The composition and abundance of functional feeding groups of the macroinvertebrate communities were investigated alongthe Chubut River in the Patagonian Precordillera and Plateau, Argentina. Chubut River (>1000 km) is the largest river in the area and the hydrological regime is modified in the lower section by an artificial reservoir (Florentino Ameghino Dam). Quantitative benthic samples were collected at 13 sites in the upper, middle and lower sections of the river basin. Sites were visited four times during 2004 and physicochemical parameters, chlorophyll a and particulate organic matter (POM) were assessed. In terms of relative abundance, collector-gatherers and scrapers/grazers were the predominant groups at most sites. Shredders were not abundant in the upper sites and were practically absent at middle and lower basin sites. Collector filterers that comprised morethan 25 % of abundance at the pre-regulated site were practically absent right below the dam. POM biomass decreased significantly with distance from the source and chlorophyll a showed a marked increase below the reservoir. We conclude that although there was a distinct headwaters fauna in the Chubut River, and sequential downstream changes in species composition, most functional feeding groups (apart from shredders) were represented down the whole length of the river. Finally, the usefulness of biotic indices and metrics in relation with main environmental features of the Chubut River basin is 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 paper presents a description of the hitherto unknown larva of Drusus nigrescens Meyer-Dür, 1875. Information on the morphological and genetic identification of this species is given, and the most important diagnostic features are illustrated. Its systematic position within the genus Drusus is affirmed and some zoogeographical and ecological notes are added.

Cladocerans are used in a wide range of applications (aquatic toxicology, experimental hydrobiology, and aquaculture). Although known to be successfully cultivated with microalgal food sources, cladoceran demographic parameters tend to be different, depending on the kind of cladoceran and concentration of food supplied. For most species, finding precise instructions on culture conditions and expected outcomes is difficult. The aim of this study was to determine the most favorable feeding conditions for the development of three cladoceran species frequently used as test organisms in aquatic toxicology. For this purpose, Ceriodaphnia dubia, Daphnia pulex, and Simocephalus mixtus were fed three concentrations (6, 12, and 18 mg L-1 dry weight) of the green microalgae Ankistrodesmus convolutus, Pseudokirchneriella subcapitata (formerly Selenastrum capricornutum), and Scenedesmus incrassatulus. Reproduction and survival were evaluated during the entire life cycle. For C. dubia, the P. subcapitata and S. incrassatulus diets produced the best reproductive results. For D. pulex, the best overall results were obtained with S. incrassatulus at 6 mg L-1 and results with P. subcapitata were similar at all concentrations. For S. mixtus fed P. subcapitata, results were similar at all concentrations. With S. incrassatulus, a decrease in longevity and an increase in fecundity occurred as the amount of food increased; the best reproductive response was achieved with the highest (18 mg L-1) concentration. The lowest reproduction and survival in the three cladocerans were recorded with A. convolutus. For the cladoceran species tested, the same microalga produced different reproductive and survival results, depending on the concentration; some of the tested foods did not support adequate cladoceran development, because they were nutritionally deficient, despite the similar conditions used for their production. Feeding and culture conditions here described could be useful for a controlled propagation of these cladocerans.

The colonization and succession of periphytic ciliate communities on the natural (Phragmites australis and Typha Iatifolia) and artificial (glass slides) substrata were studied in 2 shallow lakes (Polesie Lubelskie, Eastern Poland). Sampling was done on a monthly basis from April to November 2003-2004. During each sampling occasion 6 periphton samples were collected from each type of substrata at 3 sites: the land/water contact zone, among emergent macrophytes, and at the emergent macrophytes/open water border. Irrespective of the type of substrate and trophic state, species number and densities of periphytic ciliates reached the highest value in the land/water contact zone and decreased in the direction of the area of emergent macrophytes/open water zone. In land/water contact zone, the biggest factors limiting the ciliate communities were temperature, conductivity, concentrations of total organic carbon and nutrient (Ptot and N-NH4). In turn, in the other 2 zones, the influence of chlorophyll a concentration increased.

A catalogue of the water mites of the genus Neumania Lebert is given for the countries surrounding the Mediterranean Sea. Morphological details and taxonomical position are discussed. For each species, geographical distribution and habitat preference are given. The following synonyms are established: Neumania algeriensis Bader, 1989 = N. seurati Walter, 1931; N. atlantida Lundblad, 1942 = N. uncinata Walter, 1927. The synonymization of N. agilis Koenike, 1916 with N. limosa (Koch, 1836) is confirmed. Due to incomplete description and lack of type material, N. vietsi Husiatinschi, 1937 should be considered a species incerta. The following first records are given for national faunas: Neumania elliptica (France, Italy); N. phreaticola (Italy, Slovenia); N. uncinata (Greece, Israel, Italy, Bosnia and Herzegovina, Montenegro).

The morphology of the larval stages of Arrenurus biscissus, A. pugionifer and A. bisulcicodulus is described. The three species belong to the subgenus Micruracarus and share several characters. The larvae of the three species differ in the shape of the dorsal plate, shape of the excretory pore plate, ratio between length of coxal plate median margins, and the numbers of pectinating setae on fifth palpal segment (PV). The larva of A. biscissus is very similar to the closely related A. sinuator. Larvae of A. pugionifer and A. bisulcicodulus resemble other Micruracarus species (A. bifidicodulus, A. inexploratus, A. integrator).

As euglenophytes were found to be especially abundant in the Siemianówka Reservoir, Poland, in July 1994, a detailed floristic survey was made. Among the 40 euglenophyta taxa, Trachelomonas was most frequent, with 29 species. The other taxa were Phacus (5), Euglena (5), Lepocinclis (4) and Monomorphina (1). Nine taxa were first recorded for Poland: Trachelomonas curta var. minima, T. intermedia var. papillata, T. neotropica, T. globularis fo. punctata, T. oblonga var. australica, T. planctonica fo. longicollis, fo. ornata, and var. flexicollis, T. silvatica. Details of ultrastructure are illustrated for 29 taxa. T. volvocina var. coranata and var. papilato-punctata are documented with SEM for the first time.