Four experiments were serially carried out conducted to study foraging activity in the freshwater gastropod Lymnaea stagnalis in the absence and presence of predators (crayfish or fish) under daylight and in the dark. The snails were either parasitized by digenean trematodes (Diplostomum pseudospathaceum or Plagiorchis elegans) or remained unparasitized. The snails had an evident circadian foraging rhythm: they preferred diurnal foraging notwithstanding the predators and parasites. However, the snail's parasite status and the predation risk had an interaction effect on the number of feeding events per snail individual so that especially the snails parasitized by D. pseudospathaceum were more active in the presence of a fish predator than in the absence of predators. Some of the snails responded to cues from a crayfish predator by crawling out of the water. The results suggest that D. pseudospathaceum may be capable of manipulating the behaviour of its first intermediate snail host in ways that enhance its success of transmission to the parasite's second intermediate fish host. The results also indicate that the effects of biotic stressors, such as predation risk and parasitism, on the foraging pattern in the snails L. stagnalis may be interactive and highly specialized rather than generalized.

Plant litter breakdown, an important process for energy and matter flows in freshwater ecosystems, has been extensively studied except in the karst (and calcite depositing) habitats. The aim of this paper was to answer three questions regarding the breakdown of leaf litter in calcite depositing environment: (i) Does leaf decomposition hinder calcite deposition and vice versa?; (ii) What role do other environmental factors play?; and (iii) How long does leaf litter persist in these habitats? Leaves of beech (Fagus sylvatica) and butterbur (Petasites hybridus) were exposed for 8 weeks in 8 microhabitats: 2 calcite deposition rates × 2 flow velocities × 2 seasons. A linear model was better at predicting leaf litter persistence but only for the period after the extreme loss of leaf mass occurring during the initial leaching of highly hydrosoluble compounds in the first week (11.6% of beech and 54.2% of butterbur regardless of the studied environmental factors). Higher flow velocity and calcite deposition rates stimulated the breakdown of both leaf species. During summer, breakdown was accelerated for butterbur leaves only. Since breakdown rates of both litter types were faster at high calcite depositing sites, it can be concluded that the breakdown process is not hindered by calcite deposition in general. The amount of deposited calcite per gram of leaf litter increased linearly over time (after the first week of exposure) on both leaf species. More calcite was deposited on the fast-decomposing butterbur leaves than on beech leaves.

Aerobic anoxygenic phototrophic (AAP) bacteria are widely distributed in marine and freshwater ecosystems. The aims of this study were to investigate the diversity and abundance of AAP bacteria in cyanobacterial bloom-forming eutrophic lakes and to study the association of AAP bacteria with the bloom-forming cyanobacteria. Analysis of pufM gene (the light-reaction center gene) clone libraries indicated that in eutrophic lakes (Lake Taihu and Lake Chaohu, China) with cyanobacterium Microcystis blooms, the AAP bacteria were related to members of Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria. In Lake Taihu and Lake Chaohu, Alphaproteobacteria accounted for 81.5% and 75.0% of Microcystis-associated AAP bacteria, respectively, and 84.6% and 72.5% of free-living AAP bacteria, respectively. The predominance of Alphaproteobacteria in the two lakes was different from the previously reported predominance of Betaproteobacteria in freshwater lakes. Quantitative real-time PCR analysis indicated that in Lake Taihu and Lake Chaohu, AAP bacteria represented an important part of the bacterial community associated with Microcystis, and the abundance of Microcystis-associated AAP bacteria (18.3% and 11.7%, respectively) was higher than that of free-living AAP bacteria (5.1% and 7.9%, respectively). The abundance of AAP bacteria in the two bloom-forming lakes was higher than the previously reported level in other eutrophic freshwater bodies.

Daphnia longispina (O. F. Müller 1785) and Daphnia cucullata (G. O. Sars 1862), despite coexisting in similar densities in the lake, showed different demographic cycles. To search the causes of such variances between the two Daphnia, selected population parameters (density, body proportions, reproductive output) were correlated with the density of five dominant and potentially competitive species of Cladocera. The same parameters were estimated in relation to predation pressure of vertebrates (planktivorous fish) and invertebrates (Leptodora kindtii (Focke 1844)). The obtained results show that competition had no apparent impact on life-histories of Daphnia. Different strategies of the two Daphnia resulted from the uneven effect of invertebrate and vertebrate predators. D. longispina that was affected by planktivorous fish and Leptodora kindtii invested in reproduction and carried big egg-clutches. D. cucullata, which was insignificantly influenced by fish, displayed low reproductive output but changed their body proportions in the process of cyclomorphosis when occurring with L. kindtii. Other life-history trade-offs altered during the year, in accordance with the intensity of predation pressure.

Three new freshwater ameirid species were discovered in the Western Australian subterranean habitats and described in this paper. They all proved to belong to the genus Nitocrellopsis Galassi, De Laurentiis & Dole-Olivier, 1999, representing the first record of this genus in Australia. Nitocrellopsis operculata sp. nov. was collected in 2003 in the Pilbara region, during the Pilbara Regional Survey, led by the Western Australian Department of Environment and Conservation (DEC). It can be distinguished from all other congeners by the reduced armature of the antennal exopod, which is an autapomorphic feature. Also, no other species of Nitocrellopsis has cuticular windows on prosomal or urosomal somites, or six elements on the third exopodal segment of the second leg. Nitocrellopsis halsei sp. nov. and N. pinderi sp. nov. are sister-species, collected in 2007 in the neighbouring Yilgarn region, by the private environmental consulting company Bennelongia Pty Ltd. Numerous morphological similarities include somite ornamentation, armature patterns of the swimming legs and the fifth leg, as well as the shape and armature of the antennula, antenna and almost all mouth appendages, while the main differences between the two are observed in the body size and habitus appearance, caudal rami shape and size, presence/absence of large lateral pores on the fourth pedigerous somite, number of spinules on the anal operculum, number of setae on the madibular endopod, and shape of the exopod of the fifth leg. Although they differ from any other congener by a combination of characters, no significant autapomorphic features were observed. In order to find a more natural allocation of these three species, a cladistic analysis is performed on all current members of Nitocrellopsis and three outgroup taxa, based on 45 morphological characters. The resulting cladogram shows that the ingroup is well defined by at least four synapomorphies, but the Australian species from the two regions are only remotely related to each other, showing the importance of looking at small-scale patterns when inferring Gondwanan biogeography. Three sister-species pairs are recognized in the genus and a key to all 12 members is provided.

Although habitats of hard emergent macrophyte beds, including reed beds (Phragmites australis), are very common in the littoral zones of stagnant waters in central Europe, research investigating their macroinvertebrate communities is still lacking. In this study, the spatial distribution of macroinvertebrates was studied within large reed beds in the littoral zone of a lowland fishpond (Nesyt, SE Moravia, Czech Republic). Using a hand net, horizontal line transects in the reed bed leading from the marginal area with the open water towards the shore were sampled. The results of NMDS ordination and PERMANOVA test proved that the taxonomic composition of the macroinvertebrate assemblage changed significantly along the investigated horizontal transect from the open water towards the shore, together with gradual changes in some environmental factors. The taxa diversity was found to be the highest in the areas closest to the shore. In the reed bed areas near open water, corixids, aquatic insects larvae, leeches, water mites, some naidids and tubificids, which represented free-swimming invertebrates with tracheal gill breathing, ectoparasites, gatherers/collectors and taxa preferring pelal and inorganic substrates, were more abundant compared with the interiors of reed beds. On the other side, in the shallow dense interior of reed beds close to the shore, gastropods, water slaters, some naidids and enchytraeids, aquatic beetles and dipteran larvae were characteristic taxa, which belonged especially to grazers and scrapers, shredders and invertebrates preferring phytal and POM (particulate organic matter) microhabitats. Different predators were recorded in areas near open water and near the shore. This invertebrate spatial distribution probably reflects changes in microhabitat and environmental conditions along the investigated horizontal transect. The results of this study proved that extensive reed beds serve as refuges for many groups of aquatic macroinvertebrates within lowland fishpond ecosystems.

We characterized the responses of benthic macroinvertebrates to heavy metals released from mines in high mountain streams of the Gangqu River in the Shangrila Gorge, China. Benthic macroinvertebrates were collected with a kick-net at 32 sampling sites. In addition, 25 environmental variables including heavy metal concentrations were measured at each sampling site. Although the concentrations of heavy metals were not seriously high, their effects were reflected in the changes of community composition of benthic macroinvertebrates. Total abundance and species richness decreased with increasing heavy metal concentrations. Species richness of Plecoptera and Trichoptera, Margalef richness index, and percentage of scrapers in functional feeding groups were negatively correlated with heavy metal concentrations. A high variation was observed in the response of different taxa to heavy metals. Heavy metals mainly affected the sensitive taxa of Plecoptera, Ephemeroptera, and Trichoptera. However, some tolerant taxa were observed in Trichoptera (such as Hydropsyche sp.) and Dugesia sp. Cluster analysis and a non-metric multidimensional scaling analysis were applied to characterize specific macroinvertebrate taxa composition. The analyses revealed the effects of different environmental factors such as geographical, hydromorphological, physical, and chemical factors including heavy metals on the distribution of benthic macroinvertebrates in high mountain streams. Although the effects were compounded with different factors such as altitude, temperature, stream width, turbidity, and heavy metals, the influence of heavy metals on benthic macroinvertebrate communities was clearly identified (decreased species richness, changes in species composition). Even though the contamination of heavy metals was low in the sampling area, the consequences were clear, indicating that long-term exposure to heavy metals could seriously impact aquatic communities in high mountain streams.