Abstract
The structure of aquatic invertebrate communities in Amazonian streams is influenced by substrate type, water velocity, and resource availability. In this study, we examined the diet and habitat associations of Odonata larvae across different substrate types in “ terra firme ” streams of Central Amazonia to better understand their trophic interactions and microhabitat use. Sampling was conducted in the Ducke and Uatumã reserves during the dry and rainy seasons of 2009, encompassing nine substrate types. A total of 992 larvae representing 36 species/morphotypes were analyzed for gut contents. Habitat association patterns indicated strong substrate specificity among taxa. Burrowing taxa were predominantly associated with sandy substrates, whereas other groups were mainly related to coarse or organic substrates in riffle and depositional habitats. These distribution patterns likely reflect morphological and behavioral adaptations related to substrate use and local hydrological conditions. Only 51.4% of larvae contained prey items in the foregut, comprising 27 categories and a total of 797 recorded items. The diet was dominated by Chironomidae, followed by Ephemeroptera and Trichoptera, indicating that prey consumption largely reflects resource availability in the benthic environment. Differences in prey composition among functional groups suggest that feeding is strongly influenced by microhabitat use, with sediment-associated larvae consuming mainly benthic prey, while those inhabiting more structured substrates exploited a broader range of food resources. No relationship was observed between larval body size and the number of prey items consumed. Overall, our results indicate that Odonata larvae in Amazonian streams behave predominantly as opportunistic generalist predators, with trophic interactions shaped by substrate heterogeneity and prey availability. These findings highlight the importance of habitat complexity in structuring both the spatial distribution and feeding ecology of aquatic predators, contributing to a better understanding of trophic dynamics and supporting conservation strategies for freshwater ecosystems in the region.