RESUMO

This study investigates the impact of seasonality on estuarine soil geochemistry, focusing on redox-sensitive elements, particularly Fe, in a tropical estuary affected by Fe-rich mine tailings. We analyzed soil samples for variations in particle size, pH, redox potential (Eh), and the content of Fe, Mn, Cr, Cu, Ni, and Pb. Additionally, sequential extraction was employed to understand the fate of these elements. Results revealed dynamic changes in the soil geochemical environment, transitioning between near-neutral and suboxic/anoxic conditions in the wet season and slightly acidic to suboxic/oxic conditions in the dry season. During the wet season, fine particle deposition (83%) rich in Fe (50 g kg-1), primarily comprising crystalline Fe oxides, occurred significantly. Conversely, short-range ordered Fe oxides dominated during the dry season. Over consecutive wet/dry seasons, substantial losses of Fe (-55%), Mn (-41%), and other potentially toxic elements (Cr: -44%, Cu: -31%, Ni: -25%, Pb: -9%) were observed. Despite lower pseudo-total PTE contents, exchangeable PTEs associated with carbonate content increased over time (Cu: +188%, Ni: +557%, Pb: +99%). Modeling indicated climatic variables and short-range oxides substantially influenced PTE bioavailability, emphasizing the ephemeral Fe oxide control during the wet season and heightened ecological and health risks during the dry seasons.

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The Amazon rainforest region presents a phytophysiognomy that ranges from savannas to cerrados, all of them intimately associated to climate and soil characteristics. Evidence has been given that plant growth and development are affected by soil quality and seasonality, thus making it crucial to understand them and how they are related to each other in order to grasp the dynamics of the whole ecosystem. In this context, the goal of this research was to assess how seasonality, soil attributes, and root system biomass are related in natural cerrado, cerradão, and forest areas in southern Amazonas State, in Brazil. Soil samples were collected during dry (June/2018) and rainy (December/2018) seasons from three different layers 0.00­0.05m; 0.05­0.15m, and 0.15­0.30m deep. In each area ten sampling points were randomly chosen. Two kinds of soil samples were collected: the first using 4.0 cm height by 5.1cm internal-diameter soil sample rings; and the second were intact soil lumps. Physical and Chemical soil attributes assessed were macro-porosity (MaP), micro-porosity (MiP), total porosity (TP), soil density (SD), aggregates texture and stability (GMD and WAR), gravimetric humidity (HG), organic carbon (OC), exchangeable aluminum (Al3+), potential acidity (H+Al), sum of bases (SB), cation exchange capacity (CEC), and root biomass (RB). All data were analysed via Tukey t test and student T test to compare results between seasons and areas. Increasing vegetation density (cerrado < cerradão < forest) was followed by an increment in CEC and OC, showing the importance of these attributes to maintaining biodiversity in environments. In amazon cerrado, rainy season as well a sandier soil textures provided favourable conditions to the growth and development of plants' root system. Soil attributes were little affected by seasonality, that had greater effect on MiP, TP, SD, and OC, leading to lesser values for these variables during rainy season.

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RESUMO

Sucking pests are major threat to cotton field crop which cause unbearable losses to the crop yield. Aim of the current study was to record seasonal dynamics of major sucking insect pests including whitefly, jassid, thrips and their natural arthropod predators i.e. green lacewings and spiders in cotton field plots. The effects of surrounding field crops on pests' density and predatory efficiency of predators were also recorded. For sampling and survey of insects, the visual counting was found to be the most efficient method for recording the abundance of insects, trailed by net sweeping and tapping. Whitefly was the most dominant sucking pest found on the vegetative stage of cotton, followed by jassid and thrips. Fluctuated populations of predatory arthropods, spiders and green lacewings were also recorded during whole cropping season however, the densities of pests and predators varied with crop phenology. Spiders' population was encouraging at both vegetative and flowering stage and also the same trend of jassid and whitefly were observed at both stages of the crop. Surrounding habitats showed non-significant effect on population densities of insect pests and predators. For abiotic factors, the spiders showed strong positive correlation with humidity and temperature. However, green lacewing was only positively correlated with humidity. On the other hand, the populations of whitefly, jassid and thrips showed non-significant correlation with both temperature and humidity. Overall densities of sucking insect pests were found above economic threshold level. The plant age, crop stage and surrounding habitats effect on the population fluctuation of pests as well as the predators' abundance. The future studies are also warranted to investigate the altered habitats and multiple trap cropping to find out their impact on unattended insect predators and parasitoids in cotton crop.

As pragas sugadoras são uma grande ameaça para a cultura do algodão, causando perdas insuportáveis no rendimento da cultura. O objetivo do estudo atual foi registrar a dinâmica sazonal das principais pragas de insetos sugadores, incluindo mosca-branca, jassid, tripes e seus artrópodes predadores naturais, ou seja, crisopídeos e aranhas verdes em parcelas de algodão. Os efeitos das plantações circundantes na densidade de pragas e na eficiência predatória de predadores também foram registrados. Para amostragem e pesquisa de insetos, a contagem visual foi considerada o método mais eficiente para registrar a abundância de insetos, seguido por varredura e batida de rede. A mosca-branca foi a praga sugadora mais dominante encontrada na fase vegetativa do algodoeiro, seguida pelo jassid e tripes. Populações flutuantes de artrópodes predadores, aranhas e crisálidas também foram registradas durante toda a safra, no entanto as densidades de pragas e predadores variaram com a fenologia da cultura. A população de aranhas foi encorajadora tanto na fase vegetativa como na floração e também a mesma tendência de jassid e mosca-branca foi observada em ambas as fases da cultura. Os habitats circundantes mostraram efeito não significativo nas densidades populacionais de insetos-praga e predadores. Para os fatores abióticos, as aranhas apresentaram forte correlação positiva com umidade e temperatura. No entanto, lacewing verde foi apenas positivamente correlacionado com a umidade. Por outro lado, as populações de mosca-branca, jassid e tripes apresentaram correlação não significativa com temperatura e umidade. As densidades gerais de pragas sugadoras de insetos foram encontradas acima do nível do limiar econômico. A idade da planta, o estágio da cultura e os habitats circundantes afetam a flutuação populacional de pragas, bem como a abundância de predadores. Os estudos futuros também são necessários para investigar os habitats alterados e cultivo com armadilhas múltiplas [...].

Assuntos

RESUMO

Abstract Sucking pests are major threat to cotton field crop which cause unbearable losses to the crop yield. Aim of the current study was to record seasonal dynamics of major sucking insect pests including whitefly, jassid, thrips and their natural arthropod predators i.e. green lacewings and spiders in cotton field plots. The effects of surrounding field crops on pests density and predatory efficiency of predators were also recorded. For sampling and survey of insects, the visual counting was found to be the most efficient method for recording the abundance of insects, trailed by net sweeping and tapping. Whitefly was the most dominant sucking pest found on the vegetative stage of cotton, followed by jassid and thrips. Fluctuated populations of predatory arthropods, spiders and green lacewings were also recorded during whole cropping season however, the densities of pests and predators varied with crop phenology. Spiders population was encouraging at both vegetative and flowering stage and also the same trend of jassid and whitefly were observed at both stages of the crop. Surrounding habitats showed non-significant effect on population densities of insect pests and predators. For abiotic factors, the spiders showed strong positive correlation with humidity and temperature. However, green lacewing was only positively correlated with humidity. On the other hand, the populations of whitefly, jassid and thrips showed non-significant correlation with both temperature and humidity. Overall densities of sucking insect pests were found above economic threshold level. The plant age, crop stage and surrounding habitats effect on the population fluctuation of pests as well as the predators abundance. The future studies are also warranted to investigate the altered habitats and multiple trap cropping to find out their impact on unattended insect predators and parasitoids in cotton crop.

Resumo As pragas sugadoras são uma grande ameaça para a cultura do algodão, causando perdas insuportáveis no rendimento da cultura. O objetivo do estudo atual foi registrar a dinâmica sazonal das principais pragas de insetos sugadores, incluindo mosca-branca, jassid, tripes e seus artrópodes predadores naturais, ou seja, crisopídeos e aranhas verdes em parcelas de algodão. Os efeitos das plantações circundantes na densidade de pragas e na eficiência predatória de predadores também foram registrados. Para amostragem e pesquisa de insetos, a contagem visual foi considerada o método mais eficiente para registrar a abundância de insetos, seguido por varredura e batida de rede. A mosca-branca foi a praga sugadora mais dominante encontrada na fase vegetativa do algodoeiro, seguida pelo jassid e tripes. Populações flutuantes de artrópodes predadores, aranhas e crisálidas também foram registradas durante toda a safra, no entanto as densidades de pragas e predadores variaram com a fenologia da cultura. A população de aranhas foi encorajadora tanto na fase vegetativa como na floração e também a mesma tendência de jassid e mosca-branca foi observada em ambas as fases da cultura. Os habitats circundantes mostraram efeito não significativo nas densidades populacionais de insetos-praga e predadores. Para os fatores abióticos, as aranhas apresentaram forte correlação positiva com umidade e temperatura. No entanto, lacewing verde foi apenas positivamente correlacionado com a umidade. Por outro lado, as populações de mosca-branca, jassid e tripes apresentaram correlação não significativa com temperatura e umidade. As densidades gerais de pragas sugadoras de insetos foram encontradas acima do nível do limiar econômico. A idade da planta, o estágio da cultura e os habitats circundantes afetam a flutuação populacional de pragas, bem como a abundância de predadores. Os estudos futuros também são necessários para investigar os habitats alterados e cultivo com armadilhas múltiplas para descobrir seu impacto sobre predadores de insetos e parasitoides desacompanhados na cultura do algodão.

RESUMO

Sucking pests are major threat to cotton field crop which cause unbearable losses to the crop yield. Aim of the current study was to record seasonal dynamics of major sucking insect pests including whitefly, jassid, thrips and their natural arthropod predators i.e. green lacewings and spiders in cotton field plots. The effects of surrounding field crops on pests' density and predatory efficiency of predators were also recorded. For sampling and survey of insects, the visual counting was found to be the most efficient method for recording the abundance of insects, trailed by net sweeping and tapping. Whitefly was the most dominant sucking pest found on the vegetative stage of cotton, followed by jassid and thrips. Fluctuated populations of predatory arthropods, spiders and green lacewings were also recorded during whole cropping season however, the densities of pests and predators varied with crop phenology. Spiders' population was encouraging at both vegetative and flowering stage and also the same trend of jassid and whitefly were observed at both stages of the crop. Surrounding habitats showed non-significant effect on population densities of insect pests and predators. For abiotic factors, the spiders showed strong positive correlation with humidity and temperature. However, green lacewing was only positively correlated with humidity. On the other hand, the populations of whitefly, jassid and thrips showed non-significant correlation with both temperature and humidity. Overall densities of sucking insect pests were found above economic threshold level. The plant age, crop stage and surrounding habitats effect on the population fluctuation of pests as well as the predators' abundance. The future studies are also warranted to investigate the altered habitats and multiple trap cropping to find out their impact on unattended insect predators and parasitoids in cotton crop.

As pragas sugadoras são uma grande ameaça para a cultura do algodão, causando perdas insuportáveis no rendimento da cultura. O objetivo do estudo atual foi registrar a dinâmica sazonal das principais pragas de insetos sugadores, incluindo mosca-branca, jassid, tripes e seus artrópodes predadores naturais, ou seja, crisopídeos e aranhas verdes em parcelas de algodão. Os efeitos das plantações circundantes na densidade de pragas e na eficiência predatória de predadores também foram registrados. Para amostragem e pesquisa de insetos, a contagem visual foi considerada o método mais eficiente para registrar a abundância de insetos, seguido por varredura e batida de rede. A mosca-branca foi a praga sugadora mais dominante encontrada na fase vegetativa do algodoeiro, seguida pelo jassid e tripes. Populações flutuantes de artrópodes predadores, aranhas e crisálidas também foram registradas durante toda a safra, no entanto as densidades de pragas e predadores variaram com a fenologia da cultura. A população de aranhas foi encorajadora tanto na fase vegetativa como na floração e também a mesma tendência de jassid e mosca-branca foi observada em ambas as fases da cultura. Os habitats circundantes mostraram efeito não significativo nas densidades populacionais de insetos-praga e predadores. Para os fatores abióticos, as aranhas apresentaram forte correlação positiva com umidade e temperatura. No entanto, lacewing verde foi apenas positivamente correlacionado com a umidade. Por outro lado, as populações de mosca-branca, jassid e tripes apresentaram correlação não significativa com temperatura e umidade. As densidades gerais de pragas sugadoras de insetos foram encontradas acima do nível do limiar econômico. A idade da planta, o estágio da cultura e os habitats circundantes afetam a flutuação populacional de pragas, bem como a abundância de predadores. Os estudos futuros também são necessários para investigar os habitats alterados e cultivo com armadilhas múltiplas para descobrir seu impacto sobre predadores de insetos e parasitoides desacompanhados na cultura do algodão.

Assuntos

RESUMO

Sucking pests are major threat to cotton field crop which cause unbearable losses to the crop yield. Aim of the current study was to record seasonal dynamics of major sucking insect pests including whitefly, jassid, thrips and their natural arthropod predators i.e. green lacewings and spiders in cotton field plots. The effects of surrounding field crops on pests' density and predatory efficiency of predators were also recorded. For sampling and survey of insects, the visual counting was found to be the most efficient method for recording the abundance of insects, trailed by net sweeping and tapping. Whitefly was the most dominant sucking pest found on the vegetative stage of cotton, followed by jassid and thrips. Fluctuated populations of predatory arthropods, spiders and green lacewings were also recorded during whole cropping season however, the densities of pests and predators varied with crop phenology. Spiders' population was encouraging at both vegetative and flowering stage and also the same trend of jassid and whitefly were observed at both stages of the crop. Surrounding habitats showed non-significant effect on population densities of insect pests and predators. For abiotic factors, the spiders showed strong positive correlation with humidity and temperature. However, green lacewing was only positively correlated with humidity. On the other hand, the populations of whitefly, jassid and thrips showed non-significant correlation with both temperature and humidity. Overall densities of sucking insect pests were found above economic threshold level. The plant age, crop stage and surrounding habitats effect on the population fluctuation of pests as well as the predators' abundance. The future studies are also warranted to investigate the altered habitats and multiple trap cropping to find out their impact on unattended insect predators and parasitoids in cotton crop.(AU)

As pragas sugadoras são uma grande ameaça para a cultura do algodão, causando perdas insuportáveis no rendimento da cultura. O objetivo do estudo atual foi registrar a dinâmica sazonal das principais pragas de insetos sugadores, incluindo mosca-branca, jassid, tripes e seus artrópodes predadores naturais, ou seja, crisopídeos e aranhas verdes em parcelas de algodão. Os efeitos das plantações circundantes na densidade de pragas e na eficiência predatória de predadores também foram registrados. Para amostragem e pesquisa de insetos, a contagem visual foi considerada o método mais eficiente para registrar a abundância de insetos, seguido por varredura e batida de rede. A mosca-branca foi a praga sugadora mais dominante encontrada na fase vegetativa do algodoeiro, seguida pelo jassid e tripes. Populações flutuantes de artrópodes predadores, aranhas e crisálidas também foram registradas durante toda a safra, no entanto as densidades de pragas e predadores variaram com a fenologia da cultura. A população de aranhas foi encorajadora tanto na fase vegetativa como na floração e também a mesma tendência de jassid e mosca-branca foi observada em ambas as fases da cultura. Os habitats circundantes mostraram efeito não significativo nas densidades populacionais de insetos-praga e predadores. Para os fatores abióticos, as aranhas apresentaram forte correlação positiva com umidade e temperatura. No entanto, lacewing verde foi apenas positivamente correlacionado com a umidade. Por outro lado, as populações de mosca-branca, jassid e tripes apresentaram correlação não significativa com temperatura e umidade. As densidades gerais de pragas sugadoras de insetos foram encontradas acima do nível do limiar econômico. A idade da planta, o estágio da cultura e os habitats circundantes afetam a flutuação populacional de pragas, bem como a abundância de predadores. Os estudos futuros também são necessários para investigar os habitats alterados e cultivo com armadilhas múltiplas [...].(AU)

Assuntos

RESUMO

Abstract Dermacentor nitens is a one-host tick that uses domestic equids as main hosts. Herein, the nonparasitic phase of D. nitens was evaluated under field conditions in Pirassununga, São Paulo state, Southeastern Brazil. By exposing engorged females of D. nitens to field conditions (grass plots) for 24 consecutive months, this tick species was able to complete its nonparasitic phase by producing host-seeking larvae in the pasture throughout the year. Preoviposition and egg incubation periods were longer during autumn and winter months than during the other months. The number of larvae generated by engorged females was in most of the times lower during autumn and winter months, as demonstrated by lower egg hatching values. Such conditions could be linked to lower mean temperatures and rainfall. Larvae with the longest longevity hatched from the eggs with the shortest incubation periods. An apparent synchronism of larval hatching during spring was observed from the eggs laid by females during late winter and autumn, which is consistent with the phenomenon of "spring rise". The results indicate that D. nitens can complete up to five generations per year in southeastern Brazil, providing baseline data to develop future protocols for the appropriate control of D. nitens on horses.

Resumo Dermacentor nitens é um carrapato de um hospedeiro, que utiliza equídeos domésticos como principais hospedeiros. Neste estudo, a fase não parasitária de D. nitens foi avaliada em condições de campo, em Pirassununga, estado de São Paulo, no Sudeste do Brasil. Fêmeas ingurgitadas de D. nitens foram expostas a condições de campo (canteiros de capim) por 24 meses consecutivos. Este carrapato foi capaz de completar sua fase não parasitária, através da produção de larvas infestantes, durante todos os meses do ano. No outono e inverno, os períodos de pré-oviposição e incubação de ovos foram mais longos. O número de larvas geradas por fêmeas ingurgitadas foi menor no outono e inverno, como demonstrado pelos menores valores de eclosão dos ovos. Tal condição poderia estar ligada a temperaturas médias e índices pluviométricos mais baixos. Larvas com maior longevidade nasceram de ovos com períodos de incubação mais curtos. Observou-se um aparente sincronismo da eclosão das larvas durante a primavera, a partir de ovos postos pelas fêmeas durante o final do inverno e outono, consistente com o fenômeno do "pico da primavera". Os resultados indicam que D. nitens pode completar até cinco gerações por ano no Sudeste do Brasil, fornecendo bases para futuros protocolos de controle racional de carrapatos.

Assuntos

RESUMO

Dermacentor nitens is a one-host tick that uses domestic equids as main hosts. Herein, the nonparasitic phase of D. nitens was evaluated under field conditions in Pirassununga, São Paulo state, Southeastern Brazil. By exposing engorged females of D. nitens to field conditions (grass plots) for 24 consecutive months, this tick species was able to complete its nonparasitic phase by producing host-seeking larvae in the pasture throughout the year. Preoviposition and egg incubation periods were longer during autumn and winter months than during the other months. The number of larvae generated by engorged females was in most of the times lower during autumn and winter months, as demonstrated by lower egg hatching values. Such conditions could be linked to lower mean temperatures and rainfall. Larvae with the longest longevity hatched from the eggs with the shortest incubation periods. An apparent synchronism of larval hatching during spring was observed from the eggs laid by females during late winter and autumn, which is consistent with the phenomenon of spring rise. The results indicate that D. nitens can complete up to five generations per year in southeastern Brazil, providing baseline data to develop future protocols for the appropriate control of D. nitens on horses.(AU)

Dermacentor nitens é um carrapato de um hospedeiro, que utiliza equídeos domésticos como principais hospedeiros. Neste estudo, a fase não parasitária de D. nitens foi avaliada em condições de campo, em Pirassununga, estado de São Paulo, no Sudeste do Brasil. Fêmeas ingurgitadas de D. nitens foram expostas a condições de campo (canteiros de capim) por 24 meses consecutivos. Este carrapato foi capaz de completar sua fase não parasitária, através da produção de larvas infestantes, durante todos os meses do ano. No outono e inverno, os períodos de pré-oviposição e incubação de ovos foram mais longos. O número de larvas geradas por fêmeas ingurgitadas foi menor no outono e inverno, como demonstrado pelos menores valores de eclosão dos ovos. Tal condição poderia estar ligada a temperaturas médias e índices pluviométricos mais baixos. Larvas com maior longevidade nasceram de ovos com períodos de incubação mais curtos. Observou-se um aparente sincronismo da eclosão das larvas durante a primavera, a partir de ovos postos pelas fêmeas durante o final do inverno e outono, consistente com o fenômeno do pico da primavera. Os resultados indicam que D. nitens pode completar até cinco gerações por ano no Sudeste do Brasil, fornecendo bases para futuros protocolos de controle racional de carrapatos.(AU)

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RESUMO

The aim of the present study was to investigate the variables associated with the composition of mosquito species in rain pools of 'Bosque de Ezeiza', a large peri-urban forested park of Buenos Aires city, Argentina. A total of 12 rain pools were sampled biweekly over a 1-yr period in search of mosquito immature stages. Mosquito immature stages were present in all the occasions in which water bodies were recorded. A total of 14 species of five genera were identified, with the highest abundances observed in autumn and spring. The total abundance varied among dates according to previous temperature, precipitation, and flooding conditions. Only one species, Psorophora cyanescens (Coquillett) (Diptera: Culicidae), was associated with extreme conditions (high temperature and prolonged period of drought). Besides drought periods, two main variables were related to species composition: temperature, which accounted for seasonal changes in species composition, and flooding history, which accounted for the predominance of floodwater mosquito species on recently flooded dates and for that of stagnant water species on dates with a longer permanence of water. Regarding the pools, the most important variables accounting for species composition were the insolation level and the variability in the flooded area, with floodwater mosquitoes associated with pools with high variability in the flooded area. Interestingly, Culex (Mel.) pilosus (Dyar and Knab) (Diptera: Culicidae) showed temporal and spatial dynamics more similar to floodwater species than to stagnant water species in the rain pools studied.

Assuntos

RESUMO

The larval digenean assemblages in snail hosts are influenced by biotic and abiotic factors and by environmental disturbances due to human activities. Given their susceptibility to different types of impact, they can be useful tools for the study of temporal variations in parasite communities. The study of temporal dynamics in prevalence and species richness of larval digenean assemblages of Heleobia parchappii (DOrbigny, 1835), in two Pampean lakes, provides a good opportunity to test the supposition that seasonal variations in digenean assemblages are determined by a series of biotic and abiotic factors that operate interdependently. To analyze the temporal variations, and to evaluate how local factors influence these digenean assemblages in Los Padres and La Brava lakes (Buenos Aires province, Argentina), 2,400 specimens of H. parchappii were collected seasonally, during one year. The digenean assemblages in Los Padres and La Brava lakes were composed of 13 and 12 species respectively. These larval digenean assemblages showed similarities in the number and in the seasonal frequency of occurrence of species (eight of which were present in both lakes). However, despite these similarities, the assemblages showed different temporal dynamics in La Brava and Los Padres lakes and, also, different correlations with the abiotic and biotic factors analyzed during this study (temperature, high of the water column and snail relative abundance). Temporal dynamics in prevalence and species richness of larval digenean assemblages of H. parchappii in both lakes seems to be influenced by a series of factors (diversity and abundance of definitive hosts, intermediate and definitive host location, snail relative abundance and anthropogenic disturbances). Our results highlight the importance of analyzing the role and interaction of local factors, especially in studies dealing with spatiotemporal fluctuations or with distance decay of similarities in species richness of parasite assemblages.(AU)

Assuntos

RESUMO

The larval digenean assemblages in snail hosts are influenced by biotic and abiotic factors and by environmental disturbances due to human activities. Given their susceptibility to different types of impact, they can be useful tools for the study of temporal variations in parasite communities. The study of temporal dynamics in prevalence and species richness of larval digenean assemblages of Heleobia parchappii (DOrbigny, 1835), in two Pampean lakes, provides a good opportunity to test the supposition that seasonal variations in digenean assemblages are determined by a series of biotic and abiotic factors that operate interdependently. To analyze the temporal variations, and to evaluate how local factors influence these digenean assemblages in Los Padres and La Brava lakes (Buenos Aires province, Argentina), 2,400 specimens of H. parchappii were collected seasonally, during one year. The digenean assemblages in Los Padres and La Brava lakes were composed of 13 and 12 species respectively. These larval digenean assemblages showed similarities in the number and in the seasonal frequency of occurrence of species (eight of which were present in both lakes). However, despite these similarities, the assemblages showed different temporal dynamics in La Brava and Los Padres lakes and, also, different correlations with the abiotic and biotic factors analyzed during this study (temperature, high of the water column and snail relative abundance). Temporal dynamics in prevalence and species richness of larval digenean assemblages of H. parchappii in both lakes seems to be influenced by a series of factors (diversity and abundance of definitive hosts, intermediate and definitive host location, snail relative abundance and anthropogenic disturbances). Our results highlight the importance of analyzing the role and interaction of local factors, especially in studies dealing with spatiotemporal fluctuations or with distance decay of similarities in species richness of parasite assemblages.

Assuntos

RESUMO

ABSTRACT The larval digenean assemblages in snail hosts are influenced by biotic and abiotic factors and by environmental disturbances due to human activities. Given their susceptibility to different types of impact, they can be useful tools for the study of temporal variations in parasite communities. The study of temporal dynamics in prevalence and species richness of larval digenean assemblages of Heleobia parchappii (DOrbigny, 1835), in two Pampean lakes, provides a good opportunity to test the supposition that seasonal variations in digenean assemblages are determined by a series of biotic and abiotic factors that operate interdependently. To analyze the temporal variations, and to evaluate how local factors influence these digenean assemblages in Los Padres and La Brava lakes (Buenos Aires province, Argentina), 2,400 specimens of H. parchappii were collected seasonally, during one year. The digenean assemblages in Los Padres and La Brava lakes were composed of 13 and 12 species respectively. These larval digenean assemblages showed similarities in the number and in the seasonal frequency of occurrence of species (eight of which were present in both lakes). However, despite these similarities, the assemblages showed different temporal dynamics in La Brava and Los Padres lakes and, also, different correlations with the abiotic and biotic factors analyzed during this study (temperature, high of the water column and snail relative abundance). Temporal dynamics in prevalence and species richness of larval digenean assemblages of H. parchappii in both lakes seems to be influenced by a series of factors (diversity and abundance of definitive hosts, intermediate and definitive host location, snail relative abundance and anthropogenic disturbances). Our results highlight the importance of analyzing the role and interaction of local factors, especially in studies dealing with spatiotemporal fluctuations or with distance decay of similarities in species richness of parasite assemblages.

RESUMO

Amblyomma rotundatum is an ixodid tick strictly associated with cold-blooded animals, among them the toad Rhinella jimi. This work aimed to evaluate the seasonal dynamics of larvae, nymphs, and adults of A. rotundatum parasitizing R. jimi in an area within the semi-arid Caatinga Biome of northeastern Brazil. Monthly sampling from February 2014 to January 2016 resulted in a total of 592 R. jimi toads captured and inspected for infestation by ticks, which were counted and identified. After the procedure, the toads were released with their ticks at the same capture site. During the study period, a total of 658 A. rotundatum were counted, comprising 497 larvae, 110 nymphs, and 51 females. The two-year mean abundances of larvae, nymphs, and adults were 0.84, 0.19, and 0.09, respectively. The two-year mean infestation intensities of larvae, nymphs, and adults were 3.65, 1.45, and 1.34, respectively. Comparing the monthly values of prevalence, mean abundance, and mean infestation intensity of A. rotundatum life stages, differences were observed between the first and second year of study; however, with no clear seasonal pattern.

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The aim of this work was to generate knowledge on ecological aspects of Amblyomma sculptum in Argentina, such as seasonal dynamics, geographical range size, hosts, genetic diversity and phylogeography. Adult and immature A. sculptum ticks were collected in different localities of Argentina to know the geographical range size and hosts. The genetic diversity of this tick was studied through analyses of 16S rDNA sequences. To describe the seasonal dynamics, free-living ticks were monthly collected from October 2013 to October 2015. A. sculptum shows a marked ecological preference for Chaco Húmedo eco-region and "Albardones" forest of the great rivers in the wetlands in the Chaco Biogeographical Province, and for Selvas Pedemontanas and Selva Montana in the Yungas Biogeographical Province. This species has low host specificity, and it has large wild and domestic mammals as principal hosts to both immature and adult stages. Amblyomma sculptum is characterized by a one-year life cycle. Larvae peak in early winter, nymphs peaked during mid-spring, and adults during late summer and mid-summer. The genetic divergence was low and the total genetic variability was attributable to differences among populations. This fact could be associated to stochastics process linked to micro-habitat variations that could produce a partial restriction to gene flow among populations. The geographic regions do not contribute much to explain the A. sculptum population genetic structure, with an ancestral haplotype present in most populations, which gives rise to the rest of the haplotypes denoting a rapid population expansion.

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Given the complexity of the dynamics in litter reposition, our objective was modeling the possible main and interaction effects of tidal oscillations, seasons of the year and the moon phases over the solid waste in Santos beaches. A total of 80 collections were carried out using quadrat sampling, from which we classified, counted and weighed all residue items. We fitted mixed Hurdle models to the output datasets and performed hypotheses tests based on this framework. We found plastic to be the most abundant residue in all seasons, moon phases and tides, followed by Styrofoam and wood. Our models suggest the strongest effect was due to seasonal variations, which, in turn, may be related to different human activities. Although the dynamics of different components showed independency of all interaction structures, plastics depended on the interaction of tide and season, whose impact over estuarine life and ecosystem services shall be further investigated.

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The aim of this work was to study the distribution of Phlebotominae (Diptera: Psycodidade) abundance in time and space in an area in northeastern Argentina with vector transmission of visceral and tegumentary leishmaniasis. For this, 51 households were selected using a 'worst scenario' criterion where one light trap was set during two consecutive nights in peridomiciles in the transitions between the four seasons, and the environment was surveyed simultaneously. The relationships of phlebotomine assemblage structure and the most abundant species with seasonality and environmental variables were evaluated using a canonical correspondence analysis and generalized linear mixed models, respectively. A total of 5110 individuals were captured. Lutzomyia longipalpis (Lutz & Neiva, 1912) and Nyssomyia whitmani (Antunes & Coutinho, 1939) were the most abundant species captured in all samplings (98.3% of the total capture). The period of highest abundance of Lu. longipalpis was early autumn, and it was distributed in the most urbanized areas. Nyssomyia whitmani occupied mainly the less urbanized areas, showing peaks of abundance in early spring and summer. Other species were captured in low numbers and showed seasonal-spatial variations similar to those of Ny. whitmani. We confirmed Leishmania spp. vector persistence throughout the year in spatial patches of high abundance even during the less favorable season.

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Animal Trypanosomiasis (AT) is one of the most important problems in the Colombian livestock industry reducing its production around 30%. Caribbean and Orinoquia regions play a significant role in the development of this industry, having about 6.9 million cattle and 113,000 buffaloes. Considering the paucity in studies to understand the epidemiological features and control of AT in Colombia, the present study reports the seasonal transmission patterns and phylogeographic traits of the causal agents of AT in cattle and buffaloes from these regions. Between 2014 and 2016, a three-point longitudinal survey was designed to evaluate the mentioned characteristics. Molecular analysis in cattle showed an AT prevalence of 39.2% (T. theileri 38.6%, T. evansi 6.7% and T. vivax 0.2%), with higher values during wet and late wet seasons, while in buffaloes the prevalence was 28.2% (T. theileri 28.2% and T. evansi 1.3%), with higher values during the dry season. Additionally, variables such as tabanid abundance, vector control, breeding system, age and anemia signs were significantly associated with AT prevalence (P<0.05). Only T. theileri infection was higher in cattle with anemia signs than those with normal packed cell volume. Finally, phylogeographic analysis revealed that Colombian T. theileri isolates were associated to specific host genotypes IA and IIB, described worldwide; T. vivax isolates were related to the genotype from West Africa; while T. evansi isolates are related to the South American genotypes and to new genotypes. This is the first longitudinal survey that evaluates through molecular methods, the infection of Trypanosoma spp. in two important livestock regions from Colombia, showing that the clinical effects and prevalence of these trypanosomes in cattle and buffaloes are modulated by seasonal variations, host factors, and parasite traits. The results suggest that these factors have to be taken into account to successfully control AT in these regions.

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Environmental conditions favor the predominance of dense populations of cyanobacteria in reservoirs in northeastern Brazil. The aim of this study was to understand cyanobacterial population dynamics in the rainy and dry seasons at two depths in the Arcoverde reservoir. Microalgae and cyanobacteria samples were collected during 24 hours with intervals of 4 hours (nycthemeral) at sub-surface and 10 m using a van Dorn bottle and a determined biomass. Physical and chemical variables were obtained and the data were analyzed using the principal component analysis (PCA). No nycthemeral variations in the taxonomic composition or distribution of the populations of cyanobacteria were found between the different times of day in either the rainy or dry season. In both seasons, the greatest biomass of the phytoplankton community was made up of cyanobacteria at two depths and all times of the day. Cylindrospermopsis raciborskii (Woloszynska) Seenayya et Subba Raju was dominant at all times of the day on both the surface and at the bottom. In the rainy season, the differences in cyanobacterial biomass between the surface and bottom were less significant than in the dry season. The differences in cyanobacterial biomass between surface and bottom were less pronounced than those found in the dry season. We concluded that a) physical variables better explain the alterations of species in the phytoplankton community in an environment dominated by cyanobacteria throughout the year; b) seasonal climatic factors associated to periods of stratification and de-stratification are important for alterations in the community and variations in biomass and, c) the turbidity caused by rainfall favored the emergence and establishment of other cyanobacteria, especially Planktothrix agardhii (Gomont) Anagnostidis & Komárek.

As condições ambientais favorecem a predominância de populações densas de cianobactérias no nordeste do Brasil. O objetivo deste estudo foi entender a dinâmica das populações de cianobactérias nas estações seca e chuvosa, em duas profundidades, no reservatório de Arcoverde. Amostras de microalgas e cianobactérias foram coletadas durante 24 horas em intervalos de quatro horas (nictemerais) na subsuperfície e em 10 m, com uma garrafa de van Dorn, para a determinação da biomassa. Variáveis físicas e químicas foram obtidas, e os dados investigados por meio da Análise de Componentes Principais (ACP). Não foram encontradas variações nictemerais na composição taxonômica ou na distribuição das populações de cianobactérias entre os diferentes horários do dia, bem como entre as estações seca e chuvosa. Em ambas as estações, horários do dia e profundidades amostrais, a maior biomassa da comunidade fitoplanctônica foi constituída por cianobactérias. Cylindrospermopsis raciborskii (Woloszynska) Seenayya et Subba Raju foi dominante em todos os horários do dia, tanto na superfície como no fundo. Na estação chuvosa, as diferenças de biomassa de cianobactérias entre superfície e fundo foram menos pronunciadas do que na estação seca. Concluímos que: a) variáveis físicas explicam melhor as alterações das espécies na comunidade fitoplanctônica em um ambiente dominado por cianobactérias durante todo o ano; b) fatores climáticos sazonais associados a períodos de estratificação e desestratificação são importantes para as alterações na comunidade e as variações na biomassa, e c) a turbidez causada pela chuva favoreceu o aparecimento e o estabelecimento de outras cianobactérias, especialmente Planktothrix agardhii (Gomont) Anagnostidis & Komárek.

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Environmental conditions favor the predominance of dense populations of cyanobacteria in reservoirs in northeastern Brazil. The aim of this study was to understand cyanobacterial population dynamics in the rainy and dry seasons at two depths in the Arcoverde reservoir. Microalgae and cyanobacteria samples were collected during 24 hours with intervals of 4 hours (nycthemeral) at sub-surface and 10 m using a van Dorn bottle and a determined biomass. Physical and chemical variables were obtained and the data were analyzed using the principal component analysis (PCA). No nycthemeral variations in the taxonomic composition or distribution of the populations of cyanobacteria were found between the different times of day in either the rainy or dry season. In both seasons, the greatest biomass of the phytoplankton community was made up of cyanobacteria at two depths and all times of the day. Cylindrospermopsis raciborskii (Woloszynska) Seenayya et Subba Raju was dominant at all times of the day on both the surface and at the bottom. In the rainy season, the differences in cyanobacterial biomass between the surface and bottom were less significant than in the dry season. The differences in cyanobacterial biomass between surface and bottom were less pronounced than those found in the dry season. We concluded that a) physical variables better explain the alterations of species in the phytoplankton community in an environment dominated by cyanobacteria throughout the year; b) seasonal climatic factors associated to periods of stratification and de-stratification are important for alterations in the community and variations in biomass and, c) the turbidity caused by rainfall favored the emergence and establishment of other cyanobacteria, especially Planktothrix agardhii (Gomont) Anagnostidis & Komárek.

As condições ambientais favorecem a predominância de populações densas de cianobactérias no nordeste do Brasil. O objetivo deste estudo foi entender a dinâmica das populações de cianobactérias nas estações seca e chuvosa, em duas profundidades, no reservatório de Arcoverde. Amostras de microalgas e cianobactérias foram coletadas durante 24 horas em intervalos de quatro horas (nictemerais) na subsuperfície e em 10 m, com uma garrafa de van Dorn, para a determinação da biomassa. Variáveis físicas e químicas foram obtidas, e os dados investigados por meio da Análise de Componentes Principais (ACP). Não foram encontradas variações nictemerais na composição taxonômica ou na distribuição das populações de cianobactérias entre os diferentes horários do dia, bem como entre as estações seca e chuvosa. Em ambas as estações, horários do dia e profundidades amostrais, a maior biomassa da comunidade fitoplanctônica foi constituída por cianobactérias. Cylindrospermopsis raciborskii (Woloszynska) Seenayya et Subba Raju foi dominante em todos os horários do dia, tanto na superfície como no fundo. Na estação chuvosa, as diferenças de biomassa de cianobactérias entre superfície e fundo foram menos pronunciadas do que na estação seca. Concluímos que: a) variáveis físicas explicam melhor as alterações das espécies na comunidade fitoplanctônica em um ambiente dominado por cianobactérias durante todo o ano; b) fatores climáticos sazonais associados a períodos de estratificação e desestratificação são importantes para as alterações na comunidade e as variações na biomassa, e c) a turbidez causada pela chuva favoreceu o aparecimento e o estabelecimento de outras cianobactérias, especialmente Planktothrix agardhii (Gomont) Anagnostidis & Komárek.

RESUMO

The seasonal change and host preference of arbuscular mycorrhizal (AM) colonization and community composition of five common plant species Agropyron cristatum, Anemarrhena asphodeloides, Cleistogenes squarrosa, Leymus chinensis, and Stipa grandis in the Inner Mongolia steppe were investigated. The AM root length colonization rates were different among the five plant species and were generally high in early (May and June) and late (September) growth seasons and low in August. A total of 18 AM fungal species representing five genera were isolated from rhizosphere soils of the five plant species, and most AM fungi had not host specificity, except that Acaulospora sp., Glomus constrictum, G. diaphanum and Glomus sp. showed a certain degree of host preference. Glomus albidum, G. etunicatum and G. geosporum were the dominant species and showed various sporulation patterns in the five plants during the growth seasons. The AM fungal spore densities and species richness increased from May to September and decreased in October and were different in the same month in the five plants. Multivariate analyses revealed that season and host significantly co-affected the AM fungal spore density, species richness, and Shannon-Wiener diversity index, and the season had higher influence than the host.

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