A partir d'échantillons de vandoises capturés par pêche à l'électricité de 1971 à 1976, les principales caractéristiques de la population de l'Ourthe ont été décrites et analysées : structure par âge (longévité maximale : 15 ans), variations de l'abondance des classes d'âge 1958-1972, taux annuel de mortalité (M = 38 %), taux de croissance en longueur (21 cm à 5 ans pour les deux sexes réunis), sex ratio mâles/femelles : 1,04), âge de la maturité sexuelle (3-4 ans et 16 cm), fécondité absolue individuelle en fonction de la taille et de l'âge, cycle saisonnier de la condition et du développement des gonades, relations poids-longueur, période de ponte. La dynamique (croissance pondérale, survie, fécondité et production somatique) d'une cohorte type de vandoises est établie. Des estimations sont proposées pour la biomasse du peuplement (6,3 kg/ha), la production somatique (2,3 kg/ha/an), le potentiel reproducteur (35 ovules/m2) et l'exploitation par la pêche (2,0 kg/ha/an). La discussion traite de la démographie de la vandoise dans quelques rivières européennes.

We studied the morphology of two ‘flesh-eating’ Chydoridae Anchistropus emarginatus Sars, 1862 and Pseudochydorus globosus (Baird, 1830), using populations from Belgium, with particular attention to the structure of the trunk limbs. Both genera belong in subfamily Chydorinae, and both have morphological adaptations with implications for the interpretation of limb morphology in the subfamily. Anchistropus has a large number of specific characters, many of which directly relate to the animal’s habit of feeding on Hydra. In Pseudochydorus globosus, specializations are less numerous. A redescription of both species is offered, with an aim at allowing future comparisons with populations outside the Palaearctic, where cryptic species are expected to occur.

Mediterranean Temporary Ponds (MTPs) are priority habitats (Natura 2000) of great importance according to the EuropeanLegislation (Habitats Directive 92/43/EEC). They are being destroyed mostly because of public ignorance of their significantvalue. Today, MTPs are subject to high pressures from several human activities (agriculture, livestock, tourism etc.). In this work,the “Drivers-Pressures-State-Impacts-Responses” (DPSIR) model has been used, because it allows to evaluate the impact of thehuman socioeconomic pressure. We estimated the present condition of West Crete’s MTPs, in order to propose managementpractices for their restoration. A comparison with the Greek and European MTPs is also developed.

The congenerity of Arctomyia Lundström, 1915, with Metriocnemus van der Wulp, 1874, is confirmed. Types of Arctomyia sibirica Lundström ; Chironomus picipes Meigen, 1818 : Metriocnemus longipalpus Sinharay et Chaudhuri, 1978 ; and Apometriocnemus beringiensis Cranston et Oliver, 1988 ; are examined. Metriocnemus sibiricus is close to M. longipennis (Holmgren), M. picipes is separate from M. atriclava Kieffer, M. longipalpus is a junior synonym of M. picipes, and M. beringiensis is close to M. fuscipes (Meigen). M. obscuripes (Holmgren) is a junior homonym and replaced by M. eurynotus (Holmgren). Metriocnemus wangi sp. n., M. acutus sp. n., M. dentipalpus sp. n., M. calvescens sp. n., M. sibiricus, M. caudigus sp. n., M. intergerivus sp. n., M. aculeatus Chaudhuri et Bhattacharyay, M. unilinearis Chaudhuri et Bhattacharyay, M. exilacies sp. n., M. beringiensis and M. picipes are described as male imagines. The females of M. longipennis, M sibiricus, M. intergerivus, M. picipes and M. atriclava are described. Keys to both sexes are presented. New records from Norway and China are given for M. eurynotus, M. brusti Sæther, M. ursinus (Holmgren), M. fuscipes, M. aculeatus, M. unilinearis, M. beringiensis, and M. picipes.

Patterns of leaf colonization by Chironomidae were compared on three leaf substrates differing in rate of processing and palatability for detritivores. Each leaf species was colonized by a similar number of taxa, with Orthocladiinae and Tanytarsini comprising the dominant groups. However, the chironomid assemblage, categorized by functional feeding groups, differed greatly between the three leaf types. Black cherry leaves supported a much higher proportion of shredders (e.g. Brillia flavifrons) than either red maple or American beech packs. In contrast, beech and maple leaf packs were colonized by distinctly higher proportions of gathering-collectors (e.g. Corynoneura spp., Parametriocnemus sp., Stilocladius spp., Constempellina spp., Micropsectra spp.). Overall, the cherry packs supported a significantly higher shredder and gathering-collector biomass per g leaf pack than either the maple or beech leaves. We conclude that (1) shredders were preferentially associated with cherry leaf packs due to its higher palatability compared to the maple and beech leaves, and (2) similar colonization patterns exhibited by gathering-collectors on all three leaf species were the result of a supply of similar-quality fine detritus.

Morphology, ultrastructure and formation of resting cysts of E. agilis H.J. Carter and E. anabaena Mainx are described. TheSEM micrographs of cysts of E. anabaena and E. agilis are presented for the first time. Information on the neuston film formedby these species is given. An ecological database and list of accompanying species is also included.

Three species of Isoperla occur in Fennoscandia. The most common is I. grammatica, although it has not been recordedabove the subalpine vegetation belt. I. difformis has a similar distribution, but is less common. I. obscura occurs mainlyat high latitudes and altitudes, although it is also abundant in large rivers.Eggs were reared at temperatures of 4, 8, 12, 16, 20 and 24° C. I. difformis did not hatch at 4° C. I. grammatica at 4and 8° C while I. obscura did not hatch at 16° C and above. Egg mortality was high in I. difformis at 24° C. Incubationperiod decreased with increase in temperature and varied between 28 and 68 days in I. grammatica and between 15 and83 days in I. difformis. For I. grammatica and I. difformis, the relationship between the egg incubation period and thewater temperature was linear on logarithmic scales. For I. obscura, no such relationship was found and the mean incubation period at all temperatures was 305 ± 57 (S.D.) days. Explanations are presented to explain these differences in egg incubation characteristics.

The larvae of these three mites are described for the first time.

1. - Aturus scaber Kramer.

Females of this species lay one, very large egg at a time, suggesting a suppression of the larval stage and direct development to nymph. This expectation has been refuted and the larvae bred in the laboratory. Further information on the life-history is lacking but a parasatic stage is indicated.

2 . - Piona uncata Koenike.

The complete life-history of this mite is described. In the specimens studied the main host was Chironomus plumosus L. Work by Stout shows that this species has an alternative direct development. The larvae are similar except in size to those of P. coccinea Koch.

3. - Protzia eximia Protz.

Eggs are found throughout the winter and laboratory tests show that hatching is dependant on temperature. The larvae resemble those of Panisopsis species, and run actively on the water film. They are able to jump 2 cm from the surface and use this ability to gain a place on their hosts, an unidentified Trichopteran and the fly, Weidemannia bistigmata Curtis. There are probably two generations a year.

An up-to-date table gives hosts for 150 species and references for this information.

The genus Labiobaetis recently has been reported from Madagascar by Lugo-Ortiz and McCafferty (1997). The two described species were only known from the nymphal stage. Examination of material from more than 800 samples in Madagascar allows descriptions of six new species: Labiobaetis longicercus, L. dambrensis, L. nigrocercus, L. vulgaris, L. punctatus and L. gilliesi. They can be distinguished easily by the shape of the second segment of the labial palp, the shape of the second segment of the maxillary palp, the setation of the labrum, the number of gills, the presence or absence of hindwings and coloration of the abdomen. At present, the imagoes of only five of the eight species are known. They can be identified by the presence or absence of hindwings, coloration of the wings, shape of the sclerotized process between gonopods and shape of the third segment of the gonopods. As all the species assigned to Labiobaetis were recently reassigned to Pseudocloeon, the status and validity of the genera Labiobaetis and Pseudocloeon are discussed.

An analysis of the morphology and the prey consumed by two carnivorous species of bladderworts (Utricularia gibba and U. sp.2) from a pond (Annie pond) in the heart of the Kaw swamp (French Guiana) has allowed a comparison of the preferential prey of: 1) a single species over two different periods (the end of the rainy season and the beginning of the dry season during an oligotrophic phase); and 2) the two coexistent species within a single period (the beginning of the dry season, during a temporary mesotrophic phase). Among the immediately adjacent planktonic and periphytic animals, and despite their low prevalence relative to smaller organisms such as Gastrotricha and Rotifera, cladocerans and copepods (particularly large individuals) appeared to be strongly predated. The differing organization and size-class distributions of the traps, as well as the extent of epiphytic colonization, had a probable defining effect on the alimentary regime of the two species of Utricularia. These more or less adaptive characteristics allowed the bladderworts to take advantage of the distinct preferences of various potential prey in terms of nutrition behaviour and habitat so to limit the feeding competition between the two sympatric species. The impact of this selective zooplankton predation by bladderworts on the trophic organization and the ecological functions of this pond are also addressed.

The intensification of agriculture has drastically modified the structure of rural landscapes, changing field size, destructinghedgerow networks, and increasing nutrients and fine sediments fluxes to rivers. To evaluate the effects of these disturbances atthe catchment scale, we studied the surface and interstitial water chemistry and the invertebrate assemblages in three differenthabitats: the vegetation, the benthic, and the interstitial. Six headwater streams ranging from undisturbed to disturbed forests(wind-fallen area) and from traditional agriculture to intensive farming areas were studied. Differences between forested andagricultural streams lie in changes in water chemistry, in habitat quality, and in the composition of the assemblages with littlereduction in species richness. The forested streams were only disturbed by large-scale modifications of their catchments (i.e.wind-fallen area along the stream), which made the invertebrate assemblages similar to those of agricultural streams, even ifwater characteristics were not modified. In contrast, large scale modifications of landscape structure near the agricultural streams(hedgerow removal) had little effect on the fauna, but the destruction of the riparian strip (with direct access of the cattle to theriver) profoundly affected the system with drastic modifications of in-stream habitat quality and invertebrate assemblagecomposition. The effects of these disturbances differed according to the habitat considered, with increasing differences betweenassemblages from the interstitial, to the benthic, and to the vegetation habitats. Finally, groups of organisms based on bioecologicaltraits appeared as efficient tools for the evaluation of catchment disturbances, at least for the benthic and thevegetation fauna.

Using the epilithic diatoms as indicators of environmental conditions, 10 lakes in the High Tatra Mountains were characterised with regard to their stage of acidification. The diatom communities were diverse; 210 taxa were found, including 27 species of north and alpine preference. On the basis of cluster analysis, two groups of lakes were distinguished. The first group included shallow, moderately acidified lakes (Dlugi and Zmarzly Gasienicowy lakes), where acidophilous organisms prevailed, with Achnanthes marginulata being the most numerous. The structure of the diatom community in Dlugi lake was stable over 4 years of observations and did not show any progress in acidification. The second group included mostly very deep, non-acidified lakes where circumneutral organisms prevailed, and among them Achnanthes minutissima was dominant in most cases. The diatom community structures mostly confirmed the status of the lakes studied as judged from their water chemistry.

Les limites de survie indéfinie à température constante se sont montrées les suivantes : 12 à 14° C pour C. alpina, 16 à 17° C pour P, felina, 23 à 24° C pour P. nigra. Les trois Planaires sont néanmoins capables de résister à des températures bien plus élevées pendant un petit nombre de jours.

This study investigates a phytophylous community of Chironomidae larvae on the submerged plant species Myriophyllum spicatum L. in a eutrophic lake (Lake Sakadaš, Danube floodplain area in Croatia) during summer 2004. This macrophyte species appeared for the first time in the lake in 2004, lasted approximately three months and was considered as a temporary habitat. The chironomid community was very abundant in the stands of this macrophyte species, which developed at three sites. The recorded species belong to three subfamilies: Chironominae (Chironomini and Tanytarsini), Orthocladiinae and Tanypodinae. Species composition varied in time, though Orthocladiinae with their representative Cricotopus sylvestris gr. dominated throughout the entire sampling period, accounting for approx. 60% of the total community. However, the presence of this species group experienced a marked drop to only 10% in September when Chironomini larvulae and Paratanytarsus sp. prevailed. Furthermore, the share of Endochironomus albipennis (Meigen 1830) in relation to other species was also consistently higher. NMDS ordination and cluster analysis separated three main colonization periods based on larval abundance. RDA analysis indicated the influence of environmental variables, especially Secchi depth, macrophyte dry weight, depth and water temperature, on chironomid community structure.

The diet composition and feeding strategy of native and exotic fish species were studied from May 2005 to February 2006 in three Patagonian low-order streams. A total of 464 fish were caught, which belonged to the exotic species Oncorhynchus mykiss (270), Salmo trutta (177) and the native species Hatcheria macraei (17). The analysis of 336 stomach contents indicated that at the individual level, the three species had a generalized feeding strategy based on benthic invertebrates (Plecoptera, Trichoptera, Coleoptera and Diptera). In the three streams, the widest population niches were observed in winter. There was, however, also a slight tendency toward an increased between-phenotype contribution to the niche width in same season, indicating that a small proportion of individuals within the fish populations specialized by predominantly feeding on a few specific prey species. Hence, the wide population niche widths observed throughout the year were partly a result of mixed individual feeding strategies within the populations. The higher diet overlaps were registered between exotics O. mykiss–S. trutta at Glyn and Carbón, and O. mykiss and the native H. macraei at Manguera, but it changed markedly through the year, perhaps depending on temporal changes in food availability suggesting a competitive coexistence of these species. This is mainly related to the fact that both species changed their food preferences in spring and foraged almost exclusively on Aubertoperla illiesi. This implies that in order to reduce the predation risk or the inter-specific competition for food, the fish species might partition the feeding habitats.

Phragmites australis is a stand forming emergent macrophyte that displays large phenotypic variation within Lake Balaton. The present study assesses morphological variations of P. australis within three transects of different reed stands of Lake Balaton which differ with respect to bathymetry, reed quality and geographic position in order to achieve a morphological typization. On average the southern stable stand produced the largest and thickest plants (295±9 cm and 7.5±0.2 mm), while plants of the northern die-back stand were approximately half this size (141±2 cm and 3.5±0.1 mm). The slow growth and development of Phragmites characterizing the northern die-back stand was the result of fewer and shorter internodes, which also resulted in the low number of green leaves. The most influential factor shaping the phenotypic properties of the plants was determined to be the reed quality (general condition), although site-specific differences, shore-specific differences, water depth and spatial position within reed stand transects were also found to be significant. Despite the differences in the studied stands and almost certain genetic dissimilarities, three morphological ecotypes of Phragmites were distinguished on the basis of stem height to basal diameter ratio, stem density and phenotypic plasticity of plants. These ecotypes were primarily correlated to water depth at their position within the reed stand. The similarity of the spatial distribution of stem heights to basal diameter ratios and phenotypic plasticity of plants along all studied reed stands suggests that morphological typization should be considered to provide additional information on ecological zonation of stands.

We investigated the diel vertical distribution patterns of microcrustacean zooplankton (Cladocera, Copepoda) in a shallow pond (max. depth: 70 cm) of the Öreg-turján peatland (Ócsa, Central Hungary) during three 24-h periods in July (19–20th), August (17–18th) and September (11–12th) 2011. Environmental variables showed remarkable vertical stratification. Oxygen concentration was close to zero in the entire water column from night until sunrise, while the lower strata (from 20 cm below the surface) were close to anoxic during all three diel cycles. It proved to be the main determinant of the vertical distribution of microcrustaceans. Accordingly, the highest proportion of individuals was present in the surface layer. Chlorophyll-a concentration and phytoplankton biomass were inversely distributed compared to zooplankton. Microcrustaceans (mainly Daphnia curvirostris) migrated to the middle layer only in August, which could be explained by a trade-off between food resources, dissolved oxygen (DO) and competition with littoral zooplankters. The diurnal density patterns of microcrustaceans suggested horizontal migration into the aquatic macrophytes during night, which could be a strategy to avoid Chaoborus predation. Our results show that strong vertical gradients of abiotic and biotic factors occur even in such shallow waterbodies. Among them, DO can maintain constant vertical aggregation of zooplankters by limiting their occurrence to the surface layers.

Seasonal samples of zooplankton were taken during 1997-1999 at fifteen stations in the Salado River basin, and analysed inorder to study the rotifer fauna. Spatio-temporal changes in the rotifer plankton composition were examined in the main channeland its tributaries. The majority of species found are tolerant of a wide range of pH, whereas others prefer neutral to alkalinevalues. The total rotifer plankton density increased downstream from the headwaters to the middle sector of the river. Theassociated shallow lakes and tributaries were an important source of species. Variations in density and number of species wereshown to be associated with conductivity, and species tolerant of high conductivity conditions were especially prevalent (upper7,000 µS cm-1). Rotifer density was influenced by hydrological conditions, which promoted maximum values during low waterperiods and in the high water condition promoted the incorporation of species from shallow lakes connected with the river duringflood events. The species associations found are related to such water parameters as conductivity and nutrient availability andto the presence of ponds and shallow, waterlogged depressions connected in varying extent to the main channel.

Cylindrospermopsis raciborskii (Woloszynska) Seenayya et Subba Raju, a potentially toxic bloom forming cyanobacteria(Nostocales), was recorded in the River Seine in August 2001. The cyanobacterium was previously observed in some French ponds but this is the first report of this reputedly tropical species in a river in France.