Alimentação e desenvolvimento de macroinvertebrados límnicos frente à variação na qualidade do recurso e temperatura do ambiente
Cogo, Gláucia Bolzan
The aquatic ecosystems exhibit a diversity of biotic and abiotic characteristics, which together determine their functioning. In these environments, the macroinvertebrates community depend on the conditions found in the streams for their survival. Understanding these relationships is important to advance on knowledge of limnology. Thus, the goal of this thesis is to investigate aspects of the feeding and development of limnic macroinvertebrates relation to variation in resource quality and environment temperature. In chapter 1, we analyzed the food preference of the crustacean Aegla longirostri through standardized experiments with different plant and animal items. For aeglids, the microbial conditioning overlaps the initial leaf chemical quality. The animals prefer to consume the animal tissue, followed by conditioned leaves and lastly feed on unconditioned leaves, demonstrating preference for higher nutritional quality item. In chapter 2, we verified, under laboratory conditions, if temperature increase modifies leaf consumption, metabolites composition of the hepatopancreas and A. longirostri activity. Leaf consumption did not differ between studied temperatures (21 and 24º C). The amount of protein was higher at 21° C, and the amino acid and glycogen levels were higher at 24º C. At high temperatures the aeglids use, in hepatopancreas, energy from protein breakdown. Animals kept at 24º C showed a lower activity level, possibly a strategy to save energy. This study indicates that a future temperature increase of water streams, due to global warming, will impact the aeglids populations by changing their metabolism and behavior. In chapter 3, we investigated the relationship between temperature, adult size and growth rate of caddisflies. We conducted a field study to verify the emergent adult size at different temperatures using the altitudinal gradient as a predictor of temperature. Additionally, we measure under laboratory conditions the temperature dependence growth rates under three temperature regimes with Schizopelex festiva. We observed that the animals studied follow the temperature-size-rule, at higher temperatures the animals have a smaller body size (field experiment) and a higher growth rate (laboratory experiment). With the results of this thesis, we verified that the food resource and the temperature are factors that directly interfere in macroinvertebrates life of low orders streams. Thus, future warming of the streams freshwater due to global warming will modify their communities, and imbalances may occur in these ecosystems.