Abstract
The industrialization process and the accelerated growth of the world population that it happened in the last decades put in risk several ecosystems, especially the aquatic ones that had contact with numerous potentially toxic chemical substances. Ecotoxicity studies with organisms sensitive to small environmental imbalances are increasingly being studied with the aim of testing substances that could represent toxic effects on the human body. Within this group, the small cnidarians of the genus Hydra stand out. By having a series of favorable characteristics, this group consolidated as test organism in front of several species types. This review work had the purpose of gathering the most relevant information about the importance of the tests of ecotoxicity and the advantages and disadvantages of the use of species of the genus Hydra in such studies.
Highlights
The industrialization process and the accelerated growth of the world population that it happened in the last decades put in risk several ecosystems, especially the aquatic ones that had contact with numerous potentially toxic chemical substances
Ecotoxicity studies with organisms sensitive to small environmental imbalances are increasingly being studied with the aim of testing substances that could represent toxic effects on the human body
By having a series of favorable characteristics, this group consolidated as test organism in front of several species types
Summary
As hidras são organismos sensíveis a metais pesados (zinco, cobre, urânio, magnésio, cádmio), possivelmente por não possuírem a proteína de ligação de metal metalotioneína (Galliot 2012). Em testes de toxicidade aguda avaliando a toxicidade do cobre, cádmium e zinco, Karntanut and Pascoe (2002) constaram efeitos tóxicos destes metais utilizando Hydra vulgaris, H. oligactis e H. viridissima. Em concentrações intermediárias destes metais, as hidras sofreram modificações no tamanho e formato dos tentáculos. Os efeitos no crescimento de populações de hidra foram observados em uma concentração entre 8 e 16 mg/L para o cobre (Pollino & Holdway 1999; Karntanut & Pascoe 2005), 0,8 mg/L para o cádmio (Holdway et al 2001), 75 mg/L para o zinco (Holdway et al 2001) e 50mg/L para chumbo (Browne & Davis 1977) em Hydra viridissima e 60mg/L para níquel em Hydra littoralis (Santiago-Fandino 1983). Karntanut and Pascoe (2005) compararam a toxicidade de metais pesados tanto em Hydra viridissima com e sem algas endossimbíticas. Embora a toxicidade fosse semelhante para ambos os grupos, nas concentrações inferiores de cobre as hidras simbióticas foram mais capazes de tolerar a toxicidade. O efeito de qualquer vantagem derivada da alga endosimbiótica é de pouca importância
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