Field and laboratory studies on 11 populations of Galba truncatula were performed to determine the survival rate of snails after aestivation, to specify the range of their shell heights, and to establish the percentage of G. truncatula which burrowed in soil when summer drying occurred. These investigations were performed using six lowland populations living in central France (alt. 206-282 m) and five highland populations, located in the Massif central (alt. 806-900 m). The survival rate of G. truncatula after flooding dried soil with water was significantly higher in the highland than in the lowland populations (69.5-80.7 % in road ditches, for example, instead of 29.3-33.0%). The mean shell heights of surviving snails and the durations of snail re-activation in water did not show any significant variation, whatever the origin of snail population. The percentages of snails buried in drying soil were higher in the highland population (13.0 % and 15.0 % of juvenile snails, for example, instead of 4.0 % and 7.7 % in lowland snails). In the lowland population only young snails buried, whereas 5.8-8.3 % of adults in the highland population were partially burrowing. The local climate of the sites studied in the Massif central, and the ability of snails to burrow into the mud when stagnant water disappeared in July, might explain the higher survival rate during aestivation.

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.

L'étude phytoécologique de la Moder (rivière du Nord-Est de la France) a été réalisée en 1994 et en 1995 en effectuant des relevés végétaux associés à des analyses physico-chimiques. L'amont, situé sur grès, se caractérise par des eaux peu minéralisées et par un groupement végétal à bryophytes (Amblystegium riparium, A. tenax), Callitriche (C. platycarpa, C. obtusangula, C. hamulata), Ranunculus peltatus, Elodea (E. canadensis, E. nuttallii) et Vaucheria sp. A l'aval, la rivière s'écoule sur substrat marno-calcaire. La minéralisation augmente, une nouvelle espèce d'élodée E. ernstae et des algues du genre Cladophora apparaissent. Une comparaison entre les phytocénoses aquatiques de la Moder et celles des rivières phréatiques bicarbonatées calciques du Ried alsacien permet de préciser le rôle des différents paramètres physico-chimiques et en particulier celui de la minéralisation dans la distribution des communautés végétales.

Body size strongly influences the type and strength of species interactions. Animals with complex life cycles, such as dragonflies, usually go through different stages that include a variation in body size and may involve shifts in their trophic position in the food web. This investigation analyzes the position of the dragonfly Rhionaeschna variegata, in the food web according to its body size, in Andean wetland communities of Northwestern Patagonia (Argentina). The phenology of R. variegata larvae and their potential intraguild predators were studied in wetlands with different hydroperiods. Under controlled experimental conditions, feeding trials were performed to assess the effect of R. variegata on the survivorship of different types of prey. The effects of cannibalism and intraguild predation (IGP) on the survivorship of the small larvae of R. variegata were investigated with and without alternative prey as well as different sympatric predators. The phenology of R. variegata and intraguild predators differed among wetlands. The feeding trials showed that R. variegata has a significant effect on the survivorship of invertebrate and vertebrate prey. Cannibalism increased with body size in odonate larvae. The survivorship of small- and medium-sized larvae was mainly affected by the presence of larger predators such as belosmatids. The field and experimental data show that the effect of IGP and cannibalism is affected by the cohort dynamics of R. variegata. Body size in R. variegata determines the strength of its interaction with other components of the community.

L'auteur présente la description de Cordocythere phreaticola n.g. n.sp., Eucypris petkovskii n.sp. ainsi que des remarques systématiques sur 13 espèces citées pour la la première fois dans la faune de la Roumanie.

On donne la description détaillée de la mandibule et de la maxille de Metacypris cordata, fort utile pour la systématique de la tribu des Metacyprini nov. Une analyse comparative portant sur la structure de l'antenne I, la mandibule et la maxille des genres Limnocythere, Cytheridella, Gomphocythere, Metacypris, Elpidium et Cordocythere a permis à l'auteur d'entrevoir l'existence de deux lignées phylétiques à l'intérieur de la sous-famille des Limnocytherinae SARS 1925. Elles ont été nommées tribu des Limnocytherini nov. et des Metacyprini nov.

La redécouverte d'Isocypris arnoldi, pour la première fois depuis sa description initiale, est intéressante au point de vue systématique et zoogéographique.

La présence des espèces thermophiles Dolerocypris sinensis, Stenocypris major et Heterocypris maura dans le Sud de la Roumanie, ainsi que l'espèce phréatophile Cypridopsis subterranea dans le Nord-Est, est intéressante au point de vue zoogéographique.

Vu la répartition actuelle des représentants de la tribu des Metacyprini, Cordocythere phreaticola est considéré une relicte préglaciaire.

Some features of the chemical limnology of a hypertrophic, gravel-pit lake close to Madrid (Spain) have been studied at weekly intervals throughout a year. El Porcal Lake in an alkaline, slightly saline, water body without surface inflow or outflow. Anoxia is a common feature below the 2 m level from May to September. Dissolved oxygen oversaturation and pH above 9,00 occurred frequently in surface waters throughout the study period. Alkalinity totalled to 2,5-3,5 meq.l-1, bicarbonate being the main inorganic carbon fraction. Inorganic carbon is a key parameter in the chemistry of the lake, as indicated by statistical correlations. Nitrate and nitrite values were very high, probably as a result of high nitrification rates. Ammonia levels were lower than those of nitrite and nitrate. Soluble Reactive Phosphorus ranged over three orders of magnitude, sometimes occurring below detection limits. No plankton collapses have been observed but frequent oscillations in the chemical parameters have been the rule during the whole year. Groundwater seepage might be a very important source of nutrients. Most of the chemical features showed time lags of a week in autocorrelation functions, suggesting an unknown control mechanism for the temporal dynamics of the chemical limnology of El Porcal Lake.

Chlorophyll-a concentration and physico-chemical water quality of water bodies surrounding Santa Fe City (Argentina) wereanalyzed at 20 sampling sites during different hydroclimatic periods (August-September 2005, March-April 2006). Areas withdifferent water quality were separated by Euclidean cluster analysis, and correlation among both environmental and chlorophylldistance matrices were found (p<0.01). The areas more affected by anthropogenic influence, Los Saladillos and Salado Rivers,reached the highest trophic level as regards to chlorophyll concentration. Acceleration in the eutrophication process wasregistered in comparison with previous studies, and chlorophyll-a concentrations are similar to those encountered in othereutrophicated rivers of the world. The oligo-mesotrophic level found at the Setúbal shallow lake was lower than expected due tothe nutrient contents and human activities of its basin. However, the incoming of pristine waters from the Paraná Systemproduces a sweeping effect and a semi-lotic lake behavior that impedes eutrophication enhancement. During high-waters thisriver also improved water quality of Santa Fe and Coronda Rivers. The chlorophyll-a diminution at Setúbal Lake and Santa FeRiver in comparison to earlier studies, may be also explained by the introduction in the last decade of the bivalve Limnopernafortunei that could be responsible of important losses of algal cells. Although trophic state according to chlorophyll-aconcentration was improved with discharge increments, nitrate and total phosphorus concentration augmented in most sites as aresult of the input from polluted flooded areas. The higher ranges encountered in the present study either of chlorophyll-a ornutrient content, indicate changes in water quality and a resultant eutrophication process over a period of decades. The health ofwater bodies is not yet in danger, but it is declining due to induced man-changes.

Des simulies ont été récoltées entre 1985 et 1991 dans les principaux réseaux hydrographiques du Haut Atlas. Les stades préimaginauxdes simulies représentent un élément important de la faune benthique de ces cours d'eau. Des larves et des nymphesont été récoltées dans 54 stations (entre 450 m et 3800 m d'altitude) qui regroupent une grande variété d'eaux courantes, depuisles ruisselets jusqu'aux grandes rivières.La communauté des simulies du Haut Atlas compte 24 espèces ; six sont nouvelles pour la science. Cinq espèces ont été décritesprécédemment. La description de Simulium (Eusimulium) mellah Giudicelli & Bouzidi n. sp. est donnée dans le présent travail.Le nombre d'espèces de simulies connues actuellement du Haut Atlas est remarquablement élevé, comparé à celui d'autres régionsd'Europe et du bassin méditerranéen ; à l'inverse, on note une relative pauvreté en espèces dans les autres groupes d'invertébrésvivant dans les eaux courantes de ce massif.Beaucoup d'espèces sont communes avec la faune des simulies de l'Europe occidentale et surtout de l'Europe méditerranéenne.La faune des simulies du Haut Atlas est nettement paléarctique, dominée par des éléments à distribution ouest-méditerranéenneet circumméditerranéenne ; elle comprend aussi quelques éléments africains. Quatre espèces sont endémiques, cantonnéesdans les torrents et les sources de haute altitude.Des informations sur la biogéographie, l'écologie et la répartition des espèces sont fournies.Les affinités et les relations écologiques entre 23 espèces et 50 stations ont été déterminées par une analyse factorielle des correspondances.Cinq groupements d'espèces et de stations ont été reconnus : un premier groupement caractérise les cours d'eaufroids (torrents et sources) aux altitudes supérieures (entre 2660 et 3200 m) ; les deuxième et troisième groupements correspondentau crénal et aux secteurs initiaux du rhithral (entre 1600 et 2700 m) et à une communauté d'espèces sténothermes d'eau froide; le quatrième groupement réunit les espèces eurythermes à large répartition dans les réseaux hydrographiques et il correspondaux rivières de montagne (hypo-métarhithral) entre 1200 et 2600 m d'altitude ; le cinquième groupement contient les espècesthermophiles et potamophiles qui habitent le cours inférieur des rivières (entre 600 et 1600 m).Une analyse factorielle des correspondances a été réalisée sur des prélèvements mensuels d'invertébrés récoltés de déc. 1985à déc. 1986 dans les différents microhabitats, définis par la combinaison courant-substrat, de deux secteurs épipotamiques. Lepremier axe factoriel (F1) représente une échelle de vitesse de courant. Les stades aquatiques des 7 espèces de Simulies présentesse disposent le long de cet axe en fonction de leur rhéopréférendum.

Dans le cadre d'un programme de sélection de microalgues potentiellement valorisables, l'influence des facteurshéliothermiques sur la croissance de trois espèces de Scenedesmus (S. abundans, S. dimorphus et S. ecornis) a étéétudiée sur des cultures réalisées en milieu fini et en conditions nutritionnelles non limitantes. Pour chacune des troisespèces, les effets de l'intensité lumineuse (de 30 à 560 µmole quanta.m-2.s-1), de la température (de 10 à 35°C) etde la photopériode sur les taux de croissance ont été mesurés puis modélisés. Les résultats obtenus démontrent le caractèremésophile des trois microalgues avec un optimum thermique de 30°C pour S. ecornis et de 35°C pour lesdeux autres espèces. L'existence d'une interaction étroite entre l'intensité lumineuse et la température sur la croissancedes trois microalgues a également été mise en évidence. De même, une influence très nette de la photopériodesur la croissance des trois espèces a été relevée. Dans les conditions optimales de culture, les taux de croissancemaximaux observés sont respectivement de 2,1 d-1 pour S. ecornis, 1,95 d-1 pour S. abundans et 1,5 d-1 pour S. dimorphus.Les effets des facteurs héliothermiques sur la croissance des microalgues étudiées ont pu être restitués demanière satisfaisante par trois modèles mathématiques. Les résultats obtenus indiquent que les trois espèces de Scenedesmussont parfaitement adaptées aux conditions climatiques de la région de Marrakech. Leur culture en masse,à des fins appliquées, pourrait donc être envisageable.

Based on a literature survey and the identification of all available collection material, a checklist and distribution maps for the caddisflies occurring in Flanders were prepared. Of the 126 species that have been recorded, 16 are now extinct in Flanders, while the majority of the remaining species is rare and their populations are often vulnerable due to isolation. Caddisflies only occurred at high oxygen levels and relatively low conductivities and three species assemblages could be recognized. A first group of species lived in stagnant waters and those species tolerated slightly lower oxygen concentrations than species characteristic for running waters. In streams of the Campine region, which are characterized by a low pH and a low conductivity, a second group of species was found. The last group of species mainly occurred in the loamy region, where pH and conductivity are higher. Running waters in other ecoregions mainly contained ubiquist species and did not possess a characteristic species assemblage. Despite the fact that the ecological water quality in Flanders slightly increased during the last few decades, the ecological water quality of most waters is still too low for caddisflies. According to the European Union water framework directive, a good ecological water quality should be obtained in all surface waters. Additional measures to improve the water quality are necessary in order to obtain sustainable populations of the caddisfly species occurring in Flanders.

In the absence of recognised criteria for phosphate in rivers, this paper attempts to arrive at an independant phosphate criterion value for Irish rivers as distinct from lakes. A comparison is made between biological assessments of river water quality and phosphate values at some 800 sites over a 3-year period. This analysis demonstrated that river eutrophication begins to be a problem when median annual « ortho-phosphate » (MRP) levels exceed 30 μg P l-1 . A spreadsheet modelling technique aimed at predicting in-stream phosphate levels is illustrated by an example for the River Deel in County Mayo, Ireland. Regression equations link river flow rates or phosphate concentrations with daily rainfall figures in order to predict stream discharge and phosphate concentration on a 365-day basis. The equations — or similar site-specific equations — can be implemented using any of the standard spreadsheet packages for microcomputers.

Potamogeton perfoliatus readily adopts different morphological forms, and is therefore especially suitable for investigating variations of aquatic plants' morphology according to different environmental conditions. This paper discusses the morphological diversity of P. perfoliatus at different sites in Lake Balaton, where it occurs as one of the dominant species. We measured 11 morphological variables which were analyzed statistically within the environmental gradients present in the Lake (gradients in trophic condition, water depth and in wave exposure). We found morphological differences between the plants growing on the southern shallow shore which is more exposed to waves and those growing on the northern, deeper and sheltered shore as well as differences along the trophic and the water depth gradient. On the northern shore plants were significantly longer, their internodes were longer and their leaves were relatively thinner (greater Standard Leaf Area). Plants were larger in the more nutrient rich western basins of the Lake and also showed morphological changes along the water depth gradient. The different degrees of wave exposure probably interact partly with trophic differences due to lake morphology. However, we proved that modifications in plant morphology, of which some might be adaptive and therefore of importance in a changing environment, do occur in the common, submerged macrophyte P. perfoliatus in Lake Balaton.

Three new species of Camelobaetidius Demoulin (Ephemeroptera : Baetidae), C. hamadae sp. n., C. lassance sp. n., and C.maranhensis sp. n., are described based on nymphs from Brazil. Some of the diagnostic characters of the new taxa are : C. hamadaesp. n., two thoracic gills at base of forelegs and claws with 36-37 denticles ; C. lassance sp. n., claws with approximately60 denticles and posterior margin of terga with few, large and elevated spines ; C. maranhensis sp. n., pronotum with medialpair of tubercles and terminal filament shorter than 10th abdominal segment. Camelobaetidius cayumba (Traver & Edmunds),C. matilei Thomas &Perú, and C. tuberosus Lugo-Ortiz &McCafferty, are recorded for the first time from Brazil. A key to thespecies of Camelobaetidius recorded from Brazil based on nymphs is presented.

Ce travail donne une série de caractères morphométriques de cinq espèces de lumbriculides très communes dans les rivières du Nord de la Péninsule Ibérique. On y décrit une nouvelle variation du système reproducteur de Lumbriculus variegatus, des phénomènes tératologiques chez Stylodrilus heringianus et S. lemani, ainsi que la nouvelle sous-espèce Trichodrilus strandi campoyi.

A literature survey and the identification of all available collection material resulted in a checklist and distribution maps for the mayflies occurring in Flanders. In addition, the relationship between the occurrence of mayflies and water characteristics was analysed. Of the 32 species that have been recorded, six are now extinct in Flanders (three of which are potamal species), while the majority of the remaining species are rare and their populations are often strongly isolated and therefore extremely vulnerable. Waters with relatively low oxygen levels and high conductivities were characterized by the most tolerant mayfly species Cloeon dipterum and Caenis robusta. However, most other species only occurred at higher oxygen concentrations and lower conductivities and could be separated into two groups. The first group mainly occurred in waters with a high pH and were often restricted to the loamy region or to stagnant waters, while the second group occurred in waters with a lower pH and mainly occurred in the Campine region. For most mayfly species, sustainable populations can only be achieved when their current habitats are adequately protected and, in addition, measures should be taken to connect and enlarge the remaining populations.

In the present paper, adults of the family Gripopterygidae collected in Paranapiacaba mountains are analyzed, the new species are described and a key to species of this family from this area is presented. Twenty one species in four genera of Gripopterygidae are recorded in Paranapiacaba mountains, São Paulo State, Brazil. Gripopteryx comprises six species: Gripopteryx cancellata, Gripopteryx reticulata, Gripopteryx garbei, Gripopteryx coruja, Gripopteryx pinima and Gripopteryx flinti. Paragripopteryx is represented by eight species: Paragripopteryx klapaleki, Paragripopteryx anga, Paragripopteryx blanda, Paragripopteryx egena, Paragripopteryx hamata and three new species: Paragripopteryx intervalensis, Paragripopteryx kapilei and Paragripopteryx paranapiacabae. Tupiperla is represented by six species: Tupiperla gracilis, Tupiperla tessellata, Tupiperla eleonorae, Tupiperla umbya and two new species, Tupiperla amandae and Tupiperla froehlichi. Guaranyperla is represented by only one species: Guaranyperla guapiara.

Field investigations in two lymnaeid habitats located along river banks were carried out over three years to study snailcolonization in relation to water-level variations, to determine the number of annual generations, and to analyse the ability ofG. truncatula to emerge from water. As these river banks were located 6.7 km upstream from a dam, water recedes each day,thus permitting the study of snails on banks for several hours per day. From March to December, snails followed seasonal variationsof water-level. However, only a few G. truncatula were observed following the daily retreat of water. Two annual generationsof G. truncatula, the first from the onset of July and the second in December, were noted in these habitats. When waterreceded each day, the mean distance covered by non-aestivating snails ranged from 25 to 44 cm. However, they escaped waterrise by seeking refuge in still emerged zones of their habitats. From July to October, snails following each day water recedingshowed a significantly quicker growth than that of G. truncatula which only moved in the same zone of their habitat. Populationsof G. truncatula living along these river banks would be completely adapted to their habitat. The escape of snails from waterrise between July and October might correspond to a physiological reaction of survival when a too rapid increase of water-leveloccurs.

Les stades imaginal (♂ et ♀) et nymphal d'une nouvelle espèce Leptochironomus paraderibae sont décrits ainsi que les formes camarguaises de deux espèces à répartition méditerranéenne, Polypedilum pharao KIEFF. et Chironomus hexastictus KIEFF. Pour chacune de ces trois espèces sont également données des remarques d'ordre biologique, écologique et biogéographique.

The Mirgenbach reservoir (vol. : 7.3 Mm3, area : 90 ha, mean depth : 7.7 m) is a safety and thermal water buffer for the nuclear power station in Cattenom (Eastern France). Water used for cooling is pumped out of river Moselle, filtered, overheated, concentrated by evaporation in the atmospheric cooling towers that discharge the cooled water into this artificial lake where it continues to cool. The levels of temperature, conductivity, hardness and eutrophising capacities are higher than those of river Moselle waters. The hydrobiologjcal study was conducted from April 1986 to December 1988. Before August 1986, the lake had developed to a dimictic stratified type. Immediately after the first input in August 1986, it developed towards a polymictic unstratified type. The oxygen levels, the conductivity, the pH and the temperature were homogeneous from surface to bottom everywhere in the reservoir at any time.The trophic level study has enabled us to investigate the interrelationships between the physical and chemical factors, and the biocenoses in which the relationships between the various trophic levels could be observed. Considering the level of eutrophication and the amoun of biomass produced, exploitation of the algal and fish productions was proposed. Applied studies are planned : the aquaculture of the green alga Hydrodictyon and intensive fish farming in floating nets with an addition of dry Hydrodictyon in artificial feeding.

L'étang du Vaccarès est isolé des influences naturelles de la mer et du Rhône depuis la construction de digues au siècle dernier. Depuis 1950, des modifications de la salinité liées aux conditions climatiques et aux activités humaines ont entraîné des changements remarquables de sa végétation aquatique. Les transformations des herbiers ont pu être cartographiées grâce à des relevés effectués en 1963-64, 1974 et 1984. L'évolution saisonnière da la salinité, la bathymétrie, la nature du substrat et les qualités optiques de l'eau permettent d'interpréter les modifications de la végétation.Pendant la phase de dessalement, la végétation à Potamogeton pectinatus et Ruppia maritima évolue vers une végétation dulçaquicole à Myriophyllym spicatum et Phragmites communis. A partir de 1980, l'augmentation de la salinité a permis l'installation d'un herbier monospécifique à Zostera noltii.Par leur action sur la dispersion et la floculation des sédiments, les variations de salinité, ajoutées à l'action des vents fréquents en Camargue, influent sur la transparence de l'eau et la transmission de la lumière dans l'eau. Une meilleure transmission de la lumière serait une explication de la plus grande extension des herbiers pendant la phase de resalement du Vaccarès.L'avenir de cette végétation reste entièrement liée à la salinité dont les variations dépendent des conditions climatiques et des activités humaines.