Objective: The aim of this study was to investigate the effects of supplementation of dietary soluble fibers with high water-binding capacity (WBC) and swelling capacity (SC) on gastrointestinal tract mass, physicochemical properties of digesta, gastrointestinal mean retention time (MRT), body weight, and food intake in male rats. Methods: Thirty-two male Sprague-Dawley rats were randomized to four equal groups and fed the control diet or diet containing 2% konjac flour (KF), pregelatinized waxy maize starch plus guar gum (PWMS+GG), andPWMS plus xanthan gum (PWMS+XG) for three weeks. Results: WBC and SC of diets followed the order of PWMS+GG > KF > PWMS + XG > control. PWMS+GG and KF groups had a lower average daily food intake than the control group, but all the groups showed no difference in final body weightand the weight gain rate. The high WBC and SC of the PWMS+GG and KF groupsled to an increase of WBC and SC in the stomach digesta, and a gain of the cecal digesta weight, due to increased cecal moisture content. Conclusion: The inclusion of the novel fiber, PWMS+GG, in the diet of male rats appears to facilitate the modulation of WBC and SC of stomach digesta and the reduction of food intake.

This paper focuses on the role of invasive, omnivorous/carnivorous amphipods in the food web of lakes and evaluates their significance as food items for fishes in two major lakes and reservoirs of the northwestern region of Russia: Lake Ladoga and Rybinsk Reservoir. Fish samples from both water bodies were collected, there age determined and their stomach content analysed to assess the role of the introduced amphipod in the diet. Fish species mainly analysed were: perch Perca fluviatilis, ruffe Gymnocephalus cernuus, burbot Lota lota, roach Rutilus rutilus, vendace Coregonus albula and kilka Clupeonella cultriventris. Analysis of original and literature data showed that the energy flow from zoobenthos to fish was modified by the Baikalian amphipod Gmelinoides fasciatus, introduced in the 1960s-80s into many lakes and reservoirs of Russia. The invader established successfully in different aquatic systems, rapidly reaching high abundances. Examples from Lake Ladoga and the Rybinsk Reservoir confirmed that the species is an important food item for littoral benthivorous fishes (ruffe, perch, gobies, burbot), especially at early ontogenetic stages and also for several pelagic fish (vendace, kilka). Although these fish species are considered low food quality, they enrich the food supply for large predatory fish species. In Lake Ladoga, G. fasciatus influenced negatively the abundance and biomass of native benthic invertebrates (including Gammarus lacustris and Asellus aquaticus) which were previously important prey items for littoral fishes: in the beginning of introduction up to 24100 m⁻² and 33.5 g m⁻²; after introduction 6200-7800 m⁻² and 16.5 g m⁻², respectively. At the same time, the invader uses food sources (chironomids and oligochaetes) that would otherwise not be available to fishes. Therefore, the introduction of G. fasciatus into lakes and reservoirs of European part of Russia led to a greater share of the benthic productivity available to fishes, thereby allowing the intensive use of new ecosystem components and increasing the overall production in these systems.