A variação da diversidade de microcrustáceos (Cladocera e Copepoda) a jusante de pequenos reservatórios é influenciada por táxons litorâneos / The variation of microcrustaceans diversity downstream of small reservoirs is influenced by litoranean taxa

Testaram-se as hipóteses de que, assim como em reservatórios de grande áreas de superfície, volumes e vazão, em reservatórios pequenos também ocorrem a diluição gradual e contínua da riqueza, da diversidade e abundância de microcrustáceos (Cladocera e Copepoda) a jusante dos mesmos, sem a recomposição da riqueza a jusante pela falta de rios tributários, lagoas marginais e até pelo pequeno porte do riacho, sem condições para o desenvolvimento do potamoplâncton próprio do sistema. Foram estudados dois pequenos reservatórios e seus trechos a jusante, com coletas diárias a cada seis horas em oito pontos de amostragem, sendo dois lênticos e seis lóticos a jusante de cada. Foram encontradas 19 espécies (11 de Cladocera e oito de Copepoda), com destaque para o maior número de espécies litorâneas do que pelágicas, e a maior abundância de cladóceros litorâneos nos pontos a jusante dos reservatórios. Não houve diferença entre os horários, indicando que a escala espacial foi mais importante que a temporal. Houve maiores valores dos atributos ecológicos nos ambientes lênticos, porém houve aumentos significativos de riqueza e diversidade nos últimos pontos dos trechos de riacho, enquanto que a abundância diminuiu gradativamente a jusante. Não foram encontradas correlações significativas da abundância dos táxons com nenhuma variável limnológica (temperatura, pH, oxigênio dissolvido, turbidez, sólidos totais dissolvidos e transparência), indicando pouco ou nenhum efeito destas variáveis. A análise de cluster com distância euclidiana separou dois grandes grupos, o primeiro formado pelo trecho a jusante do primeiro reservatório e o segundo com os demais pontos. Além da presença dos táxons litorâneos vindos dos reservatórios, houve incremento de táxons litorâneos residentes nos riachos. Pode-se concluir que houve uma diluição da abundância das espécies a jusante dos riachos, mas a riqueza e a diversidade permaneceram estáveis devido à contribuição de táxons litorâneos.(AU)

The hypotheses tested were that, as well as in reservoirs of large surface areas, volumes and flow, in small reservoirs there is also a gradual and continuous dilution of the richness, diversity and abundance of microcrustaceans (Cladocera and Copepoda) downstream reservoirs, without the recomposition of richness downstream due to the lack of tributary rivers, marginal lagoons and even the small size of the stream, with no conditions for the development of its own potamoplankton. Two small reservoirs were studied and in their downstream stretches, with daily collections every six hours at eight sampling points, two lentic and six lotic downstream from each. Nineteen species were found (11 from Cladocera and eight from Copepoda), with emphasis on the greater number of coastal species than pelagic ones, and the greater abundance of coastal cladocerans at the points downstream of the reservoirs. There was no difference between the times, indicating that the spatial scale was more important than the temporal scale. There were higher values of ecological attributes in lentic environments, but there were significant increases in richness and diversity in the last points of the stretches of the stream, while the abundance decreased gradually downstream. No significant correlations were found for the abundance of taxa with any physical and chemical variable (temperature, pH, dissolved oxygen, turbidity, total dissolved solids and transparency), indicating little or no effect of these variables. The cluster analysis with Euclidean distance separated two large groups, the first formed by the stretch downstream of the first reservoir and the second with the other points. In addition to the presence of litoranean taxa coming from reservoirs, there was an increase in litoranean taxa resident in streams. It can be concluded that there was a dilution of the abundance of species downstream of the streams, but the richness and diversity remained stable due to the contribution of litoranean taxa.(AU)

A variação da diversidade de microcrustáceos (Cladocera e Copepoda) a jusante de pequenos reservatórios é influenciada por táxons litorâneos / The variation of microcrustaceans diversity downstream of small reservoirs is influenced by litoranean taxa

Testaram-se as hipóteses de que, assim como em reservatórios de grande áreas de superfície, volumes e vazão, em reservatórios pequenos também ocorrem a diluição gradual e contínua da riqueza, da diversidade e abundância de microcrustáceos (Cladocera e Copepoda) a jusante dos mesmos, sem a recomposição da riqueza a jusante pela falta de rios tributários, lagoas marginais e até pelo pequeno porte do riacho, sem condições para o desenvolvimento do potamoplâncton próprio do sistema. Foram estudados dois pequenos reservatórios e seus trechos a jusante, com coletas diárias a cada seis horas em oito pontos de amostragem, sendo dois lênticos e seis lóticos a jusante de cada. Foram encontradas 19 espécies (11 de Cladocera e oito de Copepoda), com destaque para o maior número de espécies litorâneas do que pelágicas, e a maior abundância de cladóceros litorâneos nos pontos a jusante dos reservatórios. Não houve diferença entre os horários, indicando que a escala espacial foi mais importante que a temporal. Houve maiores valores dos atributos ecológicos nos ambientes lênticos, porém houve aumentos significativos de riqueza e diversidade nos últimos pontos dos trechos de riacho, enquanto que a abundância diminuiu gradativamente a jusante. Não foram encontradas correlações significativas da abundância dos táxons com nenhuma variável limnológica (temperatura, pH, oxigênio dissolvido, turbidez, sólidos totais dissolvidos e transparência), indicando pouco ou nenhum efeito destas variáveis. A análise de cluster com distância euclidiana separou dois grandes grupos, o primeiro formado pelo trecho a jusante do primeiro reservatório e o segundo com os demais pontos. Além da presença dos táxons litorâneos vindos dos reservatórios, houve incremento de táxons litorâneos residentes nos riachos. Pode-se concluir que houve uma diluição da abundância das espécies a jusante dos riachos, mas a riqueza e a diversidade permaneceram estáveis devido à contribuição de táxons litorâneos.

The hypotheses tested were that, as well as in reservoirs of large surface areas, volumes and flow, in small reservoirs there is also a gradual and continuous dilution of the richness, diversity and abundance of microcrustaceans (Cladocera and Copepoda) downstream reservoirs, without the recomposition of richness downstream due to the lack of tributary rivers, marginal lagoons and even the small size of the stream, with no conditions for the development of its own potamoplankton. Two small reservoirs were studied and in their downstream stretches, with daily collections every six hours at eight sampling points, two lentic and six lotic downstream from each. Nineteen species were found (11 from Cladocera and eight from Copepoda), with emphasis on the greater number of coastal species than pelagic ones, and the greater abundance of coastal cladocerans at the points downstream of the reservoirs. There was no difference between the times, indicating that the spatial scale was more important than the temporal scale. There were higher values of ecological attributes in lentic environments, but there were significant increases in richness and diversity in the last points of the stretches of the stream, while the abundance decreased gradually downstream. No significant correlations were found for the abundance of taxa with any physical and chemical variable (temperature, pH, dissolved oxygen, turbidity, total dissolved solids and transparency), indicating little or no effect of these variables. The cluster analysis with Euclidean distance separated two large groups, the first formed by the stretch downstream of the first reservoir and the second with the other points. In addition to the presence of litoranean taxa coming from reservoirs, there was an increase in litoranean taxa resident in streams. It can be concluded that there was a dilution of the abundance of species downstream of the streams, but the richness and diversity remained stable due to the contribution of litoranean taxa.

A variação da diversidade de microcrustáceos (Cladocera e Copepoda) a jusante de pequenos reservatórios é influenciada por táxons litorâneos

ABSTRACT The hypotheses tested were that, as well as in reservoirs of large surface areas, volumes and flow, in small reservoirs there is also a gradual and continuous dilution of the richness, diversity and abundance of microcrustaceans (Cladocera and Copepoda) downstream reservoirs, without the recomposition of richness downstream due to the lack of tributary rivers, marginal lagoons and even the small size of the stream, with no conditions for the development of its own potamoplankton. Two small reservoirs were studied and in their downstream stretches, with daily collections every six hours at eight sampling points, two lentic and six lotic downstream from each. Nineteen species were found (11 from Cladocera and eight from Copepoda), with emphasis on the greater number of coastal species than pelagic ones, and the greater abundance of coastal cladocerans at the points downstream of the reservoirs. There was no difference between the times, indicating that the spatial scale was more important than the temporal scale. There were higher values of ecological attributes in lentic environments, but there were significant increases in richness and diversity in the last points of the stretches of the stream, while the abundance decreased gradually downstream. No significant correlations were found for the abundance of taxa with any physical and chemical variable (temperature, pH, dissolved oxygen, turbidity, total dissolved solids and transparency), indicating little or no effect of these variables. The cluster analysis with Euclidean distance separated two large groups, the first formed by the stretch downstream of the first reservoir and the second with the other points. In addition to the presence of litoranean taxa coming from reservoirs, there was an increase in litoranean taxa resident in streams. It can be concluded that there was a dilution of the abundance of species downstream of the streams, but the richness and diversity remained stable due to the contribution of litoranean taxa.

RESUMO Testaram-se as hipóteses de que, assim como em reservatórios de grande áreas de superfície, volumes e vazão, em reservatórios pequenos também ocorrem a diluição gradual e contínua da riqueza, da diversidade e abundância de microcrustáceos (Cladocera e Copepoda) a jusante dos mesmos, sem a recomposição da riqueza a jusante pela falta de rios tributários, lagoas marginais e até pelo pequeno porte do riacho, sem condições para o desenvolvimento do potamoplâncton próprio do sistema. Foram estudados dois pequenos reservatórios e seus trechos a jusante, com coletas diárias a cada seis horas em oito pontos de amostragem, sendo dois lênticos e seis lóticos a jusante de cada. Foram encontradas 19 espécies (11 de Cladocera e oito de Copepoda), com destaque para o maior número de espécies litorâneas do que pelágicas, e a maior abundância de cladóceros litorâneos nos pontos a jusante dos reservatórios. Não houve diferença entre os horários, indicando que a escala espacial foi mais importante que a temporal. Houve maiores valores dos atributos ecológicos nos ambientes lênticos, porém houve aumentos significativos de riqueza e diversidade nos últimos pontos dos trechos de riacho, enquanto que a abundância diminuiu gradativamente a jusante. Não foram encontradas correlações significativas da abundância dos táxons com nenhuma variável limnológica (temperatura, pH, oxigênio dissolvido, turbidez, sólidos totais dissolvidos e transparência), indicando pouco ou nenhum efeito destas variáveis. A análise de cluster com distância euclidiana separou dois grandes grupos, o primeiro formado pelo trecho a jusante do primeiro reservatório e o segundo com os demais pontos. Além da presença dos táxons litorâneos vindos dos reservatórios, houve incremento de táxons litorâneos residentes nos riachos. Pode-se concluir que houve uma diluição da abundância das espécies a jusante dos riachos, mas a riqueza e a diversidade permaneceram estáveis devido à contribuição de táxons litorâneos.

Vocal repertoire and group-specific signature in the Smooth-billed Ani, Crotophaga ani Linnaeus, 1758 (Cuculiformes, Aves)

Abstract Vocal plasticity reflects the ability of animals to vary vocalizations according to context (vocal repertoire) as well as to develop vocal convergence (vocal group signature) in the interaction of members in social groups. This feature has been largely reported for oscine, psittacine and trochilid birds, but little has been investigated in birds that present innate vocalization. The smooth-billed ani (Crotophaga ani) is a social bird that lives in groups between two and twenty individuals, and which presents innate vocalization. Here we analyzed the vocal repertoire of this species during group activities, and further investigated the existence of a vocal group signature. The study was conducted in the Southeast of Brazil between May 2017 and April 2018. Two groups of smooth-billed anis were followed, Guararema and Charqueada groups, and their vocalizations were recorded and contextualized as to the performed behavior. The vocal repertoire was analyzed for its composition, context and acoustic variables. The acoustic parameters maximum peak frequency, maximum fundamental frequency, minimum frequency, maximum frequency and duration were analyzed. To verify the vocal signature of the group, we tested whether there was variation in the acoustic parameters between the monitored groups. We recorded ten vocalizations that constituted the vocal repertoire of the Smooth-billed Ani, five of which (Ahnee, Whine, Pre-flight, Flight and Vigil) were issued by the two groups and five exclusive to the Charqueada group. There were significant differences in the acoustic parameters for Flight and Vigil vocalizations between the groups, suggesting vocal group signature for these sounds. We established that the Smooth-billed Ani has a diverse vocal repertoire, with variations also occurring between groups of the same population. Moreover, we found evidence of vocal group signature in vocalizations used in the context of cohesion, defense and territory maintenance.

Vocal repertoire and group-specific signature in the Smooth-billed Ani, Crotophaga ani Linnaeus, 1758 (Cuculiformes, Aves)

Abstract Vocal plasticity reflects the ability of animals to vary vocalizations according to context (vocal repertoire) as well as to develop vocal convergence (vocal group signature) in the interaction of members in social groups. This feature has been largely reported for oscine, psittacine and trochilid birds, but little has been investigated in birds that present innate vocalization. The smooth-billed ani (Crotophaga ani) is a social bird that lives in groups between two and twenty individuals, and which presents innate vocalization. Here we analyzed the vocal repertoire of this species during group activities, and further investigated the existence of a vocal group signature. The study was conducted in the Southeast of Brazil between May 2017 and April 2018. Two groups of smooth-billed anis were followed, Guararema and Charqueada groups, and their vocalizations were recorded and contextualized as to the performed behavior. The vocal repertoire was analyzed for its composition, context and acoustic variables. The acoustic parameters maximum peak frequency, maximum fundamental frequency, minimum frequency, maximum frequency and duration were analyzed. To verify the vocal signature of the group, we tested whether there was variation in the acoustic parameters between the monitored groups. We recorded ten vocalizations that constituted the vocal repertoire of the Smooth-billed Ani, five of which ("Ahnee", "Whine", "Pre-flight", "Flight" and "Vigil") were issued by the two groups and five exclusive to the Charqueada group. There were significant differences in the acoustic parameters for "Flight" and "Vigil" vocalizations between the groups, suggesting vocal group signature for these sounds. We established that the Smooth-billed Ani has a diverse vocal repertoire, with variations also occurring between groups of the same population. Moreover, we found evidence of vocal group signature in vocalizations used in the context of cohesion, defense and territory maintenance.

Vocal repertoire and group-specific signature in the Smooth-billed Ani, Crotophaga aniLinnaeus, 1758 (Cuculiformes, Aves)

Vocal plasticity reflects the ability of animals to vary vocalizations according to context (vocal repertoire) as well as to develop vocal convergence (vocal group signature) in the interaction of members in social groups. This feature has been largely reported for oscine, psittacine and trochilid birds, but little has been investigated in birds that present innate vocalization. The smooth-billed ani (Crotophaga ani) is a social bird that lives in groups between two and twenty individuals, and which presents innate vocalization. Here we analyzed the vocal repertoire of this species during group activities, and further investigated the existence of a vocal group signature. The study was conducted in the Southeast of Brazil between May 2017 and April 2018. Two groups of smooth-billed anis were followed, Guararema and Charqueada groups, and their vocalizations were recorded and contextualized as to the performed behavior. The vocal repertoire was analyzed for its composition, context and acoustic variables. The acoustic parameters maximum peak frequency, maximum fundamental frequency, minimum frequency, maximum frequency and duration were analyzed. To verify the vocal signature of the group, we tested whether there was variation in the acoustic parameters between the monitored groups. We recorded ten vocalizations that constituted the vocal repertoire of the Smooth-billed Ani, five of which (“Ahnee”, “Whine”, “Pre-flight”, “Flight” and “Vigil”) were issued by the two groups and five exclusive to the Charqueada group. There were significant differences in the acoustic parameters for “Flight” and “Vigil” vocalizations between the groups, suggesting vocal group signature for these sounds. We established that the Smooth-billed Ani has a diverse vocal repertoire, with variations also occurring between groups of the same population. Moreover, we found evidence of vocal group signature in vocalizations used in the context of cohesion, defense and territory maintenance.(AU)

Survival of the copepod Mesocyclops longisetus during simulations of transport from hatchery to target areas for biological control of mosquito larvae

Copepods have been successfully used in many countries for the biological control of larvae of mosquitoes that vector diseases. In Brazil, this line of research has been focused on the use of the copepod Mesocyclops longisetus (Thiébaud, 1914) for the biological control of the mosquito Aedes aegypti (Linnaeus, 1792). The transportation of the copepods from the place where they are reared to where they will be used often involves long distances for extended periods of time. This study assesses the survivorship of M. longisetus during simulation of transport under different conditions. Different loading densities (20, 30, 40, 80, and 120 ind.L) and stirring times (30 minutes, one hour, two hours, and four hours) were tested. Survivorship was high, with 75% of the results equal or higher than 90% survival. Reduced mortality was observed when transportation time was up to 120 minutes and densities were up to 40 ind.L. In higher densities or longer transportation times, the mortality rate was significantly affected.

Baixa riqueza zooplanctônica indicando condições adversas de seca e eutrofização em um reservatório no Nordeste do Brasil / Low zooplankton richness indicating adverse drought and eutrophication conditions in a reservoir in northeastern Brazil

This work characterized the zooplankton and the environmental variables of the Canoas reservoir (Assaré, Ceará, Brazil) through eight consecutive monthly collections during a period of intense drought. Zooplankton samples were collected by vertical plots of 50 µm plankton net at three longitudinally distributed points. Five species were found: Brachionus calicyflorus Pallas, 1938 (Brachionidae: Rotifera), Diaphanosoma spinulosum Herbst, 1967 (Sididae: Cladocera), Thermocyclops decipiens Kiefer, 1929 and T. inversus Kiefer, 1936 (Cyclopoida: Copepoda), and Notodiaptomus cearensis Wright, 1936 (Calanoida: Copepoda). Thermocyclops decipiens had the highest relative abundance, followed by N. cearensis and B. calicyflorus. The spatial and temporal variation of the zooplankton community can be explained by most of the environmental variables associated with N. cearensis and B. calicyflorus, while T. decipiens was not associated with any of them. The low species richness and dominance of T. decipiens and B. calicyflorus may be a reflection of the high trophic condition of the reservoir during severe drought, and N. cearensis is also associated with these more adverse conditions.(AU)

Esse trabalho caracterizou o zooplâncton e as variáveis ambientais do reservatório Canoas (Assaré, Ceará, Brasil) através de oito coletas consecutivas mensais, durante um período de estiagem intensa. Amostras de zooplâncton foram coletadas com arrastos verticais de rede de plâncton de 50 µm em três pontos distribuídos longitudinalmente. Foram encontradas cinco espécies: Brachionus calicyflorus Pallas, 1938 (Brachionidae: Rotifera), Diaphanosoma spinulosum Herbst, 1967 (Sididae: Cladocera), Thermocyclops decipiens Kiefer, 1929 e T. inversus Kiefer, 1936 (Cyclopoida: Copepoda), e Notodiaptomus cearensis Wright, 1936 (Calanoida: Copepoda). Thermocyclops decipiens apresentou a maior abundância relativa, seguido de N. cearensis e B. calicyflorus. A variação espacial e temporal da comunidade zooplanctônica pode ser explicada pela maioria das variáveis ambientais associadas a N. cearensis e B. calicyflorus, enquanto T. decipiens não se associou a nenhuma delas. A baixa riqueza de espécies e a dominância de T. decipiens e B. calicyflorus podem ser reflexos da elevada condição trófica do reservatório, em período de estiagem intensa, e N. cearensis está associado também com essas condições mais adversas.(AU)

Survival of the copepod Mesocyclops longisetus during simulations of transport from hatchery to target areas for biological control of mosquito larvae

Copepods have been successfully used in many countries for the biological control of larvae of mosquitoes that vector diseases. In Brazil, this line of research has been focused on the use of the copepod Mesocyclops longisetus (Thiébaud, 1914) for the biological control of the mosquito Aedes aegypti (Linnaeus, 1792). The transportation of the copepods from the place where they are reared to where they will be used often involves long distances for extended periods of time. This study assesses the survivorship of M. longisetus during simulation of transport under different conditions. Different loading densities (20, 30, 40, 80, and 120 ind.L) and stirring times (30 minutes, one hour, two hours, and four hours) were tested. Survivorship was high, with 75% of the results equal or higher than 90% survival. Reduced mortality was observed when transportation time was up to 120 minutes and densities were up to 40 ind.L. In higher densities or longer transportation times, the mortality rate was significantly affected.(AU)

Baixa riqueza zooplanctônica indicando condições adversas de seca e eutrofização em um reservatório no Nordeste do Brasil / Low zooplankton richness indicating adverse drought and eutrophication conditions in a reservoir in northeastern Brazil

This work characterized the zooplankton and the environmental variables of the Canoas reservoir (Assaré, Ceará, Brazil) through eight consecutive monthly collections during a period of intense drought. Zooplankton samples were collected by vertical plots of 50 µm plankton net at three longitudinally distributed points. Five species were found: Brachionus calicyflorus Pallas, 1938 (Brachionidae: Rotifera), Diaphanosoma spinulosum Herbst, 1967 (Sididae: Cladocera), Thermocyclops decipiens Kiefer, 1929 and T. inversus Kiefer, 1936 (Cyclopoida: Copepoda), and Notodiaptomus cearensis Wright, 1936 (Calanoida: Copepoda). Thermocyclops decipiens had the highest relative abundance, followed by N. cearensis and B. calicyflorus. The spatial and temporal variation of the zooplankton community can be explained by most of the environmental variables associated with N. cearensis and B. calicyflorus, while T. decipiens was not associated with any of them. The low species richness and dominance of T. decipiens and B. calicyflorus may be a reflection of the high trophic condition of the reservoir during severe drought, and N. cearensis is also associated with these more adverse conditions.

Esse trabalho caracterizou o zooplâncton e as variáveis ambientais do reservatório Canoas (Assaré, Ceará, Brasil) através de oito coletas consecutivas mensais, durante um período de estiagem intensa. Amostras de zooplâncton foram coletadas com arrastos verticais de rede de plâncton de 50 µm em três pontos distribuídos longitudinalmente. Foram encontradas cinco espécies: Brachionus calicyflorus Pallas, 1938 (Brachionidae: Rotifera), Diaphanosoma spinulosum Herbst, 1967 (Sididae: Cladocera), Thermocyclops decipiens Kiefer, 1929 e T. inversus Kiefer, 1936 (Cyclopoida: Copepoda), e Notodiaptomus cearensis Wright, 1936 (Calanoida: Copepoda). Thermocyclops decipiens apresentou a maior abundância relativa, seguido de N. cearensis e B. calicyflorus. A variação espacial e temporal da comunidade zooplanctônica pode ser explicada pela maioria das variáveis ambientais associadas a N. cearensis e B. calicyflorus, enquanto T. decipiens não se associou a nenhuma delas. A baixa riqueza de espécies e a dominância de T. decipiens e B. calicyflorus podem ser reflexos da elevada condição trófica do reservatório, em período de estiagem intensa, e N. cearensis está associado também com essas condições mais adversas.

Baixa riqueza zooplanctônica indicando condições adversas de seca e eutrofização em um reservatório no Nordeste do Brasil

ABSTRACT This work characterized the zooplankton and the environmental variables of the Canoas reservoir (Assaré, Ceará, Brazil) through eight consecutive monthly collections during a period of intense drought. Zooplankton samples were collected by vertical plots of 50 µm plankton net at three longitudinally distributed points. Five species were found: Brachionus calicyflorus Pallas, 1938 (Brachionidae: Rotifera), Diaphanosoma spinulosum Herbst, 1967 (Sididae: Cladocera), Thermocyclops decipiens Kiefer, 1929 and T. inversus Kiefer, 1936 (Cyclopoida: Copepoda), and Notodiaptomus cearensis Wright, 1936 (Calanoida: Copepoda). Thermocyclops decipiens had the highest relative abundance, followed by N. cearensis and B. calicyflorus. The spatial and temporal variation of the zooplankton community can be explained by most of the environmental variables associated with N. cearensis and B. calicyflorus, while T. decipiens was not associated with any of them. The low species richness and dominance of T. decipiens and B. calicyflorus may be a reflection of the high trophic condition of the reservoir during severe drought, and N. cearensis is also associated with these more adverse conditions.

RESUMO Esse trabalho caracterizou o zooplâncton e as variáveis ambientais do reservatório Canoas (Assaré, Ceará, Brasil) através de oito coletas consecutivas mensais, durante um período de estiagem intensa. Amostras de zooplâncton foram coletadas com arrastos verticais de rede de plâncton de 50 µm em três pontos distribuídos longitudinalmente. Foram encontradas cinco espécies: Brachionus calicyflorus Pallas, 1938 (Brachionidae: Rotifera), Diaphanosoma spinulosum Herbst, 1967 (Sididae: Cladocera), Thermocyclops decipiens Kiefer, 1929 e T. inversus Kiefer, 1936 (Cyclopoida: Copepoda), e Notodiaptomus cearensis Wright, 1936 (Calanoida: Copepoda). Thermocyclops decipiens apresentou a maior abundância relativa, seguido de N. cearensis e B. calicyflorus. A variação espacial e temporal da comunidade zooplanctônica pode ser explicada pela maioria das variáveis ambientais associadas a N. cearensis e B. calicyflorus, enquanto T. decipiens não se associou a nenhuma delas. A baixa riqueza de espécies e a dominância de T. decipiens e B. calicyflorus podem ser reflexos da elevada condição trófica do reservatório, em período de estiagem intensa, e N. cearensis está associado também com essas condições mais adversas.

An assessment of the factors determining rotifer assemblage in river-lake systems: the effects of seasonality and habitat

Zooplankton exhibit several trends of variation in space and time, and these trends can be more evident in natural environments without anthropic perturbations. Examples of anthropic factors are climate change, eutrophication and construction of reservoirs. This study evaluated the influence of three factors - seasonality, type of environment and the presence of aquatic macrophytes - on various ecological attributes of rotifers in a river-lake system located in the Paraná River floodplain. Monthly samplings were conducted during 1993 and 1994. The mean species richness per sample was 60 species. The seasonality and the type of environment influenced the ecological attributes of rotifer assemblages, while the presence or absence of aquatic macrophytes did not. Species richness was highest in the lake system and during the months when water levels were low. Multivariate analysis indicates a small group of species associated with the low water-level phase. In contrast, many species were associated with high water levels or increasing water levels. The seasonal variation of hydrological cycle and the type of environment are the most important factors for rotifer structure in natural conditions.

An assessment of the factors determining rotifer assemblage in river-lake systems: the effects of seasonality and habitat

Zooplankton exhibit several trends of variation in space and time, and these trends can be more evident in natural environments without anthropic perturbations. Examples of anthropic factors are climate change, eutrophication and construction of reservoirs. This study evaluated the influence of three factors - seasonality, type of environment and the presence of aquatic macrophytes - on various ecological attributes of rotifers in a river-lake system located in the Paraná River floodplain. Monthly samplings were conducted during 1993 and 1994. The mean species richness per sample was 60 species. The seasonality and the type of environment influenced the ecological attributes of rotifer assemblages, while the presence or absence of aquatic macrophytes did not. Species richness was highest in the lake system and during the months when water levels were low. Multivariate analysis indicates a small group of species associated with the low water-level phase. In contrast, many species were associated with high water levels or increasing water levels. The seasonal variation of hydrological cycle and the type of environment are the most important factors for rotifer structure in natural conditions.(AU)

Estimating cyclopoid copepod species richness and geographical distribution (Crustacea) across a large hydrographical basin: comparing between samples from water column (plankton) and macrophyte stands

Species richness and geographical distribution of Cyclopoida freshwater copepods were analyzed along the "La Plata" River basin. Ninety-six samples were taken from 24 sampling sites, twelve sites for zooplankton in open waters and twelve sites for zooplankton within macrophyte stands, including reservoirs and lotic stretches. There were, on average, three species per sample in the plankton compared to five per sample in macrophytes. Six species were exclusive to the plankton, 10 to macrophyte stands, and 17 were common to both. Only one species was found in similar proportions in plankton and macrophytes, while five species were widely found in plankton, and thirteen in macrophytes. The distinction between species from open water zooplankton and macrophytes was supported by nonmetric multidimensional analysis. There was no distinct pattern of endemicity within the basin, and double sampling contributes to this result. This lack of sub-regional faunal differentiation is in accordance with other studies that have shown that cyclopoids generally have wide geographical distribution in the Neotropics and that some species there are cosmopolitan. This contrasts with other freshwater copepods such as Calanoida and some Harpacticoida. We conclude that sampling plankton and macrophytes together provided a more accurate estimate of the richness and geographical distribution of these organisms than sampling in either one of those zones alone.

Estimating cyclopoid copepod species richness and geographical distribution (Crustacea) across a large hydrographical basin: comparing between samples from water column (plankton) and macrophyte stands

Species richness and geographical distribution of Cyclopoida freshwater copepods were analyzed along the "La Plata" River basin. Ninety-six samples were taken from 24 sampling sites, twelve sites for zooplankton in open waters and twelve sites for zooplankton within macrophyte stands, including reservoirs and lotic stretches. There were, on average, three species per sample in the plankton compared to five per sample in macrophytes. Six species were exclusive to the plankton, 10 to macrophyte stands, and 17 were common to both. Only one species was found in similar proportions in plankton and macrophytes, while five species were widely found in plankton, and thirteen in macrophytes. The distinction between species from open water zooplankton and macrophytes was supported by nonmetric multidimensional analysis. There was no distinct pattern of endemicity within the basin, and double sampling contributes to this result. This lack of sub-regional faunal differentiation is in accordance with other studies that have shown that cyclopoids generally have wide geographical distribution in the Neotropics and that some species there are cosmopolitan. This contrasts with other freshwater copepods such as Calanoida and some Harpacticoida. We conclude that sampling plankton and macrophytes together provided a more accurate estimate of the richness and geographical distribution of these organisms than sampling in either one of those zones alone.(AU)

Rediscovered after 77 years: Odontodiaptomus thomseni - a rare species of calanoid (Crustacea: Copepoda) from South America

The freshwater copepod Odontodiaptomus thomseni (Brehm, 1933) (Calanoida: Diaptomidae) is a rare species that has been reported only once - in its original description (BREHM 1933). The lack of subsequent records led to its inclusion in the Red List of threatened species (IUCN). Here we present a new record for O.thomseni. It was discovered in Salto Grande reservoir, which is located in the lower stretches of the Uruguay River, between Uruguay and Argentina, at the River Plate basin. In January 2010, three specimens (two males and one female) were found, and these were studied in detail using scanning electron microscopy (SEM). We only had material of Odontodiaptomus paulistanus (Wright, 1936) for comparison, but the position of the lateral spine in right P5 of the male, and the shape and size of lateral wings of the female are especially distinctive. Odontodiaptomus thomseni remains a rare species and we recommend keeping it on the IUCN Red List.

Rediscovered after 77 years: Odontodiaptomus thomseni - a rare species of calanoid (Crustacea: Copepoda) from South America

The freshwater copepod Odontodiaptomus thomseni (Brehm, 1933) (Calanoida: Diaptomidae) is a rare species that has been reported only once - in its original description (BREHM 1933). The lack of subsequent records led to its inclusion in the Red List of threatened species (IUCN). Here we present a new record for O.thomseni. It was discovered in Salto Grande reservoir, which is located in the lower stretches of the Uruguay River, between Uruguay and Argentina, at the River Plate basin. In January 2010, three specimens (two males and one female) were found, and these were studied in detail using scanning electron microscopy (SEM). We only had material of Odontodiaptomus paulistanus (Wright, 1936) for comparison, but the position of the lateral spine in right P5 of the male, and the shape and size of lateral wings of the female are especially distinctive. Odontodiaptomus thomseni remains a rare species and we recommend keeping it on the IUCN Red List.

Rediscovered after 77 years: Odontodiaptomus thomseni - a rare species of calanoid (Crustacea: Copepoda) from South America

The freshwater copepod Odontodiaptomus thomseni (Brehm, 1933) (Calanoida: Diaptomidae) is a rare species that has been reported only once - in its original description (BREHM 1933). The lack of subsequent records led to its inclusion in the Red List of threatened species (IUCN). Here we present a new record for O.thomseni. It was discovered in Salto Grande reservoir, which is located in the lower stretches of the Uruguay River, between Uruguay and Argentina, at the River Plate basin. In January 2010, three specimens (two males and one female) were found, and these were studied in detail using scanning electron microscopy (SEM). We only had material of Odontodiaptomus paulistanus (Wright, 1936) for comparison, but the position of the lateral spine in right P5 of the male, and the shape and size of lateral wings of the female are especially distinctive. Odontodiaptomus thomseni remains a rare species and we recommend keeping it on the IUCN Red List.

Record of Argyrodiaptomus bergi (Crustacea: Copepoda: Calanoida) after 36 years and first record in Brazil

The first record of Argyrodiaptomus bergi (Richard, 1897) from a small roadside pool at high altitude in the southern region of Brazil is presented. This is the ninth record of this species in South America (previously known from Argentina and Uruguay) since its original description, and a new occurrence after 36 years, extending its known distribution to the northeast. The environments where this species was found differ sharply, and possible explanations include the loss of habitat, high species selectivity or deficient sampling efforts. An additional description is provided, with scanning electron microscopy (SEM) photomicrographs and line drawings. Similarly to other species of Argyrodiaptomus, such as Argyrodiaptomus falcifer (Daday, 1905), Argyrodiaptomus denticulatus (Pesta, 1927) and Argyrodiaptomus granulosus (Brehm, 1933), this species shows a restricted distribution in the lower stretches of the Paraná and Uruguay rivers, particularly in small pools. The importance of better understanding the dynamics and diversity of small water bodies is discussed.

Record of Argyrodiaptomus bergi (Crustacea: Copepoda: Calanoida) after 36 years and first record in Brazil

The first record of Argyrodiaptomus bergi (Richard, 1897) from a small roadside pool at high altitude in the southern region of Brazil is presented. This is the ninth record of this species in South America (previously known from Argentina and Uruguay) since its original description, and a new occurrence after 36 years, extending its known distribution to the northeast. The environments where this species was found differ sharply, and possible explanations include the loss of habitat, high species selectivity or deficient sampling efforts. An additional description is provided, with scanning electron microscopy (SEM) photomicrographs and line drawings. Similarly to other species of Argyrodiaptomus, such as Argyrodiaptomus falcifer (Daday, 1905), Argyrodiaptomus denticulatus (Pesta, 1927) and Argyrodiaptomus granulosus (Brehm, 1933), this species shows a restricted distribution in the lower stretches of the Paraná and Uruguay rivers, particularly in small pools. The importance of better understanding the dynamics and diversity of small water bodies is discussed.