Feeding habits and their implications for the conservation of the endangered semiaquatic frog Atelognathus patagonicus (Anura, Neobatrachia) in a northwestern Patagonian pond. Atelognathus patagonicus (Gallardo, 1962) is an endemic frog species whose distribution is restricted to an endorheic pond system in basaltic basins in the northwest of the Argentinean Patagonia. Atelognathus patagonicus has two morphotypes: aquatic and littoral. This study presents data on the diet of A. patagonicus in Laguna del Burro, in Neuquén Province. Digestive tracts were analyzed for 20 specimens: 17 of the aquatic form and 3 of the littoral form. Diversity and trophic niche breadth, and index of relative importance (IRI) were calculated for the aquatic form. Nine food categories were found in the stomachs and intestine with the most important being Odonate naiads (Rhionaeschna sp.; IRI% = 86.57) and amphipod crustaceans (Hyalella sp.; IRI% = 12.89). There was not a statistically significant correlation between snout-vent length and mouth width of the frogs and mean prey lengths. For the littoral form of A. patagonicus, 25 prey categories were found, and all preys were adult terrestrial arthropods. Conclusions about the feeding habits of Atelognathus patagonicus and their implications for the design of conservation programs for the species are also given.

Relationship between morphotypes of Atelognathus patagonicus (Anura, Neobatrachia) and environmental conditions: evidence and possible explanation. The frog Atelognathus patagonicus (Gallardo, 1962) is endemic to an endorheic pond system in basaltic basins, in Laguna Blanca National Park and its surroundings, in northwest Argentinean Patagonia. The species has two morphotypes, aquatic and littoral, which were studied in Laguna Batea, a semi permanent pond. Aquatic and terrestrial samples were taken over a period of 31 months, including periods of drought and periods of normal precipitation. Evidence was found of the reversible character of the two morphotypes. The changes in the phenotype were consistent with the water level and limnological conditions in the pond. We believe that the change and subsequent reversal of the somatic features in these frogs are an opportunistic alternative showing remarkable plasticity of the species, which can thus inhabit both permanent and temporary ponds. Therefore, the two morphotypes, aquatic and littoral, cannot be considered as "fixed forms" within a given population, as other authors have speculated, and do not correspond to ontogenetic states.

The Patagonia frog Atelognathus patagonicus (Anura, Ceratophryidae) is endemic to north-western Patagonia where it inhabits permanent and temporary water bodies in a system of endorheic ponds on the basaltic plateau in and around Laguna Blanca National Park, northwestern Patagonia, Argentina. This Endangered species is emblematic of the decline and extinction of amphibian populations as a result of the introduction of fish to Laguna Blanca. Therefore, the aims of this study were to determine the patterns of larval development in ponds with different hydro periods and to evaluate the occurrence of different developmental strategies and their implications for conservation management. In permanent ponds, A. patagonicus tadpoles showed a double strategy, with the presence of both seasonal (short larval period; metamorphs in the same growing season) and overwintering tadpoles (undergoing metamorphosis the following spring). In temporary ponds, desiccation seems to exert great pressure, with accelerated larval development, resulting in short larval periods. Atelognathus patagonicus showed plasticity in the length of larval development, adjusting to the different hydroperiods observed in these wetlands. As a result of this dual strategy, overwintering tadpoles in permanent ponds are larger than seasonal tadpoles. This notable plasticity in developmental strategy enables this species to colonize widely varying environments. These results highlight the importance of preserving a variety of wetlands, including both temporary and permanent ponds, to allow this species to continue to breed and develop in the face of current and potential anthropogenic disturbance, in particular that caused by the activity of local native pastoralists.

Estudios realizados en la última década determinaron una evidente perturbación ambiental del río Chicú a causa de actividades antrópicas que ejercen presión sobre el cuerpo hídrico. La calidad del agua del río se detrmino aplicando índices bióticos (BMWP, Y ABI) a partir de la identificación de macroinvertebrados acuáticos. Los muestreos fueron realizados en cuatro sitios distribuidos en la cuenca alta y baja y en tres temporadas climatológicas (baja precipitación, transición y alta precipitación). Se aplicó un análisis de correspondencia canónica con el que se llegó a determinar la correlación existente entre las diferentes variables e índices en cuestión. Se identificaron 9 órdenes, 16 familias y 7094 individuos en los cuatro sitios, encontrando que la mayor cantidad de individuos pertenecen a las familias Sphaeriidae (49,71%) y Physidae (21,83%). La calidad del agua en el río Chicú presenta un comportamiento decreciente desde la parte alta de la cuenca a la parte baja.

Seasonal trophic activity of the aquatic morphotype of Atelognathus patagonicus (Anura, Neobatrachia) and prey availability in the littoral benthos of a permanent pond in Argentinean Patagonia. The diet of the aquatic morphotype of Atelognathus patagonicus was studied in frogs collected from the Laguna Verde pond (Laguna Blanca National Park, Neuquén, Argentina). The content of 35 gastrointestinal tracts of post-metamorphic specimens from November 2003 to April 2006 was related to the composition of the benthos in their microhabitat. Number, size, occurrence and relative importance of preys, diversity of the diet, trophic niche breadth and electivity were estimated for each season of the year. The diet consisted of aquatic arthropods. The composition of both the benthos and the food (number and occurrence of organisms in the diet) were dominated by the amphipod Hyalella sp. The relative importance (IRI) of Hyalella sp. in the diet was over 99% in summer and autumn, and 100% in winter and spring. Diptera and Copepoda in summer, and Dytiscidae and Ostracoda in autumn, had seasonal IRI values ≤ 0.2%. Trophic niche breadth was very low in summer and autumn, and null (= 0) in winter and spring. The mean number of preys per individual was highest in spring (19 preys/frog) and lowest in winter (4 preys/frog). Frogs continued with their trophic activity in winter, even when the surface of the pond was frozen. There is a correspondence between the frogs' main food item and its presence in the benthos. O número, o tamanho, a ocorrência e a importância relativa das presas, a diversidade da dieta, a amplitude do nicho trófico e a eletividade foram estimados para cada estação do ano. A dieta consistiu de artrópodes aquáticos. A composição do bentos e da dieta (número e ocorrência de organismos na dieta) foram dominadas pelo anfípode Hyalella sp. A importância relativa (IRI) de Hyalella sp. na dieta foi maior que 99% no verão e no outono e de 100% no inverno e na primavera. Diptera e Copepoda no verão e Dytiscidae e Ostracoda no outono tiveram valores sazonais de IRI ≤ 0,2%. A amplitude do nicho trófico foi muito baixa no verão e no outono e nula (= 0) no inverno e na primavera. O número médio de presas por indivíduo foi maior na primavera (19) e menor no inverno (4). Os anuros continuaram a se alimentar no inverno, mesmo após o congelamento da superfície da lagoa. Há uma correspondência entre o principal item alimentar desses anuros e sua presença no bentos.