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Abstract. Life cycles, ploidy levels, reproductive modes, and regeneration capacities of laboratory populations of the southern Brazil freshwater planarians Girardia tigrina and Girardia schubarti were studied. The mating behavior and life cycle of different populations from both species were analyzed regarding their karyotype, body size, modes of reproduction, and regeneration potential. Reproduction was evaluated according to fecundity, fertility, and fissiparity indices. In both species we observed that diploid planarians are ∼25% larger than triploid or mixoploid ones and that sexually reproducing populations have more offspring than asexual ones. Cocoon incubation time was shorter for G. tigrina, and G. schubarti showed a higher frequency of spontaneous malformations. G. tigrina was both more fecund (produced more cocoons) and more fertile (produced more hatchlings) than G. schubarti. The effects of alternative food sources (liver or egg yolk), demographic density, and water–salt concentration were evaluated in different populations of both species. All evaluated environmental factors had effects on fecundity and fertility indices and were more prominent for G. schubarti than for G. tigrina. Our data suggest that the populations of G. schubarti were more sensitive to environmental factors, and thus may be useful as bioindicators.

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Environmental contamination has become an increasing global problem. Different scientific strategies have been developed in order to assess the impact of pollutants on aquatic ecosystems. Planarians are simple organisms with incredible regenerative capacity due to the presence of neoblastos, which are stem cells. They are easy test organisms and inexpensive to grow in the laboratory. These characteristics make planarians suitable model-organisms for studies in various fields, including ecotoxicology. This article presents an overview of biological responses measured in planarians. Nine biological responses measured in planarians were reviewed: 1) histo-cytopathological alterations in planarians; 2) Mobility or behavioral assay; 3) regeneration assay; 4) comet assay; 5) micronucleus assay; 6) chromosome aberration assay; 7) biomarkers in molecular level; 8) sexual reproduction assay; 9) asexual reproduction assay. This review also summarizes the results of ecotoxicological evaluations performed in planarians with metals in different parts of the world. All these measurement possibilities make Planarians good bioindicators. Due to this, planarians have been used to evaluate the toxic, cytotoxic, genotoxic, mutagenic, and teratogenic effects of metals, and also to evaluate the activity of anti-oxidant enzymes. Planarians are also considered excellent model organisms for the study of developmental biology and cell differentiation process of stem cells. Therefore, we conclude that these data contributes to the future establishment of standardized methods in tropical planarians with basis on internationally agreed protocols on biomarker-based monitoring programmes.

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