Edson Silva

Marine reservoir effect on the Southeastern coast of Brazil: results from the Tarioba shellmound paired samples.

On the Southeastern coast of Brazil the presence of many archaeological shellmounds offers a great potential for studying the radiocarbon marine reservoir effect (MRE). However, very few such studies are available for this region. These archaeological settlements, mostly dating from 5 to 2 kyr cal BP, include both terrestrial and marine remains in good stratigraphic context and secure association, enabling the comparison of different carbon reservoirs. In a previous study the chronology of the Sambaqui da Tarioba, located in Rio de Janeiro state, Brazil, was established based on marine mollusc shells and charcoal samples from hearths, from several layers in two excavated sectors. We now compare the different materials with the aim of studying the MRE in this region. Calibration was performed with Oxford software OxCal v4.2.3 using the marine curve Marine13 with an undetermined offset to account for local corrections for shell samples, and the atmospheric curve SHCal13 for charcoal samples. The distribution of results considering a phase model indicates a ΔR value of -127 ± 67 (14)C yr in the 1 sigma range and the multi-paired approach leads to a mean value of -110 ± 94 (14)C yr.

Archaeozoology of marine mollusks from Sambaqui da Tarioba, Rio das Ostras, Rio de Janeiro, Brazil

A reference inventory of prehistoric marine mollusks from the Rio das Ostras region was created based on an excavation carried out at the Sambaqui da Tarioba shellmound. Patterns of richness and biogeography were studied, and the representativeness of bivalve and gastropod diversities found at this archaeological site were inferred. A total of 47 taxa belonging to 28 families, most of which from unconsolidated substrates, was identified. The shellmound species composition does not differ from the present-day composition. All recorded species are characteristic of a wide transition zone between the south of the states of Espirito Santo (21°S) and Rio Grande do Sul (32°S). Thus, the data show little evidence of evolution in the composition, richness,and biodiversity distribution patterns of mollusks in the Rio das Ostras region. Likewise, a reconstitution of the paleoenvironment from the functional characteristics of the shellmound species indicates that the localitys geomorphology and climate remained largely unchanged in the last 4,000 years BP.

Chronological Model of a Brazilian Holocene Shellmound (Sambaqui da Tarioba, Rio de Janeiro, Brazil)

Since the beginning of the Holocene, hunter-gatherers have occupied the central-south Brazilian coast, as it was a very productive estuarine environment. Living as fishers and mollusk gatherers, they built prehistoric shellmounds, known as sambaqui, up to 30 m high, which can still be found today from the Espirito Santo (21°S) to Rio Grande do Sul (32°S) states, constituting an important testimony of paleodiversity and Brazilian prehistory. The chronology of the Sambaqui da Tarioba, situated in Rio das Ostras, Rio de Janeiro, is discussed herein. Selected well-preserved shells of Iphigenia brasiliana and charcoal from fireplaces in sequential layers were used for radiocarbon dating analysis. Based on a statistical model developed using OxCal software, the results indicate that the settlement occupation begun most probably around 3800 cal BP and lasted for up to 5 centuries.

Genetic variation and population homogeneity of the sea star Coscinasterias tenuispina (Forcipulatida: Asteroidea) on the coast of Rio de Janeiro, Brazil

Genetic variation and population structure of the sea star Coscinasterias tenuispina were investigated using allozyme electrophoresis (seven polymorphic loci out of nine sampled) at seven sites on the coast of Rio de Janeiro State. Observed values of heterozygosities were high (H OBS = 0.31 - 0.53), although similar to those found for others marine invertebrates. Departures from Hardy-Weinberg expectations were found only for one locus in three populations. No evidence of linkage disequilibrium was found among any loci for any population. The genetic identities vary from 0.882 to 0.988. The average q was low and insignificant statistically ( q = 0.017). Furthermore, Bayesian analysis of population partitioning showed that the highest LnP(D) value was achieved for K = 1. These results do not corroborate any affect by upwelling limiting gene flow among the analysed populations or the hypothesis that the strong sex ratio imbalance previously recorded to Itaipu population has been maintained by asexual reproduction

Taxonomic status of two morphotypes of Coryphaena hippurus (Perciformes: Coryphaenidae)

Dois morfotipos de Coryphaena hippurus (dourado e palombeta) encontrados ao longo da costa brasileira sao considerados especies diferentes por pescadores e mercadores das regioes de desembarque do estado do Rio de Janeiro. Alem disso, esses morfotipos sao comercializados por valores diferentes e sofrem diferentes pressoes de pesca. Desta forma, a definicao do status taxonomico desses morfotipos e importante, tanto em termos economicos quanto biologicos. A fim de investigar esse problema foi utilizado o metodo de eletroforese de aloenzimas com a amostragem de dezessete loci para 117 individuos dos dois morfotipos de C. hippurus obtidos em desembarques pesqueiros na regiao de Cabo Frio/RJ (Brasil). Os dados indicaram uma homogeneidade entre os conjuntos genicos dos morfotipos. A despeito disso, diferencas entre os conjuntos genicos de dourado e palombeta foram encontradas, devido, especialmente, ao locus alcool desidrogenase. A hipotese de selecao natural e discutida como possivel explicacao para esses resultados.