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Freshwater Habitats (freshwater + habitat)
Selected AbstractsDiversity, extinction risk and conservation of Malaysian fishesJOURNAL OF FISH BIOLOGY, Issue 9 2010V. C. Chong A total of 1951 species of freshwater and marine fishes belonging to 704 genera and 186 families are recorded in Malaysia. Almost half (48%) are currently threatened to some degree, while nearly one third (27%) mostly from the marine and coral habitats require urgent scientific studies to evaluate their status. Freshwater habitats encompass the highest percentage of threatened fish species (87%) followed by estuarine habitats (66%). Of the 32 species of highly threatened (HT) species, 16 are freshwater and 16 are largely marine,euryhaline species. Fish extinctions in Malaysia are confined to two freshwater species, but both freshwater and marine species are being increasingly threatened by largely habitat loss or modification (76%), overfishing (27%) and by-catch (23%). The most important threat to freshwater fishes is habitat modification and overfishing, while 35 species are threatened due to their endemism. Brackish-water, euryhaline and marine fishes are threatened mainly by overfishing, by-catch and habitat modification. Sedimentation (pollution) additionally threatens coral-reef fishes. The study provides recommendations to governments, fish managers, scientists and stakeholders to address the increasing and unabated extinction risks faced by the Malaysian fish fauna. [source] Environmental signature in the otolith elemental fingerprint of the tapertail anchovy, Coilia mystus, from the Changjiang estuary, ChinaJOURNAL OF APPLIED ICHTHYOLOGY, Issue 5 2006J. Yang Summary The ontogenetic patterns of habitat use and the migratory history of the tapertail anchovy, Coilia mystus, collected in the Changjiang estuary around Chongming Island, China, were studied by examining the environmental signature in the otolith strontium (Sr) and calcium (Ca) fingerprints using electron probe microanalysis (EPMA). Our results suggest that the migration strategy of C. mystus is much more flexible than supposed in the literature to date. The spring spawning population of C. mystus from the studied area was found to consist of individuals with different migration histories. Although the tapertail anchovy seems to be an anadromous fish that spawns and hatches in a freshwater habitat, it can also use a freshwater environment in non-spawning seasons. The otolith EPMA of the elemental fingerprint (Sr x-ray maps and Sr : Ca ratios) is an environmental indicator that can be applied to the migratory ecology of other important diadromous species in China. [source] Evolutionary history shapes the association between developmental instability and population-level genetic variation in three-spined sticklebacksJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 8 2009S. VAN DONGEN Abstract Developmental instability (DI) is the sensitivity of a developing trait to random noise and can be measured by degrees of directionally random asymmetry [fluctuating asymmetry (FA)]. FA has been shown to increase with loss of genetic variation and inbreeding as measures of genetic stress, but associations vary among studies. Directional selection and evolutionary change of traits have been hypothesized to increase the average levels of FA of these traits and to increase the association strength between FA and population-level genetic variation. We test these two hypotheses in three-spined stickleback (Gasterosteus aculeatus L.) populations that recently colonized the freshwater habitat. Some traits, like lateral bone plates, length of the pelvic spine, frontal gill rakers and eye size, evolved in response to selection regimes during colonization. Other traits, like distal gill rakers and number of pelvic fin rays, did not show such phenotypic shifts. Contrary to a priori predictions, average FA did not systematically increase in traits that were under presumed directional selection, and the increases observed in a few traits were likely to be attributable to other factors. However, traits under directional selection did show a weak but significantly stronger negative association between FA and selectively neutral genetic variation at the population level compared with the traits that did not show an evolutionary change during colonization. These results support our second prediction, providing evidence that selection history can shape associations between DI and population-level genetic variation at neutral markers, which potentially reflect genetic stress. We argue that this might explain at least some of the observed heterogeneities in the patterns of asymmetry. [source] Genetic and morphological characterization of a Lake Ohrid endemic, Salmo (Acantholingua) ohridanus with a comparison to sympatric Salmo truttaJOURNAL OF FISH BIOLOGY, Issue A 2006S. Su Analysis of both uni-(two mtDNA gene sequences) and bi-parentally (seven microsatellite loci) inherited genetic markers, together with analysis of 40 morphological characters, described Salmo ohridanus as a highly divergent member of the genus Salmo. Based on comparative substitution rate differences at the cytochrome b gene, and a rough estimated age of the Salmo trutta complex (i.e. at least 2 million years), the S. ohridanus and Salmo obtusirostris clade probably split from a common ancestor of brown trout Salmo trutta >4 million years ago, overlapping with minimum age estimates of the formation of Europe's oldest freshwater habitat, Lake Ohrid. Comparative analysis with Lake Ohrid brown trout (known regionally as Salmo letnica), supported the notion that these fish have more recently colonized the lake and phylogenetically belong to the Adriatic lineage of brown trout. It is further suggested that species-specific saturation in the mtDNA control region underestimated the divergence between S. ohridanus and S. trutta. Evidence of rare hybridization between S. ohridanus and Lake Ohrid brown trout was seen at both mtDNA and microsatellite markers, but there was no support for extensive introgression. [source] The colonization of Europe by the freshwater crustacean Asellus aquaticus (Crustacea: Isopoda) proceeded from ancient refugia and was directed by habitat connectivityMOLECULAR ECOLOGY, Issue 14 2005R. VEROVNIK Abstract Recent continental-scale phylogeographic studies have demonstrated that not all freshwater fauna colonized Europe from the classic Mediterranean peninsular refugia, and that northern or central parts of the continent were occupied before, and remained inhabited throughout the Pleistocene. The colonization history of the ubiquitous aquatic isopod crustacean Asellus aquaticus was assessed using mitochondrial COI and a variable part of nuclear 28S rDNA sequences. Phylogeographic analysis of the former suggested that dispersion proceeded possibly during late Miocene from the western part of the Pannonian basin. Several areas colonized from here have served as secondary refugia and/or origins of dispersion, well before the beginning of the Pleistocene. Postglacial large-scale range expansion was coupled with numerous separate local dispersions from different refugial areas. Connectivity of the freshwater habitat has played an important role in shaping the current distribution of genetic diversity, which was highest in large rivers. The importance of hydrographic connections for the maintenance of genetic contact was underscored by a discordant pattern of mtDNA and nuclear rDNA differentiation. Individuals from all over Europe, differing in their mtDNA to a level normally found between species or even genera (maximal within population nucleotide divergence reached 0.16 ± 0.018), shared the same 28S rRNA gene sequence. Only populations from hydrographically isolated karst water systems in the northwestern Dinaric Karst had distinct 28S sequences. Here isolation seemed to be strong enough to prevent homogenization of the rRNA gene family, whereas across the rest of Europe genetic contact was sufficient for concerted evolution to act. [source] A cross-system synthesis of consumer and nutrient resource control on producer biomassECOLOGY LETTERS, Issue 7 2008Daniel S. Gruner Abstract Nutrient availability and herbivory control the biomass of primary producer communities to varying degrees across ecosystems. Ecological theory, individual experiments in many different systems, and system-specific quantitative reviews have suggested that (i) bottom,up control is pervasive but top,down control is more influential in aquatic habitats relative to terrestrial systems and (ii) bottom,up and top,down forces are interdependent, with statistical interactions that synergize or dampen relative influences on producer biomass. We used simple dynamic models to review ecological mechanisms that generate independent vs. interactive responses of community-level biomass. We calibrated these mechanistic predictions with the metrics of factorial meta-analysis and tested their prevalence across freshwater, marine and terrestrial ecosystems with a comprehensive meta-analysis of 191 factorial manipulations of herbivores and nutrients. Our analysis showed that producer community biomass increased with fertilization across all systems, although increases were greatest in freshwater habitats. Herbivore removal generally increased producer biomass in both freshwater and marine systems, but effects were inconsistent on land. With the exception of marine temperate rocky reef systems that showed positive synergism of nutrient enrichment and herbivore removal, experimental studies showed limited support for statistical interactions between nutrient and herbivory treatments on producer biomass. Top,down control of herbivores, compensatory behaviour of multiple herbivore guilds, spatial and temporal heterogeneity of interactions, and herbivore-mediated nutrient recycling may lower the probability of consistent interactive effects on producer biomass. Continuing studies should expand the temporal and spatial scales of experiments, particularly in understudied terrestrial systems; broaden factorial designs to manipulate independently multiple producer resources (e.g. nitrogen, phosphorus, light), multiple herbivore taxa or guilds (e.g. vertebrates and invertebrates) and multiple trophic levels; and , in addition to measuring producer biomass , assess the responses of species diversity, community composition and nutrient status. [source] Diversity and abundance of freshwater Actinobacteria along environmental gradients in the brackish northern Baltic SeaENVIRONMENTAL MICROBIOLOGY, Issue 8 2009Karin Holmfeldt Summary Actinobacteria are highly abundant in pelagic freshwater habitats and also occur in estuarine environments such as the Baltic Sea. Because of gradients in salinity and other environmental variables estuaries offer natural systems for examining factors that determine Actinobacteria distribution. We studied abundance and community structure of Bacteria and Actinobacteria along two transects in the northern Baltic Sea. Quantitative (CARD-FISH) and qualitative (DGGE and clone libraries) analyses of community composition were compared with environmental parameters. Actinobacteria accounted for 22,27% of all bacteria and the abundance changed with temperature. Analysis of 549 actinobacterial 16S rRNA sequences from four clone libraries revealed a dominance of the freshwater clusters acI and acIV, and two new subclusters (acI-B scB-5 and acIV-E) were assigned. Whereas acI was present at all stations, occurrence of acII and acIV differed between stations and was related to dissolved organic carbon (DOC) and chlorophyll a (Chl a) respectively. The prevalence of the acI-A and acI-B subclusters changed in relation to total phosphorus (Tot-P) and Chl a respectively. Community structure of Bacteria and Actinobacteria differed between the river station and all other stations, responding to differences in DOC, Chl a and bacterial production. In contrast, the composition of active Actinobacteria (analysis based on reversely transcribed RNA) changed in relation to salinity and Tot-P. Our study suggests an important ecological role of Actinobacteria in the brackish northern Baltic Sea. It highlights the need to address dynamics at the cluster or subcluster phylogenetic levels to gain insights into the factors regulating distribution and composition of Actinobacteria in aquatic environments. [source] Contrasting bacterioplankton community composition and seasonal dynamics in two neighbouring hypertrophic freshwater lakesENVIRONMENTAL MICROBIOLOGY, Issue 11 2001K. Van der Gucht We characterized the bacterioplankton community and its seasonal dynamics in two neighbouring hypertrophic lakes by denaturing gradient gel electrophoresis (DGGE) analysis of short (193 bp) 16S ribosomal DNA polymerase chain reaction (PCR) products obtained with primers specific for the domain Bacteria. Lake Blankaart is turbid and has a high phytoplankton biomass and episodic cyanobacterial blooms, whereas biomanipulated Lake Visvijver is characterized by clearwater conditions and the establishment of a dense charophyte vegetation. Both lakes were dominated by bacterial groups commonly found in freshwater habitats (e.g. ACK4 cluster of Actinomycetes; ACK stands for clones isolated from the Adirondack mountain lakes). Yet, cluster analysis and principal components analysis (PCA) revealed that taxon composition of the bacterioplankton community of the two lakes differs substantially and consistently throughout the season. During the study year (1998), the bacterioplankton community of both lakes showed a distinct seasonal pattern. Lake Blankaart showed a clear differentiation between winter, spring, summer and autumn. In Lake Visvijver, summer samples differed greatly from spring, autumn and winter samples. We hypothesize that the contrasting bacterioplankton in the two neighbouring shallow lakes is determined largely by the presence or absence of macrophytes. [source] Fatty acid analyses reveal high degrees of omnivory and dietary plasticity in pond-dwelling tadpolesFRESHWATER BIOLOGY, Issue 7 2010MATT R. WHILES Summary 1.,Understanding the trophic relationships of consumers is central to ecology, but constructing meaningful food webs is often difficult because of a lack of detailed information on consumption versus assimilation and high degrees of omnivory. 2.,We used fatty acid analyses to examine the trophic relationships of three common larval anurans (Pseudacris crucifer, Lithobates catesbeianus and Lithobates clamitans) that are often classified as grazers or detritivores. Tadpoles and potential food sources were sampled in four ponds in southern Illinois and analysed for fatty acid composition. Single linkage cluster analysis was then used to compare fatty acid profiles among tadpole gut contents, tadpole muscle tissues and available food resources. 3.,Diets varied among species and within species among ponds, but organic sediments consistently contributed most to the fatty acid composition of the gut contents of all species. Fatty acid profiles also indicated that larval insects and phytoplankton were consumed by both L. catesbeianus and L. clamitans in one pond, while L. clamitans and P. crucifer consumed mainly periphyton along with sediments in another pond, and these diet differences appeared linked to physical differences among ponds, with periphyton and/or phytoplankton contributing more to tadpole diets in less shaded ponds. 4.,The fatty acid composition of muscle tissues of L. clamitans, the dominant tadpole in these systems, indicated that plant detritus and bacteria, which were the dominant components of organic sediments in the ponds, were common components of the assimilatory diet. 5.,Results demonstrate the utility of fatty acid analyses for assessing both consumption and assimilation. The tadpole assemblages we examined derive much of their energy from heterotrophic and allochthonous sources and exhibit high dietary plasticity. This information will allow for more accurate and comprehensive assessments of trophic interactions in freshwater habitats, as well as aid in amphibian conservation, management and captive propagation efforts. [source] To sink or float: the fate of dormant offspring is determined by maternal behaviour in DaphniaFRESHWATER BIOLOGY, Issue 3 2008LUSARCZYK, MIROS Summary 1As the ephippia (chitinous shells enclosing diapausing eggs) of pelagic crustaceans of the genus Daphnia have been occasionally reported to float at the water surface, we considered that this might be an adaptation promoting their passive dispersal. We investigated the mechanisms by which ephippia appear at the water surface. 2While field surveys revealed that floating Daphnia ephippia are often numerous in various freshwater habitats, laboratory tests showed that newly formed ephippia are not buoyant initially. Once transferred to the surface by whatever means, however, they may remain there due either to surface tension or gas absorption. 3Video recordings showed that all ephippia at the water surface in laboratory vessels were shed there by ephippial females when moulting (despite the attendant risk of exposure to UV radiation). This implies that the moulting behaviour of female Daphnia may determine the fate of their dormant offspring, predetermining whether they remain in the natal environment (when the ephippium is released into the water column) or disperse (when it is deposited at the water surface). 4Our findings reveal a potential mechanism underlying the high dispersal capacity of freshwater cladocerans inhabiting island-like aquatic habitats. [source] Foraging tactics in alternative heterochronic salamander morphs: trophic quality of ponds matters more than water permanencyFRESHWATER BIOLOGY, Issue 9 2007MATHIEU DENOEL Summary 1. In lentic freshwater habitats, the composition of animal assemblages shifts along a gradient from temporary to permanent basins. When habitats with different degrees of permanence are at the scale of the home range of species, they constitute alternatives in terms of energy acquisition through feeding. 2. In this context, previous studies showed an advantage of metamorphic over paedomorphic tiger salamanders (Ambystoma tigrinum) in temporary ponds which are only available to metamorphs. The aim of this study was to establish whether salamanders obtain similar benefits in ponds that do not differ in water permanence and whether salamanders shifted from detrimental to advantageous ponds. To this end, we determined the feeding habits, body condition and movement patterns of the two morphs in a complex of four permanent and four temporary ponds. 3. Consistent with previous studies, metamorphs consumed higher-quality diets than paedomorphs in term of energy intake. However, these differences occurred because metamorphs consumed fairy shrimp in a single temporary pond. Individual movement patterns confirmed that most of the metamorphs used different aquatic habitats both within and between years and that most of them moved from permanent ponds for breeding towards the most profitable temporary pond in terms of foraging. 4. These results indicate that habitat selection by salamanders is optimal in term of energy intake in metamorphs that use high quality ponds independently of hydroperiod. It seems that both spatial and temporal variation can influence the relative foraging success of each morph. [source] Neritid and thiarid gastropods from French Polynesian streams: how reproduction (sexual, parthenogenetic) and dispersal (active, passive) affect population structureFRESHWATER BIOLOGY, Issue 3 2000Marilyn J. Myers Summary 1The streams of French Polynesia contain several species of Neritidae and Thiaridae (Mollusca: Gastropoda). The neritids are dioecious and amphidromous with a freshwater adult stage and a poorly known, marine larval stage. The thiarids are parthenogenetic and viviparous, and rely on passive dispersal for colonisation of new habitats. 2Populations of the neritid Clithon spinosus and the thiarids Melanoides tuberculata and Thiara granifera were analysed using mitochondrial DNA sequences from COI to compare the population structure of the snails at three different scales: between streams (N = 9), between islands (N = 4), and between age and distance of paired islands. 3The amphidromous C. spinosus showed no evidence of genetic isolation at any of the scales tested (Fst values 0.02). Parsimony analyses resulted in two haplotype clusters separated by a three-step segment, which were not linked to geographic isolation. The larval phase of C. spinosus is most likely a long-lived planktotroph and a very effective disperser. 4Two haplotypes of M. tuberculata, separated by 16 base pairs, were found. Both haplotypes were found in snails on all islands, and individuals representing both were often collected in the same habitat. One haplotype of T. granifera was found. M. tuberculata has the characteristics of the ,general-purpose genotype' of clonal population structure and although it relies on passive dispersal, it has colonised nearly all freshwater habitats on the islands. [source] Changes in clutch size, brood size and numbers of nesting Squacco Herons Ardeola ralloides over a 32-year period in the Camargue, southern FranceIBIS, Issue 1 2001HEINZ HAFNER Changes in numbers of nesting pairs, clutch size, and brood size of Squacco Herons Ardeola ralloides in the Camargue, southern France were analysed over a 32-year period. The annual numbers of breeding pairs [average 84 pairs pL 30 sd, n = 32 years) exhibited a possible increasing trend, but with considerable variability. This variability is associated with local spring rainfall, which may influence the available surface area of their preferred freshwater habitats. In contrast to population size, clutch size decreased substantially in recent years. Our data do not provide a causal explanation for this change in clutch size, although the reduction temporally corresponds with increasing rice cultivation and with a dramatic increase in the number of Cattle Egrets Bubulcus ibis in the Camargue. [source] Why amphibians are importantINTERNATIONAL ZOO YEARBOOK, Issue 1 2008T. R. HALLIDAY The world's amphibians face an imminent extinction crisis, with nearly a third of species categorized as threatened. The principal cause of amphibian declines is the destruction of freshwater habitats. Many other causes have been identified, which act synergistically; these include pollution, climate change and disease. Amphibian declines and extinctions are evidence of the harmful effects of humans on natural ecosystems. [source] Current issues with fish and fisheries: editor's overview and introductionJOURNAL OF APPLIED ECOLOGY, Issue 2 2003S. J. Ormerod Summary 1.,By any measure, fishes are among the world's most important natural resources. Annual exploitation from wild populations exceeds 90 million tonnes, and fish supply over 15% of global protein needs as part of total annual trade exceeding $US 55 billion. Additionally, with over 25 000 known species, the biodiversity and ecological roles of fishes are being increasingly recognised in aquatic conservation, ecosystem management, restoration and aquatic environmental regulation. 2.,At the same time, substantial management problems now affect the production, exploitable stocks, global diversity, trophic structure, habitat quality and local composition of fish communities. 3.,In marine systems, key issues include the direct effects of exploitation on fish, habitats and other organisms, while habitat or water quality problems arise also from the atmospheric, terrestrial and coastal environments to which marine systems are linked. In freshwaters, flow regulation and obstruction by dams, fragmentation, catchment management, pollution, habitat alterations, exotic fish introductions and nursery-reared fish are widespread issues. 4.,Management responses to the problems of fish and fisheries include aquatic reserves in both marine and freshwater habitats, and their effectiveness is now being evaluated. Policies on marine exploitation increasingly emphasise fishes as integral components of aquatic ecosystems rather than individually exploitable stocks, but the rationalisation of fishing pressures presents many challenges. In Europe, North America and elsewhere, policies on freshwaters encourage habitat protection, integrated watershed management and restoration, but pressures on water resources will cause continued change. All these management approaches require development and evaluation, and will benefit from a perspective of ecological understanding with ecologists fully involved. 5.,Synthesis and applications. Although making a small contribution to the Journal of Applied Ecology in the past, leading work on aquatic problems and fish-related themes appear increasingly in this and other mainstream ecology journals. As this special profile of five papers shows, significant contributions arise on diverse issues that here include the benefit of aquatic reserves, river restoration for fish, the accumulation of contaminants, interactions with predators, and the fitness of salmonids from nurseries. This overview outlines the current context in which papers on the applied ecology of fish and fisheries are emerging, and it identifies scope for further contributions. [source] Annual dynamics variation of a landlocked Galaxias maculatus (Jenyns 1842) population in a Northern Patagonian river: occurrence of juvenile upstream migrationJOURNAL OF APPLIED ICHTHYOLOGY, Issue 2 2007J. P. Barriga Summary Galaxias maculatus, broadly distributed in the southern hemisphere, presents both diadromic and landlocked populations. The upstream migration of larvae and juveniles from the sea to freshwater habitats is a characteristic phenomenon of diadromous populations, but upstream migration has never been reported in those that are landlocked. The objective of this study was to establish the population dynamics of a peculiar riverine landlocked population that presents an upstream migration at the larvae,juvenile transition from the Piedra del Águila Reservoir to the Caleufú River (Argentina). A spawning season from September to November and the arrival of shoals of metamorphic larvae and juveniles from February to April to the adult habitat were coincidental with lacustrine landlocked populations, but not with diadromous populations. Growth rate and age at migration, 147 ± 22.6 days, were also similar to other landlocked and diadromous populations. The arrival of these shoals produced a 20-fold increase in fish density while the two cohorts of G. maculatus overlapped in time and space. No significant differences in morphology or vertebrae number were detected when riverine and reservoir adults were compared. The great life history plasticity of G. maculatus, shown to be even greater in our results, could be the key to explain the wide distribution of this species in the southern hemisphere. Likewise, discovering this juvenile potamodromous behaviour in a landlocked population will provide a new view for the analysis of the ways of this species' dispersion in continental waters. [source] The effect of body size on food consumption, absorption efficiency, respiration, and ammonia excretion by the inland silverside, Menidia beryllina (Cope) (Osteichthyes: Atherinidae)JOURNAL OF APPLIED ICHTHYOLOGY, Issue 4 2003M. A. Peck Summary The inland silverside, Menidia beryllina (Cope), is an annual zooplanktivore that occurs in estuarine and freshwater habitats along the Atlantic and Gulf of Mexico coasts and drainages of the United States. Experiments were conducted at 25 ± 1°C to quantify the relationship between mean dry weight (WD) and rates of energy gain from food consumption (C), and energy losses as a result of respiration (R) and ammonia excretion (E) during routine activity and feeding by groups of fish. The absorption efficiency of ingested food energy (A) was also quantified. Rates of C, E, and R increased with WD by factors (b in the equation y = aWDb) equal to 0.462, 0.667, and 0.784, respectively. Mean (±SE) rates of energy loss during feeding were 1.6 ± 0.1 (R) and 3.4 ± 0.6 (E) times greater than those for unfed fish. Absorption efficiency was independent of WD and estimated to be 89% of C. From these measurements, the surplus energy available for growth and activity (G) and growth efficiency (K1) were estimated. Over the range in sizes of juveniles and adults (5,500 mg WD), predicted G and K1 values decreased from 7.42 to 0.20 J mg fish,1 day,1 and 63 to 21%, respectively. Measured and predicted bioenergetic parameters are discussed within an ecological context for a northern population of this species. [source] Trophic diversity of the otter (Lutra lutra L.) in temperate and Mediterranean freshwater habitatsJOURNAL OF BIOGEOGRAPHY, Issue 5 2003Miguel Clavero Abstract Aim To analyse the geographical patterns in the composition and diversity of otter's (Lutra lutra L.) diet and their relationship with climatic characteristics. Location European freshwater habitats under Mediterranean and temperate climatic regimes. Methods Thirty-seven otter diet studies were reviewed, twenty-one from temperate and sixteen from Mediterranean areas. All studies were based on spraint analysis and their results expressed as relative frequency of occurrence of seven main prey categories. Principal Component Analysis was performed to extract the main gradients of diet composition. Pearson's correlation and t -tests were used to assess the relationship between diet characteristics (composition, diversity and taxonomic richness) and geographical and climatic variables. Results A clear latitudinal gradient in diet composition was observed. Otter diet was more diverse and featured more prey classes in southern localities, while the species was more piscivorous towards the north, where it predated upon a higher number of fish families. This pattern was similar when temperate and Mediterranean localities of Europe were compared. Mediterranean otters behaved as more generalist predators than temperate ones, relying less on fish, and more on aquatic invertebrates and reptiles. Main conclusions Geographical differences in otter feeding ecology in Europe seem to be related with the two contrasted climatic conditions affecting prey populations. The otter can act as a highly specialized piscivorous predator in temperate freshwater ecosystems, which do not suffer a dry season and have a comparatively stable water regime compared to Mediterranean ones. However, the unpredictable prey availability in Mediterranean areas, affected by strong spatial and temporal water shortages, favours a diversification of the otter's diet. [source] Swimming activity and behaviour of European Anguilla anguilla glass eels in response to photoperiod and flow reversal and the role of energy statusJOURNAL OF FISH BIOLOGY, Issue 9 2009S. Bureau Du Colombier To better understand migratory divergences among Anguilla anguilla glass eels, the behaviour of individuals caught at the time of their estuary entrance was studied through their response to a light:dark cycle and then to both water current reversal and light:dark cycle. In a first experiment, fish moving with the flow in response to dusk (M+ fish) and fish that had not exhibited any movement (M, fish) were distinguished. Anguilla anguilla from these two groups were then individually marked and their response to water current reversal compared. M+ individuals mainly exhibited negative rheotaxis with a tidal periodicity, whereas positive rheotaxis was mainly exhibited by M, individuals. Thus, M+A. anguilla glass eels showing negative rheotaxis appear to have the strongest propensity to migrate, the converse applies to M, ones showing positive rheotaxis. A small percentage of individuals (5%) were hyperactive, alternately swimming with and against the current with almost no resting phase. These fish lost c. 2 mg wet mass day,1, whereas individuals which were almost inactive lost c. 1 mg day,1. Wet and dry mass changes in relation to activity levels were compared with previous experiments and it was concluded that A. anguilla glass eel energy status might be involved in differences in migratory tendencies but other factors that might be important are discussed. It is proposed that any decrease in A. anguilla glass eel energy stores associated with global warming might lead to an increase in the proportion of sedentary individuals and thus be involved in the decrease in the recruitment to freshwater habitats. [source] Molecular phylogeny of grapsoid crabs (Decapoda, Brachyura) and allies based on two mitochondrial genes and a proposal for refraining from current superfamily classificationJOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 3 2006C. D. Schubart Abstract Grapsoid and ocypodoid crabs receive a lot of attention in the literature due to their predominance and important role as primary and secondary consumers in intertidal as well as supratidal marine habitats. They are especially species-rich in the tropics, where they have been found to repeatedly invade terrestrial and freshwater habitats. However, the systematics of the crabs belonging to these two superfamilies is still not settled, despite recent steps clarifying phylogenetic relationships and introducing new taxa. In this study, a molecular phylogeny of grapsoid crabs primarily based on East African representatives is constructed based on DNA sequences of the mitochondrial small and large ribosomal subunits (12S and 16S rRNA), thus complementing previous molecular taxonomic studies that had been carried out with the American and East Asian fauna. In addition, selected representatives of all ocypodoid families and subfamilies were included. The monophyly of Grapsidae, Ocypodidae (sensu stuctu), Sesarmidae and Varunidae is well confirmed, if the genera Cyclograpsus, Helice are considered Varunidae and Euchirograpsus a Plagusiidae, as previously suggested. The monophyly of the family Gecarcinidae cannot be supported with our data. The family Plagusiidae in its present composition is polyphyletic. Special attention was given to the large family Sesarmidae, which has many endemic genera in the Indo-West Pacific. According to this study, two of the most speciose genera, Chiromantes and Parasesarma, are not monophyletic and need to be redefined. On the higher taxonomic level, it becomes evident that both superfamilies, Grapsoidea and Ocypodoidea, are not monophyletic in their current composition, as exemplified by a proposed sister group relationship of Varunidae and Macrophthalmidae. These results confirm those from previous molecular studies and we therefore propose to refrain from the traditional use of the Grapsoidea and Ocypodoidea as monophyletic superfamilies and treat the constituent families separately. Riassunto I granchi appartenenti alle superfamiglie Grapsoidea e Ocypodoidea da sempre sono oggetto di notevole interesse scientifico a causa del loro importante ruolo ecologico negli ambienti intertidali o sopratidali. Le due superfamiglie sono particolarmente rappresentate, in termini di numero di specie e d'abbondanza relativa, nelle zone tropicali e subtropicali, dove hanno invaso ripetutamente anche ambienti dulcacquicoli e terrestri. La sistematica delle specie appartenenti a queste due superfamiglie è ancora lontana dall'essere completamente risolta, nonostante studi molecolari recenti abbiano chiarito specifiche relazioni filogenetiche e definito nuovi taxa. Questo studio ha ricostruito la filogenesi di alcune specie di Grapsoidea dell'Africa Orientale sequenziando una porzione delle due subunità ribosomali del DNA mitocondriale (12S e 16S rRNA), confermando e completando precedenti studi molecolari condotti su specie americane e asiatiche. In questo studio sono stati inclusi anche rappresentanti di tutte le famiglie e sottofamiglie di ocipodidi. I nostri risultati confermano la monofilia della famiglia Grapsidae, Ocypodidae (sensu stuctu) Sesarmidae e Varunidae a condizione che, secondo quanto recentemente suggerito, i generi Cyclograpsus e Helice siano rimossi dalla famiglia Sesarmidae ed attribuiti ai Varunidae, ed Euchirograpsus dalla famiglia Varunidae ai Plagusiidae. Invece, i nostri dati supportano solo debolmente o non supportano per niente la monofilia della famiglia Gecarcinidae. La famiglia Plagusiidae è probabilmente polifiletica. Questo studio pone inoltre particolare attenzione alle relazioni interne alla famiglia Sesarmidae che include molti generi endemici nell'area Indo-Pacifica occidentale. Sulla base dei nostri dati, i generi Chiromantes, Parasesarma e Perisesarma sono polifiletici e necessitano di essere ridefiniti. Infine, i risultati di questo studio mostrano chiaramente che la superfamiglia Grapsoidea e Ocypodidea non sono monofiletiche così come attualmente definite, come evidenziato dalla relazione di sister group tra Varunidae e Macropthalmidae. Questo conferma i risultati di precedenti studi molecolari e pertanto proponiamo di non attenersi al tradizionale uso delle superfamiglie Grapsoidea ed Ocypodoidea. [source] Conservation of the Eurasian beaver Castor fiber: an olfactory perspectiveMAMMAL REVIEW, Issue 4 2010Róisín CAMPBELL-PALMER ABSTRACT 1Chemical communication in mammals includes an array of specific behaviours that are often ignored in terms of their potential relevance to conservation. Often used during territorial or social interactions between animals, chemical communication can also be used as a tool in reintroduction programmes. Reintroductions still exhibit high failure rates and methods to improve success should be investigated. The Eurasian beaver Castor fiber has been widely reintroduced across Europe after its near extinction in the 19th century. 2Using olfactory studies in the beaver, we aim to demonstrate how scent transfers a range of information about the sender which can be used to monitor social and territorial behaviour along with general well-being. Scent manipulation can be used to reduce human,beaver conflicts, and aid reintroduction success through reducing stress and territorial conflicts, and by influencing dispersal and settlement. 3Two species of beavers, the Eurasian beaver and the North American beaver Castor canadensis, occupy freshwater habitats throughout North America and in parts of South America, most of Europe and parts of Asia. Most of the reviewed literature concerns the wild Eurasian beaver, its chemical communication and conservation; however, captive studies and those addressing North American beavers are also included. 4Chemical communication is advanced and has been well documented in this highly territorial species. However, few studies directly link olfaction with conservation practices. 5Olfactory studies in beavers can provide non-invasive methods to monitor translocated animals and indicators of health. We conclude that chemical analysis, olfactory studies and behavioural manipulations involving semiochemicals have important impacts on conservation and can generate practical solutions to conservation problems including aiding animal capture, captive stress reduction, breeding pair formation and release site fidelity. [source] Contrasting patterns in genetic diversity following multiple invasions of fresh and brackish watersMOLECULAR ECOLOGY, Issue 12 2006DAVID W. KELLY Abstract Biological invasions may combine the genetic effects of population bottlenecks and selection and thus provide valuable insight into the role of such processes during novel environmental colonizations. However, these processes are also influenced by multiple invasions, the number of individuals introduced and the degree of similarity between source and receiving habitats. The amphipod Gammarus tigrinus provides a useful model to assess these factors, as its invasion history has involved major environmental transitions. This species is native to the northwest Atlantic Ocean, although it invaded both brackish and freshwater habitats in the British Isles after introduction more than 65 years ago. It has also spread to similar habitats in Western Europe and, most recently, to Eastern Europe, the Baltic Sea, and the Laurentian Great Lakes. To examine sources of invasion and patterns of genetic change, we sampled populations from 13 native estuaries and 19 invaded sites and sequenced 542 bp of the mitochondrial COI gene. Strong native phylogeographical structure allowed us to unambiguously identify three allopatrically evolved clades (2.3,3.1% divergent) in invading populations, indicative of multiple introductions. The most divergent clades occurred in the British Isles and mainland Europe and were sourced from the St Lawrence and Chesapeake/Delaware Bay estuaries. A third clade was found in the Great Lakes and sourced to the Hudson River estuary. Despite extensive sampling, G. tigrinus did not occur in freshwater at putative source sites. Some European populations showed reduced genetic diversity consistent with bottlenecks, although selection effects cannot be excluded. The habitat distribution of clades in Europe was congruent with the known invasion history of secondary spread from the British Isles. Differences in salinity tolerance among lineages were suggested by patterns of habitat colonization by different native COI clades. Populations consisting of admixtures of the two invading clades were found principally at recently invaded fresh and brackish water sites in Eastern Europe, and were characterized by higher genetic diversity than putative source populations. Further studies are required to determine if these represent novel genotypes. Our results confirm that biological invasions need not result in diminished genetic diversity, particularly if multiple source populations, each with distinctive genetic composition, contribute to the founding populations. [source] Rules for macroorganisms applied to microorganisms: patterns of endemism in benthic freshwater diatomsOIKOS, Issue 4 2007Cathy Kilroy Ecological theory based on the dynamic equilibrium model (DEM) suggests that maintenance of endemic taxa is most likely in stable, unproductive environments. We tested whether this hypothesis, which was developed mainly using terrestrial plant examples, held when applied to distributions of benthic freshwater diatoms in New Zealand. Given current arguments for the ubiquity of microbial organisms, with distributions determined mainly by environmental tolerances, demonstration that distinctive taxa with evidently restricted distributions conform to theory applicable to larger organisms would lend support to the opposite point of view, that barriers to dispersal do exist. We examined diatom communities from over 320 sites representing the entire spectrum of freshwater habitats in New Zealand and assessed relative abundances of the main taxa present. Each taxon distinguished was assigned to one of five distribution categories ranging from cosmopolitan to endemic. We derived indices of disturbance and productivity for each site using the River Environment Classification (REC), a GIS-based classification system developed for New Zealand rivers. Diatom taxa assigned to endemic or distinctive potential endemic categories were significantly more abundant in low disturbance sites but occurred across a range of productivities. However, bogs and tarns, both of which fell mainly into low disturbance and productivity classes, were distinctive in supporting relatively high proportions of endemic and potential endemic diatoms. Thus our findings in general conformed to the patterns predicted by the DEM, thereby supporting the role of dispersal limitation in diatoms. At the same time, conformity with the DEM helps to explain the continued coexistence in New Zealand freshwaters of many common and apparently cosmopolitan taxa with endemic diatoms, since the DEM explanation for maintenance of endemism does not rely on geographic isolation of species. [source] Distribution and Host Range of the Microsporidian Pleistophora mulleriTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 4 2008JOSEPH E. IRONSIDE ABSTRACT. Microsporidia of the genus Pleistophora are important parasites of fish and crustacea. Pleistophora mulleri has been described previously as a parasite of the gammarid amphipod crustacean Gammarus duebeni celticus in Irish freshwater habitats. Through a survey of European G. duebeni populations, P. mulleri was found to be widely distributed in the western British Isles (Wales, Scotland, and the Isle of Man), and populations of the subspecies Gammarus duebeni duebeni as well as G. d. celticus were infected. Pleistophora infections were also detected in G. d. duebeni sampled from the Bay of Gdansk on Poland's Baltic coast, indicating a wide distribution of Pleistophora in European G. duebeni. Sequencing and phylogenetic analysis of the 16S rRNA, 18S rRNA, and Rpb1 genes of P. mulleri suggest that this species may be synonymous with P. typicalis, a parasite of fish. These findings suggest that amphipod crustaceans may act as intermediate or reservoir hosts for microsporidian parasites of fish. [source] Modulation of proteins in Naegleria fowleri amebae by bacteriaTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2005ANGELA E. FRITZINGER Naegleria fowleri are free-living amebae found in soil and freshwater habitats that cause a fatal disease in humans called Primary Amoebic Meningoencephalitis. In the natural environment, amebae feed on bacteria. In the infected host, the amebae lyse and ingest nerve tissue. Proteins that lyse and degrade bacteria and mammalian cells have been described and are termed as naegleriapores or pore-forming proteins (PFP). In order to prevent autolysis from PFPs, Naegleria may have developed mechanisms that enable the amebae to survive in the presence of cytolytic molecules. Recently, we have established that N. fowleri express a "CD59-like" surface protein, but the function of this protein in amebae has not been elucidated. In mammalian cells, CD59 is a complement,regulatory protein that inhibits complement-mediated lysis of cells expressing this protein. In the present study, expression of the "CD59-like" protein in response to bacteria and bacterial toxins was investigated. Co-culture of N. fowleri with log phase Escherichia coli or Pseudomonas aeruginosa resulted in differential expression of the "CD59-like" protein. Treatment of the amebae with bacterial toxin also affected expression of the protein. Scanning and transmission electron microscopy demonstrated morphological changes in N. fowleri following co-incubation with the bacteria. Under all conditions examined, the amebae remained intact and viable. The results of our study implicate a possible protective role of the "CD59-like" protein in response to bacterial predators and bacterial toxins. [source] The development of bird indicators for British fresh waters and wetlandsAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue S1 2010Mark Everard Abstract 1.Population trends of breeding birds in freshwater habitats generated from long-term monitoring in the UK provide biodiversity indicators for some wetland habitats. 2.Bird species were assigned to target wetland habitats based on evidence of their association and data availability. Species trends for each habitat were then modelled using a range of survey data from BTO schemes including the Common Bird Census, Breeding Bird Survey, Waterways Bird Survey and Waterways Breeding Bird Survey. 3.Smoothed population trends for the selected species were combined to produce a composite indicator for birds of selected waterways and wetland habitats for England. This forms one of the three strands of a new aggregate bird indicator in the UK. 4.These indicators show generally that breeding bird species associated with slow-moving waterways and standing waters have increased over the past 30 years. Over the same period, species associated with fast-flowing waters show modest declines, species associated with reed habitats have declined and recovered, while species associated with wet grasslands, including marshes, have declined. 5.Further monitoring and exploration of the relationship between these indicators is needed to improve confidence in species trends and identifying potential drivers of change in freshwater and wetland habitats. Copyright © 2009 John Wiley & Sons, Ltd. [source] Making agricultural landscapes more sustainable for freshwater biodiversity: a case study from southern EnglandAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 4 2009Bella Davies Abstract 1.Agriculture is known to have a range of deleterious impacts on freshwater habitats and biota and many countries have introduced measures to attempt to mitigate these impacts through agri-environment initiatives. Despite the protection they provide, water bodies (any discrete body of surface fresh water) in farmland landscapes commonly remain impaired by agriculture. In some areas of the UK there have been calls to halt farming completely, indicating that the measures offered for the widespread protection of aquatic systems, particularly the use of buffer strips, may not be extensive enough to provide sufficient protection for freshwater biota. 2.This study investigated whether existing agri-environment measures for the widespread protection of aquatic habitats could be better deployed to provide a higher level of protection for the aquatic macrophytes and macroinvertebrates of a study area in southern England. 3.Reserve selection procedures were used to reallocate the area of land that could be remunerated under the Environmental Stewardship scheme as buffer strips bordering water bodies, so that a higher level of protection was provided for both the richness and rarity of aquatic species in the study area. 4.Almost 395 ha were available for reallocation in the reserve selection process, which was found to provide a satisfactory level of protection for up to 90% of the surveyed species. 5.The results showed that the agri-environment scheme in England has a great deal of potential to provide more effective protection for the aquatic biodiversity of agricultural landscapes if measures are targeted. Copyright © 2008 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||