The aim of the study was to test the hypothesis that patterns of cross-Eurasian longitudinal distribution of lotic mayflies are determined by species' ecological requirements and the presence of the West Siberian Lowland. In particular, the objective was to test whether this great lowland is an environmental barrier preventing longitudinal dispersal of the rheophilic (i.e., preferring fast-running highland waters), but not the potamophilic (i.e., preferring slow-current lowland waters) mayflies, as its entire territory contains no rapidly-flowing streams suitable for rheophilic species. This hypothesis was tested indirectly by comparison of altitudinal ranges of species characterised by different cross-Eurasian distribution patterns (mainly East Palaearctic and Transpalaearctic species distributed over the Asian part of Palaearctica and entire Palaearctica respectively). The material used for the analyses was collected in the centre of Eurasia, south-western Siberia, Russia. The region covered both lowland and mountain territories. The studied biogeographical groups of mayflies have distinctly different altitudinal distribution: the Transpalaearctic species inhabit lowland watercourses only, while the East Palaearctic species inhabit the entire altitudinal range with most of the species preferring high elevations (on average 700 m a.s.l.). These results confirmed the stated hypothesis and showed that for most of the East Palaearctic (but not Transpalaearctic) species the West Siberian Lowland can be an environmental barrier preventing their westward dispersal and therefore precluding mixing of the East and West Palaearctic rheophilic faunas. However, possible alternative hypotheses cannot be ruled out, as altitudinal ranges of some of these species do not fall out of the elevation range of the West Siberian Lowland. Remarkably, the East Palaearctic species, which by definition have narrower distribution than the Transpalaearctic species, have broader altitudinal ranges than the Transpalaearctic species. This pattern is related to the altitudinal Rapoport effect recently detected for mayfly distribution over the river systems.

In the present work, based on material from several localities in Brazil, we present a contribution to the taxonomy of the Terpides lineage, a monophyletic group of Neotropical mayflies that encompasses three genera: Terpides, Tikuna, and Fittkaulus. A new species of Terpides is described from the States of Espírito Santo and Mato Grosso, based on nymphs, male and female imagos. The male imago of the type species of Terpides, T. guyanensis, the nymph and male imago of Tikuna bilineata, and the nymph of Fittkaulus cururuensis are described for the first time.

In the present paper, based on the rearing of nymphs in the field, we present for the first time the description of the adult stage of Rivudiva Lugo-Ortiz and McCafferty and of its type species, R. minnatena Lugo-Ortiz and McCafferty. Adults of Rivudiva can be distinguished from the other genera of Baetidae by the following combination of characters: (1) hindwings present or absent, when present with two longitudinal veins and with costal projection pointed, placed in the basal fourth of anterior margin; (2) forceps three-segmented, segment III long, about 2× as long as wide; (3) distal margin of subgenital plate with small pointed projection. Besides that, R. coveloae (Traver, 1971 [Proc. Entomol. Soc. Washington, 73, 58–63]), new combination, and R. venezuelensis (Traver, 1943 [Bol. Entomol. Venezolana, 2, 79–98]), new combination, are proposed based on the characteristics listed above, specially the distal margin of subgenital plate with a small pointed projection. Comments on the biology of the nymphs are also provided.

The changes in the dynamics of cladocerans in Lake Vela (Portugal), as well as the morphologic and life history traits of the small-bodied cladoceran Ceriodaphnia pulchella, were studied intensively during one month characterized by deep and fast changes in the phytoplankton community: the beginning of the cyanobacteria dominance. Lake Vela, located in the Mediterranean region, is a polymictic shallow lake exhibiting characteristics typical of an advanced trophic status, namely the permanently turbid water, the reduction in biodiversity and the occurrence of cyanobacteria blooms. The density and composition of the cladocerans populations varied considerably during the short-term period analyzed. Coincident with the increase of cyanobacteria, the density of Daphnia longispina decreased drastically, associated with an increase of Bosmina longirostris and Chydorus sp. The constant density of C. pulchella, even during the cyanobacteria dominance, and the strong relationship found between weight and size, suggests that the low quality of phytoplanktonic food in Lake Vela did not play an important role in its fitness. Besides the small size of C. pulchella, this fact could be also related to its diversified diet. Nevertheless, a closer examination of the life history parameters of C. pulchella revealed a reduction in the fecundity, size at first reproduction, mean size of ovigerous females and maximum size of the population, which suggest an increase of the fish pressure after the decline of Daphnia. C. pulchella showed also a short-life cycle and a fast turnover of individuals, which constitutes also an advantage, allowing a fast adaptive response of the population.

The population dynamics of the red swamp crayfish (Procambarus clarkii Girard, 1852) was studied from May 2005 to May 2006 in a pond (PCD) subjected to drought between June and December and in a continuously flooded rice field drainage channel (PMG) located in the Tejo river basin, Portugal. The proportion of females in the population was not independent from the season and was negatively correlated with both female and male maturation status. Male and female maturation was synchronous but males remained in a reproductive form after recruitment while females reverted quickly to lower maturation indexes. At PCD and PMG, respectively 2 and 5 cohorts were detected by modal analysis. Large crayfish were abundant in spring, summer and early autumn and juveniles were abundant in autumn, especially at PCD. Crayfish density at PCD was lower than at PMG and mortality rate (Z) was 3.99 at PCD and 2.43 at PMG. The average lifespan of the crayfish populations was 91 days at PCD and 150 days at PMG. Our study indicated faster growth and larger maximum sizes at the site with the more stressed environment and lowest relative crayfish densities (PCD), suggesting that any exploitation or control strategies for these two populations should consider management of the hydroperiod and of maximum crayfish densities.

As part of a wetland conservation programme for the Southern shore of lake Neuchatel (Western Switzerland), an experiment was started in 1993 to slow down the terrestrialization of the wetland. Sediments were removed in a reed-belt adjacent to an existing pond, at three different depths (0.20, 0.30 and 0.40 m), thus creating a new shallow pond. The colonisation by aquatic vegetation and invertebrates was monitored during three years (1994–1996) to evaluate the effect of the creation of a new pond on the chironomid diversity and abundance through time. Chironomids (78 taxa) were among the most diverse group colonising this fringing wetland. Significant differences in abundance were found between the reed-belt and the pond habitats (existing and recently created ponds). As expected, the latter was more productive, especially during the first two years of colonization. However, the chironomid diversity in the newly created pond, measured by the rarefied richness, was intermediate between the reed-belt (low diversity) and the pre-existing pond. Ordination of the sites on the basis of their chironomid assemblages confirmed this trend. The depth at which the sediment was scrapped off, had no major influence upon the chironomid assemblages. Finally, within the three years after creation of open water habitats, the production of chironomids and consequently their availability for dabbling ducks and wetland birds, were enhanced. However, this time was not enough for the chironomid community to reach the diversity of the pre-existing pond, to which it is connected. The creation of shallow ponds seemed to be crucial to slow down terrestrialization processes in this lacustrine wetland and to have only slight effects on the chironomid communities.

We assessed the effects of land use on the structure of stream fish assemblages in Northwest Patagonia, Argentina. To this end, a total of 18 sites distributed in 15 streams were sampled during the low water period. At each site, 26 regional and local scale variables were used to describe the environmental conditions. The macroinvertebrate density, and the composition and abundance of fish were then recorded. Statistical associations between local assemblage structures and environmental variables were quantified by canonical correspondence analyses. The results revealed that, at a regional scale, the fish assemblages were primarily determined by watershed features like altitude and catchment area, and by land use effects (exotic forest and pasture). Assemblage compositions were also related to some local-scale features such as water velocity, food availability (density of benthic macroinvertebrates), instream characteristic and riparian features. Also, the observed fish species richness was low. Overall, exotic salmonids largely dominated in the samples both in numbers of individuals (98.9%) and in biomass (99.9%), whereas native fish (Hatcheria macraei and Odontesthes hatcheri) were scarcely represented. Rainbow trout (Oncorhynchus mykiss) was the most abundant fish, and was present in all streams. Native species were restricted to five streams located in the ecotone between the Andes and the steppe, where salmonids were also present. Salmonids were the only fish at Andean streams which suggest the existence of a strong geographic segregation between native and exotic species. Some aspects related to the incidence of the introduced species in the structure of fish assemblages are discussed.

We investigated crustacean zooplankton communities and their relationships to environmental factors in 13 lakes of Yunnan-Guizhou plateau to determine whether there is a consistent relationship between trophic indicators and crustacean zooplankton biomass or size structure. The lakes showed a wide range of trophic status, with total phosphorus (TP) ranging from 0.013 to 0.268 mg.L−1, and chlorophyll a from 0.9 to 76.26 μg.L−1. Continuous stocking with exotic planktivorous fish had taken place on a wide scale in these plateau lakes. About 36 species of Crustacea were found, of which Cladocera were represented by 20 taxa (12 genera), and Copepoda by 16 taxa (13 genera). Canonical correspondence analysis partitioned these species into two clusters. Physicochemical features and food-webs of different lakes seemed to be the key factors determining zooplankton species composition and distribution patterns. Between the 13 lakes, there was no significant relationship between cladocerans and chlorophyll a suggesting phytoplankton biomass was little controlled by macrozooplankton. The positive correlation between chlorophyll a and copepods suggested the high copepods biomass or size structure caused by the invasion of exotic planktivorous fish had a negative effect on water quality.