This study evaluated the feeding habits of the franciscana dolphin (Pontoporia blainvillei) in south-eastern Brazil. Stomach contents were collected from a total of 145 dead specimens found incidentally caught by fishing vessels or stranded between 2005 and 2015. Fish otoliths, cephalopod beaks and whole non-digested prey were used for prey species identification. A total of 9337 prey items were identified, including 26 species of teleost fishes and three species of cephalopods. The most important prey families were Sciaenidae among fish and Loliginidae among cephalopods. Franciscana dolphins tended to feed on small fish (mean = 5.25 cm) and cephalopods (mean = 8.57 cm). The index of relative importance (IRI) showed that Pellona harroweri and Doryteuthis plei were the most important prey for both males and females. The PERMANOVA test confirmed that there is no significant difference between the feeding habits of different sexes, but detected a significant difference among seasons. Overall, our results show that franciscana dolphins are predominantly ichthyophagous and non-selective in relation to the type of prey, feeding on pelagic, demersal and pelagic-demersal prey.

The stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) and total mercury concentrations (THg) of the three marine catfish species Aspistor luniscutis, Bagre bagre and Genidens genidens were evaluated to understand their trophic relationship in northern Rio de Janeiro state, south-eastern Brazil. The δ13C was similar among the three marine catfishes, whereas δ15N was similar in A. luniscutis and B. bagre and lower in G. genidens. THg was higher in G. genidens and lower in B. bagre. The greater assimilation of Sciaenidae fishes and squids by A. luniscutis and B. bagre resulted in smaller isotopic niche areas and trophic diversity but higher isotopic niche overlap, trophic redundancy and evenness. For G. genidens, the similar assimilation of all prey items resulted in the broadest isotopic niche among the marine catfishes. The higher mercury content in G. genidens is consistent with an increased important contribution of prey with a higher Hg burden. The bioaccumulation process was indicated by significant correlations of δ15N and THg with total length and total mass. Additionally, a significant correlation between THg and δ15N reflected the biomagnification process through the food web.

Stomach contents analysis and stable isotope results indicate M. hubbsi is a generalist predator that feeds mainly on demersal fishes, followed by crustaceans and cephalopods. Ontogenetic changes in diet were identified, with fish importance increasing in the diet with hake size. Smaller hake (<250 mm) fed mostly on the sepiolid Semirossia tenera (89.45%IRI) and engraulid fish (89.96%IRI). Mid-sized hake (250–300 mm) fed mainly on benthic fish such as Bellator brachychir (95.63%IRI) and euphausiids (56.46%IRI), while larger hake (>300 mm) fed heavily on Dactylopterus volitans (94.80%IRI) and occasionally on a variety of teleosts. Significant correlations between δ13C (P < 0.05), THg (P < 0.001) and hake size occurred, whereas no relationship was observed between δ15N and hake size or δ15N and total mercury. Signatures were lowest in smaller hake with a tendency of increasing with size. Smaller and larger hake were significantly different in δ13C. Differences regarding isotopic niche width were quantified for each size group; trophic diversity and trophic redundancy among them were negligible, but hake >300 mm possibly have a larger feeding plasticity due to the combination of prey from a wide trophic level range.

Edwardsiidae is one of the most speciose families within order Actiniaria with ~75 valid species of burrowing sea anemones. Five edwardsiids have been recorded in South Atlantic waters with only two species known for Brazil: Nematostella vectensis and Edwardsia migottoi. Such low diversity is probably the result of a historical small number of specialists in the region combined with difficulties in collecting and identifying these small burrowing animals. Although edwardsiids have been reported from Brazil since at least the 1960s, these reports did not include proper descriptions or specific identification, making comparison to other valid species impossible. Here we describe a new genus, Isoscolanthus gen. nov., and two new species: Isoscolanthus iemanjae sp. nov., Isoscolanthus janainae sp. nov. and we also describe Scolanthus crypticus sp. nov., the first species of the genus for Brazil. Isoscolanthus gen. nov. is easily distinguished from other edwardsiid genera by a combination of external (i.e. presence of periderm and nemathybomes in proximal end and 12 tentacles), microanatomical (i.e. four microcnemes) and cnidom features (i.e. pterotrichs in nemathybomes). In addition to the description of the new genus and species, we expand the range distribution of Nematostella vectensis and Edwardsia migottoi in the South-western Atlantic. The number of edwardsiids known from Brazil is raised from two to five species, substantially increasing the diversity of soft-bottom sea anemones for South Atlantic waters.

Thyone and Havelockia are worldwide-distributed genera represented in the Western Atlantic by eight and three species, respectively. In this paper, we describe two new shallow-water species from the Brazilian coast: Thyone waltinhoi sp. nov. and Havelockia oraneae sp. nov. These genera are very similar morphologically but the presence of subdivisions in their calcareous rings separates them into different families, Thyone in Phyllophoridae and Havelockia in Sclerodactylidae. To observe the presence of subdivisions, we submerged the calcareous rings in an iodine solution prior to morphological analyses. Thyone waltinhoi sp. nov. differs from its Western Atlantic congeners in its dermal ossicles and Havelockia oraneae sp. nov. differs from its South-western Atlantic congeners in the composition of its introvert ossicles. In addition to species descriptions, illustrations and morphological diagnoses of both genera are provided, along with a synoptic table of their Western Atlantic species, and a discussion of the taxonomic significance of the dermal ossicles and the calcareous ring.

Estuarine chaetognath population dynamics are poorly known worldwide. We have conducted eight seasonal campaigns (October 2007–August 2008) sampling three sectors in the subtropical Babitonga Bay estuary (26°S 48°W) in order to depict chaetognath abundance and population structure dynamics and test the influence of hydrography and food availability and type. Of three species sampled, Parasagitta friderici represented >93% of abundance in all samples and was examined in detail. There were no differences in P. friderici abundance between the sectors of the estuary, related to its high tolerance to low salinity, a feature not common for most chaetognath species. Salinity tolerance is an important adaptive characteristic to thrive within estuarine systems, and probably is responsible for the dominance of P. friderici in coastal and brackish water environments throughout most of its distribution. Juveniles dominated the population most of the year, except in February–April when abundances were lower and adults predominated. These results suggest that recruitment occurs continuously throughout the year, being more intense between October and January (spring to early summer) and in May (autumn) when densities and proportion of juveniles were higher. General Additive Models suggest that temperature and zooplankton biomass are significant (P < 0.05) factors influencing juvenile abundance while only the latter influenced the adults. We conclude that food availability is the most important driver in the studied population of P. friderici and recruitment peaks, which lead to high densities, seem to occur following peaks of their copepod prey along with particular temperature conditions (22–23°C).

Sponges interact in various ways with a wide variety of organisms in benthic communities and ecological interactions may influence the distribution, abundance and diversity of these organisms in different sites. Although several studies have already been developed for Demospongiae, knowledge of ecological interactions in the class Calcarea is lacking. Some calcareous sponges are considered weak competitors for space and to have developed strategies to survive in highly dynamic environments, such as exploitation of micro refuges and epibiosis. We aimed to investigate the influence of intra- and interspecific interactions in the abundance, growth and lifespan of the calcareous sponge Clathrina aurea in south-eastern Brazil. Two peaks of abundance and area coverage were observed during the studied year, probably associated with reproductive effort. We found no evidence of intra- or interspecific competition between the sponge and the benthic community. Clathrina aurea was found using parts of other organisms as substrate (epibiosis), such as algae, demosponges and corals. It was seen that the interaction of the sponge with coral polyps positively affects the lifespan of sponge individuals and the interstices of corals probably promote a micro refuge for C. aurea against competitors for space and predators.

Sampling of the demersal ichthyofauna of Guanabara Bay was conducted bimonthly for 2 years at 10 stations distributed along a hydrobiological gradient. A total of 16,081 Tetraodontiformes specimens were collected, representing 10 species distributed among Ostraciidae, Monacanthidae, Tetraodontidae and Diodontidae. Tetraodontiformes appear to be well adapted to hydrological variations and inhospitable conditions prompted by intense eutrophication. However, abiotic factors traditionally considered important in estuarine community structure play a secondary role in the distribution of Tetraodontiformes. The type of sediment appears to be the most important physical factor but acts only as an indicator of ecological domain. The low explanatory power of physicochemical variables, in addition to the relative stability of the bay's ichthyofauna, suggests an influence of biological parameters. The species exhibited wide variation in their use of Guanabara Bay and utilized it as a resting, feeding and growing area. Among the species captured, Stephanolepis hispidus, Lagocephalus laevigatus, Sphoeroides greeleyi, Sphoeroides testudineus, Sphoeroides tyleri, Chilomycterus reticulatus and Chilomycterus spinosus were categorized as marine estuarine opportunists, and Aluterus heudelotii and Aluterus schoepfii were classified as marine stragglers. Acanthostracion sp. could not be categorized. The boom of C. spinosus indicates an ecological misbalance and must be carefully investigated.

Although oogenesis is the best-known stage of development in sponges of the subclass Calcinea (Porifera, Calcarea), several aspects of this process await further investigation. In the present study, we examined by light and electron microscopy the oogenesis of three species of the order Clathrinida (Clathrina aurea, Borojevia aspina and B. brasiliensis) from the coast of Rio de Janeiro state (Brazil). Oogenesis in these species was a rare and not synchronized event, neither in the individual nor in the population level. Oocytes grew between the choanoderm and the pinacoderm. They did not form any special structure for nourishing the egg and phagocytosis of somatic cells was not observed. The vitellogenesis of B. aspina and B. brasiliensis was performed in a mixed pathway, while in C. aurea it was not possible to observe the vitellogenesis. In the Borojevias, the surrounding choanocytes provided small clear vesicles at the same time that oocytes modified phagosomes to produce fibrous yolk inclusions. The phylogenetic character mapping analysis indicated that egg development in the mesohyl is the ancestral state for Calcinea, while the ancestral condition of the vitellogenesis is still uncertain.

Including a multi-year collection of samples (2004–2011) the present research fills 20 years of an information gap regarding the PCB burden in south-west Atlantic franciscana dolphins (Pontoporia blainvillei) while aiming to test the null hypothesis that PCBs congeners are increasingly bioaccumulating in south-west Atlantic specimens in relation to northern hemisphere records. In addition, the present survey analyses indicators of potential biological impairment associated to PCBs tissue burden. The results could associate each sampling area group of dolphins to one or two Aroclor® patterns and point to dominant regional diffuse sources entering PCBs mixtures to the marine environment with a possible regional/long-range atmospheric contribution. In addition, total PCB levels were from four to seven times lower than the closer precedents for the area (18–26 years ago) indicating a progress in the environmental release and biota exposure of PCBs and posing an objective indicator of success of the present international elimination programme. Further, when compared with regional and global bioaccumulation patterns, PCBs congeners in Argentinean specimens appeared to occur in a decreasing tendency. Finally, calculated TEQs TCDD levels raised a concern in regards to environmental safety, showing guideline values to be widely exceeded and the occasional occurrence of positive correlations between PCBs bioaccumulation vs. sexual immaturity.

The family Polychelidae includes thirty-eight species of blind deep-sea lobsters distributed in six genera. Five species are recorded from the south-western Atlantic region: Pentacheles laevis; Pentacheles validus; Polycheles typhlops; Stereomastis sculpta; and Willemoesia forceps. Herein we analysed material sampled in deep Brazilian waters adding the first record of Stereomastis nana to the south-western Atlantic region. An identification key to all south-western Atlantic polychelids is provided.

Astracme mucronata and Ophiopaepale goesiana are recorded for the first time from the Brazilian coast. The specimens examined were collected from the States of Ceará (Canopus Bank) and Rio Grande do Norte (Potiguar Basin) in north-eastern Brazil. Descriptions, geographical range and taxonomy notes about the species are provided. This study expands the number of species of Ophiuroidea for the Brazilian coast from 134 to 136 species.

The ultrastructure of spermatogenesis, the euspermatozoa and paraspermatozoa, is investigated in Trophon geversianus. Spermatogenesis follows the general developmental pattern of caenogastropods. Paraspermatid development is characterized by elongation of the cell, concurrent with the appearance of a cytoplasmic elongation at the apex of the cell and the breakdown of the nucleus into small round fragments (caryomerites). Euspermatozoa consist of: a tall, conical acrosomal vesicle (with a invagination); a rod-shaped, highly electron-dense nucleus with an internal axoneme; an elongate midpiece consisting of the axoneme sheathed by helical mitochondrial elements; an elongate glycogen piece; and a short free-tail region. Paraspermatozoa of T. geversianus are vermiform. They contain approximately 12–16 axonemes arranged peripherally, numerous oblong dense vesicles, numerous less dense (round) vesicles, and scattered mitochondria. Most of the euspermatozoal features of T. geversianus are also observed in many neogastropods. However, the presence of the axoneme continuously located inside of the nucleus has not been reported before, and may prove to be a diagnostic feature of the Muricidae.

Rocky shore intertidal communities along the cold- and warm-temperate coasts of the south-western Atlantic are dominated by small mussels of the genus Brachidontes s.l. (Mytilidae), yet the status of species occurring in the region remains unresolved. Taxonomic studies have been based on shell morphology, but high phenotypic variability has led to much confusion. Based on mitochondrial and nuclear genes (COI, 28S rDNA and ITS1) from nine localities in Uruguay and Argentina we confirmed the occurrence of three species in the south-western Atlantic: Brachidontes darwinianus and B. rodriguezii in the warm-temperate and B. purpuratus in the cold-temperate sector. The latter two species coexist in the same beds along the transition zone (41–43°S). The phylogeny based on mitochondrial and nuclear genes, indicate an early divergence of B. purpuratus. At the intra-specific level, low genetic differentiation and absence of fossil record for B. purpuratus from the earlier Quaternary marine terraces of Patagonia likely result from a relatively recent (post-LGM) colonization originated from populations in the south-eastern Pacific. In the case of B. rodriguezii, by contrast, genetic intraspecific differentiation, a fossil record of phenotypically-related forms going back to the Late Miocene, and phylogenetic position in the COI-based phylogeny, prompts the hypothesis that this species is derived from a local stock with a long history of occurrence in the warm-temperate region of the south-western Atlantic. While intertidal mussel beds from the south-western Atlantic are ecologically similar in appearance, their assembly involves components clearly differentiated in terms of historical biogeography and phylogeny.

We present a species checklist, characterizing the ichthyofaunal composition of four coastal archipelagos in waters off the metropolitan area of Rio de Janeiro, Brazil. Data were obtained from ~120 h of underwater observations, published and unpublished information, including new species records. A total of 197 fish species (78 new records), belonging to 130 genera and 61 families, were observed. The family Carangidae (17) dominated in number of species, followed by Labridae and Serranidae (10 each), Epinephelidae and Scaridae (9 each). Most species are distributed along the tropical western Atlantic (51.8%) or on both sides of the Atlantic Ocean (20.5%). A minor part is endemic to Brazil (9.7%) or range to temperate rocky reefs of Patagonia (6.7%). Fourteen species are threatened, according to the IUCN, and listed under the Brazilian Ministry of the Environment red list (6.6%). Despite an increment of fish species listed herein, and the recent establishment/creation of a Marine Protected Area (Monumento Natural das Ilhas Cagarras—MoNa Cagarras), research efforts are clearly needed along these archipelagos, as nearshore environmental threats increase due to lack of regulatory practices.

Killer whale (Orcinus orca) is frequently encountered in coastal and high productive pelagic waters, near the shelf break. In the south-western Atlantic Ocean, spatial and temporal occurrence patterns are poorly known. However, the monitoring of the interaction between killer whales and longline fishery suggests that the species is frequent in this region. We analysed the killer whale presence within the Uruguayan pelagic longline fishing zone. Data were collected from 1996 to 2007, during 2189 fishing events, by vessel skippers and on-board observers. We estimated the sighting rate (SR = sightings days/fishing days * 100) for different time scales and in 1 × 1 degree grids. Generalized linear models were used to evaluate the effect of spatial, temporal, environmental and operational variables on the species presence. Killer whales were sighted in 100 fishing days (SR = 4.5%), this occurrence being explained by distance from shore and sea surface temperature, varying among months and fishing boats. Although sightings occurred year round, they were more frequent in autumn and winter, at 150–400 nautical miles (nm) from shore (mean = 250 nm) and in waters with temperatures ranging from 19 to 24°C (mean = 22°C). Sets took place between 19°–40°S and 21°–54°W, while killer whales occurred mostly from 34°–37°S and 48°–53°W. In this region, the high productive Brazil—Malvinas Confluence Zone is located, and concentrates fishing effort and also killer whales.

Morphological differences in the otoliths of Macrodon atricauda from Rio Grande do Sul State (southern Brazil) and of M. ancylodon from Pará State (northern Brazil) were examined. Until recently, these were considered two populations of the same species. Although relatively similar in their general shape, those of large M. atricauda (>300 mm total length) were shorter and thinner and their outer surface was convex (those of the smallest specimens had a more lobullated antero-dorsal margin) whereas those of similarly sized M. ancylodon were larger, thicker and less lobullated. These features of the otoliths allow these morphologically similar species to be discriminated. The pattern of translucent and opaque bands in sectioned otoliths also differed. The otoliths of M. atricauda showed clear annual banding which allowed ageing, while those of M. ancylodon had no distinct alternate bands.

This paper reports the first well-documented specimen of the goblin shark, Mitsukurina owstoni in the south-western Atlantic, based on a mature male measuring 3152 mm total length, caught on 27 November 2008 off the Rio de Janeiro coast, south-east Brazil.

Three new species of Strongylacidon from north-east Brazil are described: Strongylacidon oxychaetum sp. nov. and Strongylacidon solangeae sp. nov. from Bahia State, and Strongylacidon chelospinata sp. nov. from Fernando de Noronha Archipelago, Pernambuco State. Strongylacidon oxychaetum sp. nov. has thinly encrusting shape with lobate projections, strongyles, oxychaetes and arcuate chelae; S. solangeae sp. nov. is characterized by having massive shape with hispid surface, strongyles and unguiferate chelae; and S. chelospinata sp. nov. present thinly encrusting shape, strongyles, and arcuate isochelae with large spines on the outer edge of the axis. An identification key for the nine valid species of Strongylacidon from the Tropical Western Atlantic is provided. New morphological characters, viz., oxychaetes and spined arcuate isochelae (here termed acanthochelae), are added to the definition of the genus Strongylacidon and of the family Chondropsidae.