Larval feeding habits of Diptera, Coleoptera, and Megaloptera in the Ranchería river, La Guajira, Colombia

Abstract

Studies on feeding habits of aquatic insects in Colombia are scarce. Previous research on Andean rivers has categorized trophic guilds, finding a predominance of detritivores and omnivory, while studies in the Sierra Nevada de Santa Marta have reported trophic plasticity in macroinvertebrates. This study aimed to characterize the feeding habits of larvae from three insect orders in a section of the Ranchería River. The study was conducted in the middle basin during the dry season using a Surber net. We examined 300 digestive tracts. Gut contents were mounted on slides with polyvinyl alcohol and observed under microscope to identify six food categories: fine particulate organic matter (<1mm), coarse particulate organic matter (>1mm), microalgae, animal material and fungi. Relative proportions of each food item were estimated by examining random fields using ImageJ software. Detritivores mainly consumed fine (FPOM) and coarse particulate organic matter (CPOM). Some taxa specialized in microalgae, hyphae, or animal material. Principal component analysis, heat map, and NPMANOVA segregated trophic groups. FPOM predominated in these insects' diet, similar to findings in other Neotropical rivers. However, some taxa showed trophic plasticity, differing from previous studies in temperate latitudes. Further research on feeding habits across different basins in the region is needed to validate the functional categorization of these communities.