Considerable spatial and temporal variability was detected in the environmental conditions in 30 coldwater springs in southernOntario, Canada. Using standard pyramidal emergence traps, a total of 86 insect species was recorded from these springs (notincluding the Chironomidae). These represented nine taxonomic groups, among which the Limoniidae (Diptera) was the mostdiverse with 38 species. Fifty-five per cent of all species recorded had a low frequency (found at three or fewer sites), and onlyfor very few of these rare species were more than 10 individuals m-2 collected. Interannual differences were also apparent.Continuous sampling over time showed that emergence records from a single year, on average, contained only around 50% ofthe total number of species obtained during the entire study. Species-environment relationships analyzed by CanonicalCorrespondence Analysis indicated that temperature and discharge correlated most strongly with insect community similarityamong spring sites. The prospects for developing regional typologies of coldwater springs, based on their environmental conditions,and the implications of species loss to the continuity of function of coldwater spring ecosystems are discussed.

In French Guyana, the dynamics of young prawn migrations from marine to estuarine waters remains equivocal, raising thequestion of habitat utilization in the adjacent mangrove systems. The temporal distribution of juvenile penaeid species was thusinvestigated in the main drainage channel of a Guianese coastal mangrove. A total of 2275 juvenile prawns belonging to fivespecies, including two penaeid species (Penaeus subtilis, Xiphopenaeus kroyeri) were collected by stake net on four occasionsduring the wet season. Catches were dominated by large-sized, highly-valued P. subtilis and exclusively occurred (a) at the endof flood tide and (b) at the beginning of ebb tide, when water velocity was maximum. Size structures were very similar betweenflood- and ebb tides, suggesting that the same assemblages entered then withdrawed from the mangrove on a given tidal cycle.Residence times of prawns in the mangrove were short (3-4 hours per tidal cycle), as juveniles gained access to the coastal mangroveonly a few hours per day during high tide. These results will need further confirmation at larger (Guianese) scale, but provideevidence for original, tidal-dominated mangrove utilization patterns by juvenile prawns. Given the economic importance ofP. subtilis in French Guyana, there is an urgent need to assess the contribution of coastal mangrove habitats to sustaining nearshore fisheries.

This study evaluated the status of the Asian clam Corbicula fluminea (Müller, 1774) in the River Lima estuary (Portugal),which it first invaded in 2002. During the summers of 2004 and 2005, spatial and temporal variations in the abundance, biomassand population structure of C. fluminea were investigated in this estuary. This species was present in a limited intertidal area ofthe estuary and was rarely found in the subtidal zone. Its abundance and biomass were considerably lower than those found inother estuarine systems. Based on these studies it appears that salinity fluctuations and possibly other factors such as nutrientsand environmental contaminants are keeping this invasive species from reaching its full potential. Given the lower abundanceand biomass recorded and the restrict distribution of the species in this estuary, the eradication of this nonindigenous invasivespecies is still possible. The findings of this study may be useful for the management of this species not only in the River Limaestuary but also in other locations it may invade.

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.

Obtaining an adequate and representative sample is a continuing challenge of community ecology. The present study focuseson what sample area represents adequately the structural composition of the caddisfly fauna of a riffle, at a given sampling occasion.Sixty-two Surber samples were collected from a riffle in a second-order reach of the Bernecei Stream (BörzsönyMountains, Hungary). This data set was used to estimate sample representativeness at different sample sizes (from 1 to 31 Surbersamples, 0.09 m2 - 2.79 m2) generated a re-sampling procedure. Sample representativeness was measured with mean JaccardCoefficient and Bray-Curtis Index between samples for species presence-absence data and abundance data, respectively. Wefound that a sample size of 2.25 m2 represented well (mean similarity 0.998) the species composition of the caddisfly fauna ifrare species were excluded from the analysis. In contrast, sample representativeness of species composition proved to be relativelylow (0.719) if rare species were included in the analysis. Curves of sample representativeness based on both raw-, or transformedabundance data were less sensitive to the presence of rare species and showed lower representativeness than samplerepresentativeness based on presence/absence data.

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.

The morphology of the larval stages of Arrenurus nodosus, A. knauthei and A. stecki is described. Particular attention is paidto the different characters separating the three species. The larvae of the three species differ in the size and shape of the dorsalplate. Distinct differences appear between the proportions in the length of the lateral margins of the epimeres, which are similar in A. knauthei and A. stecki, but different in A. nodosus. There are differences in the shape of the excretory pore plates. InA. stecki the shape of the anal plate is slightly different owing to the truncated proleg. The structure of the pedipalps are verysimilar. The PIII1 setae are always bipectinate, the PIV1 is pectinate in A. knauthei and smooth in the other species, the PV6 isshort and thick in A. nodosus, and long and thin in the other two species. Distinct differences also occur in the feathering oflegs. The ITi8 seta is short in A. knauthei and long in the other two, the LITi10 seta is long in A. nodosus and short in the othertwo, and IIITi10 is thick and pectinate in A. nodosus, and smooth and fairly thin in the other two.