Frog tadpoles are an important component of freshwater ecosystems. After hatching they form the largest biomass in mountain lakes, which are usually oligotrophic. Tadpoles use a large amount of different nutritional resources, including biofilm, dead animals and plants, and algae. They themselves are food for fishes, reptiles, birds, mammals and other amphibians. Therefore, tadpoles have a central role in the nutrient cycle in mountain lakes. Generally, the life of tadpoles is tough, as for most species time from egg-laying to becoming a small froglet (finishing metamorphosis) is quite restricted. The restriction may come from two major points, 1) onset of spring, which melts the ice opening up the living space for tadpoles, and 2) rainfall and water availability, which determines when some of the habitats fall dry. For some species, it is a bet-hedging strategy between small water bodies, heating up quickly, and too shallow water bodies drying out too quickly, not allowing tadpoles to become terrestrial froglets. That's why amphibians cannot survive in all water bodies, even so they are quite tough animals with an enourmous plasticity in adapting to local environments. Generally, amphibians are valuable indicators of environmental change. Since they spend part of their life in water and on land, amphibians are monitored and analyzed to measure the effects of water, air, and land pollution. More recently, a range of amphibian specific pathogens also make life less easy for them. In P³, we will determine how the amphibians fare in the focal mountain ranges and what needs to be expected for their future.
The video shows tadpoles of Rana temporaria in the French Pyrenees. To grow, they need to feed and they constantly do so, exploiting their energy-poor living space.