Field investigations on 12 populations of Omphiscola glabra were carried out in central France over a 5-year period to determine the ability of the species to aestivate in its habitats when summer drying occurred. In the department of Haute-Vienne, spring-born snails aestivated with their apertures applied to the surface of a substratum and most of them were located on the banks of ditches. With the return of wet conditions, the survival of these snails was low. In the department of Indre, most springborn snails aestivated by burrowing into the marl and were distributed over the whole surface area of their habitats. Higher survivals were noted for these O. glabra after aestivation. Despite a significant difference in the frequencies of buried lymnaeids, the position of snails with a natural infection with F. hepatica in their dried habitats was similar to that found for uninfected ones. The variations found in the aestivation of O. glabra might be explained by the dominant substratum (granite gravel and scarce mud in Haute-Vienne, or a thick layer of marl in Indre) and the plant cover on ditch bottoms.

The alien and potentially invasive species Elodea nuttallii was observed for the first time in Slovenia's Drava River in 2007, when its huge biomasses were observed at some locations. Changes in biomass of submerged macrophyte communities and abiotic factors such as water temperature, discharge and level were monitored at two impoundments of the Drava River (2009, 2010 and 2011). The correlations between abiotic factors and developed final biomass were assessed to determine if the level of abiotic factors has an impact on the final biomass and invasive behaviour of E. nuttallii. The results obtained showed that biomass of E. nuttallii was not excessive in 2009 and 2010, while in the year 2011 it developed huge biomass at locations, which were not directly exposed to the main water current. The biomass of Myriophyllum spicatum was also higher in 2011 in comparison with 2009 and 2010 but not in such high degree. The key factor for the development of the final biomass of E. nuttallii was the water temperatures in winter and spring and also the point at which water temperatures in spring surpassed 10°C. The invasive behaviour of E. nuttallii is expected in the years with higher temperatures in January and March and at the locations which are not directly exposed to the main water current. We assume that continuation of the deposition of silt in the impoundments of the Drava River could contribute to invasive behaviour of species E. nuttallii in the years with mild winters and warmer springs.

Since 1978 a sampling program is being conducted on various basins of Catalonia (NE-Spain), covering the whole ofthe basins of the rivers Tordera, Llobregat, Besòs, Ter, Foix and Segre (Andorran rivers included).A total of 51 species of Plecoptera has been collected in a range of altitudes from 100 m to 2 250 m. Among them, thereare stenothermal species of high altitude and a group of species that live in temporary water courses. Some species of Leuctridae, Capniidae and Chloroperlidae are members of the interstitial fauna in some instars of their life.

L'auteur propose de grouper les Darwinula sans cavité incubatrice dans un nouveau genre, Microdarivinula. Il redécrit l'espèce type de ce genre, M. zimmeri (MENZ), d'après le matériel recueilli en Roumanie et discute ses particularités morphologiques en les comparant à celles de Darwinula stevensoni BR. et ROB., D. a ricana brasiliensis, PINTO et Korz. et D. paglioli PINTO et Korz. Il présente aussi, un bref aperçu sur la répartition des darwinulides actuelles et fossiles.

Aspects of the egg biology of the perlid stonefly, Dinocras cephalotes (Curtis), were studied experimentally. Development under constant laboratory conditions did not differ from development under variable field conditions. Exposure to 4°C, the lower threshold temperature for egg development, caused abrupt interruptions of embryonic development. Development was resumed after return to favourable temperatures, with an approximate two-week-delay. Up to six interruptions of egg development did not negatively affect hatching success, regardless of developmental stage at which disturbances occurred. However, the older embryos grew, the more rapidly development was resumed after a cold disturbance; embryos from fully developed eggs hatched even at 4°C, although this is too cold to support larval growth. While eggs at 4°C remain dormant and vital for long periods of time, eggs exposed to suboptimal temperatures (10°C) remain only temporarily dormant and eventually develop and hatch.D. cephalotes is assumed to satisfy its high thermal demand for egg development under harsh conditions, for example in arctic Scandinavia, by opportunistically using summer warmth and spreading embryogenesis over more than one year. I suggest that high cue temperatures required to initiate egg development in Scandinavian populations are adaptive and ensure that larvae in the Arctic hatch under favourable seasonal conditions.

This paper reports data on a community of Trachelomonas species (Euglenophyta) occurring during Planktothrix agardhii bloom formation in a shallow, highly eutrophic dam reservoir. The results come from a long-term study of Siemianówka Dam Reservoir, located on the upper Narew River (NE Poland). From April to October 2007, 132 alga taxa were identified, including 32 Trachelomonas taxa, 23 of which are new for the reservoir; of those, three are first records for Poland: T. armata (Ehrenberg) Stein var. heterospina Swirenko, T. atomaria Skvortzov var. minor Hortobagi and T. minima Dreżepolski. One variety, T. curta var. pappilata Wołowski, is described as new for science. The ultrastructural details of Trachelomonas species are illustrated. The highest number of Trachelomonas taxa was recorded in August in the shore zone of the reservoir. At the end of summer 2007, the conspicuous development of P. agardhii (Gomont) Anagnostidis et Komarek, caused a rapid decrease of Trachelomonas biomass due to lower water transparency and the oxygen concentration. In addition, a decline in the Trachelomonas taxa and biomass was associated with a decrease of water temperature. The negative impact of extracellular microcystin on the Trachelomonas development requires further study.

Les prélèvements de dérive en période de décrue réalisés conjointement dans le chenal principal et un chenal secondaire de la Durance ont mis en évidence l'importance de la dérive dans le repeuplement du lit principal. Une partie de cette dérive provient du champ d'inondation temporairement colonisé par les organismes benthiques dispersés, l'autre vient des chenaux latéraux.

Cross-transplantations of Omphiscola glabra between two French departments (Haute-Vienne and Indre) were carried out to study snail settlement in these new sites during six years and to determine if this snail species was well adapted to its local parasites (Fasciola hepatica and Paramphistomum daubneyi). Local snails placed in new sites for each department were used as controls. In Indre furrows, the number of adults per population and the area of each habitat peaked on the third year post-introduction. Similar findings were also noted in the Haute-Vienne furrows occupied by local snails but peaks were only observed on the fourth year. In contrast, in Haute-Vienne sites populated by introduced snails, there was a progressive decrease in snail abundance and habitat area from the second year. The local O. glabra transplanted in Haute-Vienne kept their same degree de susceptibility to F. hepatica and P. daubneyi, thus demonstrating a good adaptation of these snails to their parasites. In other groups of transplanted snails, the first natural infections were only noted from the second or third year post-introduction and their prevalence progressively increased over time. Local adaptation of these latter snails to parasites would be more progressive in time and would stretch over several snail generations.

In a high mountain stream, Baetis alpinus at emergence is significantly smaller downstream than upstream. These size differences are used to demonstrate migration of adults upstream: downstream, the size of adult females caught after oviposition corresponds with the size of subimagines which have emerged there; upstream, the size of adult females corresponds with the size of subimagines which have emerged both up and downstream. The migration is clearly an upstream movement.

Patterns of parasite infestation by plerocercoid forms of the tapeworm Ligula intestinalis (Cestoda, Pseudophyllidea) in the second intermediate host, the roach Rutilus rutilus, were analysed in three fish populations of South-Western France during 1998. In all three studied sites, i.e. Pareloup Lake, Lavernose-Lacasse and Muret gravel pits, roach were commonly parasitized with plerocercoids. A strong increase in prevalence, mean number of parasites and parasitic load was observed in the youngest hosts with a maximum peak reached in the medium-age (2+, 3+)roach classes. Such trends as a function of host fish age would indicate the occurrence of parasite-induced host mortality, with the most heavily infected fish specimens being removed from the three roach populations. The three roach populations infected by L. intestinalis exhibit different patterns of parasite-induced mortality which could correspond to different possible ecological and evolutionary responses associated with local variation in host-parasite interactions. The parasite-induced host mortality observed, i.e. direct mortality caused by pathogenic effects and /or enhanced fish predation by piscivorous birds to increase parasitic transmission is discussed within the context of the adaptative parasite-induced manipulation hypothesis.

Intraspecific variability in life-history traits was investigated comparing four geographically isolated populations of the shrimp Palaemonetes argentinus (Crustacea, Caridea, Palaemonidae) in the Province of Buenos Aires, Argentina. One population inhabits a creek (Vivoratá Creek, VC), which drains into the brackish coastal lagoon Mar Chiquita; three others live in inland lakes (Lakes Chascomús, LC; La Brava, LB; Los Padres, LP). Female size at the onset of sexual maturity, both realized and actual fecundity (i.e. number of eggs in an early stage of embryonic development and number of freshly hatched larvae per female, respectively), as well as the size of freshly hatched larvae were consistently largest at VC, intermediate at LC and LB, and lowest at LP. The opposite pattern was found in egg loss (estimated as difference between realized and actual fecundity), being lowest at VC, highest at LP, and intermediate in the other two populations. Initial embryonic dry weight (W) was higher at VC than in all other populations. However, the W of freshly hatched larvae was similarly high at VC, LC and LB, but significantly lower at LP. Intraspecific variation in life-history traits, in particular between shrimps from VC (lotic, slightly brackish; highly variable salinities) and those from inland lakes (lentic; low but stable ion concentrations) are discussed in relation to local variation in hydrological and other ecological conditions that may wield differential selection pressures in the life-history evolution of a species with a wide range of ecological and geographic distribution.

Dans 2 ruisseaux artificiels similaires, 500 alevins vésiculés de Truite commune Salmo trutta L. sont introduits et les alevins "dévalants" de ces ruisseaux sont recueillis et déversés dans un troisième ruisseau identique aux 2 premiers. Le comportement et l'activité des alevins "dévalants" et sédentaires sont observés : une liaison apparaît entre l'activité de dévalaison nocturne des très jeunes alevins et le comportement d'immobilité sur le substrat le jour. Les alevins "dévalants" sont moins actifs globalement que les alevins sédentaires. L'hypothèse du retard de développement des alevins "dévalants" se trouve renforcée.

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.

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.

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.

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.

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.

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.

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.