This study focuses on the host-parasite relationships between species of non-biting midges (Diptera: Chironomidae) and watermites (Acari: Hydrachnidia) in seven springs in Luxembourg. Emergence traps were operated through the season, and identificationof the catches enabled an overview of species composition, abundance and host-parasite associations in the spring communities.Our results show that the Luxembourg springs have similar chironomid diversity to other springs in Europe, and thatparticular species are more often found in certain spring habitats. Furthermore, we show that prevalence of water mite parasitismis highly variable among the sampled chironomid hosts, and that there are several species which were not parasitized despitebeing numerous in our samples. The reasons for the latter observation are discussed, and most of the cases can be explainedby general unavailability of host or parasite, or life cycle incompatibility.

Ecological requirements of ostracods in two limnocrene springs (Usta and Çetin Bey) were investigated between January 2000and July 2002 in Bolu, Turkey. Ten taxa (Candona neglecta, Darwinula stevensoni, Eucypris virens, Eucypris sp., Heterocyprisincongruens, Herpetocypris sp., Ilyocypris bradyi, Potamocypris sp., Scottia pseudobrowniana, Tonnacypris lutaria) werefound. Canonical correspondence analysis (CCA) showed that species with wide cosmopolitan distribution could tolerate highlevels of changes in environmental variables. CCA explained about 80 % and 77 % of the relationships between species andenvironmental variables in Usta and Çetin Bey springs, respectively. Electrical conductivity and dissolved oxygen were the twomost influential factors on species occurrence in each spring. According to Spearman correlation analysis, there were no significantrelationships between the numbers of species and environmental variables in both springs. When dissolved oxygen showedsignificant negative correlations to electrical conductivity, water and air temperature in Usta spring, such correlation wasonly negatively significant (P <0.05, r = -0.46) between electrical conductivity and dissolved oxygen in Çetin Bey spring.Clustering analysis (UPGMA) of presence/absence data divided species into four main groups. Results may suggest that anthropogenicactivities were responsible for decreasing water quality of these springs and reducing species richness. Although increasingincentives for conservation of natural springs were proposed, Çetin Bey spring and especially Usta spring are now highlydegraded.

Perennial Oued Zegzel and temporary Oued Cherraa are parts of the same watercourse. Coinertia analysis showed the cleardistinction between these two parts and the close relationship of the faunal assemblages with the characteristics of the water. Theheadwater course of the Zegzel is covered with dense terrestrial vegetation whose debris were consumed by abundant shreddersdominated by the prosobranch Melanopsis praemorsa. The lower course of the Zegzel has sparse riparian vegetation and muchfine detritus, and collectors such as Ecdyonurus rothschildi, Caenis luctuosa, the Diptera Corynoneurinae and Tanytarsini,occurred. In contrast, dry, flowing-, and standing-water periods succeed each other in the Cherraa and terrestrial vegetation oftengrows in its bed. M. praemorsa was replaced by the air-breathing pulmonate Physa acuta, accompanied by the adults and larvaeof flying insects. However many shredders did not develop on the abundant plant litter. The short length of the submersionperiod was probably responsible for this lack of efficiency in the exploitation of such a non-limiting food resource.

The pupa of Calamoceras marsupus Brauer, 1865 (Trichoptera : Calamoceratidae) is described and the main taxonomic characteristicsare illustrated. This pupa is compared with those of six genera of Calamoceratidae. The pupa of Calamoceras marsupusshares some characteristics with Banyallarga, Phylloicus, and Ganonema.

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.

The presence of different species of hydrophytes was investigated in relation to Secchi disk visibility, pH, dissolved oxygen,electrical conductivity, total Kjeldahl nitrogen, total phosphorus and chlorophyll-a concentration in two tropical ponds nearbyKolkata, India, during a three years period (June 1999 to May 2002). The dominant flora in the ponds namely, Alternantheraphiloxeroides, Nymphoides hydrophylla, Lemna aequinoctialis, and Vallisneria spiralis were found to subsist over a wide amplitudeof nutrient levels thereby showing their adaptability to highly eutrophic ecosystems, a common feature of the tropics.However, the presence of some minor species could be associated with a narrow range of specific limnological variables.

Blooms of Ceratium hirundinella (O. F. Müller) Bergh. have been detected in different water bodies in the Neotropical Regionsince 1990. The colonization began in southern lakes, and during the last decade the dinoflagellate arrived and bloomed in subtropicalreservoirs. In this context the colonization of C. hirundinella and its population development have been analyzed fromits first record in the Río Tercero Reservoir (February 1999 to February 2001). Phytoplankton and physicochemical sampleswere obtained from three sampling stations at the Reservoir, one in the outlet of the water cooling channel of the nuclear powerplant, and one in the nearest tributary (Quillinzo River). Two blooms of C. hirundinella were detected during the warm seasonswith temperatures higher than 18°C, and pH ranging between 8.5 and 8.9. Environmental conditions such as certain light intensityrange and percentage of dissolved oxygen mentioned as favorable for Ceratium development were always recorded in RíoTercero Reservoir. Cysts were observed in spring and summer months. Another dinoflagellate (Peridinium gatunense Nygaard)bloomed in previous summer in this water body but its population density decreased during the invasive phase of colonizationof C. hirundinella. Asplanchna girodi, became the dominant zooplankter after the first bloom of C. hirundinella. We believe thatthe presence of this dinoflagellate in the Neotropical Region could be a regional phenomenon associated with some dispersalmechanisms and favorable local conditions for its proliferation like those recorded in the Rio Tercero Reservoir.