Basin in SE Brazil.

Currently, 16 species of Flabelligeridae have been recorded in Brazil, four in the genus Diplocirrus: D. glaucus Malmgren, 1867 from Ubatuba, D. capensis Day, 1961 from Santos (São Paulo State) and Diplocirrus sp. from off north of Rio de Janeiro. Diplocirrus glaucus australis Nonato, 1981 is considered a nomen nudum. In the present study, three new species are described: Diplocirrus rugosus sp. nov., Diplocirrus salazarvallejoi sp. nov. and Diplocirrus acafi sp. nov., all collected from soft bottoms off southeast Brazil. A key to all Diplocirrus species is provided.