Phytoplankton dynamics in freshwater ecosystems can be faced as a meaningful natural stressor for its main grazers, and henceconstrain bottom-up interactions within the trophic structure of the food-web. Filter-feeding zooplankters, such as Daphnia, copewith resources fluctuations by adjusting their life-history as a function of balances in the energy allocation rules. Additionally,Daphnia populations often withstand interspecific competition within coexisting related species, and it is generally assumedthat body size is a strategic trait conditioning exploitative ability and the related competitive advantage of species. The lifehistoryresponses of one Daphnia magna population and three populations of Daphnia cf longispina to a discrete gradient of algaeconcentration were assessed. This experiment was focused on (i) how these distinct populations regulate life-history when feedingover low, intermediate and high food-levels; and on (ii) whether the large-bodied D. magna can be better in exploiting resourcesover the gradient than can the smaller D. cf longispina populations. We found evidences that body size might not be the singletrait influencing the exploitative ability of related species. The D. cf longispina populations were often better than D. magna inexploiting different levels of resources, and remarkable differences in fitness were found between these similar-sized individualswithin food-level; indeed, these differences were frequently of higher scale than those found between the larger D. magna and anyof the D. cf longispina populations.

Microvelia picinguaba sp. nov., Microvelia ubatuba sp. nov., Paravelia gabrielae sp. nov. and Rhagovelia pseudotijuca sp. nov. are described. The male of Microvelia ioana is described. Microvelia mimula and Microvelia aemulana are synonymized. Microvelia hinei, M. ioana, Microvelia longipes, Microvelia pulchella, Microvelia venustatis, Oiovelia brasiliensis, Oiovelia cunucunumana, Paravelia basalis, Paravelia itatiayana, Rhagovelia denticulata, Rhagovelia hambletoni, Rhagovelia janeira, Rhagovelia robusta, Rhagovelia tenuipes, Rhagovelia zela and Stridulivelia ayacucho are recorded for the first time from São Paulo State. New locality records are given for Husseyella diffidens, Rhagovelia accedens, Rhagovelia aiuruoca, Rhagovelia henryi, Rhagovelia lucida, Rhagovelia modesta, Rhagovelia occulcata, Rhagovelia trepida and Rhagovelia triangula.

The west palearctic species of Marthamea are reviewed. Adults are distinct from other European genera, but larvaeand eggs are very similar to those of genus Phasganophora. M. beraudi (Navás) (Antilebanon Mts.) is re-instated as a species distinct from M. vitripennis (Burmeister). A lectotype of the latter is designated. Its range includes south-west, centraland south-east Europe. Records from Syria are unconfirmed, those from Israel are erroneous. The species has in thepast been confused with larvae of a Phasganophora species. M. selysii (Pictet) has brachypterous males and is known fromSpain north to Meuse and Moselle rivers. Keys to adults and larvae are presented, but larval M. selysii and M. vitripenniscan presently not be separated. The European Marthamea species are inhabitants of the potamon and are endangered ;they are presently already extinct in parts of their former ranges.

Abiotic heterogeneity of the littoral zone of Lake Balaton influences both horizontal and vertical distribution of macrophytes, but biotic differences could shape the nature of a community. Vertical and temporal (small timescale) biomass distributions of Potamogeton perfoliatus and Myriophyllum spicatum were analysed in relation to their photosynthetic capacities to understand their coexistence, general presence over the northern shore of the lake seasonal shift of dominance within the community.

Our results indicated the adaptation of these macrophytes to the rapidly changing and mostly low irradiance of the Lake Balaton originated from its high turbidity: both P. perfoliatus and M. spicatum had high photosynthetic activity (20 to 50 mg O2.g drw−1.h−1), low dark respiration (around 12–14% of maximal photosynthetic capacity) and high shade tolerance (Ic of plants were 29±18 and 26±18 μmol.m−2.s−1, respectively). The majority of photosynthetic parameters had no (or little) seasonal changes. On the other hand, in Lake Balaton P. perfoliatus and M. spicatum differed in vertical distribution of biomass: Myriophyllum concentrated its biomass in the upper, well-lit region of the water more strongly than the Potamogeton.

Results suggest that the autogenic shift of dominance from Potamogeton to Myriophyllum in Lake Balaton can't be explained only by seasonal patterns of photophysiological changes, but supported by constitutive differences in plants architecture could led to the described phenomena.

Des clés de détermination (larve, nymphe et imagos) sont données pour les 37 espèces pyrénéennes de Simulies, récoltées par l'auteur entre 400 et 3000 mètres d'altitude.

Apobaetis insolitus n. sp., Apobaetis kallawaya n. sp. and Apobaetis niger n. sp. (Ephemeroptera: Baetidae) are described fromnymphs collected in Argentina and Bolivia. Apobaetis insolitus can be distinguished by the labrum with anterior margin with aU-shaped emargination, segment II of labial palpi with triangular apically rounded distomedial projection. Apobaetis kallawayacan be distinguished by segment II of labial palpi with triangular, slender and apically pointed distomedial projection, the posteriormargins of the abdominal terga with blunt spines and paraprocts with blunt spines apically. Apobaetis niger can be distinguishedby the anterior margin of labrum with medial lobe and segment II of labial palpi with triangular apically rounded distomedialprojection. The three new species possess tarsal claws with two rows of denticles. A key to all species known fromnymphs is presented.

De 1984 à 1991, 114 stations du crénal et de l'épirhithral ont été régulièrement prospectées dans les hauts massifs montagneux du Sud-Ouest de l'Europe (Alpes françaises et italiennes, Pyrénées et principales sierras de la Péninsule Ibérique). Parmi les 33 espèces recensées, peu sont crénophiles : S. (N.) carpathicum, P. (P.) latimucro et S. (N.) oligotuberculatum se développent en très haute altitude ; S. (N.) vernum, S. (N.) brevidens, S. (N.) quasidecolletum et S. (E.) petricolum en haute montagne ; S. (N.) costatum, S. (R.) lamachi et P. (P.) tomosvaryi en moyenne montagne et piémont ; la majorité d'entre elles fréquentent également l'épirhithral. Des espèces peu alticoles dans les Alpes ou les Pyrénées peuvent atteindre des altitudes de plus en plus élevées vers le sud de l'Europe (sierras andalouses en Espagne, Haut-Atlas marocain), par exemple : S (N.) costatum, S. (S.) intermedium, S. (R.) lamachi.

We test the possibility of a hybrid origin for Chaetopteryx morettii using cross-breeding experiments and molecular analysis. We show that species within the Chaetopteryx villosa group can hybridize, but that C. moretti is not of hybrid origin. We discuss the applicability of our approach for testing ideas on hybrid speciation and detecting hybrids in natural populations, e.g., for conservation purposes.

Quarante-deux espèces de Plécoptères, seize espèces d'Elminthidac et cinq espèces d'Hydraena ont été capturées dans seize stations situées sur la partie amont du Lot et sur son principal affluent, la Truyère. En aval, les débits estivaux sont très perturbés par le fonctionnement des usines hydro-électriques. Ces perturbations éliminent la plupart des Plécoptères, puis les Coléoptères. Toutefois, deux Leuctra automnales, L. fusca et L. geniculata, se maintiennent dans cette zone. Des données morphologiques sont précisées pour certaines espèces de Plécoptères.

Alpine areas are extreme habitats that require special adaptations and involve major trade-offs in terms of life history. Amphibians have the ability to adapt both their life history and developmental traits to alpine environments. Temperate amphibians depend on the quality and availability of aquatic habitats for reproduction. We explored the aquatic habitat used by amphibians in the alpine area of Retezat Mountains, Southern Carpathians, Romania. We surveyed 40 aquatic habitats in a 380 ha area delimited by mountain crests and drained by a steep valley. Each aquatic habitat was characterized using 10 environmental variables. Only three amphibian species occur at elevations above 1900 m, the most widespread being the Common Frog Rana temporaria. The Common Frog showed preference for breeding aquatic habitats, the variables of importance being altitude, solar radiation, water chemistry and grazing. Higher elevation and lower solar radiation decreased frog occurrence, while the impact of grazing favored the use of water bodies. Acidification is eminent in the area with pH dropping below 5 in 20% of the water bodies. Overall, amphibian occurrence in alpine area can be partly explained by the characteristics of aquatic habitats.

Les changements du zooplancton lacustre à la suite des feux et des coupes à blanc dans la forêt boréale ont été évalués en 1996 en comparant trois groupes de lacs du Québec méridional : 20 lacs de référence aux bassins versants non perturbés, 9 lacs ayant subi en 1995 des feux de forêt sur la majorité de leur bassin versant et 9 lacs ayant eu en 1995 une coupe à blanc sur une partie de leur bassin versant. Les communautés zooplanctoniques ont été caractérisées par différentes variables : 1) la composition, la richesse spécifique et la densité du zooplancton, 2) la masse organique du limnoplancton (seston > 53 µm) et 3) le biovolume du méso- et macrozooplancton (> 250 µm). La richesse spécifique et les assemblages d'espèces en juillet 1996 ne différaient pas entre les groupes de lacs ; la variation inter-réplicats dans les assemblages d'espèces de chaque lac était très faible en comparaison de la variation inter-lacs. Par contre, la densité du zooplancton et la masse organique du limnoplancton étaient en moyenne significativement plus élevées dans les lacs de feux que dans les lacs de coupes et les lacs de référence. Le biovolume du méso et macrozooplancton suivait les mêmes tendances. L'effet des traitements (groupes de lacs : référence, feu, coupe) expliquait moins de 15 % de la variance totale de la masse organique du limnoplancton et du biovolume du méso et macrozooplancton tandis que les différences inter-lacs expliquaient la majorité (> 70 %) de la variance totale dans ces indicateurs. Les 15 % de variance résiduelle étaient attribuables à la variation inter-réplicats dans chaque lac. Notre étude préliminaire indique que les feux de forêts provoquent une poussée trophique du zooplancton et du limnoplancton mais n'ont pas d'effet sur la biodiversité et les assemblages d'espèces de zooplancton. Par contre, les coupes de forêt n'accroissent pas la biomasse du zooplancton en dépit d'une légère augmentation des nutriments, car les apports plus importants en carbone organique dissous après la coupe limitent la production biologique. Les changements limnologiques d'un lac à l'autre ont beaucoup plus d'importance que les feux et les coupes de forêts dans le contrôle environnemental du zooplancton des lacs de la forêt boréale.

La minéralisation des eaux de la rivière Lot augmente de l'amont vers l'aval ; ses variations sont essentiellement déterminées par les fluctuations de débit de l'affluent principal (la Truyère) moins minéralisé. Les teneurs en sels nutritifs (azote, phosphore, silice) évoluent selon un cycle saisonnier parallèlement au développement des algues planctoniques. Le transport chimique, faible dans la partie haute, augmente dans la zone aval du bassin versant où se concentrent les activités agricoles. Les caractéristiques chimiques témoignent cependant d'une influence humaine relativement modérée sur l'ensemble du cours.

Typology schemes are useful in partitioning natural spatial variability and thus helping implementing bioassessment methods. They have become widely accepted in Europe after the publication of the Water Framework Directive (WFD). The major objective of this study was to test if six Portuguese pre-defined physical stream-types (using System-B of the WFD) are concordant with macroinvertebrate assemblages collected in 31 undisturbed sites in a Portuguese river basin. A top-down (stream types defined by physical attributes) and a bottom-up approach (river classes defined by biological communities) were used. No significant differences were found in the mean number of taxa and abundance of different physical stream types and few taxa are characteristic of specific stream types. Discriminant analysis (DA) considering family-level composition revealed that all stream-types were significantly different and the cross-validation process showed that all stream-types had more than 50% of their samples correctly assigned. On the other hand, the bottom-up approach based on a correspondence analysis (CA) showed some overlap of the  macroinvertebrate communities of pre-defined stream types, indicating that variations in the macroinvertebrate community structure was primarily related to altitude, mineralisation and a temporal gradient. DA cross-validation and CA results suggest that tested stream types do not account for natural temporal changes known to affect macroinvertebrate communities in this Mediterranean basin and that the WFD typology should account for these natural variations. The exclusion of natural variability could indicate impairment when it does not exist or no impairment when it does exist (type I and II statistical errors).

Une étude des peuplements benthiques de la Seine portant sur plus de 250 échantillons prélevés sur 39 stations échelonnées entre la source et Rouen, a permis de localiser la prolifération d'une diatomée considérée comme "endémique" des régions tropicales, à l'aval immédiat d'une centrale thermique (E.D.F. Porcheville). La morphologie, l'ultrastructure et la répartition géographique sont examinées succinctement. Les données écologiques recueillies à Porcheville, confrontées à celles de la littérature conduisent à considérer Navicula confervacea comme une espèce saprophyte polluorésistante, sténotherme des eaux chaudes (25-31°C).

We evaluated the concordance between assemblages of Ephemeroptera and Trichoptera to verify if they respond similarly to environmental gradients in the basin of Suiá-Missu river in Mato Grosso, central Brazil. We tested the predictions that: (i) the distributional pattern of mayfly and caddisfly larvae is concordant along the spatial and (ii) environmental variation along the basin, and if (iii) taxa are concordant between themselves along the seasons and with the environmental gradients disregarding the seasons of the year. We found a concordance between species composition of mayfly and caddisfly in fall-water and rainy period, when analyzed separately by each season. The concordance between environmental variables and the two taxa analyzed separately also was concordant, but only on the fall-water season. Finally, we found congruence when both analyzed groups disregarded the temporal effect, but it was less representative than when we consider the seasons variation. Our results suggest that the hydrological cycle could be a driver of changes in species composition of mayflies and caddisflies.

Les auteurs rapportent ici quelques données sur la variabilité des soies spermathécales constatée chez des exemplaires du Tubificidae Potamothrix heuscheri (Bretscher), récoltés dans le lac de Nemi (Italie Centrale). L'étude systématique, basée sur l'anatomie de l'appareil efférent mâle et sur la morphologie des soies génitales permet de conclure qu'il existe un écotype de l'espèce dans ce lac.La distribution de P. heuscheri dans les lacs français et italiens, en particulier dans le lac de Nemi, est discutée dans ce travail pour tenter de clarifier le problème posé par les exigences écologiques de cette espèce, actuellement peu connues et parfois contradictoires, en milieu lacustre.

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.

Le cycle vital de Pachyleuctra benlocchi (Navas) dure 4 ans dans un cours d'eau des Pyrénées centrales. Situé à 1 930 m d'altitude, le ruisseau est enneigé 4 à 5 mois par an ; les températures annuelles varient de 0 °C (hiver) à 17 °C (été). Les larvules éclosent en automne, les adultes émergent 4 années plus tard, dès la fonte des neiges.

The freshwater scud Echinogammarus stammeri is a very abundant benthic crustacean in riverine systems of northern Italy.The molecular physiology of L-[3H]leucine transport across cell membranes of E. stammeri was investigated. At pH 7.4, thepresence of a NaCl gradient stimulated the leucine transport rate, when compared with KCl gradient. By contrast, alkaline pHstrongly inhibited transport activity. In NaCl medium at acidic pH, leucine uptake displayed a specific activity 2.1-fold lowerthan that measured at neutral pH. Analysis of the uptake as a function of external leucine concentration revealed saturation kinetics.Leucine uptake appeared broadly unspecific and it was much strongly inhibited by the non-polar amino acids phenylalanine,methionine, and BCH, as well as by hydrophobic hydroxyacids. These results revealed important differences with respect toamino acid transport systems described in marine crustaceans. Their relevance in the feeding adaptation of the scud is brieflydiscussed.