Paulo Cesar Paiva

Benthic megafauna of the nearshore zone of Martel Inlet (King George Island, South Shetland Islands, Antarctica): depth zonation and underwater observations

Abstract The benthic megafauna from the soft bottoms of the shallow coastal zone of Martel Inlet (Admiralty Bay, King George Island, South Shetland Islands, Antarctica) was studied during three austral summers (1989/1990, 1990/1991 and 1994/1995) in relation to the bathymetric features. Surveying and sampling, based on specimen counting and underwater observations, were undertaken by scuba-diving at depths down to 25 m. The depth zonation appears to be influenced by the nature of the substrate and especially by the action of the ice. The multiple action of ice flows prevents the occurrence of sessile forms in the shallower areas, where a low-diversity community, dominated by motile animals, was found. In the area around 18 m in depth, the action of icebergs generated faunistic and sedimentary patches of impacted and non-impacted areas. The more stable conditions prevailing below depths of 20–25 m allowed the establishment of a more diversified epifauna, including many sessile forms. The interannual differences observed in the densities of the mobile isopod Serolis polita may be associated with the summer period when the sampling was undertaken.

The curious case of Hermodice carunculata (Annelida: Amphinomidae): evidence for genetic homogeneity throughout the Atlantic Ocean and adjacent basins

Over the last few decades, advances in molecular techniques have led to the detection of strong geographic population structure and cryptic speciation in many benthic marine taxa, even those with long‐lived pelagic larval stages. Polychaete annelids, in particular, generally show a high degree of population divergence, especially in mitochondrial genes. Rarely have molecular studies confirmed the presence of ‘cosmopolitan’ species. The amphinomid polychaete Hermodice carunculata was long considered the sole species within its genus, with a reported distribution throughout the Atlantic and adjacent basins. However, recent studies have indicated morphological differences, primarily in the number of branchial filaments, between the East and West Atlantic populations; these differences were invoked to re‐instate Hermodice nigrolineata, formerly considered a junior synonym of H. carunculata. We utilized sequence data from two mitochondrial (cytochrome c oxidase subunit I, 16S rDNA) markers and one nuclear (internal transcribed spacer) marker to examine the genetic diversity of Hermodice throughout its distribution range in the Atlantic Ocean, including the Mediterranean Sea, the Caribbean Sea, the Gulf of Mexico and the Gulf of Guinea. Our analyses revealed generally low genetic divergences among collecting localities and between the East and West Atlantic, although phylogenetic trees based on mitochondrial data indicate the presence of a private lineage in the Mediterranean Sea. A re‐evaluation of the number of branchial filaments confirmed differences between East and West Atlantic populations; however, the differences were not diagnostic and did not reflect the observed genetic population structure. Rather, we suspect that the number of branchial filaments is a function of oxygen saturation in the environment. Our results do not support the distinction between H. carunculata in the West Atlantic and H. nigrolineata in the East Atlantic. Instead, they re‐affirm the older notion that H. carunculata is a cohesive species with a broad distribution across the Atlantic Ocean.

Genetic and morphometric differences between yellowtail snapper (Ocyurus chrysurus, Lutjanidae) populations of the tropical West Atlantic

Populations of Ocyurus chrysurus were compared genetically and morphometrically along the West Atlantic coast to test the null hypothesis of population homogeneity in the area. Brazilian populations were found to be differentiated in shape (canonical variates analysis; F[48,515] = 10.84, p < 0.0001). Analyses of mitochondrial DNA sequences (663 bp of the control region) did not show any differences between Brazilian populations but could detect differences between Brazilian and Caribbean (Belize) populations. The samples from Pernambuco differed significantly from the other Brazilian populations in allozyme frequencies (11 loci; FST = 0.167; p < 0.05), but this may have resulted from the small number of samples analysed for that population. Sequence variation of Belize samples departed from neutral expectations (Fus FS = -8.88; p < 0.001). A mismatch distribution analysis points to an ancient population expansion in that area. We conclude that the genetic data do not allow the rejection of the null hypothesis of panmixia for Brazilian yellowtail snapper populations which should be treated as a single genetic stock, with a latitudinal gradient on their morphology which probably results from phenotypic plasticity. On the other hand, there is a severe restriction to gene flow between O. chrysurus populations from the Caribbean and from the southwestern Atlantic.

Anaesthetization and fixation effects on the morphology of sabellid polychaetes (Annelida: Polychaeta: Sabellidae)

(Grube, 1870), a sabellid polychaete, were submitted to different anaesthetization and fixation procedures: a control group with living animals, immediate fixation with formaldehyde 4% (FO), ethanol 100% (AE) or ethanol 70% (ET), and anaesthetization with magnesium chloride (MC), refrigeration (RE), menthol crystals (ME) or freshwater (FW). Twenty-three morphometric variables of the body were measured and analysed with size-free multivariate statistics. The first three canonical variables explained 80% of the variation, being significantly correlated with 19 measured variables, mainly those related to the shape of the body setigers. Besides morphometric variables, some morphological characters commonly used in polychaete taxonomy also presented variation among fixation procedures, such as the release of parapodial elements and the integument. Among the procedures tested, AE, ET and FW were the best in approximating the shape of living specimens. Specimens submitted to FO and RE had shorter, wider, and thicker bodies, whereas those submitted to MC and ME were more elongated, narrower, flatter, and had wider pygidia than living specimens. Lengths of branchial crown, setiger 1 and pygidium seem to be the most informative morphometric characters for taxonomic purposes since they did not present deformation due to fixation procedures.INTRODUCTIONSystematists are often interested in quantifying morpho-logical differences among species, conspecific populations, or ontogenetic stages (Strauss & Bookstein, 1982). Body shape represents an important set of animal characters that are used for several purposes, such as studies in taxonomy, ecology, evolution, growth and morphological abnormali-ties (Rohlf & Marcus, 1993; Lestrel, 2000). Therefore, mor-phometrics became a fundamental tool to assess shape and shape variation in biology (Rohlf, 1990).Numerous taxonomic studies have used multivariate morphometrics successfully to analyse differences among species and even among populations (e.g. Debuse et al., 2001; Jordaens et al., 2002; O’Reilly & Horn, 2004). However, there are few morphometric studies on polychaete worms, such as Mackie (1984), Fauchald (1991), Sigvaldadottir & Mackie (1993) and Martin et al. (2003). For soft-bodied animals or structures, body shape depends on the degree of relaxation (Gustus, 1972). Hence, the measurements of some soft-bodied animals or structures after fixation may not reflect their real shape, due to deformation. Consequently, morphometric differences observed among groups of animals submitted to different methods of fixation and/or anaesthetization could be merely methodological artefacts (Howe, 2002).The effects of fixatives on body shape are difficult to predict due to variability related to the type and concentration of fixative, life stage, life habit and other factors (Sagnes, 1997). Methodological artefacts owing to anaesthetisation and fixation procedures are noticeable when comparing material from different origins, such as museum and fresh material. Even for museum specimens, the lack of information concerning anaesthetization and prior fixation methods could restrict comparisons among specimens when shape information is necessary.Experimental studies on potential morphological modifications related to methods of fixation are still scarce for most animal groups (Fowler & Smith, 1983; Kruse & Dalley, 1990; Quinonez-Velazquez & Chaumillon, 1996; Sagnes, 1997; Jordaens et al., 2002) and absent in polychaetes. Mostly, studies regarding anaesthetization methods are more engaged in the maintenance of living animals for transportation rather than on shape recovery of dead or fixed animals (Heasman et al., 1995; White et al., 1996; Bower et al., 1999).In the present study, the effects of different methods of anaesthetization and fixation on morphometric variables were assessed in the polychaete marine worm

Factors influencing spatial patterns of molluscs in a eutrophic tropical bay

r.a.f. neves, c.a. echeverria, l.a. pessoa, p.c. paiva, r. paranhos and j.l. valentin Programa de Pós-Graduação em Ecologia, Departamento de Ecologia, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, CEP 21941-902, Brazil, Laboratório de Pesquisas Costeiras e Estuarinas, Núcleo Interdisciplinar UFRJ-Mar, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil, Instituto Virtual Internacional de Mudanças Globais (IVIG–COPPE, UFRJ), Instituto Alberto Luiz Coimbra de Pós-Graduação e Pesquisa de Engenharia, Universidade Federal do Rio de Janeiro, Brazil, Programa de Pós-Graduação em Biologia Marinha, Departamento de Biologia Marinha, Instituto de Zoologia, Universidade Federal Fluminense, Laboratório de Polychaeta, Departamento de Zoologia, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Laboratório de Hidrobiologia, Departamento de Biologia Marinha, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Laboratório de Zooplâncton Marinho, Departamento de Biologia Marinha, Instituto de Biologia, Universidade Federal do Rio de Janeiro

The relationship between sandy beach nematodes and environmental characteristics in two Brazilian sandy beaches (Guanabara Bay, Rio de Janeiro)

We investigated if the differences in density and nematode communities of intertidal sediments from two Brazilian sheltered sandy beaches were related to environmental characteristics. The upper tide level (UTL) and the low tide level (LTL) of both beaches were surveyed in January (austral summer) and June 2001 (austral winter) during low-spring tides, by collecting samples of nematodes and sediments. Differences in density between beaches, tidal level and seasons, and nematode community structure were investigated. Sediments from both beaches were composed of medium to very coarse sand. The highest nematode densities were found at the UTL, and significant differences between beaches, tidal levels and months were found. A total of 54 genera were found and the genera composition on both sheltered beaches was similar to other exposed worldwide sandy beaches. The density and structure of the nematode community at both beaches clearly varied along the spatial and temporal scales. Gravel percentage was the most important variable explaining the spatial distribution of the nematodes, determining the four sub-communities; this suggests that the sediment characteristics influence the nematode community, rather than physical hydrodynamic forces. Temperature and salinity were suggested to be important variables affecting the temporal variation.

Composition and biomass of shallow benthic megafauna during an annual cycle in Admiralty Bay, King George Island, Antarctica

Composition and biomass of an Antarctic megafauna community were studied during a discontinuous 12 months cycle (March–December 1999 and December 2000–March 2001) at two stations (12 and 25 m depth) in Admiralty Bay, King George Island, Antarctica. During this period iceberg impacts were monitored in order to analyse their role in structuring the community. Organic matter content of the sediment showed a seasonal cycle for both depths, with lower values during winter and higher in summer. Composition and biomass of the megafauna were comparable to those described in previous surveys for the maritime Antarctica. Interannual or summer/winter changes in the density or biomass of the megafauna community were not significant, although significant differences between depths occurred during the whole survey. The observed community composition can be the considered result of a continuous invasion from a deeper fauna, constrained at shallower waters by the effects of ice and storms.

The Multitentaculate Cirratulidae of the Genera Cirriformia and Timarete (Annelida: Polychaeta) from Shallow Waters of Brazil

A large number multitentaculate cirratulids have been described worldwide but most are only known through the original descriptions. Type material, voucher and recently collected specimens from Brazil were revisited in order to reveal their true identity and confirm the records of widely distributed species in this region. Six species are described, three of which are new, Cirriformia capixabensis sp. nov., Cirriformia chicoi sp. nov. and Timarete ceciliae sp. nov. COI and 16S sequences were obtained and used for inter-specific comparisons. Timarete caribous is reported from several localities along the Brazilian coast and a new synonym, Cirratulus melanacanthus, is proposed. The species Timarete oculata, originally described from Brazil and lumped into the Timarete filigera species complex, is herein revalidated and redescribed. The occurrence of the species Timarete filigera and Cirriformia tentaculata is not confirmed from the Brazilian coast. Descriptions, illustrations and a key to genera and species are provided.

On the occurrence of the fireworm Eurythoe complanata complex (Annelida, Amphinomidae) in the Mediterranean Sea with an updated revision of the alien Mediterranean amphinomids

Abstract The presence of two species within the Eurythoe complanata complex in the Mediterranean Sea is reported, as well as their geographical distributions. One species, Eurythoe laevisetis, occurs in the eastern and central Mediterranean, likely constituting the first historical introduction to the Mediterranean Sea and the other, Eurythoe complanata, in both eastern and Levantine basins. Brief notes on their taxonomy are also provided and their potential pathways for introduction to the Mediterranean are discussed. A simplified key to the Mediterranean amphinomid genera and species of Eurythoe and Linopherus is presented plus an updated revision of the alien amphinomid species reported previously from the Mediterranean Sea. A total of five exotic species have been included; information on their location, habitat, date of introduction and other relevant features is also provided.

Espécies de Scolelepis (Polychaeta, Spionidae) de praias do Estado do Rio de Janeiro, Brasil

Spionidae is one of the most abundant and diverse taxa among polychaetes. Scolelepis is one of the most abundant genus in shallow waters being widely distributed worldwide. Seven Scolelepis species have been reported to the Brazilian coast, but their taxonomy should be verified owing to a discussion on correct species identification and the possibility of being a species complex. The aim of this study was to make an inventory the species of the genus Scolelepis found in the beaches of Rio de Janeiro State, Brazil. Two species were found: S. chiliensis, very abundant and occurring in several beaches and S. goodbodyi with a more restricted distribution.