No abstract

The urban effects on macroinvertebrate trophic structure were evaluated in a stream located in central Brazilian Cerrado. Samplings were evaluated from May/ 2004 to March/2005 in the upper, middle and lower sections. Characterization of ecological conditions and habitat diversity indicated headwater as ''natural'' site, up and downstream the urban region were ''altered'' ones, and the sites located nearest to urban area were considered ''impacted''. A well oxygenated and transparent water, acid pH, low electrical conductivity (\0.22 lS/cm), and low nutrients concentrations (\0.03 mg/L PO 4 -2 , \0.05 mg/L N-NH 4 and \3.0 mg/L N-NO 3 -2 ) was registered for headwater area. Stretches located near the urban region had higher electrical conductivity (48-100 lS/cm), higher ammonium (7.16 mg/L), and poor oxygenated water. The trophic organization was different along the stream and related to environmental preservation degree. Shredders occurred only in the headwater (Phylloicus sp., Trichoptera). Predators were dominant in upstream sites of the urban area ([90 % of biomass). In the sites located near the urban area, an alternative predominance was observed between gathering collectors and predators, with the gathering collectors dominance in the area impacted by city sewage inflow ([90 %). There was a progressive participation of scrapers in stretches located downstream of the city. Biomass was dominated by predators ([50 % in six sites) encompassing larger organisms ([20 mm), and gathering collectors were density dominants (from 53 to 99 %). Predators were the most dominant functional feeding group (22 taxa), followed by scrapers (eight), gathering collectors (seven) and filtering collectors (five). The results state that the Sobradinho stream is under different degrees of environmental impacts with lower preservation levels of its natural conditions, even in areas close to its headwater.

The order Odonata (Insecta) is composed of aquatic insects popularly known as dragonflies and damselflies. Members of this order are closely linked to the conservation status of their habitats; however, the Wallacean shortfall in some regions still remains high. The Volta Grande do Xingu region is known to have high endemism of some groups, such as Actinopterygii (fish), which can be applied to other groups that do not yet have their fauna known at the site, such as the order Odonata. The Wallacean shortfall and constant anthropic changes (for example, the construction of the Belo Monte Hydroelectric) have been obstacles in the preservation of these and other groups. In that regard, the main aim of this paper is to provide a checklist of Odonata (Insecta) adult species from the streams of Volta Grande do Xingu, Pará, Brazil. The collections were carried out in 19 streams in the Volta Grande do Xingu region in September 2019, corresponding to the drought period. A total of 526 specimens were collected, where two suborders, six families, 26 genera and 43 species were identified. Three species of Odonata were registered for the first time in the state of Pará: Erythrodiplax famula (Erichson in Schomburgk, 1848); Acanthagrion chacoense Calvert, 1909 and Epipleoneura lamina Williamson, 1915. These data allow us to help increase the knowledge of Odonata fauna in the streams of Volta Grande do Xingu, a region that is under intense anthropic pressure. This helps to reduce the Wallacean shortfall, with another area sampled for the state of Pará.

No abstract

Aim The aquatic larvae of the Phylloicus (Trichoptera: Calamoceratidae) caddisflies are typical shredders. However, the trophic classification of Phylloicus has been based on the morphology and behaviour of the larvae. The aim of this study was to investigate the diet of caddisfly larvae Phylloicus in streams. Methods In order to provide a more reliable classification of Phylloicus diet, we analyzed the stomach contents of 185 larvae collected, sampled with D-frame entomological net from 18 streams located in the tropical forests of western Pará, Brazil. We compared the stomach contents between the larval stages, seasons (dry and rainy), and substrates (i.e., sand, leaf litter, roots, clay and mixed substrates). Results We identified the stomach contents as fine particulate organic matter (FPOM), coarse particulate organic matter (CPOM) and plant tissue. The diet of the Phylloicus larvae was composed basically of FPOM, independent of the larval stage (90,4%), was a higher consumption of FPOM in the dry season and there were no significant differences in food resource between substrates. Conclusions These findings indicate that the classification of Phylloicus as a shredder may in fact be based on the processing of leaves for the building of larval cases, rather than the diet, which is in fact detritivorous, enjoying the availability of FPOM in the streams. The great quantity of FPOM consumed by caddisfly larvae Phylloicus highlight the importance of this food resource for macroinvertebrate communities from tropical streams. Therefore, regional studies of feeding habits are needed for accurate classification trophic of Phylloicus.