Os crustáceos límnicos do gênero Hyalella contam com 51 espécies amplamente distribuídas pelas regiões Neártica e Neotropical. Na América do Sul o Brasil apresenta a segunda maior diversidade para o gênero que é apenas superada pela diversidade encontrada no lago Titicaca. São 13 espécies distribuídas pelos estados do sul e sudeste. A identificação das espécies de Hyalella é um processo complexo que exige muita experiência no conhecimento do grupo. Além disto faltam informações sobre morfologia, ecologia e comportamento para a maioria das espécies. Este estudo teve como objetivo descrever a ultraestrutura cuticular de H. castroi e H. pleoacuta. Ambas as espécies foram coletadas em tanques de cultivo de peixes (trutas) próximo à nascente do Rio das Antas no município de São José dos Ausentes, RS, Brasil (28º 47’ 00’’S 49º 50’ 53’’W). A superfície cuticular de espécimes das duas espécies foi examinada em microscopia eletrônica de varredura e observações complementares foram realizadas em microscopia óptica. Os resultados mostraram que uma grande diversidade de estruturas está presente na cuticula de ambas as espécies, entre elas 30 tipos de setas, sendo dois destes exclusivos de machos, quatro tipos de microtríquia, dois tipos de poros e uma grande variedade de sétulas e dentículos. O tipo distribuição a morfologia e a ornamentação destas estruturas não difere entre as duas espécies. Muitas das estruturas observadas são semelhantes àquelas registradas para Amphipoda e Isopoda com alguma variação em sua ornamentação. O padrão de inserção da seta plumosa nas duas espécies de Hyalella difere daquele observado para crustáceos decápodos, e foi considerado uma característica importante na separação dos grupos de Malacostraca. O padrão de distribuição das microtríquias na superfície dorsal das duas espécies difere daquele encontrado para outros anfípodos e foi considerado uma característica exclusiva do gênero Hyalella. Os apêndices bucais concentram a maior diversidade de setas e demais microestruturas, e não diferem entre as duas espécies. Diferenças encontradas na ornamentação do lobo carpal dos gnatópodos 1 e 2 em ambas as espécies, na ornamentação do bordo anterior dos gnatópodos das fêmeas e o número de setas no télson foram consideradas características diagnósticas importantes no nível específico. Estes resultados mostraram que as microestruturas constituem ferramentas importantes para a separação das espécies do gênero.

Considerando a importância dos anfípodos como bioindicadores de qualidade ambiental e por serem espécies representativas da fauna de invertebrados aquáticos continentais, este trabalho teve por objetivo o estudo do ciclo biológico de duas espécies simpátricas, Hyalella pleoacuta González, Bond-Buckup & Araujo 2006 e H. castroi González, Bond-Buckup & Araujo 2006. Com vistas à caracterização da dinâmica populacional das duas espécies em campo foram avaliados o tamanho dos animais, a distribuição de freqüência em classes de tamanho, a maturidade sexual, a proporção sexual, o período reprodutivo, o recrutamento, a fecundidade e o sucesso de pareamento e o sucesso reprodutivo. Os espécimes foram coletados com auxílio de puçá, durante 12 meses, em 4 pontos distintos em 2 tanques de cultivo de trutas na localidade de Vale das Trutas, próximo as nascentes do Rio das Antas, município de São José dos Ausentes, RS (28°47’00”S - 49°50’53”O). O sexo e a condição ovígera das fêmeas foram registrados e todos os espécimes foram medidos quanto ao comprimento do cefalotórax (mm). Em laboratório as duas espécies foram cultivadas a 19 °C ± 1 °C e 12h luz / 12h escuro, identificando a duração do comportamento pré-copulatório, o tamanho de machos e fêmeas em pré-copula, o tamanho corpóreo das fêmeas ovígeras, o tempo médio de desenvolvimento embrionário e pósembrionário, a fecundidade, a viabilidade (número médio de juvenis liberados), a duração do ciclo de muda e a longevidade. Em laboratório os animais foram alimentados com ração para peixe (43% de proteína), macrófitas (Salvinia sp. e Callitriche rimosa) e alga (Ankistrodesmus sp.). A idade da primeira muda, a freqüência de muda, a idade da determinação do sexo e a maturidade sexual foram similares entre as espécies de Hyalella em condições laboratoriais. Entretanto, o período de intermuda total, o tamanho corpóreo máximo e a longevidade diferiram entre H. pleoacuta e H. castroi.Foi observada correlação entre o tamanho dos machos e fêmeas nos casais em pré-copula, ou seja, machos grandes carregam fêmeas grandes em ambas espécies de Hyalella. O sucesso de pareamento e sucesso reprodutivo dos machos aumenta a medida que o seu tamanho corpóreo também aumenta em ambas espécies de Hyalella. Fêmeas de tamanho corpóreo intermediário apresentaram maior sucesso reprodutivo em ambas espécies de Hyalella. Tanto H. pleoacuta como H. castroi mostraram as mesmas estratégias reprodutivas, especialmente quanto a duração do comportamento de pré-copula, a duração do período embrionário, fecundidade e fertilidade. Com relação à produção de ovos, H. pleoacuta produziu mais ovos do que H. castroi, mas nesta última os ovos são maiores. Em ambas espécies foi observada diminuição no número de ovos ao longo do desenvolvimento. Ambas espécies de Hyallela apresentaram uma estrutura populacional muito similar, especialmente a distribuição de freqüência em classes de tamanho, o maior tamanho corpóreo dos machos em relação às fêmeas, o padrão de proporção sexual com predominância de fêmeas e a reprodução e recrutamento contínuos. Entretanto, as espécies diferiram quanto ao número de exemplares amostrados, sendo H. pleoacuta aproximadamente 3 vezes mais freqüente do que H. castroi e também pelo fato de H. pleoacuta apresentar um tamanho corpóreo menor do que H. castroi. Além disso, H. pleoacuta reproduz-se com maior intensidade no outono e H. castroi no inverno. Diante dos resultados obtidos pode-se inferir que a coexistência de H. pleoacuta e H. castroi nos tanques de cultivo de trutas é facilitida pelas diferenças observadas no ciclo de vida, especialmente no tamanho corpóreo e nas estratégias reprodutivas. / Considering the importance of the amphipods as bioindicators of environmental quality and by being representative species of the aquatic invertebrate fauna of the continents, this work it was performed with the aim to analyze and to compare the biologic cycle of the sympatric species, Hyalella pleoacuta and H. castroi. Population dynamics was characterized by means of the frequency distribution in size classes, body size, size at sexual maturity, sex ratio, breeding period, recruitment, fecundity and pairing and reproductive success. The amphipods were collected monthly with nets from August 2003 through July 2004 in four distinct sites of two trout ponds at Vale das Trutas locality, São José dos Ausentes County, southern Brazil (28°47’00”S - 49°50’53”W). In the laboratory, the specimens were measured as cephalothorax length (mm), being the sex and ovigerous conditions checked. Two species of Hyalella were cultivated to 19 °C ± 1 °C and 12h light / 12h dark, being that the duration of the precopulatory mate-guarding phase, body size of males and females in precopulatory mating behavior, body size of ovigerous females, embryonic and postembryonic periods, fecundity, viability (mean number of juveniles liberated), time to first molt, intermolt duration, molt frequency, sex determination, sexual maturation, growth and longevity were estimated.At the laboratory cultures, the amphipods were feed with fish food (43% of protein), macrophytes (Salvinia sp. and Callitriche rimosa) and algae (Ankistrodesmus sp.). The time to first molt, the molt frequency, the age of the sex determination and the sexual maturation were very similar between species of Hyalella in laboratory culture. However, the total intermolt period, the maximum body size and the longevity differed between H. pleoacuta and H. castroi. Positive assortative mating by size was observed in both species, i.e., larger males tended to pair with larger females. Male pairing success increased sharply with size. In bothspecies, reproductive success in males increased with body size; however, the females of intermediate size classes showed greater reproductive success. Both species of Hyalella showed the same reproductive strategies, specially the duration of the precopulatory mateguarding behavior, the duration of embryonic period, fecundity and viability. Egg production was greater in H. pleoacuta, but their eggs are minor than eggs produced by H. castroi. The number of eggs carried by females decreased with developmental stage in both H. pleoacuta and H. castroi, suggesting that egg loss may have occurred. Both species of Hyalella showed a population structure very similar, specially the frequency distribution in size classes, the larger body size of males and the reproduction and recruitment continuous. However, the species differed as number of specimens sampled, being H. pleoacuta about 3 times more frequent than H. castroi and also by the fact of H. castroi showed a larger body size than H. pleoacuta. Besides, H. pleoacuta reproduces with more intensity at the autumn and H. castroi at the winter. Probably the differences in the life cycle of H. pleoacuta and H. castroi, especially the body size and the reproductive strategies, can facilite the coexistence of these two species in the trout pond.

Os crustáceos límnicos do gênero Hyalella contam com 51 espécies amplamente distribuídas pelas regiões Neártica e Neotropical. Na América do Sul o Brasil apresenta a segunda maior diversidade para o gênero que é apenas superada pela diversidade encontrada no lago Titicaca. São 13 espécies distribuídas pelos estados do sul e sudeste. A identificação das espécies de Hyalella é um processo complexo que exige muita experiência no conhecimento do grupo. Além disto faltam informações sobre morfologia, ecologia e comportamento para a maioria das espécies. Este estudo teve como objetivo descrever a ultraestrutura cuticular de H. castroi e H. pleoacuta. Ambas as espécies foram coletadas em tanques de cultivo de peixes (trutas) próximo à nascente do Rio das Antas no município de São José dos Ausentes, RS, Brasil (28º 47’ 00’’S 49º 50’ 53’’W). A superfície cuticular de espécimes das duas espécies foi examinada em microscopia eletrônica de varredura e observações complementares foram realizadas em microscopia óptica. Os resultados mostraram que uma grande diversidade de estruturas está presente na cuticula de ambas as espécies, entre elas 30 tipos de setas, sendo dois destes exclusivos de machos, quatro tipos de microtríquia, dois tipos de poros e uma grande variedade de sétulas e dentículos. O tipo distribuição a morfologia e a ornamentação destas estruturas não difere entre as duas espécies. Muitas das estruturas observadas são semelhantes àquelas registradas para Amphipoda e Isopoda com alguma variação em sua ornamentação. O padrão de inserção da seta plumosa nas duas espécies de Hyalella difere daquele observado para crustáceos decápodos, e foi considerado uma característica importante na separação dos grupos de Malacostraca. O padrão de distribuição das microtríquias na superfície dorsal das duas espécies difere daquele encontrado para outros anfípodos e foi considerado uma característica exclusiva do gênero Hyalella. Os apêndices bucais concentram a maior diversidade de setas e demais microestruturas, e não diferem entre as duas espécies. Diferenças encontradas na ornamentação do lobo carpal dos gnatópodos 1 e 2 em ambas as espécies, na ornamentação do bordo anterior dos gnatópodos das fêmeas e o número de setas no télson foram consideradas características diagnósticas importantes no nível específico. Estes resultados mostraram que as microestruturas constituem ferramentas importantes para a separação das espécies do gênero.

This study investigated whether principles of the Biotic Ligand Model (BLM), originally developed to predict acute metal toxicity to fish, may be applied to metal accumulation and toxicity in short-term and long-term exposures of Hyalella azteca, an epibenthic invertebrate. In both short-term and long-term exposures, hydrogen and calcium were the only cations found to significantly influence nickel accumulation and toxicity, although some influence by magnesium was suggested in solutions of low calcium and alkalinity. Analysis of short-term (seven-day) bioaccumulation and long-term (28-day) toxicity data established three potential models to explain the observed accumulation and/or toxicity. One of the models included calcium and hydrogen as competitors to nickel (consistent with BLM theory), while the other two models incorporated the non-competitive effect of calcium on the biotic ligand in addition to, or instead of, the competitive action of calcium (not currently considered by BLM theory). Short-term accumulation observed in the tests with adults was best predicted by the competitive (BLM-type) model. However, long-term accumulation and toxicity were predicted equally well by both competitive and non-competitive models. In short-term cadmium exposures the models including calcium as a competitor, rather than an influence on the ligand, predicted accumulation and toxicity best. Hydrogen did not appear to have a significant influence. Although both competitive and non-competitive calcium models were able to predict long-term toxicity within a factor of two of the observed for most tests, the relationship between predicted and observed LC50s was not linear. Instead, for a given calcium concentration, a wide range of LC50s was observed but was associated with a relatively constant predicted LC50 (based on the influence of calcium alone). The predicted LC50s fell roughly in three lateral bands, according to calcium concentrations of approximately 0.3, 1 and 3 mmol/L. The broad range of observed LC50s associated with a relatively constant predicted LC50 reflected variability in organism response in four-week exposures in similar media and/or may have suggested that other factors influencing cadmium toxicity were not accounted for in the models.

This study investigated whether principles of the Biotic Ligand Model (BLM), originally developed to predict acute metal toxicity to fish, may be applied to metal accumulation and toxicity in short-term and long-term exposures of Hyalella azteca, an epibenthic invertebrate. In both short-term and long-term exposures, hydrogen and calcium were the only cations found to significantly influence nickel accumulation and toxicity, although some influence by magnesium was suggested in solutions of low calcium and alkalinity. Analysis of short-term (seven-day) bioaccumulation and long-term (28-day) toxicity data established three potential models to explain the observed accumulation and/or toxicity. One of the models included calcium and hydrogen as competitors to nickel (consistent with BLM theory), while the other two models incorporated the non-competitive effect of calcium on the biotic ligand in addition to, or instead of, the competitive action of calcium (not currently considered by BLM theory). Short-term accumulation observed in the tests with adults was best predicted by the competitive (BLM-type) model. However, long-term accumulation and toxicity were predicted equally well by both competitive and non-competitive models. In short-term cadmium exposures the models including calcium as a competitor, rather than an influence on the ligand, predicted accumulation and toxicity best. Hydrogen did not appear to have a significant influence. Although both competitive and non-competitive calcium models were able to predict long-term toxicity within a factor of two of the observed for most tests, the relationship between predicted and observed LC50s was not linear. Instead, for a given calcium concentration, a wide range of LC50s was observed but was associated with a relatively constant predicted LC50 (based on the influence of calcium alone). The predicted LC50s fell roughly in three lateral bands, according to calcium concentrations of approximately 0.3, 1 and 3 mmol/L. The broad range of observed LC50s associated with a relatively constant predicted LC50 reflected variability in organism response in four-week exposures in similar media and/or may have suggested that other factors influencing cadmium toxicity were not accounted for in the models.

This study investigated whether principles of the Biotic Ligand Model (BLM), originally developed to predict acute metal toxicity to fish, may be applied to metal accumulation and toxicity in short-term and long-term exposures of Hyalella azteca, an epibenthic invertebrate. In both short-term and long-term exposures, hydrogen and calcium were the only cations found to significantly influence nickel accumulation and toxicity, although some influence by magnesium was suggested in solutions of low calcium and alkalinity. Analysis of short-term (seven-day) bioaccumulation and long-term (28-day) toxicity data established three potential models to explain the observed accumulation and/or toxicity. One of the models included calcium and hydrogen as competitors to nickel (consistent with BLM theory), while the other two models incorporated the non-competitive effect of calcium on the biotic ligand in addition to, or instead of, the competitive action of calcium (not currently considered by BLM theory). Short-term accumulation observed in the tests with adults was best predicted by the competitive (BLM-type) model. However, long-term accumulation and toxicity were predicted equally well by both competitive and non-competitive models. In short-term cadmium exposures the models including calcium as a competitor, rather than an influence on the ligand, predicted accumulation and toxicity best. Hydrogen did not appear to have a significant influence. Although both competitive and non-competitive calcium models were able to predict long-term toxicity within a factor of two of the observed for most tests, the relationship between predicted and observed LC50s was not linear. Instead, for a given calcium concentration, a wide range of LC50s was observed but was associated with a relatively constant predicted LC50 (based on the influence of calcium alone). The predicted LC50s fell roughly in three lateral bands, according to calcium concentrations of approximately 0.3, 1 and 3 mmol/L. The broad range of observed LC50s associated with a relatively constant predicted LC50 reflected variability in organism response in four-week exposures in similar media and/or may have suggested that other factors influencing cadmium toxicity were not accounted for in the models.

This study investigated whether principles of the Biotic Ligand Model (BLM), originally developed to predict acute metal toxicity to fish, may be applied to metal accumulation and toxicity in short-term and long-term exposures of Hyalella azteca, an epibenthic invertebrate. In both short-term and long-term exposures, hydrogen and calcium were the only cations found to significantly influence nickel accumulation and toxicity, although some influence by magnesium was suggested in solutions of low calcium and alkalinity. Analysis of short-term (seven-day) bioaccumulation and long-term (28-day) toxicity data established three potential models to explain the observed accumulation and/or toxicity. One of the models included calcium and hydrogen as competitors to nickel (consistent with BLM theory), while the other two models incorporated the non-competitive effect of calcium on the biotic ligand in addition to, or instead of, the competitive action of calcium (not currently considered by BLM theory). Short-term accumulation observed in the tests with adults was best predicted by the competitive (BLM-type) model. However, long-term accumulation and toxicity were predicted equally well by both competitive and non-competitive models. In short-term cadmium exposures the models including calcium as a competitor, rather than an influence on the ligand, predicted accumulation and toxicity best. Hydrogen did not appear to have a significant influence. Although both competitive and non-competitive calcium models were able to predict long-term toxicity within a factor of two of the observed for most tests, the relationship between predicted and observed LC50s was not linear. Instead, for a given calcium concentration, a wide range of LC50s was observed but was associated with a relatively constant predicted LC50 (based on the influence of calcium alone). The predicted LC50s fell roughly in three lateral bands, according to calcium concentrations of approximately 0.3, 1 and 3 mmol/L. The broad range of observed LC50s associated with a relatively constant predicted LC50 reflected variability in organism response in four-week exposures in similar media and/or may have suggested that other factors influencing cadmium toxicity were not accounted for in the models.

Polycyclic aromatic hydrocarbons (PAH) are a class of common environmental contaminants known to be phototoxic. PAH Photoinduced toxicity is caused by two mechanisms: photomodification and photosensitization. The photomodification process results in modified PAHs, usually via oxygenation, forming new compounds (oxyPAHs), which are often more soluble than their parent PAHs. The process of photosensitization usually leads to the production of singlet oxygen, a reactive oxygen species (ROS), which in turn is extremely damaging to organic molecules. Both of these processes occur at environmentally relevant levels of actinic radiation. Metals are ubiquitous environmental contaminants found extensively in many aquatic systems. Many metals are toxic at very low levels, and exhibit toxicity via ROS production or via direct binding to a ligand in an organism (Biotic Ligand Model). PAHs and metals often occur as co-contaminants in the environment, and there combined effects have only been examined in a few organisms. The goal of this thesis was to examine the toxicity of PAHs, oxyPAHs, metals and their mixtures to Hyalella azteca in 96 h acute toxicity tests. All of the tests were performed under varying spectra of light; photosynthetically active radiation (PAR), PAR + UVA or simulated solar radiation (SSR) (PAR + UVA radiation + UVB radiation). In addition, chemical exposures in the Dark were performed to assess toxicity in the absence of light. The PAHs chosen represent 3 of the most common PAHs anthracene (ANT), phenanthrene (PHE), benzo(a)anthracene (BAA). The 12 oxyPAHs studied were quinolated analogues of the 3 parent compounds as well as anthraquinone derivatives that are hydroxylated at various positions. The toxicity of the parent PAHs increased in the presence of increasing amounts of actinic radiation. The toxicity of the oxyPAHs also increased as PAR, UVA and UVB was added. Furthermore, most PAHs and oxyPAHs were found to be more toxic than the parent PAHs in the absence of actinic radiation. The metals cadmium (Cd), copper (Cu), nickel (Ni) and zinc (Zn) were used in toxicity tests. These metals were selected based on their high prevalence in aquatic environments and the large amount of data in the published work. The order of metal toxicity in the Dark was Cd > Cu > Zn > Ni. The order of metal toxicity for the PAR and PAR/UV-A regime was Cd = Cu > Ni > Zn. The order of metal toxicity for the SSR treatment was Cu > Cd > Ni > Zn. The toxicity of several metal/PAH mixtures was determined using one of the four metals and ANT, ATQ and 1-hATQ. The mixtures generally had additive toxicity under Dark and PAR lighting regimes. Under SSR lighting most mixtures showed a strictly additive toxicity, however synergistic toxicity was observed for the redox active metals (Cu, Ni) mixed with ANT. In the aquatic environment complex mixtures of PAHs and metals occur. The results of this study illustrate the effects that these mixtures may have on benthic invertebrates.

Polycyclic aromatic hydrocarbons (PAH) are a class of common environmental contaminants known to be phototoxic. PAH Photoinduced toxicity is caused by two mechanisms: photomodification and photosensitization. The photomodification process results in modified PAHs, usually via oxygenation, forming new compounds (oxyPAHs), which are often more soluble than their parent PAHs. The process of photosensitization usually leads to the production of singlet oxygen, a reactive oxygen species (ROS), which in turn is extremely damaging to organic molecules. Both of these processes occur at environmentally relevant levels of actinic radiation. Metals are ubiquitous environmental contaminants found extensively in many aquatic systems. Many metals are toxic at very low levels, and exhibit toxicity via ROS production or via direct binding to a ligand in an organism (Biotic Ligand Model). PAHs and metals often occur as co-contaminants in the environment, and there combined effects have only been examined in a few organisms. The goal of this thesis was to examine the toxicity of PAHs, oxyPAHs, metals and their mixtures to Hyalella azteca in 96 h acute toxicity tests. All of the tests were performed under varying spectra of light; photosynthetically active radiation (PAR), PAR + UVA or simulated solar radiation (SSR) (PAR + UVA radiation + UVB radiation). In addition, chemical exposures in the Dark were performed to assess toxicity in the absence of light. The PAHs chosen represent 3 of the most common PAHs anthracene (ANT), phenanthrene (PHE), benzo(a)anthracene (BAA). The 12 oxyPAHs studied were quinolated analogues of the 3 parent compounds as well as anthraquinone derivatives that are hydroxylated at various positions. The toxicity of the parent PAHs increased in the presence of increasing amounts of actinic radiation. The toxicity of the oxyPAHs also increased as PAR, UVA and UVB was added. Furthermore, most PAHs and oxyPAHs were found to be more toxic than the parent PAHs in the absence of actinic radiation. The metals cadmium (Cd), copper (Cu), nickel (Ni) and zinc (Zn) were used in toxicity tests. These metals were selected based on their high prevalence in aquatic environments and the large amount of data in the published work. The order of metal toxicity in the Dark was Cd > Cu > Zn > Ni. The order of metal toxicity for the PAR and PAR/UV-A regime was Cd = Cu > Ni > Zn. The order of metal toxicity for the SSR treatment was Cu > Cd > Ni > Zn. The toxicity of several metal/PAH mixtures was determined using one of the four metals and ANT, ATQ and 1-hATQ. The mixtures generally had additive toxicity under Dark and PAR lighting regimes. Under SSR lighting most mixtures showed a strictly additive toxicity, however synergistic toxicity was observed for the redox active metals (Cu, Ni) mixed with ANT. In the aquatic environment complex mixtures of PAHs and metals occur. The results of this study illustrate the effects that these mixtures may have on benthic invertebrates.

Thesis (M.S.)--Baylor University, 2008. / In abstract "14" is superscript. Includes bibliographical references (p. 35-38).