RESUMO

Inland waters are crucial in the carbon cycle, contributing significantly to the global CO2 fluxes. Carbonate lakes may act as both sources and sinks of CO2 depending on the interactions between the amount of dissolved inorganic carbon (DIC) inputs, lake metabolisms, and geochemical processes. It is often difficult to distinguish the dominant mechanisms driving CO2 dynamics and their effects on CO2 emissions. This study was undertaken in three groundwater-fed carbonate-rich lakes in central Spain (Ruidera Lakes), severely polluted with nitrates from agricultural overfertilization. Diel and seasonal (summer and winter) changes in CO2 concentration (CCO2) DIC, and CO2 emissions-(FCO2)-, as well as physical and chemical variables, including primary production and phytoplanktonic chlorophyll-a were measured. In addition, δ13C-DIC, δ13C-CO2 in lake waters, and δ13C of the sedimentary organic matter were measured seasonally to identify the primary CO2 sources and processes. While the lakes were consistently CCO2 supersaturated and FCO2 was released to the atmosphere during both seasons, the highest CCO2 and DIC were in summer (0.36-2.26 µmol L-1). Our results support a strong phosphorus limitation for primary production in these lakes, which impinges on CO2 dynamics. External DIC inputs to the lake waters primarily drive the CCO2 and, therefore, the FCO2. The δ13C-DIC signatures below -12‰  confirmed the primary geogenic influence on DIC. As also suggested by the high values on the calcite saturation index, the Miller-Tans plot revealed that the CO2 source in the lakes was close to the signature provided by the fractionation of δ13C-CO2 from calcite precipitation. Therefore, the main contribution behind the CCO2 values found in these karst lakes should be attributed to the calcite precipitation process, which is temperature-dependent according to the seasonal change observed in δ13C-DIC values. Finally, co-precipitation of phosphate with calcite could partly explain the observed low phytoplankton production in these lakes and the impact on the contribution to increasing greenhouse gas emissions. However, as eutrophication increases and the soluble reactive phosphorus (SRP) content increases, the co-precipitation of phosphate is expected to be progressively inhibited. These thresholds must be assessed to understand how the CO32- ions drive lake co-precipitation dynamics. Carbonate regions extend over 15% of the Earth's surface but seem essential in the CO2 dynamics at a global scale.

Assuntos

RESUMO

Aedes aegypti is the main vector of arboviruses in the world. This mosquito species is distributed from tropical to temperate regions. In Argentina, it has been reported in 20 out of 23 provinces and reaches its southernmost distribution in the world. Its distribution and persistence are affected by meteorological, demographic and environmental factors, such as temperature, precipitation, and population. The aim of this study was to update and model the occurrence of Aedes aegypti in its southern limit of distribution in Argentina. To this end, a total of 37 sites were inspected in La Pampa and Río Negro provinces. Generalized Linear Models were used to explain the occurrence of Aedes aegypti based on meteorological, environmental and demographic variables. Aedes aegypti was found in 11 cities of La Pampa province where it had not been previously reported, but was not found in any of the cities evaluated in Río Negro province. The averaged model explaining the occurrence of Aedes aegypti included the minimum temperature, precipitation and interactions between maximum temperature and precipitation as explanatory variables. Although precipitation was statistically significant, other factors such as minimum temperature are also important in modeling the occurrence of Aedes aegypti in its southernmost distribution limit.

Assuntos

RESUMO

There is substantial evidence showing that temperature have a great impact on insects behavior, phenology and life histories. Because of mosquito global importance as disease vectors, in temperate regions where climatic conditions could be only borderline suitable for mosquito development, there is a growing interest in understanding the effect of temperature shifts on vital statistics to more accurately define how such changes could impact distribution and abundance patterns, as well as disease transmission cycles. We determined the role of ambient temperature under fluctuating conditions in shaping Culex acharistus (Diptera: Culicidae) life history traits, and estimated its development threshold and physiological time, in its southern limit of distribution in the Argentine Patagonia region. Four horizontal life tables were conducted under natural fluctuating temperature range in Esquel city (42°S - 71°W; 563 m a.s.l.), during spring-summer (17°C), summer (15.4°C), summer-autumn (12.7°C) and autumn-winter (5.6°C) seasons. Larvae, pupae and adult traits were recorded. The mean duration of the experiments varied between 28 to ≅100 days for spring-summer and autumn-winter seasons. Only during the cold season experiment pupae experienced the most severe temperatures and freeze-thaw cycles, and failed to reach adult stage. We found that larva and pupa development time, adult emergence time and longevity significantly increased with decreasing temperatures, while larval survival was greatest at an intermediate temperature and decreased toward low and high values. Also, protandry was observed and males emerge 2 days before females across seasons. Temperature development threshold and physiological time estimated for larva + pupa were 5.98°C and 211.24°C-days. Our study contributes to a growing body of knowledge by examining the effect of seasonal changes in temperature on mosquito life history traits. Results obtained here can be applied as useful parameters in the development of population dynamic models, improving current mosquito control strategies in cold-temperate regions.

RESUMO

Many insects use photoperiod as a signal to anticipate upcoming unfavorable conditions. Photoperiod sensitivity may be a relevant factor in Aedes (Stegomyia) aegypti (L.) populations at the cool margins of the species' range, where winter conditions have a strong effect on population dynamics. In this study, we evaluated the effect of parental photoperiod on preimaginal survival and developmental time, and on wing length for the first generation of Ae. aegypti from a temperate region (Buenos Aires City, Argentina). Our experiment started with eggs from parents exposed to short-day (SD; 10:14 [L:D]) or long-day (LD; 14:10 [L:D]) photoperiods during their entire life span. Eggs were stored under the same photoperiod (SD or LD) as their parents for 91 d, until immersion. After hatching, larvae were reared until adult emergence in thermal baths at one of two constant temperatures (17 or 23°C), at a photoperiod of 12:12 (L:D) h and fed ad libitum. Survival from larva I to adult emergence was not affected either by parental photoperiod or rearing temperature. At a rearing temperature of 23°C, female offspring from the SD parental photoperiod developed faster and had shorter wings compared with those from the LD parental photoperiod. No effect of parental photoperiod was observed on female offspring reared at 17°C. In male offspring, parental photoperiod had no effect on developmental time and wing length, independently of the rearing temperature. Results indicate that the parental photoperiod may affect some offspring traits. This effect may be a characteristic of Ae. aegypti populations in temperate regions to deal with the winter conditions.

Assuntos

Assuntos

RESUMO

Nativa da região Asiática, a Vespa mandarinia pode chegar a 50 mm de comprimento, sendo popularmente conhecida como ‘vespa assassina ou ‘vespa-gigante-asiática. Devido ao seu comportamento de caça em grupo, a espécie traz grande preocupação aos apicultores, já que são capazes de exterminar uma colmeia de abelhas em poucas horas. No entanto, o risco aos seres humanos é baixo e pode ser comparado a qualquer outra espécie peçonhenta. Recém chegada ao continente americano, a grande preocupação trazida, sobretudo pela mídia, é de que a espécie se torne invasora e colonize outros países. No entanto, a expansão dessa espécie é limitada pelo clima, já que sua região de origem é de clima temperado. Visto isso, dificilmente a V. mandarinia se adaptaria e se estabeleceria em regiões de clima tropical como no Brasil. É importante a cautela diante da avalanche de informações divulgadas pela mídia e redes sociais sobre a invasão da V. mandarinia. Portanto, recomenda-se a busca por informações certificadas publicadas e divulgadas por especialistas, núcleos de pesquisa e jornais especializados.(AU)

Native to the Asian region, the Vespa mandarinia can reach 50 mm in length, being popularly known as ‘murder hornet or ‘asian-giant-hornet. Due to their group hunting behavior, the species causes great concern to beekeepers, since they are able to exterminate a bee hive in a few hours. However, the risk to humans is low and can be compared to any other venomous species. Newly arrived in the American continent, a major concern raised, mainly by the media, is that the species becomes invasive and colonizes other countries. However, an expansion of this species is limited by the climate, since its region of origin is the temperate climate. In view of this, it is difficult for V. mandarinia to adapt and establish itself in tropical regions such as Brazil. It is important to be cautious in face of the avalanche of information disseminated by the media and social media regarding the invasion of V. mandarinia. It is recommended to search for certified information published and disseminated by specialists, research centers and specialized newspapers.(AU)

Assuntos

RESUMO

Nativa da região Asiática, a Vespa mandarinia pode chegar a 50 mm de comprimento, sendo popularmente conhecida como ‘vespa assassina’ ou ‘vespa-gigante-asiática’. Devido ao seu comportamento de caça em grupo, a espécie traz grande preocupação aos apicultores, já que são capazes de exterminar uma colmeia de abelhas em poucas horas. No entanto, o risco aos seres humanos é baixo e pode ser comparado a qualquer outra espécie peçonhenta. Recém chegada ao continente americano, a grande preocupação trazida, sobretudo pela mídia, é de que a espécie se torne invasora e colonize outros países. No entanto, a expansão dessa espécie é limitada pelo clima, já que sua região de origem é de clima temperado. Visto isso, dificilmente a V. mandarinia se adaptaria e se estabeleceria em regiões de clima tropical como no Brasil. É importante a cautela diante da avalanche de informações divulgadas pela mídia e redes sociais sobre a invasão da V. mandarinia. Portanto, recomenda-se a busca por informações certificadas publicadas e divulgadas por especialistas, núcleos de pesquisa e jornais especializados.

Native to the Asian region, the Vespa mandarinia can reach 50 mm in length, being popularly known as ‘murder hornet’ or ‘asian-giant-hornet’. Due to their group hunting behavior, the species causes great concern to beekeepers, since they are able to exterminate a bee hive in a few hours. However, the risk to humans is low and can be compared to any other venomous species. Newly arrived in the American continent, a major concern raised, mainly by the media, is that the species becomes invasive and colonizes other countries. However, an expansion of this species is limited by the climate, since its region of origin is the temperate climate. In view of this, it is difficult for V. mandarinia to adapt and establish itself in tropical regions such as Brazil. It is important to be cautious in face of the avalanche of information disseminated by the media and social media regarding the invasion of V. mandarinia. It is recommended to search for certified information published and disseminated by specialists, research centers and specialized newspapers.

Assuntos

RESUMO

In temperate regions, the seasonal dynamics of Aedes aegypti (L.) (Diptera: Culicidae) is mainly influenced by temperature. It is assumed that, during the winter season, the population remains as eggs and that the development and population growth of surviving eggs begin during the following spring. The aim of the current study was to assess egg hatching of Ae. aegypti during the winter in Buenos Aires city (Argentina), and analyze the survival of immature stages. The experiments consisted of immersing eggs and studying the development of immature stages of cohorts from June and September under natural temperature conditions. The proportion of hatched eggs was compared between weeks of immersion and related to environmental variables. Survival was compared among cohorts and the development rate was related to the mean temperature during development. The results showed that, with few exceptions, egg hatching was over 45% during the winter period. The proportion of hatched eggs was positively associated with immersion temperature, pre-immersion temperature and photoperiod. The immature stages completed the development during the cold season, with a trend toward increased survival of late-hatching cohorts. Survival was 30% at 13.2 °C and above 90% at 20 °C, whereas the development time at low temperatures was 49.4 d at 13.2 °C and 17.7 d at 20 °C. The high hatching and survival compared with other studies suggest that the local population might be adapting to winter conditions. The anticipated emergence of adults would be adaptive if they are able to reproduce successfully in the early spring.

Assuntos

RESUMO

We investigated the following aspects of the biology of a population of Cnemidophorus vacariensis Feltrim & Lema, 2000 during the four seasons: thermal biology, relationship with the thermal environment, daily and seasonal activity, population structure and growth rate. Cnemidophorus vacariensis is restricted to rocky outcrops of the "campos de cima da serra" grasslands on the Araucaria Plateau, southern Brazil, and is currently listed as regionally and nationally threatened with extinction. Data were collected from October 2004 through September 2007 in the state of Rio Grande do Sul. Sampling was conducted randomly from 08:00 a.m. to 6:00 p.m. The capture-mark-recapture method was employed. The lizards were captured by hand, and their cloacal temperature, sex, snout-ventral length (SVL), mass, and the temperature of their microhabitat (substrate temperature and air temperature) were recorded. Individuals were then marked by toe-clipping and released at the site of capture. Body temperatures were obtained for 175 individuals, activity data for 96 individuals, and data on population structure and growth for 59 individuals. All data were obtained monthly, at different times of the day. Cnemidophorus vacariensis average body temperature was 23.84ºC, ranging between 9.6 and 38.2ºC. Temperatures ranged between 21 and 29ºC. The correlation between external heat sources, substrate and air were positive and significant and there was a greater correlation between lizard's temperature and the temperature of the substrate (tigmothermic species). The relatively low body temperatures of individuals are associated with the climate of their environment (altitude up to 1,400 m), with large variations in temperature throughout the day and the year, and low temperatures in winter. The average body temperature observed for C. vacariensis was low when compared with that of phylogenetically related species, suggesting that the thermal biology of this species reflects adaptations to the temperate region where it lives. The monthly rates of activity of lizards were related to monthly variations in the ambient temperatures. Our data suggest that the daily and seasonal activity of C. vacariensis result from the interaction between two factors: changes in the environment temperature and the relationship between individuals and their thermal environment. The population structure of C. vacariensis varied throughout the study period, with maximum biomass in January and maximum density in February (recruitment period). The sex ratio diverged from the expected 1:1. The growth analysis showed a negative relationship between the growth rate of individuals and the SVL, revealing that young individuals grow faster than adults, a typical pattern for short-lived species. The population studied showed a seasonal and cyclical variation associated with the reproductive cycle. The life strategy of C. vacariensis seems to include adaptations to the seasonal variations in temperature, typical of its environment.

Este estudo teve por objetivo investigar a biologia termal, as relações térmicas com o ambiente, atividade diária e sazonal, estrutura da população e crescimento de C. vacariensis Feltrim & Lema, 2000, durante as quatro estações do ano. A espécie é restrita aos afloramentos rochosos dos "campos de cima da serra", no Planalto das Araucárias, sul do Brasil, e é considerada ameaçada de extinção regional e nacionalmente. Os dados foram coletados de outubro de 2004 até setembro de 2007 percorrendo-se as áreas de amostragem aleatoriamente entre 08:00 h e 18:00 h. Utilizou-se o método de captura-marcação-recaptura. Os lagartos eram capturados manualmente, sendo registrada sua temperatura cloacal, o sexo, comprimento rostro-cloacal, a massa, e as temperaturas do micro-hábitat (substrato e ar). Após, eram marcados por amputação da última falange dos dígitos e liberados no local da captura. Foram obtidas as temperaturas cloacais de 175 indivíduos, dados de atividade de 96 indivíduos e dados de estrutura da população e crescimento de 59 indivíduos. Todos os dados foram obtidos com periodicidade mensal, em diferentes horários. A temperatura média corporal foi de 23,84ºC, variando entre 9,6 e 38,2ºC. A faixa de temperaturas mais frequentes variou entre 21 e 29ºC. A correlação entre as fontes de calor externas, substrato e ar foram positivas e significativas, verificando-se uma correlação maior entre a temperatura do lagarto e a temperatura do substrato (espécie tigmotérmica). As temperaturas corpóreas relativamente baixas nesta espécie estão associadas à região que habita, a qual pode atingir até 1.400 m de altitude, apresentando grandes variações de temperatura ao longo do ano e do dia, com baixas temperaturas no inverno. A temperatura corpórea observada para C. vacariensis é baixa quando comparada às espécies filogeneticamente relacionadas, o que permite inferir que a biologia termal da espécie reflete sua adaptação à região de clima temperado onde habita. As taxas mensais de atividade dos lagartos estiveram relacionadas às variações mensais das temperaturas ambientais. Os dados sugerem que a atividade diária e sazonal da espécie resulta da interação de dois fatores: variações das temperaturas ambientais e relações térmicas com o ambiente. Cnemidophorus vacariensis apresentou variação na estrutura populacional ao longo do estudo, com a máxima biomassa ocorrendo em janeiro e a máxima densidade em fevereiro (período de recrutamento). A proporção sexual encontrada para a população foi diferente de 1:1. As análises de crescimento demonstram uma relação negativa entra a taxa de crescimento e o tamanho dos indivíduos, revelando que os jovens crescem mais rapidamente que os adultos, o que é típico em espécies de vida curta. A população estudada apresentou uma variação cíclica e sazonal associado ao ciclo reprodutivo. Cnemidophorus vacariensis parece ter sua estratégia de vida adaptada às variações sazonais da temperatura de seu ambiente.

RESUMO

We investigated the following aspects of the biology of a population of Cnemidophorus vacariensis Feltrim & Lema, 2000 during the four seasons: thermal biology, relationship with the thermal environment, daily and seasonal activity, population structure and growth rate. Cnemidophorus vacariensis is restricted to rocky outcrops of the "campos de cima da serra" grasslands on the Araucaria Plateau, southern Brazil, and is currently listed as regionally and nationally threatened with extinction. Data were collected from October 2004 through September 2007 in the state of Rio Grande do Sul. Sampling was conducted randomly from 08:00 a.m. to 6:00 p.m. The capture-mark-recapture method was employed. The lizards were captured by hand, and their cloacal temperature, sex, snout-ventral length (SVL), mass, and the temperature of their microhabitat (substrate temperature and air temperature) were recorded. Individuals were then marked by toe-clipping and released at the site of capture. Body temperatures were obtained for 175 individuals, activity data for 96 individuals, and data on population structure and growth for 59 individuals. All data were obtained monthly, at different times of the day. Cnemidophorus vacariensis average body temperature was 23.84ºC, ranging between 9.6 and 38.2ºC. Temperatures ranged between 21 and 29ºC. The correlation between external heat sources, substrate and air were positive and significant and there was a greater correlation between lizard's temperature and the temperature of the substrate (tigmothermic species). The relatively low body temperatures of individuals are associated with the climate of their environment (altitude up to 1,400 m), with large variations in temperature throughout the day and the year, and low temperatures in winter. The average body temperature observed for C. vacariensis was low when compared with that of phylogenetically related species, suggesting that the thermal biology of this species reflects adaptations to the temperate region where it lives. The monthly rates of activity of lizards were related to monthly variations in the ambient temperatures. Our data suggest that the daily and seasonal activity of C. vacariensis result from the interaction between two factors: changes in the environment temperature and the relationship between individuals and their thermal environment. The population structure of C. vacariensis varied throughout the study period, with maximum biomass in January and maximum density in February (recruitment period). The sex ratio diverged from the expected 1:1. The growth analysis showed a negative relationship between the growth rate of individuals and the SVL, revealing that young individuals grow faster than adults, a typical pattern for short-lived species. The population studied showed a seasonal and cyclical variation associated with the reproductive cycle. The life strategy of C. vacariensis seems to include adaptations to the seasonal variations in temperature, typical of its environment.

Este estudo teve por objetivo investigar a biologia termal, as relações térmicas com o ambiente, atividade diária e sazonal, estrutura da população e crescimento de C. vacariensis Feltrim & Lema, 2000, durante as quatro estações do ano. A espécie é restrita aos afloramentos rochosos dos "campos de cima da serra", no Planalto das Araucárias, sul do Brasil, e é considerada ameaçada de extinção regional e nacionalmente. Os dados foram coletados de outubro de 2004 até setembro de 2007 percorrendo-se as áreas de amostragem aleatoriamente entre 08:00 h e 18:00 h. Utilizou-se o método de captura-marcação-recaptura. Os lagartos eram capturados manualmente, sendo registrada sua temperatura cloacal, o sexo, comprimento rostro-cloacal, a massa, e as temperaturas do micro-hábitat (substrato e ar). Após, eram marcados por amputação da última falange dos dígitos e liberados no local da captura. Foram obtidas as temperaturas cloacais de 175 indivíduos, dados de atividade de 96 indivíduos e dados de estrutura da população e crescimento de 59 indivíduos. Todos os dados foram obtidos com periodicidade mensal, em diferentes horários. A temperatura média corporal foi de 23,84ºC, variando entre 9,6 e 38,2ºC. A faixa de temperaturas mais frequentes variou entre 21 e 29ºC. A correlação entre as fontes de calor externas, substrato e ar foram positivas e significativas, verificando-se uma correlação maior entre a temperatura do lagarto e a temperatura do substrato (espécie tigmotérmica). As temperaturas corpóreas relativamente baixas nesta espécie estão associadas à região que habita, a qual pode atingir até 1.400 m de altitude, apresentando grandes variações de temperatura ao longo do ano e do dia, com baixas temperaturas no inverno. A temperatura corpórea observada para C. vacariensis é baixa quando comparada às espécies filogeneticamente relacionadas, o que permite inferir que a biologia termal da espécie reflete sua adaptação à região de clima temperado onde habita. As taxas mensais de atividade dos lagartos estiveram relacionadas às variações mensais das temperaturas ambientais. Os dados sugerem que a atividade diária e sazonal da espécie resulta da interação de dois fatores: variações das temperaturas ambientais e relações térmicas com o ambiente. Cnemidophorus vacariensis apresentou variação na estrutura populacional ao longo do estudo, com a máxima biomassa ocorrendo em janeiro e a máxima densidade em fevereiro (período de recrutamento). A proporção sexual encontrada para a população foi diferente de 1:1. As análises de crescimento demonstram uma relação negativa entra a taxa de crescimento e o tamanho dos indivíduos, revelando que os jovens crescem mais rapidamente que os adultos, o que é típico em espécies de vida curta. A população estudada apresentou uma variação cíclica e sazonal associado ao ciclo reprodutivo. Cnemidophorus vacariensis parece ter sua estratégia de vida adaptada às variações sazonais da temperatura de seu ambiente.