ABSTRACT
Changes in food quality can dramatically impair zooplankton fitness, especially in eutrophic water bodies where cyanobacteria are usually predominant. Cyanobacteria are considered a food with low nutritional value, and some species can produce bioactive secondary metabolites reported as toxic to zooplankton. Considering that cyanobacteria can limit the survival, growth and reproduction of zooplankton, we hypothesized that the dietary exposure of neotropical Daphnia species (D. laevis and D. gessneri) to saxitoxin-producing cyanobacteria impairs Daphnia feeding rates and fitness regardless of a high availability of nutritious algae. Life table and grazing assays were conducted with different diets: (1) without nutritional restriction, where neonates were fed with diets at a constant green algae biomass (as a nutritious food source), and an increasing cyanobacterial concentration (toxic and poor food source), and (2) with diets consisting of different proportions of green algae (nutritious) and cyanobacteria (poor food) at a total biomass 1.0 mg C L-1. In general, the presence of high proportions of cyanobacteria promoted a decrease in Daphnia somatic growth, reproduction and the intrinsic rate of population increase (r) in both diets with more pronounced effects in the nutritionally restricted diet (90% R. raciborskii). A two-way ANOVA revealed the significant effects of species/clone and treatments in both assays, with significant interaction between those factors only in the second assay. Regarding the grazing assay, only D. laevis was negatively affected by increased cyanobacterial proportions in the diet. In the life table assay with constant nutritious food, a reduction in the reproduction and the intrinsic rate of the population increase (r) of all species were observed. In conclusion, we found adverse effects of the toxic cyanobacterial strain R. raciborskii on Daphnia fitness, regardless of the constant amount of nutritious food available, proving the toxic effect of R. raciborskii and that the nutritional quality of the food has a greater influence on the fitness of these animals.
ABSTRACT
Introduction: The prevalence of hepatitis B virus (HBV) infection has been declining nationwide throughout Brazil since the introduction of universal child vaccination. The vaccine is currently available for all ages. However, most of the adult population has not been vaccinated and may still be susceptible to it. Most of the cases reported to the Brazilian Notifiable Diseases Information System (Sistema de Informação de Agravos de Notificação - SINAN) are chronic, a consequence of early exposure in life. However, acute cases are the result of current transmission and may reveal the current dynamics of HBV circulation. Objective: To evaluate whether there is a change in the age distribution of acute hepatitis B in Brazil. Methods: To analyze the historical series of reported cases and incidence rates of acute hepatitis B by age group between 2007 and 2018, based on data reported to SINAN. Temporal trend was tested with non-parametric Cusick test. Results: The incidence rate fell from 1.02 (/ 100,000 inhabitants) in 2007 to 0.67 in 2018 (p=0.01). The drop was significant at all ages, except under 15 and over 60. The highest incidences (@1.0 / 100,000 inhab.) occurred between 20 and 59 years old. Conclusion: There is a progressive "aging" of acute hepatitis B cases in the country, probably due to the vaccine protection of younger people. A considerable portion of the older population is susceptible to HBV and may be exposed, especially by sexual route. Control measures such as vaccination and guidance for safe sex are needed.
Introdução: A prevalência da infecção pelo vírus da hepatite B (HBV) vem diminuindo em todo o Brasil desde a introdução da vacinação universal de crianças. Atualmente a vacina está disponível para todas as idades, porém a maior parte da população brasileira não foi vacinada e pode ainda ser suscetível. A maioria dos casos notificados ao Sistema de Informação de Agravos de Notificação (SINAN) é crônica, consequência de contágio antigo. Contudo os casos agudos são fruto de transmissão atual e podem revelar-nos a dinâmica atual da circulação do HBV. Objetivo: Avaliar se há mudança na distribuição etária da incidência da hepatite B aguda no Brasil. Métodos: Analisar a série histórica de casos notificados e as taxas de incidência de hepatite B aguda por faixa etária entre 2007 e 2018, tendo como base os dados notificados ao SINAN. Testar tendência temporal pelo teste não paramétrico de Cusick. Resultados: Houve queda da taxa de incidência de 1,02 (/100.000 hab.), em 2007, para 0,67, em 2018 (p=0,01). A queda foi significativa em todas as idades, exceto abaixo dos 15 e acima dos 60 anos. As maiores incidências (@1,0/100.000 hab.) ocorreram entre 20 e 59 anos. Conclusão: Há progressivo "envelhecimento" dos casos agudos de hepatite B no país, provavelmente pela proteção dos mais jovens por vacina. Parcela considerável da população mais idosa é suscetível ao HBV e continua exposta, principalmente por via sexual. São necessárias medidas de controle, como vacinação e orientação para prática de sexo seguro.
Subject(s)
Humans , Hepatitis B virus , Acute Disease , Hepatitis B , Vaccination , Disease Transmission, Infectious , InfectionsABSTRACT
Abstract: The population of humpback whales from breeding stock A is increasing, and little is known about the routes used by humpbacks that move north of the main calving area of Brazil, the Abrolhos Bank. The aim of this study was to describe the movements of humpback whales in a reoccupation wintering area (Serra Grande, Bahia state, Brazil) based on land-based surveys to test if movement patterns change during the season and between years, due to group composition, behavioral state, and distance to the coast. The mean leg speed of the groups sighted was 6.88 (±2.92) km/h, and leg speed was positively correlated with distance to the coast. There was an increase in leg speed and distance to the coast with increasing number of escorts in the groups with calves. The mean linearity value for group trajectory was 0.81 (±0.19) and the mean reorientation rate was 25.72 (±19.09) º/min. We observed a predominance of trajectories heading south throughout the study. Groups exhibiting more erratic movements early in the season, and groups moving south showed more linear trajectories than groups moving north, indicating the beginning of their migration back to the feeding grounds. Energy conserving strategies and social context affect the movements of humpback whales in Serra Grande, resulting in the observed patterns of the reoccupation of available and suitable habitat north of Abrolhos. Thereby, special attention should be given managing activities with the potential to disturb or displace whales using the region to calve and breed.
Resumo: A população das baleias-jubarte do estoque reprodutivo A está aumentando, e pouco se sabe sobre as rotas usadas pelas baleias que se movem a norte da maior área de reprodução do Brasil, o Banco dos Abrolhos. O objetivo deste estudo foi descrever os movimentos das baleias-jubarte em uma área de reocupação (Serra Grande, estado da Bahia, Brasil) através do monitoramento por ponto fixo para testar se os padrões de movimento mudam ao longo da temporada e entre os anos, devido à composição de grupos, estado comportamental, e distância à costa. A média da velocidade da pernada dos grupos observados foi de 6,88 (±2,92) km/h, apresentando uma correlação positiva com a distância à costa. Houve um aumento da velocidade da pernada e da distância à costa com o aumento do número de escortes nos grupos com filhotes. A linearidade média das trajetórias dos grupos foi de 0,81 (±0,19) e a taxa média de reorientação foi de 25,72 (±19,09) º/min. Observamos uma predominância das rotas com rumo para sul ao longo do estudo. No início da temporada, os grupos apresentaram movimentos mais erráticos, e os grupos se deslocando para sul apresentaram trajetórias mais lineares que grupos se movendo para norte ou para outras direções, indicando o início da migração de volta ao seu sítio alimentar. Estratégias para economizar energia e o contexto social afetam o movimento das baleias-jubarte em Serra Grande, resultando nos padrões observados de reocupação de habitat disponível e adequado a norte de Abrolhos. Desse modo, uma atenção especial deve ser dada para a gestão de atividades com o potencial para perturbar ou deslocar as baleias que usam a região para se reproduzir.
ABSTRACT
Understanding how biodiversity and ecosystem functioning respond to changes in the environment is fundamental to the maintenance of ecosystem function. In realistic scenarios, the biodiversity-ecosystem functioning path may account for only a small share of all factors determining ecosystem function. Here, we investigated the strength to which variations in environmental characteristics in a Neotropical savanna affected functional diversity and decomposition. We sought an integrative approach, testing a number of pairwise hypotheses about how the environment, biodiversity, and functioning were linked. We used structural equation modelling to connect fire frequency, soil fertility, exchangeable Al, water availability, functional diversity of woody plants, tree density, tree height, and litter decomposition rates in a causal chain. We found significant effects of soil nutrients, water availability, and Al on functional diversity and litter decomposition. Fire did not have a significant direct effect on functional diversity or litter decomposition. However, fire was connected to both variables through soil fertility. Functional diversity did not influence rates of litter decomposition. The mediated effects that emerged from pairwise interactions are encouraging not only for predicting the functional consequences of changes in environmental variables and biodiversity, but also to caution against predictions based on only environmental or only biodiversity change.
Subject(s)
Biodiversity , Fires , Plants , Soil , Tropical Climate , Water , Models, TheoreticalABSTRACT
Environmental filtering prevents species without certain attributes from occurring in local communities. Traits respond differently to different abiotic factors, assembling communities with varying composition along environmental gradients. Here, we measured proxies of soil fertility, disturbance by fire, response and physiological traits to assess how these variables interact to determine woody species richness and density in a Neotropical savannah. We explicitly incorporated our assumptions about how different abiotic filters influence different subsets of traits into a statistical model using structural equation modelling, yielding a more accurate representation of the assembly process. Fire had an effect on resistance traits, whereas soil fertility influenced physiological traits. Resistance traits explained both the richness and density of plots, whereas physiological traits explained only the density. Fewer fire events led to richer and denser plots. Similarly, areas with lower cation exchange capacity assembled less dense communities. Furthermore, we showed that structural equation modelling yielded a realistic representation of the bivariate interactions of distinct environmental filters with different subsets of traits.
