Monthly collections were made for one year (August 1995 to July 1996) in the intertidal zone of two beaches (Engenho d'Água and São Francisco) located in the São Sebastião Channel, State of São Paulo, Brazil, in order to establish the seasonal fluctuations of the species and the factors determining these fluctuations. On each beach, a 10 m wide sector of varying width was established, from which 15 samples/month were collected with a cylindrical corer (0·01 m2). The salinity of the interstitial water and the temperature of the sediment were measured monthly, while the granulometric parameters and calcium carbonate and organic matter concentrations were recorded seasonally. The temporal distribution of the species was more homogeneous at Engenho d'Água, where the highest diversity and evenness values were also found, although the number of individuals was lower. At São Francisco, the monthly abundance was higher, but the richness, diversity, and evenness values were lower, showing some heterogeneity in the temporal distribution patterns of the species. Most species at Engenho d'Água reached their peak of abundance in summer and autumn. The most abundant and frequent species at Engenho d'Água were Nematonereis hebes, Cirriformia filigera (summer), Scyphoproctus djiboutiensis (spring), Owenia fusiformis and Isolda pulchella (winter). At São Francisco, the capitellids Capitella capitata, Heteromastus filiformis, and Capitomastus minimus, and the tubificid oligochaetes dominated in the summer, and Laeonereis acuta and Scolelepis squamata in the winter. The log-normal distribution of the species was used to group those species that are sensitive to and those that are tolerant of organic enrichment, over the four seasons of the year.

Whale falls are important environments contributing to biodiversity, connectivity and evolutionary novelty in deep-sea ecosystem. Notwithstanding, most of this knowledge is based in studies from NE Pacific basin. Interestingly, the only known natural whale fall on the SW Atlantic has faunal composition affinities with carcasses from other deepocean basins. In this carcass, annelid worms belonging to Hesionidae are abundant and species-rich, and include some shared species with NE Pacific Ocean. Here we evaluate the diversity of Hesionidae on the SW Atlantic using new information of implanted whale bones and explore whether some species have interbasin distribution or if they represent cryptic species in different basins. We described, using morphological and molecular data, a total of 10 new hesionid species and report of a new lineage Sirsoe 'BioSuOr,' not formally described herein. Two hesionids found exclusively in deep-sea chemosynthetic environments, Sirsoe Pleijel (1998) and Vrijenhoekia Pleijel et al. (2008), are primarily distinguished from each other by the presence of a median antenna on the former and its absence on the latter. However, our analyses showed that Vrijenhoekia should be synonymized with Sirsoe and for this reason we emended the diagnosis of Sirsoe. We also emphasized the presence of Sirsoe balaenophila comb. nov. and S. sirikos in SW Atlantic whale falls confirming their interbasin distribution. Moreover, COI and 16S rDNA data reveal that S. balaenophila comb. nov. also comprises cryptic species on the SW Atlantic (S. pirapuan sp. nov. and S. ypupiara sp. nov) and perhaps also in the Pacific Ocean (herein named as S. balaenophila lineage-2). The new species, S. maximiano, is shared between whale falls from SW Atlantic and vent sites from Mid-Cayman Spreading Center. Our data adds to the growing literature showing species are shared between deep ocean basins and among cognate deep-sea environments.

On the basis of extensive intertidal and subtidal samplings in South-Southeastern Brazil, five hesionid species were found; four are newly described and Podarkeopsis levisfuscina Perkins, 1984 is redescribed. Micropodarke pleijeli n. sp. differs from the other species because it lacks eyes, and by having a large number of pharynx papillae and by neurochaetal features; this species differs from M. dubia (Hessle, 1925) by lacking eyes, having a pharynx with more papillae, and by the neurochaetal features. Syllidia amaralae n. sp. resembles more closely S. armata sensu Day, 1967 (non S. armata de Quatrefages, 1865) because both have dorsal and tentacular cirri annulated or moniliform, and 10-15 pharyngeal papillae. However, S. amaralae n. sp. specimens differ from Day's ones because they have a quadrangular prostomium, by the relative size and arrangement of eyes, and by a reduced number of chaetae which are disposed in two bundles; these features are consistent and present in juveniles and mature specimens. Neogyptis nonatoi n. sp. is distinguishable from the others by having four types of neurochaetae; this species resembles N. crypta (Pleijel, 1993), and N. plurisetis (Hilbig, 1992). It differs from N. crypta by having a few acicular notochaetae with blunt tip, a small number of compound neurochaetae, simple capillary neurochaetae distally curved, and much slender notopodial and neuropodial lobes. The new species also differs from N. plurisetis by having four types of neurochaetae instead of having only falciger chaetae; there are less pharyngean papillae and they are far apart to each other, conical and shorter in N. plurisetis when compared to those of N. nonatoi n. sp., which are fringed, longer and closer among them, having some other longer lateral papillae. Oxydromus lanai n. sp. resembles O. obscurus (Verrill, 1873) as recorded by Uebelacker (1984), O. pugettensis by Hilbig (1994), O. guanicus by Hoagland (1919), and O. cf. guanicus by Hartman (1951). The pharynx of O. obscurus does not have fringe or papilla on its border, and it has two types of neurochaetae, differing from O. lanai n. sp. which has a single furcate notochaeta, with its shorter tine serrated. Oxydromus pugettensis and O. cf. guanicus also have usually two, instead of one, furcate notochaeta, differing from O. lanai n. sp. Oxydromus guanicus differs from our new species in having a characteristic pigmentation pattern, to be very large, its median antenna is less than one-third as long as lateral antennae, and its cirrophores are distally constricted producing a colorless ring, whereby the cirrostyle is inserted. These species are the first Brazilian records for the genera Podarkeopsis and Syllidia, and for Micropodarke, it is newly recorded from the Atlantic Ocean. Keys are included to identify hesionid genera and the species of Syllidia, Micropodarke, Neogyptis, and Podarkeopsis.

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LacydoniaMarion & Bobretzky in Marion, 1874 is the only known genus in Lacydoniidae Bergström, 1914, which is composed of small polychaetes scarcely sampled. Studies on the biology and ecology of this group are rare and most species descriptions are based on one or a few specimens. There are 13 nominal species from different parts of the world. We revise herein the morphological characters used for species description on the basis of a lacydoniid assemblage collected in Campos Basin, Southern Brazil. Material was obtained in two sampling campaigns during the Project Habitats/Petrobras – Heterogeneidade Ambiental da Bacia de Campos, coordinated by CENPES/Petrobras. Lacydoniids were collected from the continental shelf, canyons and slope, at depths from 25 to 2500 m. This polychaete family is recorded for the first time in Brazilian waters, three new species are described and all others are new records to the South Atlantic. The new species areLacydonia anapaulaesp. nov.,L. brasiliensissp. nov. andL. jackisp. nov. Newly recorded species areL. cirrata(Hartman & Fauchald, 1971),L. laureciLaubier, 1975,L. mirandaMarion & Bobretzky in Marion, 1874,L. oculata(Hartman, 1967) andL. cf.papillataUschakov, 1958. An updated key to all described species ofLacydoniais included.