Fishes of the family Cichlidae generally show low karyotype variability. Nevertheless, karyotype variants have been identified within some genera, providing information about their evolutionary history. In the present study, karyotype characteristics of Crenicichla lepidota and Australoheros facetus, two sympatric species found in the São Gonçalo-Mangueira basin, were studied. Besides conventional procedures, double fluorochromes staining chromomycin A 3 /DAPI and fluorescent in situ hybridization (FISH) with rDNA probes were also used. Both species presented 2n = 48 chromosomes, but karyotypes were differentiated by fundamental number, which was equal to 70 in A. facetus and 56 in C. lepidota. Similar heterochromatin distribution patterns were also observed on the pericentromeric region of most chromosomes, although C. lepidota presented an additional heterochromatic block in the first pair. The Ag-NORs, 18S rDNA probe and CMA 3 /DAPI were coincident in location on the first and second pairs of C. lepidota and A. facetus, respectively. The minor rDNA loci (5S rDNA) were found in four sites located on two distinct chromosomal pairs in C. lepidota. Although the data obtained here to C. lepidota and to A. facetus show chromosomal characteristics considered ancestral to the family, new data are presented to both species. Additionally, this study corroborates the hypothesis in which evolutionary processes like non-Robertsonian rearrangements are involved in the diversification of the major groups of Neotropical Cichlidae. Thus, the karyotype diversification observed in A. facetus have the high fundamental number pathway while C. lepidota has others evolutionary chromosomal mechanisms.
Predation is considered a game between two players-predator and prey-where such pressure might affect the interactions, acting on prey and predator distribution and abundance. We evaluate whether the predation level in chelonian nests varies according to the presence of eggs in nests. Our hypothesis is that owing to the clues (visual and olfactory) of upturned soil left in newly constructed nests, predators attack nests regardless of the presence of eggs on nests. We constructed artificial nests organized in two treatments (15 with eggs, and 15 without eggs) in ESEC Taim, southern Brazil, and checked the nests during two consecutive days. We identified the possible predators through photographic traps installed near the nests, associated with the identification of footprints on disturbed nests. We verified high predation rates in both nests, which corroborate our hypothesis. We identified two canids (Cerdocyon thous and Lycalopex gymnocercus) as predators around the nests. Our results suggest that turtle nests are highly detectable by predators, and the location cues used by pampa fox to find newly constructed nests are related to soil disturbance and not to egg presence on nests.
Resumo Análises da água do rio Uruguai constataram a presença de compostos em concentrações acima dos limites
Extra chromosomes are found in all major taxa, and their characteristics, function, and evolution are not yet completely understood. Known as B chromosomes, they are additional and dispensable genetic material that are present in particular individuals of certain populations of some species. In this work, we present the occurrence of B chromosomes in the cichlid Crenicichla lepidota from southern Brazil. The analyzed population showed 2n = 48 chromosomes, plus 0, 2, 3, or 4 B chromosomes, being variable among metaphases (intraindividual variation). Morphologically, these B chromosomes were variable in size, similarly to the A chromosomes. B chromosomes did not show heterochromatization. Other cytogenetic markers, such as Nucleolar Organizing Region, CMA3/DAPI base-specific dyes, and Fluorescent in situ hybridization with 18S rDNA probe, showed no differences in relation to previous studies with C. lepidota. Although this is the second description of B chromosomes for this species, we highlight the specific features of this population, especially the similarity to A chromosomes, in relation to size, morphology, and heterochromatin accumulation. In summary the B chromosomes described herein are large to small-sized, euchromatic chromosomes, a result that contrasts with that obtained so far for Neotropical cichlids.
Due to intense agricultural activity in the rio Uruguai (South Brazil), there is the potential for aquatic contamination by agrochemicals. In this region, there are many reservoirs to meet the water demand for rice fields, forming lentic environments. In line with this information, the aim of this study was to show a comparative analysis of some biomarkers, such as lipid peroxidation (TBARS), gluthatione S-transferase (GST), non-protein thiols (NPSH), amino acids (AA) and piscine micronucleus tests (MNE) in Astyanax jacuhiensis from lentic and lotic environments in the middle rio Uruguai region, comparing warm and cold seasons. Eight pesticides were found in water samples, with propoxur having the highest concentration found in both environments and seasons. Fish from the warm season showed higher levels of biochemical biomarkers, and fish from the cold season showed higher levels of MNE and AA. TBARS and AA presented higher levels in fish from the river, while GST, NPSH, MNE and AA presented higher levels in fish from dams. These environments have different characteristics in terms of redox potential, aeration, sedimentation, trophic structure, agrochemicals input and others, which may affect the physiological and biochemical responses of fish in against adverse situations.Devido à intensa atividade agrícola no rio Uruguai (Sul do Brasil), há potencial para contaminação aquática por agrotóxicos. Há muitos reservatórios para atender a demanda de água de campos de arroz, formando ambientes lênticos. De acordo com estas informações, o objetivo do presente estudo foi mostrar uma análise comparativa de alguns biomarcadores como a peroxidação lipídica (TBARS), glutationa S-transferase (GST), tióis não-protéicos (NPSH), aminoácidos (AA) e teste písceo de micronúcleos (MNE) em Astyanax jacuhiensis amostrados em ambientes lóticos e lênticos da região do médio rio Uruguai, comparando estações quentes e frias. Oito pesticidas foram encontrados em amostras de água, sendo propoxur a maior concentração encontrada em ambos os ambientes e estações. Peixes da estação quente apresentaram maiores níveis de biomarcadores bioquímicos e peixes da estação fria apresentaram maiores níveis de MNE e AA. TBARS e AA apresentaram maiores níveis nos peixes de rio, enquanto GST, NPSH, MNE e AA apresentaram níveis mais elevados em peixes da represa. Estes ambientes têm características diferentes, com potencial redox, aeração, sedimentação, estrutura trófica, a entrada de agroquímicos e outros que podem afetar as respostas fisiológicas e bioquímicas de peixe contra situação adversa.
Atividades antrópicas podem causar alterações nas características físicas, químicas e biológicas de ecossistemas aquáticos. Sendo assim, este trabalho apresenta avaliação da qualidade da água de um córrego que recebe efluentes de uma piscicultura, utilizando insetos como bioindicadores. Foram amostrados insetos no verão e no inverno de 2012 em três pontos (à montante-P01; e no local de lançamento do efluente-P02; à jusante-P03) do córrego Felizardo, Uruguaiana, Brasil. Foram utilizadas redes de bloqueio, redes de deriva e puçás e também analisados parâmetros físico-químicos da água (temperatura, oxigênio dissolvido, nitrogênio amoniacal, condutividade elétrica, pH). No verão ocorreram diferenças quanto à riqueza de famílias, abundância e densidade de espécimes, tendo o ponto P02 valor abaixo de P01 e P03 e grau de dominância mais elevado que P01 e P03. Os parâmetros físico-químicos estiveram com valores dentro do permitido pela legislação, porém os índices bióticos sugerem que ocorre a influência direta de efluentes de piscicultura sobre a entomofauna aquática em P02, existindo evidências de efeitos moderados de poluição da água, ou com alguma poluição orgânica provável. Segundo os resultados obtidos, o Arroio Felizardo ainda permanece com suas águas identificadas na classe II, mesmo sofrendo influência de efluentes da piscicultura.
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