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Hyalella azteca, an amphipod crustacean, is frequently used in freshwater toxicity tests. Since the mid-1980s, numerous organizations have collected and established cultures of H. azteca originating from localities across North America. However, H. azteca is actually a large cryptic species complex whose members satisfy both the biological and the phylogenetic species concepts. Recently, two publications reported that members of the H. azteca cryptic species complex have different toxicity responses to anions and an insecticide. In this study, four members of the H. azteca species complex were identified with DNA barcoding. The genetic variation among the four clades was consistent with interspecific distances between species. These lineages (clades 1, 3, 6, and 8) were cultured in identical conditions and monitored on a weekly basis to determine two life history traits: adult mortality and juvenile production. The large-bodied clades had significantly better survival and juvenile production compared to the small-bodied clade 3. Clade 6 had very low juvenile production and high mortality; therefore, was not included in this study. Unique culture protocols may be required for each clade to optimize growth, survival, and juvenile production in laboratory conditions. Genetic barcoding has identified only two clades in a survey of 17 laboratories. Therefore these two clades (1 and 8) were compared after exposure to copper and nickel 14-day toxicity tests. Clade 8 was 2.3-2.6 times more tolerant to copper exposure than clade 1 based on their LC50 and LC25. Similarly, clade 8 was more tolerant to nickel exposure than clade 1: LC50 was 1.8 times higher for the former. Nickel LBC50 and LBC25 were significantly different between clades by a factor of 2.1-2-8. Mortality (relative to copper concentrations in tissue), growth, and bioaccumulation responses were not significantly different based on overlapping confidence intervals. Although clades 1 and 8 are both large-bodied ecomorphs, these lineages had significantly different body mass (i.e., dry weight) after 14 days. The results of this study indicate that genetically characterized cultures of H. azteca should be used in toxicity tests.

Made available in DSpace on 2014-12-17T14:01:59Z (GMT). No. of bitstreams: 1 EmersonESM.pdf: 931852 bytes, checksum: f768665fe7e8aa27e4023b4def16f98d (MD5) Previous issue date: 2009-03-27 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Considering their commercial importance, as these are the species of freshwater fish more commercialized in Brazil, their occurence in different kinds of aquatic environments (lakes, rivers and dams) and for being tolerant to a wide range of variation of various physical parameters and chemical water, the fish species Oreochromis niloticus, Cyprinus carpio and Colossoma macropomum were chosen for this study, furthermore, to test the toxicity we used the herbicide Roundup. The fingerlings of tilapia (Oreochromis niloticus), commun carp (Cyprinus carpio) and tambaqui (Colossoma macropomum) were submitted to the herbicide roundup in the following concentrations: 0.0 (control); 18,06; 19,10; 20,14; 21,18 and 22,22 mg.L-1, 0.0 (control); 13,89; 14,86; 15,83; 16,81 and 17,78 mg.L-1, and 0.0 (control); 18,06; 19,10; 20,14; 21,18 and 22,22 mg.L-1, respectively, three for 96 hours. The LC50 - 96h for O. niloticus, C. carpio and C. macropomum was 21,63, 15,33 and 20,06 mg.L-1 of the herbicide roundup, respectively. The results show that this herbicide is classified as slightly toxic to the three species. The values of dissolved oxygen, pH and temperature recorded in the aquarium control and aquarium experimental of the three fish species have remained without significant variations during the tests, which reduces the possibility of death caused by sudden variations of these parameters during the 96 hours the experiment. The values of LC50 between different species of fish were observed, noting that the species O.niloticus, C. carpio and C. macropomum showed no expressive differences. The values of environmental risk of Roundup were calculated to obtain more stringent parameters in assessing the dangerousness of those on nontargets. The risk of environmental contamination by Roundup for the Nile tilapia, common carp, and tambaqui are low for the lowest application rate (1 L.ha-1) and depths (1.5 and 2.0 m). The dilution of 100%, the highest recommended dose (5 L.ha-1) and depths (1.5 and 2.0 m) the risk is moderate for the three species. The values of the Risk Ratio (QR) were greater than 0,1, indicating that the values of the CAE and LC50 are above acceptable levels and there is a need, this study, a refinement in ecotoxicological tests / Considerando a import?ncia comercial, por se tratarem das esp?cies de ?gua-doce mais comercializadas no Brasil, por ocorrerem em diversos tipos de ambientes aqu?ticos (lagos, rios e a?udes) e ainda por serem tolerantes a um amplo espectro de varia??o de diversos par?metros f?sicos e qu?micos da ?gua, as esp?cies de peixes Oreochromis niloticus, Cyprinus carpio e Colossoma macropomum foram escolhidas para este estudo com a finalidade de testar a toxicidade do herbicida roundup. Diante do exposto, o presente trabalho teve como objetivo determinar a toxicidade aguda e avaliar o risco de contamina??o ambiental dessas tr?s esp?cies de peixes pelo herbicida Roundup. Os alevinos de Til?pia do Nilo (Oreochromis niloticus), Carpa-comum (Cyprinus carpio) e Tambaqui (Colossoma macropomum) foram submetidos ao herbicida roundup nas seguintes concentra??es: 0,0 (controle); 18,06; 19,10; 20,14; 21,18 e 22,22 mg.L-1, 0,0 (controle); 13,89; 14,86; 15,83; 16,81 e 17,78 mg.L-1 e 0,0 (controle); 18,06; 19,10; 20,14; 21,18 e 22,22 mg.L-1, respectivamente, os tr?s por 96 horas. A CL50 96h para O. niloticus, C. carpio e C. macropomum foi de 21,63, 15,33 e 20,06 mg.L-1 do herbicida roundup, respectivamente. Os resultados obtidos demonstram que esse herbicida est? classificado como levemente t?xico para as tr?s esp?cies. Os valores de oxig?nio dissolvido, pH e temperatura registrados no aqu?rio controle e nos aqu?rios experimentais das tr?s esp?cies estudadas mantiveram-se sem varia??es significativas ao longo dos testes, o que reduz a possibilidade de mortalidade causada por varia??es bruscas desses par?metros, durante as 96 horas de experimento. Os valores das CL50 entre as diferentes esp?cies de peixes foram observadas, constatando que as esp?cie Oreochromis niloticus, Colossoma macropomum e Cyprinus carpio n?o apresentaram diferen?as expressivas. Os valores de risco ambiental do Roundup foram calculados para a obten??o de par?metros mais rigorosos na avalia??o da periculosidade desses sobre organismos n?o-alvos. O risco de contamina??o ambiental por roundup para a til?pia do Nilo, carpa-comum e tambaqui s?o baixos para a menor dose de aplica??o (1 L.ha-1) e nas profundidades (1,5 e 2,0 m). Na dilui??o de 100%, na maior dose recomendada (5 L.ha-1) e nas profundidades (1,5 e 2,0 m) o risco ? moderado para as tr?s esp?cies. Os valores de Quociente de Risco (QR) foram maiores que 0,1, indicando que os valores da rela??o CAE e CL50 est?o acima dos n?veis aceit?veis, havendo a necessidade de um refinamento nas an?lises ecotoxicol?gicas

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