Navegando por Assunto "Ostracodes"

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Análise ecológica da ostracofauna (crustacea) e meiofauna bentônica associada como bioindicadores ambientais na ilha de Cotijuba, Belém (PA), Amazônia
(Universidade Federal do Pará, 2025-02-27) BRITO, Maurício de Souza; PEREIRA, Ana Paula Linhares; http://lattes.cnpq.br/8369046011837903
The uncontrolled occupation of environmental protection areas (APA) in Belém-PA and candidates for APA, such as Cotijuba Island, has intensified the environmental impacts in the region. To mitigate these effects, Conservation Paleobiology integrates historical data on the distribution of fauna and flora, connecting past, present, and future. In turn, ostracods, small crustaceans sensitive to environmental variations, which are part of the benthic meiofauna, provide information about changes in ecosystems through the analysis of their communities and shells, formed from the calcium carbonate in the water. In this way, the survey of the ostracofauna and associated meiofauna on the island of Cotijuba allowed the use of these groups as bioindicators. The research was conducted during the rainy, transitional, and less rainy seasons, at two beaches: Flexeira, less impacted, and Farol, more influenced by human activities. During the campaigns, surface samples were collected in the inframarine, intertidal and supramarine zones, as well as sediment cores, physico-chemical water measurements, and beach profiles. The results showed Farol beach as reflective and Flexeira beach as dissipative, in addition to physical-chemical parameters with low influence on the organisms. The benthic meiofauna recorded 10 distinct classes: Oligochaeta, Polychaeta, Insecta (Diptera and Trichoptera), Malacostraca (Amphipoda), Arachnida, Ostracoda, Hydrozoa, Gastropoda, Bivalvia, and Rhabditophora. Approximately 84% of the specimens are from Flexeira beach, with this proportion being higher when only ostracods are analyzed (89%). Despite the lower abundance at Farol beach, a large number of cocoons of Trichoptera pupae were observed, known for their sensitivity to pollution and environmental changes, indicating a relatively healthy environment. However, a low abundance of ostracods was observed, which may be related to abiotic factors, such as the type of beach and coarse sediments. Moreover, the overall abundance of meiofauna in Cotijuba was also considered low, even without indications of significant anthropogenic intervention, which suggests a relationship between the low number of specimens and hydrodynamic conditions that intensify erosive and depositional processes. The record of a new species is highlighted: Cyprideis cotijubensis sp. nov., as a potential bioindicator of recent ostracofauna in river estuaries in the Amazon. The project also resulted in the digital book “Cartilha Digital Preserva Amazônia”, aimed at raising awareness about the conservation of the Amazon.
Acesso aberto (Open Access)
Análise tafonômica da ostracofauna do testemunho 1AS-5-AM: contribuição para a interpretação paleoambiental dos depósitos neógenos da Formação Solimões, AM, Brasil.
(Universidade Federal do Pará, 2019-11-01) SANTOS, Katiane Silva dos; RAMOS, Maria Inês Feijó; http://lattes.cnpq.br/4546620118003936
The Solimões Formation corresponds to the miocenic sedimentation from the Solimões Basin; it is constituted, essentially by mudstone, siltstone and fine sandstone, poorly consolidated, interspersed by lignite and carbonate levels, whose deposition took place in a fluvial and fluvio-lacustrine environment. Among the invertebrates from Solimões Formation the ostracode stand out for their abundance and diversity. Initially, the studies on those microcruteacea focused mainly on taxonomy. Subsequently, contributions on the bioestigraphy field suggest Early Miocene - Late Miocene age for this unit; while geochemical and paleontological analysis point to predominantly freshwater environmental conditions, with sporadic marine influence. However, taphonomic studies with emphasis on ostracode from Solimões Formation have not yet been performed. Taphonomic analysis of fossil concentrations can provide important data on paleoenvironmental hydrodynamics, sediments geochemistry, sedimentation rates and diagenetic processes. This paper deals with the biostratinomy and fossildiagenesis of ostracodes from Solimões Formation, as well as the mineralogical composition and sedimentological aspects of lithotypes. The material analyzed comes from thecore 1AS-5-AM, drilled in the village Cachoeira, near the Itacuaí river, Amazonas State. According to lithological characteristics, types of preservation and occurrence of ostracodes it was possible to individualize three intervals along the analyzed core. The interval I (284.50-119.30 meters) corresponds to the lower portion of the core. In this, the ostracofauna is poorly preserved, occurring only few juveniles (A-2, A-3 stages) and adults, with strong dissolution process. The lithology of this interval comprises solid, dark greenish gray to black mudstone, with rich organic matter content. The Interval II (116.70-107.10 meters) presents a higher occurrence of ostracodes in excellent preservation state and several ontogenetic stages, higher occurrence of closed carapaces and low degree of dissolution (occurs partially and punctually), suggesting a rapid burial event and little influence of methanogenesis on the lower organic matter content of the samples. The lithology of these layers are the same from interval I, however the organic matter content is fewer. Interval III (106.90-41.00 meters) has a moderate preservation stage, where the highest dissolution rate is associated to oxidation of monosulfides and iron sulfides that occurs adherent to the specimens surface, which were exposed by bioturbating organisms of sediments. The predominance of juvenile ostracodes in this interval indicates high mortality in ontogeny probably due to environmental stress. The lithology of this interval is made up of light to medium solid greenish gray, locally siltitic and lignite. Bioturbations (Skolitos) were recorded only at this interval. Organic matter content varies from low to moderate. Related to the color change of the ostracodes, opaque white valves were recorded in interval I more frequently; in II predominate black, dark gray, white and in smaller quantity, amber and hyaline colored valves; while in the III predominate reddish brown specimens, followed by light gray and opaque white. The taphonomic analysis of the ostracodes allowed to verify carapaces/valves with original chemical composition preserved, however, contaminated by chemical elements from the siliciclastic sediments and thin mineral layers adhered to its surface. The following types of preservation were identified: 1) ostracode valves and carapaces covered by thin mineral layers of iron monosulfide, iron phosphate, iron and thallium sulfide; 2) preserved in iron oxides; 3) recrystallized; and 4) pyritized molds. Preservation types identified predominantly reflect conditions of early (thin mineral layers mineralization and mold formation), and late (recrystallization, oxide formation) diagenesis. Fossildiagenetic alterations correspond to mineral filling of carapaces by pyrite, dissolution, color change and recrystallization. The first is related to iron phosphate present in sediments and rapid burial events. The dissolution resulted from the oxidation of the thin mineral layers adherent in the valves and the organic matter content; while carapaces/valves with alterations to reddish brown, dark gray, black and amber reflect the deposition of thin mineral layer on the specimens surface, opaque white valves result from partial dissolution. The punctual recrystallization of few valves reflects the mineral stability of the low magnesian calcite, the main constituent of ostracod carapace. The biostratinomic alterations identified are equivalent to fragmentation, disarticulation (from death, ecdysis and transport of ostracodes), bioerosion (due to chitinolytic bacteria) and transport. In interval I juvenile allochthonous ostracodes suggest postmortem transport. In interval II the predominance of native fauna shows low energy environment. Allochthonous and autochthonous (predominant) ostracodes of interval III reflect energy variation in scenery near the coastal lake zone. Based on the types of preservation and lithological characteristics, the environment was interpreted as lacustrine, with low to moderate energy. The absence of evaporitic minerals and dispersed pyrite in sediments attest to the low salinity of the environment.
Acesso aberto (Open Access)
Estudo taxonômico do gênero Cyprideis, Formação Pebas, região de Iquitos, Peru
(Universidade Federal do Pará, 2020-12-16) SOUSA, Fabricia Silva de; RAMOS, Maria Inês Feijó; http://lattes.cnpq.br/4546620118003936; 4546620118003936
The Genus Cyprideis belongs to the Cytherideidae Family and recognized for its ecophenotypic plasticity, influenced by several physical-chemical parameters (eg. Salinity, temperature, hydrochemistry, dissolved oxygen content and energy level) that considerably influence its morphological characteristics. In addition, the various adaptive radiation of the genus is recorded mainly in ancient lake systems, for example, on lake Tanganyika, lake Pannon, PaleoMediterraneo, Caribbean and ―lake Pebas" in the Western Amazon. Previous researches were mainly focused on taxonomic studies that contributed to the recognition of a wide variety of taxa; Cyprideis, however the high intraspecific variability of the genus makes it difficult to recognize some species, since the morphological characteristics between then are very similar, which makes it difficult to recognize the actual number of species that currently occur in the Neogene of Western Amazon. Thus, the present work aims the taxonomic study of the Genus Cyprideis of the Pebas Formation, region of Iquitos (Peru), located between the border west of the Marañon basin and the Iquitos arch. The studied samples come from nine outcrops located on the banks of the Amazon River and the Napo River, which provided recognition of eight genera (Cyprideis, Cypria, Penthesilenula, Heterocypris, Macrocypris, Pelocypris, Perissocytheridea and Skopaeocythere) and 22 species of ostracodes. Among these genera, Cyprideis corresponds to 92.5% of the ostracofauna, with 15 species identified, and three are new. Among these are the first record of Cyprideis anterospinosa, Cyprideis marginuspinosa, Cyprideis retrobispinosa and Cyprideis krsticae for the Pebas Formation, previously recorded only in the Solimões Formation. Additionally, the associations identified allowed to infer a predominantly lacustrine environment, which sazonal variations probably influenced in the salinity rate, without evidence of marine influence; besides inferring the age interval between the Middle Miocene and Late Miocene.
Acesso aberto (Open Access)
O gênero Haplocytheridea Stephenson, 1936 (Crustacea-ostracoda) na Formação Pirabas, Pará
(Universidade Federal do Pará, 2010-01-28) NOGUEIRA, Anna Andressa Evangelista; RAMOS, Maria Inês Feijó; http://lattes.cnpq.br/4546620118003936
The genus Haplocytheridea has a wide stratigraphical distribution, occurring from the Cretaceous to Recent. Although the genus has a wide paleobiogeographical distribution it is restricted to the circumtropical regions occuring, mainly, in the North and Central America. This is the first record of this genus in Brazil occurring in the carbonate rocks from Pirabas Formation (Early Miocene) Pará state, northern part of the Brazilian coast. Ten species were identified: five are very similar to the species described to others localities from Europe, North, Central and South America: Haplocytheridea cf. H. larosaensis; H. aff. C. multipunctata; H. cf. dacica elegantior, H. cf. H. placentiaensis and H.? cf. C. (Leptocytheridea) hopikinsi; three are described as new species: H. sandbergi n. sp., H. pirabensis n. sp. and H. sinuosa n. sp.; and others two species were left in open nomenclature H. sp.1 and H. sp.2. The distribution of the genus Haplocytheridea in the studied area showed a cyclical depositional sequence of transitional/coastal to marine neritic paleoenvironments. Haplocytheridea is normally associated to nearshore deposits in tropical, carbonate shallow marine waters and sometimes is associated with coral reefs. Its descontinuous distribution in the studied sequence attests to T-R cycles conditions in the Quarry B-17 sequence.
Acesso aberto (Open Access)
Ostracoda (crustacea) da Formação El Descanso (mioceno-plioceno), sul do Peru: reconstrução paleoambiental e evidências paleoclimáticas
(Universidade Federal do Pará, 2015-04-21) RÍOS, Andrés Felipe Salazar; RAMOS, Maria Inês Feijó; http://lattes.cnpq.br/4546620118003936
The Descanso-Yauri is an intra-mountain basin located in the southern Peru, between the Altiplan and the Western Cordillera of the Central Andes, over 4,000 meters of altitude. The sedimentary fill of the basin is approximately of 1,500 m thick, with ages from the Lower Miocene to Pliocene. In this study, taxonomic and morphometric geometric analysis of ostracods, unknowed until now, from various sections in the basin allowing to identify 4 genera and 11 species: Cyprideis (8 species, 4 described as new); Limnocythere (1 species?), Alicenula (1 species) and Heterocypris (1 species). In the northern of the section, greater abundance and diversity of Cyprideis represented by endemic species, make the term Cyprideis flock of El Descanso Basin apropriated, as proposed here. The endemism of Cyprideis is typical in long-lived lake (ancient lake). The analysis of sieve pores in Cyprideis indicates that the conditions of the ancient lake were freshwater. The occurrence of Limnocythere and Alicenula to the top of this section may indicate depth variation of this paleolake. In the central and southern sections, the presence of genus Heterocypris is associated to temporary lakes and ponds. The possible relationship between the changes in the ostracofauna with paleogeographic and/or paleoclimatic implications is discussed. Recent palynological and isotopic researches suggest that the rise of Andean Plateu causes abrupt climate changes in the Upper Miocene to Pliocene in the studied area. This assemblage of stable and temporary lakes and the radiation event of Cyprideis in the basin are probably related to these climatic changes. The occurrence of the flock of Cyprideis species of El Descanso Basin and the coincidence with the decline of the Miocene Cyprideis flock of western Amazon seems to correspond to these tectonic and climatic events.
Acesso aberto (Open Access)
Ostracodes da Formação Solimões, Neógeno do estado do Amazonas, Brasil: taxonomia, paleoecologia e bioestratigrafia
(Universidade Federal do Pará, 2011-08-16) PEREIRA, Ana Paula Linhares; RAMOS, Maria Inês Feijó; http://lattes.cnpq.br/4546620118003936
The analysis of 123 samples from 1AS-31-AM and 1AS-34-AM cores from the southwest of Amazonas State, Brazil allowed to recognize the abundance and diversity of ostracodes with register of five families: Cytherideidae, Limnocytheridae, Cyclocyprididae, Darwinulidae and Candonidae, distributed in six genera (Candona, Cypria, Cytheridella, Darwinula, Perissocytheridea e Cyprideis) and 23 species, 15 of them previously recorded to adjacent areas. The family Cytherideidae is the most representative with two genera and 19 species. The Cyprideis genera, as recorded in previous studies, is the most abundant representing 96% of ostracofauna and most diverse with 18 species. The ostracod stratigraphic distribution and the associated microfauna allowed the reconstruction the paleoenviromental evolution, The paleoenvironmental interpretation reveal an evolution of the depositional system in the Amazonia, which grades from continental (lacustrine) environments, at the base to a sporadically marine influenced settings into fluvial conditions at the top of the core sequence. This vertical variation might be better observed in 1AS-31-AM core. Probably, the radiation of Cyprideis is associated with sudden changes (mainly related to salinity change), supported by the presence of nodules in its shell. The biostratigraphic distribution of the Cyprideis species possibilited the determination of three biozones (OS1, OS2 e OS3), aged between the later Early Miocene/earlier Middle Miocene to later Middle Miocene/early Late Miocene. In the 1AS-34-AM core the analyzed range possibly corresponds to Middle Miocene/Late Miocene. The short-lived marine ingression reached the central part of Amazonia, probably in the Early-Middle Miocene based on the biostratigraphic model proposed here and supported by ostracod, palinological and mollusk biozonations.