474. Bianchini, A. and Wood, C.M. (2008) Sodium uptake in different life stages of crustaceans: The water flea Daphnia magna Strauss. J. Exp. Biol. 211 pp: 539-547. (PDF). ...
Grand Isle, VT - The Lake Champlain Basin Aquatic Invasive Species Rapid Response Task Force has determined that eradication of spiny water flea in Lake Champlain is not technically feasible. Spread prevention measures should be implemented as soon as possible.. The Rapid Response Task Force reviewed the technical feasibility of preventing the spiny water flea from spreading from Lake Champlain to other inland water bodies. There are no known methods to eradicate spiny water flea once they have been detected in a water body. Initial sampling has confirmed its presence at multiple lake stations in the Main Lake segment of Lake Champlain. In 2012, spiny water flea was discovered in both the Champlain Canal and Lake George. Spiny water fleas have been detected in the southern Adirondacks in Great Sacandaga Lake (2008), Peck Lake (2009), and Stewarts Bridge Reservoir and Sacandaga Lake (2010). This summer they were detected in Lakes Piseco and Pleasant (2014). It is unknown how the spiny water flea ...
rdf:RDF xmlns:dcterms=http://purl.org/dc/terms/ xmlns:dc=http://purl.org/dc/elements/1.1/ xmlns:rdf=http://www.w3.org/1999/02/22-rdf-syntax-ns# xmlns:bibo=http://purl.org/ontology/bibo/ xmlns:dspace=http://digital-repositories.org/ontologies/dspace/0.1.0# xmlns:foaf=http://xmlns.com/foaf/0.1/ xmlns:void=http://rdfs.org/ns/void# xmlns:xsd=http://www.w3.org/2001/XMLSchema# , ,rdf:Description rdf:about=https://kops.uni-konstanz.de/rdf/resource/123456789/17951, ,dcterms:abstract xml:lang=eng,Small filter-feeding zooplankton organisms like the cladoceran Daphnia spp. are key members of freshwater food webs. Although several interactions between Daphnia and bacteria have been investigated, the importance of the microbial communities inside Daphnia guts has been studied only poorly so far. In the present study, we characterised the bacterial community composition inside the digestive tract of a laboratory-reared clonal culture of Daphnia magna using 16S rRNA gene libraries and ...
The ubiquitous, freshwater microcrustacean Daphnia pulex provides a model system for both human health research and monitoring ecosystem integrity. It is the first crustacean to have a well annotated, reference genome assembly that revealed an unusually high gene count highlighted by a large gene orphanage,-i.e., previously uncharacterized genes. Daphnia are capable of either clonal or sexual reproduction, making them ideally suited for genetic manipulation, but the establishment of gene manipulation techniques is needed to accurately define gene functions. Although previous investigations developed an RNA interference (RNAi) system for one congener D. magna, these methods are not appropriate for D. pulex because of the smaller size of their early embryos. In these studies, we develop RNAi techniques for D. pulex by first determining the optimum culture conditions of their isolated embryos and then applying these conditions to the development of microinjection techniques and proof-of-principle RNAi
A study was performed to assess the effects of a chronic exposure to test item NOPOL on the reproduction of the freshwater crustacean Daphnia magna. The method followed was designed to be compliant with the OECD Guideline for Testing of Chemicals No. 211, Daphnia magna, Reproduction Test, referenced as Method C.20 of Commission Regulation No. 440/2008. Based on the results of an acute toxicity test on D. magna (LPL Project D12 -002; 48h-EC50= 28.8 mg.L-1) and on QSAR predictions (iSafeRat: 21d-NOEC = 1.17 mg.L-1), daphnids were exposed to an aqueous solution of the test item at the required nominal test concentrations of 0.5, 1.2, 2.7, 6.4 and 15 mg test item.L-1and to an untreated control for a total period of 21 days in closed vessels. Each treatment group consisted of 10 replicates each of one Daphnia magna (one individual per replicate). The test media was renewed three times a week and the daphnids were fed five days a week. Effects on reproductive performance were investigated by ...
Data on the population dynamics of five Daphnia species, viz. D. galeata mendotae, D. obtusa, D. pulicaria, D. pulex and D. magna, were collected from the literature. The experiments with constant food input were re-analysed for the oscillatory behaviour of the populations. Some populations appear to stabilize, whereas others continue to fluctuate. Some fluctuations are apparently caused by external factors. A decline to far below the average population size is always followed by a large population overshoot. Even populations that tend to stabilize do so by way of a series of damped oscillations. The oscillation period depends on, among other things, the Daphnia species, and increases with its size. Sometimes the same feeding regime leads to an equal or greater population size for a larger Daphnia species. This suggests that the chosen food species was not equally suitable for the two Daphnia species. No effect of crowding on the population size of Daphnia is found.
Water flea eye. Polarised light micrograph of the eye of a Sida crystallina water flea. Water fleas (order Cladocera) are small crustaceans, commonly found in fresh water. They are filter feeders that ingest algae, protozoa or organic matter, and are a constituent of plankton. Magnification: x400 when printed 10 centimetres wide. - Stock Image C028/9152
There is considerable interest in the pathways by which carbon and growth-limiting elemental and biochemical nutrients are supplied to upper trophic levels. Fatty acids and sterols are among the most important molecules transferred across the plant-animal interface of food webs. In lake ecosystems, in addition to phytoplankton, bacteria and terrestrial organic matter are potential trophic resources for zooplankton, especially in those receiving high terrestrial organic matter inputs. We therefore tested carbon, nitrogen, and fatty acid assimilation by the crustacean Daphnia magna when consuming these resources. We fed Daphnia with monospecific diets of high-quality (Cryptomonas marssonii) and intermediate-quality (Chlamydomonas sp. and Scenedesmus gracilis) phytoplankton species, two heterotrophic bacterial strains, and particles from the globally dispersed riparian grass, Phragmites australis, representing terrestrial particulate organic carbon (t-POC). We also fed Daphnia with various mixed ...
Though only occurring rarely, synergistic interactions between chemicals in mixtures have long been a point of focus. Most studies analyzing synergistic interactions used unrealistically high chemical concentrations. The aim of the present study is to determine the threshold concentration below which proven synergists cease to act as synergists towards the aquatic crustacean Daphnia magna. To do this, we compared several approaches and test-setups to evaluate which approach gives the most conservative estimate for the lower threshold for synergy for three known azole synergists. We focus on synergistic interactions between the pyrethroid insecticide, alpha-cypermethrin, and one of the three azole fungicides prochloraz, propiconazole or epoxiconazole measured on Daphnia magna immobilization. Three different experimental setups were applied: A standard 48h acute toxicity test, an adapted 48h test using passive dosing for constant chemical exposure concentrations, and a 14-day test. Synergy was ...
Microcrustacean emergence from the dry sediments is an important colonization pathway that allows these microfauna to recover and repopulate temporary aquatic habitats after months or years of dryness. Viable microcrustacean propagules in sediments of three different temporary aquatic habitats - rainpools located within the rarely flooded portions, frequently flooded floodplains and rarely flooded floodplains - were assessed experimentally by flooding the soils. Three major groups of microcrustaceans - cladocerans, copepods and ostracods - emerged from the sediments. Species richness and mean total numbers of emerged microcrustaceans per sample varied across the studied temporary aquatic habitats (Kruskal-Wallis, p , 0.05). Both species richness and mean total number of emerged microcrustacean per sample were lowest in sediments of rarely flooded floodplains. The highest species richness of microcrustaceans emerged from the treatments with soils of the frequently flooded floodplains. The mean ...
During their aquatic life cycle, nanoparticles are subject to environmentally driven surface modifications (e.g. agglomeration or coating) associated with aging. Although the ecotoxicological potential of nanoparticles might be affected by these processes, only limited information about the potential impact of aging is available. In this context, the present study investigated acute (96 h) and chronic (21 d) implications of systematically aged titanium dioxide nanoparticles (nTiO2; ~90 nm) on the standard test species Daphnia magna by following the respective test guidelines. The nTiO2 were aged for 0, 1, 3 and 6 d in media with varying ionic strengths (Milli-Q water: approx. 0.00 mmol/L and ASTM: 9.25 mmol/L) in the presence or absence of natural organic matter (NOM). Irrespective of the other parameters, aging in Milli-Q did not change the acute toxicity relative to an unaged control. In contrast, 6 d aged nTiO2 in ASTM without NOM caused a fourfold decreased acute toxicity. Relative to the 0 d aged
Predation is a primary force driving adaptation in prey. When predatory threats are fluctuating in natural environments, inducible defences may evolve in prey organisms. For example, behavioural adaptations reduce the chance of predator encounter and life-history changes increase survival chances under size selective predation [1]. Prominent examples of inducible defences are the various defensive morphological traits observed in the model freshwater crustacean Daphnia. Several Daphnia species display spectacular morphological defences [2,3] including crowns of thorns [4], spines [5], crests [6] and helmets [7-9]. All these defensive strategies are induced via predator-specific chemical cues known as kairomones. The chemical perception of kairomones initiates a series of internal physiological reactions including neuronal signal integration [10] and subsequent conversion into endocrine agents [11-13]. These substances in turn modulate developmental changes, which result in the growth of a ...
(YouTube link) Aint science wonderful? Here is a video of the microscopic water flea performing a little musical ditty. -via Improbable Research, where youll find an additional video of a water flea playing with a toy....
Daphnia pulex (Water flea) is the first fully sequenced crustacean genome. The crustaceans and insects have diverged from a common ancestor. It is a model organism for studying the molecular makeup for coping with the environmental challenges. In the complete proteome, there are 30,550 putative proteins. However, about 10,000 of them have no known homologues. Currently, the UniProtoKB reports on 95% of the Daphnias proteins as putative and uncharacterized proteins. We have applied ProtoNet, an unsupervised hierarchical protein clustering method that covers about 10 million sequences, for automatic annotation of the Daphnias proteome. 98.7% (26,625) of the Daphnia full-length proteins were successfully mapped to 13,880 ProtoNet stable clusters, and only 1.3% remained unmapped. We compared the properties of the Daphnias protein families with those of the mouse and the fruitfly proteomes. Functional annotations were successfully assigned for 86% of the proteins. Most proteins (61%) were mapped to only
Daphnia (Daphnia pulex) is the most common freshwater species known to tropical fish keeping enthusiasts as Water Fleas, Moina, or Water Bugs.
Free Online Library: Embryotoxicity of the Alkylphenol Degradation Product 4-Nonylphenol to the Crustacean Daphnia magna. by Environmental Health Perspectives; Health, general Environmental issues
Persistence OECD guideline 301F: The results showed that propofol is not biodegradable, with ,5% biodegradation after 28 days. However, ,91% removal of propofol from the aqueous phase was observed, which was noted at the time as being possibly due to adsorption to the solid phase.. ISO Guideline 11734: The results showed that propofol was not biodegradable under the anaerobic conditions of the test, although a degree of elimination was observed.. The medicine is potentially persistent.. Bioaccumulation: Log P = 3.9 (at pH 8). BCF 28 D = 27 (at 2 μg/L) and 28 D = 26 (at 0.2 μg/L).. Toxicity: There are data for 3 trophic levels, most sensitive crustacean (Daphnia magna) NOEC chronic toxicity 230 microg/L. ...
Microbial polysaccharides, due to their unique physiochemical properties, have found application in the food industry, cosmetics, pharmacy and medicine. In the environment, microbes can use polysaccharides to alleviate the adverse effects of heavy metals in their close proximity. This adaptive property shows interesting potential for bioremediation. Herein, the effects of the exopolysaccharides (EPS) levan, produced by the bacterium Bacillus licheniformis NS032 and pullulan, produced by the fungus Aureobasidium pullulans CH-1 in the presence of copper (Cu2+) have been investigated for the first time on antioxidant enzyme activity, respiration and Cu2+ bioaccumulation of Daphnia magna as well as the bioluminescence of Vibrio fischeri. Both EPS decreased toxicity of Cu2+ in the acute test with D. magna. The activity of catalase (CAT) was significantly diminished after acute exposure to Cu2+ in comparison to treatments with Cu2+ and EPS, while in the prolonged acute exposure the CAT activ...ity did ...
This Iowan eighth-grader turned her love of nature into a long-term study of water pollution. Shes continuing to investigate the mysterious growths that have formed on her Daphnia magna.
BACKGROUND: Shotgun sequences of DNA extracts from whole organisms allow a comprehensive assessment of possible symbionts. The current project makes use of four shotgun datasets from three species of the planktonic freshwater crustaceans Daphnia: one dataset from clones of D. pulex and D. pulicaria and two datasets from one clone of D. magna. We analyzed these datasets with three aims: First, we search for bacterial symbionts, which are present in all three species. Second, we search for evidence for Cyanobacteria and plastids, which had been suggested to occur as symbionts in a related Daphnia species. Third, we compare the metacommunities revealed by two different 454 pyrosequencing methods (GS 20 and GS FLX). RESULTS: In all datasets we found evidence for a large number of bacteria belonging to diverse taxa. The vast majority of these were Proteobacteria. Of those, most sequences were assigned to different genera of the Betaproteobacteria family Comamonadaceae. Other taxa represented in all ...
Introduction. The effect of caffeine on heart rate Aim: To investigate the effect of caffeine on the heart rate of Daphnia (water fleas). Introduction: Plants produce caffeine as an insecticide. Cocoa in South America, coffee in Africa and tea in Asia have all been used for hundreds of years to produce pick me up drinks containing caffeine. These days, caffeine is also used as a flavour enhancer in a wide range of cola and other soft drinks. ...read more. Middle. This can lead to heart and circulation problems. Daphnia are small, planktonic crustaceans commonly called water fleas because of their saltatory swimming style (although fleas are insects and thus only very distantly related). They live in various aquatic environments ranging from acidic swamps to freshwater lakes, ponds, streams and rivers. Hypothesis: Caffeine will increase the heart rate of the Daphnia (water fleas). Equipment needed: * Culture of Daphnia (water fleas) * Cavity slides * Dropping pipettes * Distilled water and pond ...
We reconstructed the genetic structure of a planktonic crustacean Daphnia longispina living in high mountain lakes and ponds in the Pyrenees to investigate whether it was shaped by persistent founder effects originating shortly after the last glacial maximum or by ongoing dispersal and effective migration (gene flow). We found that the genetic structure can largely be explained by a single colonization event following gradual deglaciation of the Pyrenees c. 10-15 000 years ago. Nuclear genetic diversity declined steeply from southeast to northwest, suggestive of serial colonization of available habitats with advancing deglaciation. The spatial genetic structure suggests that founder effects were major determinants of the present-day diversity, both at the catchment level and at the level of individual water bodies, further supporting extremely low effective migration rates. This study reveals a prime example of a founder effect that is both long-lasting and maintained at small spatial scales. ...
To study on a spatial scale the composition of Daphnia populations we surveyed Daphnia populations north and south of the Swiss Alps. We found that Lakes North of the Alps were invaded with one species (D. galeata) and hypothesize that lakes south of the Alps were invaded with D. longispina. A first life history experiment shows some evidence for this hypothesis. Further, testing of this hypothesis needs to come from sediment cores from lakes from the south side of the alps. I will present recent data about these studies.. 10.06.2013. Urban Friberg - Genetics of sexual dimorphism. Evolutionary Biology Centre, Uppsala University, Sweden. Abstract: Evolution of sexual dimorphism (SD) is a paradox. On the one hand it shouldbe constrained, because it is restricted to occur only through geneexpression and because it relies on gene expression having a sex-specificgenetic architecture. On the other hand SD is common and SD traits are amongthose that evolve the fastest. How is this possible? Is ...
Sample gene map views of Daphnia pulex Genes 2010, including Hemoglobin cluster, Rhodopsin, Chorion peroxidase and galactosyltransferase gene clusters ...
Evolutionary dynamics of hosts and their parasites are complex processes. In order to study these processes on genotype level, reliable molecular tools have to be developed. The goal of this thesis was to develop such tools for freshwater crustaceans - Daphnia longispina species complex and its parasites. On one hand, from the host side - an interspecific hybridization plays an important role. For tracing community dynamics and reticulate evolution in such a hybrid species complex, long-term comparative studies of natural populations are necessary. In order to conduct such a study, it is essential to access historical samples. These samples are usually suffering from low DNA quality due to the preservation chemical such as formaldehyde or denaturated ethanol, therefore traditional genotyping through length-based markers (such as microsatellites or allozymes) proved to be insufficient. For circumventing these issues, SNP- based markers were developed. Based on transcriptome data of one species ...
Acute Toxicity Evaluation to Daphnia magna of Disease Resistant(OsCK1) Rice - Daphnia magna;Disease resistant transgenic rice;Risk assessment;
The common evergreen dwarf shrub Empetrum hormaphroditum has influence on the functioning of boreal terrestrial ecosystems in northern Sweden. The negative effects of E. hermaphroditum are partly attributed to the production of the dihydrostilbene, batatasin-III, which is released from leaves and litter by rain and snowmelt. In this study, we investigated whether batatasin-III is carried by runoff into streams and lakes during the snowmelt period and whether it is also potentially hazardous to aquatic fauna. Sampling of water from streams and a lake for which the surrounding terrestrial vegetation is dominated by E. hermaphroditum was done during the snowmelt period in May 1993 and in 1998, and analyzed for batatasin-III. Using 24- and 48-hr standard toxicity tests, we analyzed toxicity to brown trout (Salmo trutta) alevins and juvenile water fleas (Daphnia magna). Toxicity (proportion of dead individuals) to trout was tested at pH 6.5 and compared with that of a phenol within a range of ...
James Tour, lead researcher on the study, said: This work shows that whole organisms, such as small worms and water fleas, can be killed by nanomachines that get into them. This is not only single-cell death, but also the entire organism, which causes thousands of cells to die. . In a subsequent test, the researchers shifted the target to a larger animal, the mouse. They smeared a local mixture containing micromachines on the skin of mice, and once activated, the drill bits caused skin damage and ulcers. While this doesnt sound good for poor animals, the researchers say the test shows how nanodrills will eventually be used in beneficial ways. They can be used on human skin to penetrate melanoma, kill parasites such as worms or fight eczema and other skin diseases.. The idea is that nanodrills can be trained to target only certain cells so that they dont harm healthy human cells.. The study was published in the journal ACS Applied Materials and Interfaces.. ...
Earthworms and tiny water fleas could help deliver clean water to billions of people in remote areas of the world by eating up sewage and other pollution.
From York University - quite possibly the most poorly written science by press release Ive seen this year. The leaps of may are profound, and the footbal team analogy is designed to elicit sympathy. I suppose if Daphnia populations were collapsing in lakes due to lack of helmets and shoulder pads, wed see a collapse…
I love listening to live blues music. One of my favorite venues is the Canyon Club in Agoura Hills, CA, about an hour and a half drive from my house. Discovering the Canyon Club, one of the premier hot spots for the blues in Southern California, has afforded me the pleasure of seeing legends like Johnny Winter, John Mayall (the father of the British blues), and Charlie Musselwhite play.. In the realm of biology, a team of researchers has recently discovered hot spots in the genome of the water flea Daphnia pulex. Unfortunately for evolutionary biologists, this finding is forcing them to change their tune about the origin of introns (regions of noncoding DNA within genes). At the same time it has creationists and intelligent design proponents making joyful sounds. Thats because this discovery helps provide an explanation from a creation perspective for genome features considered junk DNA, supposedly the most compelling evidence for biological evolution.. According to evolutionary biologists, ...
We show that the stable (C, N, O) isotopic composition of the water flea Daphnia pulicaria is strongly related to that of its diet (C, N) and the water they live in (O). We also show that the stable isotopic composition of the sheaths of Daphnia resting eggs (ephippia) is indicative of the isotopic composition of Daphnia that produced them. This implies that stable isotope ratios of fossil Daphnia ephippia can provide information on past ecological and climatic developments in and around lakes ...
Sigma-Aldrich offers abstracts and full-text articles by [David J Civitello, Rachel M Penczykowski, Aimee N Smith, Marta S Shocket, Meghan A Duffy, Spencer R Hall].
The dual role of recombination in TE proliferation has generated great interest in the effects of sexual versus asexual reproduction on TE loads in the genome over time (Arkhipova & Meselson 2000; Wright & Finnegan 2001; Dolgin & Charlesworth 2006). Sex can facilitate the spread of a new TE throughout a population, but it also provides a mechanism through which new copies can be lost. Thus, sex can lead to an accelerated rate of increase and decrease in TEs over time relative to asexuals, and also impact the distribution of TEs among individuals within a population where sex has been lost (Schaack et al. in press). We surveyed six families of transposable elements in populations of D. pulex, which reproduce either with or without sex and find that both the number and distribution of TEs differ between cyclical parthenogens and obligate asexuals, despite the fact that obligately asexual populations in this species are thought to be relatively young (Lynch et al. 2008). Even though purging ...
Background The cladoceran crustacean Daphnia pulexproduces female offspring by parthenogenesis under favorable conditions, but in response to various unfavorable external stimuli, it produces male...
THE efficacy of natural selection may be severely reduced in asexual compared to sexual organisms due to the absence of recombination and segregation (Fisher 1930; Barton and Charlesworth 1998; Otto and Lenormand 2002; Agrawal 2006). Consequently, asexual populations may adapt more slowly to changing environments (Peck 1994; Orr 2000; Roze and Barton 2006) and suffer from an increased genetic load (Muller 1964; Crow and Kimura 1970; Pamilo et al. 1987; Kondrashov 1988; Charlesworth 1994). Both of these factors may contribute to the rarity of obligate asexuality in eukaryotes (Bell 1982), despite its immediate advantages over sexual reproduction (Maynard Smith 1978). The main reason for the decreased efficiency of selection in asexual organisms is that due to the complete linkage of their genomes, selection cannot operate on different mutations independently (the Hill-Robertson effect, Hill and Robertson 1966). Thus, deleterious mutations anywhere in the genome reduce the effective population ...
This study was performed to assess the acute toxicity of Cedrol, Cedarwood Texas oil distilled on Daphnia magna, and was conducted in accordance with OECD Guideline for Testing of Chemicals No. 202. A full test was performed based on the results of a preceding range-finding test. Water Accommodated Fractions (WAFs) of Cedrol, Cedarwood Texas oil distilled were prepared and used as test concentrations. Twenty daphnids per group (5 per replicate, quadruplicate) were exposed to an untreated control and to WAFs prepared at loading rates of 10, 18, 32, 56 and 100 mg/L under static conditions. The total exposure period was 48 hours and samples for Total Organic Carbon (TOC) analyses were taken at the start and at the end of the test. Due to the potential volatile nature of the test item, the exposure was performed in airtight closed vessels with headspace reduced to minimum. The measured TOC concentrations increased with the loading rate at the three lowest loading rates the start. At the higher ...
Lipidomics, an under-utilised and rapidly developing field aims to identify the full complement of hydrophobic constituents in a cell, tissue or organism. Lipid peroxidation, a major consequence of oxidative stress, represents a mechanistically illuminating marker for numerous toxicants. Lipidomics offers the ideal technique to acquire a greater level of mechanistic detail compared to currently utilised methodologies. Here, I present a study into lipid peroxidation from simple in vitro models to complex in vivo systems utilising mass spectrometric techniques. Initially, oxidised products from a systematic range of phospholipids were induced and comprehensively annotated to allow the development of OxyLipidBlast. This is the first tool facilitating the identification of oxidised lipids and provides utility to numerous fields. Secondly I present the first annotated lipidome of the keystone ecotoxicological species Daphnia magna and the first annotated lipidome of algal species Chlamydomonas ...
Every day we are exposed to carcinogens, including ultraviolet radiation (UVR). High levels of ultraviolet radiation are known to cause DNA damage. One of the most common forms of UVR-induced damage, the pyrimidine dimer, is repaired by an enzymatic reaction powered by visible light. We wanted to find out if there is variation in the level of UVR-induced DNA damage induced in two different clones of Daphnia magna, a model organism for ecotoxicology. One clone was derived from a mid-latitude deep reservoir, where escape from UVR is possible via vertical migration. The second clone was from a high-latitude shallow rock pool, where D. magna are exposed to high levels of UVR. Pregnant mothers from each clone line were subjected to ecologically relevant levels of UVR in the lab. Immediately afterwards, we extracted the embryos, suspended the cells in agarose, and performed a comet assay, which allows for quantification of DNA damage within individual cells. The slides were viewed under a fluorescent
The primary objective of the test is to assess the effect of chemicals on the rate of reproduction of Daphnia magna. The concentrations used in the study are based on the results of an acute immobilisation test. The duration of the study is 21 days and the number of offspring produced, together with adult and juvenile survival, is reported. A semi-static system is recommended and the frequency of test media renewal depends on the stability of the substance. The study is started with juveniles which are female and start to produce live young by parthenogenesis after about 7 days.. Juvenile production is compared to that of the controls to determine the lowest observed effect concentration (LOEC) and the no effect concentration (NOEC) in addition of the EC50. Other adverse effects are recorded such as abnormal development of juveniles in the brood pouch (white eggs). Shedding of un-hatched eggs, presence of male Daphnia, ephippial eggs and differences in the size of adults at the end of the test ...
WALSER, B. and HAAG, C. R. (2012), Strong intraspecific variation in genetic diversity and genetic differentiation in Daphnia magna: the effects of population turnover and population size. Molecular Ecology, 21: 851-861. doi: 10.1111/j.1365-294X.2011.05416.x ...
Cry-toxin genes originating from Bacillus thuringiensis are inserted into genetically modified (GM) plants, often called Bt-plants, to provide insect resistance to pests. Significant amounts of Bt-plant residues, and thus Cry-toxins, will be shed to soil and aquatic environments. We exposed Daphnia magna to purified Cry1Ab and Cry2Aa toxins for the full life-span of the animals. We used single toxins in different doses and combinations of toxins and Roundup, another potential stressor on the rise in agricultural ecosystems. Animals exposed to 4.5 mg/L (ppm) of Cry1Ab, Cry2Aa and the combination of both showed markedly higher mortality, smaller body size and very low juvenile production compared to controls. Animals exposed to 0.75 mg/L also showed a tendency towards increased mortality but with increased early fecundity compared to the controls. Roundup stimulated animals to strong early reproductive output at the cost of later rapid mortality. We conclude that i) purified Cry-toxins in high ...
Yang, Y.; May, L.; Gunn, I.D.M.; Huang, X.; Liu, J.. 1999 Comparative studies on effects of predation by fish on Daphnia in Lake Donghu (China) and Loch Leven (Scotland). In: Ecosystem Approaches for Fisheries Management. American Fisheries Society, 265-281. (Alaska Sea Grant Report, 1). Full text not available from this repository. (Request a copy ...
Zeis et al. (2004) recently reported that hemoglobin concentration in daphnids increased with increasing temperature. Mitchell (2001) noted a low incidence of sexually ambiguous offspring when daphnids were reared at 30°C. Elevated temperature may prove to be an environmental signal that stimulates both hemoglobin induction and male sex determination through the common signaling pathway. Preliminary experiments in our laboratory support this premise. However, elevated temperature may stimulate different signaling pathways, resulting in multiple outcomes. For example, oxygen saturation decreases with increasing water temperature, which may stimulate hemoglobin production via the hypoxia signaling pathway. Increased temperature may also adversely impact the uptake or assimilation of nutrients resulting in male production via the terpenoid signaling pathway.. The minimum components to the putative terpenoid signaling pathway described in this study would consist of the hormone (i.e. methyl ...
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By John K. Colbourne, Michael E. Pfrender, Donald Gilbert, W. Kelley Thomas, Abraham Tucker, Todd H. Oakley, Shinichi Tokishita, Andrea Aerts, Georg J. Arnold, Malay Kumar Basu, Darren J. Bauer, Carla E. Cáceres, Liran Carmel, Claudio Casola, Jeong-Hyeon Choi, John C. Detter, Qunfeng Dong, Serge Dusheyko, Brian D. Eads, Thomas Fröhlich, Kerry A. Geiler-Samerotte, Daniel Gerlach, Phil Hatcher, Sanjuro Jogdeo, Jeroen Krijgsveld, Evgenia V. Kriventseva, Dietmar Kültz, Christian Laforsch, Erika Lindquist, Jacqueline Lopez, J. Robert Manak, Jean Muller, Jasmyn Pangilinan, Rupali P. Patwardhan, Samuel Pitluck, Ellen J. Pritham, Andreas Rechtsteiner, Mina Rho, Igor B. Rogozin, Onur Sakarya, Asaf Salamov, Sarah Schaack, Harris Shapiro, Yasuhiro Shiga, Courtney Skalitzky, Zachary Smith, Alexander Souvorov, Way Sung, Zuojian Tang, Dai Tsuchiya, Hank Tu, Harmjan Vos, Mei Wang, Yuri I. Wolf, Hideo Yamagata, Takuji Yamada, Yuzhen Ye, Joseph R. Shaw, Justen Andrews, Teresa J. Crease, Haixu Tang, Susan M. ...
The last ten years have witnessed increasing interest in host-pathogen interactions involving invertebrate hosts. The invertebrate innate immune system is now relatively well characterised, but in a limited range of genetic model organisms and under a limited number of conditions. Immune systems have been little studied under real-world scenarios of environmental variation and parasitism. Thus, we have investigated expression of candidate innate immune system genes in the water flea Daphnia, a model organism for ecological genetics, and whose capacity for clonal reproduction facilitates an exceptionally rigorous control of exposure dose or the study of responses at many time points. A unique characteristic of the particular Daphnia clones and pathogen strain combinations used presently is that they have been shown to be involved in specific host-pathogen coevolutionary interactions in the wild. We choose five genes, which are strong candidates to be involved in Daphnia-pathogen interactions, ...
Daphnia species are normally r-selected, meaning that they invest in early reproduction and so have short lifespans. An individual Daphnia life-span depends on factors such as temperature and the abundance of predators, but can be 13-14 months in some cold, oligotrophic fish-free lakes.[9] In typical conditions, however, the life cycle is much shorter, not usually exceeding 5-6 months.[9]. Daphnia are typically filter feeders, ingesting mainly unicellular algae and various sorts of organic detritus including protists and bacteria[3][10] Beating of the legs produces a constant current through the carapace which brings such material into the digestive tract. The trapped food particles are formed into a food bolus which then moves down the digestive tract until voided through the anus located on the ventral surface of the terminal appendage.[10] The second and third pair of legs are used in the organisms filter feeding, ensuring large unabsorbable particles are kept out, while the other sets of ...
Food quality is highly dynamic within lake ecosystems and varies spatially and temporally over the growing season. Consumers may need to continuously adjust their metabolism in response to this variation in dietary nutrient content. However, the rate of metabolic responses to changes in food nutrient content has received little direct study. Here, we examine responses in two metabolic phosphorus (P) pools, ribonucleic acids (RNA), and adenosine triphosphate (ATP) along with body mass and body P content in Daphnia magna exposed to chronic and acute dietary P-limitation. First, we examined food quality effects on animals consuming different food carbon (C):P quality over a 14 day period. Then, we raised daphnids on one food quality for 4 days, switched them to contrasting dietary treatments, and measured changes in their metabolic responses at shorter time-scales (over 48 h). Animal P, RNA, and ATP content all changed through ontogeny with adults containing relatively less of these pools with increasing
Daphnia are tiny crustaceans, closely related to a shrimp. They are often called water fleas. They are small, but not microscopic. They can be seen with the naked eye, but you will need a dissecting microscope to view the beating heart. Daphnia can be purchased from any of the companies that sell lab supplies and equipment. Since Daphnia are arthropods, they demonstrate the three major arthropod characteristics: exoskeleton, jointed appendages, and segmented body. The exoskeleton is clear, allowing the student to easily view the heart. Daphnia are ectotherms and their body temperature changes with the surrounding environment. This further means that there is a direct relationship between the internal body activities and the external temperature of the water in which it lives ...