pkgogl.blogg.se

Like other amphibian species that may inhabit temporary ponds, long-toed salamanders are potentially vulnerable to a wide array of pollutants, including those associated with nitrate and nitrite fertilizers. Laboratory tests suggest that larvae from populations from high elevations may be more resistant to UV-B radiation than larvae from low-elevation populations.

The only way for these ponds to empty is by very slow movement of water through the ground or by evaporation, which can take days, weeks or months depending on the amount of rainfall, the air temperature and the size of the pool. UV radiation reduces hatching success and increases deformities. An ephemeral pond has no permanent above-ground outlet. The results of field experiments suggest that long-toed salamander embryos are highly susceptible to ambient levels of UV-B radiation. Morphological plasticity may therefore play an important role in resource partitioning and in alleviating intraspecific competition. During periods of food limitation, individuals capable of using alternative food sources, including conspecifics, may experience a competitive advantage over their conspecifics. The ingestion of different types of prey contributes to plasticity in head shape but other cues are essential to induce extreme trophic polymorphism. Long-toed salamanders living in ephemeral ponds, like some other salamander species, exhibit trophic polymorphism, with some individuals having disproportionately broader and longer heads and enlarged vomerine teeth. These include biotic interactions focusing on cannibalism and predation, and abiotic factors, including ultraviolet (UV) radiation, an agent that can harm developing amphibians. But as mysterious as that sounds, these ponds are actually naturally occurring. What you have just stumbled across is called an ephemeral pond. We have been studying several factors that may influence long-toed salamander behavior, growth, and survival in ephemeral montane ponds in the Cascade Range. In fact, that pond has always been there you just didn’t notice because it didn’t have water in it. In Oregon (U.S.A.), larval long-toed salamanders (Ambystoma macrodactylum) often inhabit temporary ponds that gradually dry during the summer. Aquatic amphibians developing in ephemeral habitats must find food, avoid predators, and cope with potentially great fluctuations in abiotic parameters under increasingly harsh conditions. Amphibians provide an excellent model for studying factors associated with survival in temporary habitats. For example, pond drying can lead to increased predation and competition as resources become limited and temperature and water quality undergo drastic fluctuations.

Animals living in ephemeral habitats are subjected to various abiotic and biotic selection pressures that may not be present to the same degree in permanent habitats.