13 Amphibians PAOLA M. PELTZER 1,2,3 AND RAFAEL C. LAJMANOVICH 1,2 13.1 Introduction The unpredictable nature of flood and flow pulses and river floodplain net- works create challenges for organisms, such as a variety of anuran amphibian species, in their aquatic larval and terrestrial or semi-terrestrial life stages. These vertebrates undoubtedly form an important component of the fauna of floodplains and may contribute to the rapid recycling of detritus and mud (Welcomme 1990). Moreover, anuran species is adapted reproductively and developmentally to expansion/contraction of surface waters of riparian- derived food organisms and water volume (McDiarmid and Altig 1999). In freshwater amphibian ecology have been emphasized the need to consider ecological processes at multiple scales. It is important to note that the complexity of river–floodplain systems results from interactions between the process that operates at spatial and temporal scales. The insight is especially relevant if we consider the diversity of waterbodies within the floodplain, which provides an interesting background for the study of the organization of amphibian communities (Joly and Morand 1994). For example, in these aquatic habitats, amphibian survivorship and breeding activities depend heavily upon large- scale processes (landscape characteristics), such as frequency and duration of hydrologic connections to waterbodies in a floodplain (Peltzer and Lajmanovich 2004). Moreover, anurans are not solely dependent upon within-pond features to determine the suitability of aquatic sites to their life requirements. Most anurans spend the bulk of their life in the upland habi- tats close to waterbodies, while others live in close proximity to ponds and have small home ranges during their terrestrial life stages. In this context, anuran are a sensitive indicator of environmental change and can be consid- ered good measures of the state, quality, or condition of both terrestrial and aquatic ecosystems (US EPA 2002) due to a number of inherent biological and ecological factors (e.g., complex life cycles, thin and highly permeable 1 Instituto Nacional de Limnología (INALI-CONICET-UNL), José Maciás 1933, 3016 Santo Tomé, Santa Fe, Argentina 2 Facultad de Bioquímica y Ciencias Biológicas (ESS-FBCB-UNL), Ciudad Universitaria, Pje. El Pozo s/n, 3000, Santa Fe, Argentina 3 e-mail: paolapeltzer@hotmail.com M.H. Iriondo, J.C. Paggi, and M.J. Parma (Eds.) The Middle Paraná River: Limnology of a Subtropical Wetland © Springer-Verlag Berlin Heidelberg 2007