A B S T R A C TWe studied the input of allochthonous plant material in Crab Creek, a first-order Neotropical stream and its processing by Aegla longirostri Bond-Buckup and Buckup, 1994, a crustacean shredder. Three experiments were performed: (1) to evaluate the input of allochthonous organic material, five suspended and ten lateral collectors were installed. The yearly input of litter was 1254 g m −2 year −1 , with no difference among the seasons of the year. (2) To evaluate the importance of A. longirostri for litter shredding, two types of experimental channels were placed in the stream, both containing litter bags with leaves of Ficus luschnathiana; open channels which allowed individuals of A. longirostri to access the leaves, and channels that were closed with a 5-mm mesh to exclude the crustaceans. The leaves decomposed more rapidly in the presence of aeglids (one-way ANOVA; F = 10.1795; P = 0.0005), indicating their potential role as shredders. In addition to accelerating the decomposition rate, the presence of A. longirostri altered the community composition and density of the other macroinvertebrates associated with the litter bags. (3) To evaluate the proportion of leaf input that A. longirostri was able to process, a laboratory experiment was performed. Leaves of Cabralea canjerana, F. luschnathiana, and Nectandra megapotamica, which are common species in the vicinity of the study site, were placed in litter bags and incubated in the stream for 20 days. These leaves were offered to the aeglids, and their consumption was recorded. Leaf consumption did not differ between adult (males and females), but did differ between adults and the juveniles (one-way ANOVA; F = 4.1633; P = 0.0279). These data indicated that the adult population of A. longirostri is able to process approximately 5% of the leaves that fall in the creek. These results indicate that Crab Creek receives different types of plant material that will be accessed by the aquatic community. These locations may show a scarcity of insect shredders, with crustaceans, especially aeglids, assuming this role in the community.

Through field and laboratory experiments we investigated the effects of leaf traits of two tree species and microbial conditioning on the abundance, biomass, and feeding preference of a typical macroinvertebrate shredder. In the field, we compared the association of Phylloicus (Calamoceratidae, Trichoptera) with two tree species commonly found in riparian zones, which are representative of high and low nutritional quality, respectively: Nectandra megapotamica and Chusquea tenella. In the laboratory, we investigated the feeding preference of Phylloicus using unconditioned leaves and leaves conditioned by aquatic fungi. The same tree species used in the field experiment were used in the laboratory. Initially, C. tenella leaves were proved to be more nutritious and softer, while N. megapotamica leaves were harder and more lignified. The shredders preferred conditioned leaf detritus of reduced toughness (field: C. tenella; laboratory: N. megapotamica, both conditioned for 14 days). These leaf traits seem to be crucial for the choice process of Phylloicus. After 14 days, N. megapotamica leaves showed a decreased toughness associated with the microbial conditioning, which explained its consumption rate by Phylloicus. In both field and laboratory experiments, we found evidence that Phylloicus is a selective feeding shredder, and that the leaf traits, especially leaf structure (e.g., leaf toughness and lignin content), determine its association and preferences.

The objective of the present study was to analyse the movement, feeding and case-building behaviours of Phylloicus in the presence and absence of a likely decapod predator, Aegla longirostri. We used aquaria divided by a perforated acrylic plate, with one side containing a Phylloicus and the other containing A. longirostri. Movement was quantified through the time spent in active movement, feeding was quantified through the amount of consumed leaves and the case-building was assessed by comparing the number of leaf discs selected of each plant species. The Phylloicus movement activity was affected by A. longirostri, being higher in the predator absence than in its presence. The caddisfly feeding behaviour was not affected by the presence of the crab. Phylloicus was selective in the choice of plant species for case-building; in the presence of the predator, harder discs were more often employed, whereas softer and less resistant discs were chosen in the absence of the predator. The anti-predator responses of caddisfly demonstrated that they are able to detect the presence of crabs and modify their activities, thereby increasing their chances of survival.

AIM: This study tested whether the macroconsumer Aegla longirostri is able to modify the invertebrate community associated with decomposing leaves. METHODS: The study was performed in a first-order stream located in central Rio Grande do Sul state. Two types of channels containing leaf litter of Ficus luschnathiana were placed in the stream; one type allowed aeglids to access the leaf litter (PA), and the other type did not (AA). Both types allowed aquatic insects to access the leaf litter. In addition, a control treatment (C) was established, in which no channel was used. After 3, 7, 11, 15 and 19 days, a litter bag was removed from each replicate of each treatment. RESULTS: A total of 926 organisms belonging to 19 families were identified. The most common taxon in all treatments was Chironomidae, which comprised 71% of the total and was represented by 16 genera. The presence of aeglids decreased the total abundance of organisms by 89% and the taxonomic richness by 35%. The presence of A. longirostri altered the taxonomic composition of the invertebrates and the structure of the trophic groups, causing a decrease in the abundance of all groups, except for shredders and predators. The gathering-collectors trophic group was the most important (65%), in both the presence and absence of A. longirostri. CONCLUSION: Our study showed that A. longirostri, as well as other macroconsumers, was able to modify the structure of the invertebrate community associated with decomposing leaves in the stream.

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Ecological processes in small-order streams are dependent on their community. A threat to the appropriate functioning of these processes is the water warming of streams since changes in temperature can modify the behavior, abundance, and distribution of the species. A way to predict the consequences of global warming on ecological processes in these ecosystems is to study their aquatic community. Here we evaluated behavioral and metabolic changes in Aegla longirostri at different temperatures (21 °C and 24 °C). Experiments were performed in laboratory conditions. We calculated leaf consumption and quantified glycogen, protein and amino acid composition in the hepatopancreas. We also conducted a behavioral test to investigate the activity level of aeglids. Leaf consumption did not differ between temperatures. However, the amount of protein was higher at 21 °C, and the amino acid and glycogen levels were greater at 24 °C. In the present study we evaluated only the activity of hepatopancreas, so we can assume that the organ may have used glucose through the breakdown of glycogen and also performing some protein break. However, this hypothesis needs to be confirmed by checking for muscle activity. Animals kept at 24 °C showed a lower level of activity. This strategy possibly occurs to save energy, as in elevated temperature crustaceans spend extra energy to maintain their homeostasis. This study indicates that a future increase temperature of streams will impact the populations of aeglids by changing their metabolism and behavior.

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The aim of this study is to estimate the population size of Aegla longirostri Bond-Buckup and Buckup, 1994 in a subtropical low-order stream using the mark-recapture technique. We also tested if the Bayesian model is a promising estimator of population size. Data were collected in two periods, in spring 2010 (seven-day sampling) and in fall 2011(five-day sampling). The animals were sexed, measured, marked in the field, and released in the same spots from which they were collected. During the study period, 445 adults were captured (343 in the spring and 102 in the fall). The estimated population size was 1,005-1,028.8 individuals in the spring and 234-236 in the fall, according to the Schumacher-Eschmeyer and Schnabel methods,