RESUMO
Abstract Hylorina sylvatica (Anura: Batrachyidae), or the emerald frog, is a pond-breeding anuran endemic to the austral temperate forests of Chile and Argentina. It is considered a vulnerable species in Argentina, where it has a narrow distribution; records and biological information relating to the frog in this area are scarce. In this study, conducted in 2016, the reproductive parameters of the emerald frog were investigated in detail in a semi-temporary wetland of Northwestern Patagonia, Argentina. During the spring, the wetland was visited weekly in search of calling males, adults and individuals in amplexus. When amplexus was observed, eggs and larvae were collected from among the aquatic vegetation using dip-nets. Egg size and larval stage at hatching were registered. Calling males were registered during the second week of October, and the first couples were observed on 26 October. Three pairs of emerald frogs were captured and placed in enclosures within the wetlands in the afternoon. The males were smaller than the females. After 24 h the number of eggs laid in each enclosure was counted, and the males and females were released. The eggs were kept in each enclosure until hatching. Hatching occurred after 10-14 days in the enclosures. This information contributes to our knowledge of the biology of the emerald frog in Patagonia, Argentina, and is the only information currently available on this species in Nahuel Huapi National Park, where the species breeds in various aquatic environments, from semi-temporary wet meadows to large permanent ponds.
Resumen Hylorina sylvatica (Anura: Batrachyidae) o rana esmeralda, es un anuro que se reproduce en estanques, endémico de los bosques templados australes de Chile y Argentina. Actualmente es considerada una especie vulnerable en Argentina. La distribución es estrecha en Argentina con pocos registros de la especie y muy limitada información sobre la biología de esta especie en la región. En este estudio realizado durante 2016, investigué en detalle los parámetros reproductivos de la rana esmeralda en un humedal semitemporal del Noroeste de la Patagonia Argentina. Durante la primavera de 2016, visité el humedal semanalmente en busca de coros, adultos y amplexos. También después de que se observaron amplexos, recolecté huevos y larvas entre la vegetación acuática utilizando un muestreo con redes de mano. Se registró el tamaño del huevo y el estado larvario al eclosionar. Los coros de machos se registraron durante la tercera semana de octubre y los primeros amplexos se observaron el 26 de octubre. Tres parejas de rana esmeralda fueron capturadas y colocadas en clausuras dentro de los humedales durante la tarde. Los machos eran más pequeños que las hembras. Después de 24 h conté el número de huevos puestos en cada recinto y luego se liberaron machos y hembras. Los huevos se mantuvieron en cada clausura hasta que eclosionaron. La eclosión se produjo entre 10-14 días en las clausuras. Esta información contribuye al conocimiento de la biología de la rana esmeralda que habita la Patagonia Argentina y es la única información disponible al momento de esta especie en el Parque Nacional Nahuel Huapi, donde la especie se reproduce en diferentes ambientes acuáticos, desde humedales semitemporales hasta lagos y lagunas permanentes.
RESUMO
Copepods are hosts to various oomycete parasite species, but the effects of pathogens on copepod populations have rarely been studied. This study aimed to characterize oomycete infection in the freshwater copepod Parabroteas sarsi in a temporary pond in Patagonia (Argentina). A complete hydroperiod was monitored, evaluating environmental variables as influencing factors in the oomycete infections. Laboratory experiments were performed to evaluate the susceptibility of infected copepods to consumption by predators. Although 5 species of copepods were present in the pond, only ovigerous P. sarsi females were parasitized by oomycetes. Two species of oomycetes were always found together: Aphanomyces ovidestruens and Pythium flevoense. Infections were detected at water temperatures >20°C, with a positive relationship between temperature and parasite prevalence. Infection occurred after a decrease in large filter-feeder densities. The pathogens were not lethal to P. sarsi females in the short-term, but did produce mortality of entire egg sacs, thus negatively impacting subsequent recruitment. Mean prevalence of infection in females was 53%, reaching 83% in December. Females have the capacity to release an infected egg sac and generate a new one in a few days. This infection does not affect the susceptibility of P. sarsi to the predator Notonecta vereertbruggheni. The decrease in female abundance registered towards the end of the hydroperiod could be related to a combination of factors that may have a differential effect on female survival, such as increasing temperature, the energy cost of egg sac development and carrying and oomycete infection.
Assuntos
Copépodes/parasitologia , Oomicetos/fisiologia , Animais , Argentina , Feminino , Interações Hospedeiro-Parasita , Masculino , Estações do AnoRESUMO
Most studies of predator-induced plasticity have focused on documenting how prey species respond to predators by modifying phenotypic traits and how traits correlate with fitness. We have previously shown that Pleurodema thaul tadpoles exposed to the dragonfly Rhionaeschna variegata responded strongly by showing morphological changes, less activity, and better survival than non-exposed tadpoles. Here, we tested whether there is a functional link between morphological plasticity and increased survival in the presence of predators. Tadpoles that experienced predation risk were smaller, less developed, and much less active than tadpoles without this experience. Burst speed did not correlate significantly with morphological changes and predator-induced deeper tails did not act as a lure to divert predator strikes away from the head. Although we have previously found that tadpoles with predator-induced morphology survive better under a direct predator threat, our results on the functional link between morphology and fitness are not conclusive. Our results suggest that in P. thaul tadpoles (1) burst speed is not important to evade predators, (2) those exposed to predators reduce their activity, and (3) morphological changes do not divert predator attacks away from areas that compromise tadpole survivalEE. Our results show that morphological changes in P. thaul tadpoles do not explain burst speed or lure attraction, although there was a clear reduction of activity, which itself reduces predation. We propose that changes in tadpole activity could be further analyzed from another perspective, with morphological change as an indirect product of behavior mediated by physiological mechanisms.
