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At least 19 recordsLinked to original sources
PubMed2003

Laboratory evaluation of the toxicity of Perfluorooctane Sulfonate (PFOS) on Selenastrum capricornutum, Chlorella vulgaris, Lemna gibba, Daphnia magna, and Daphnia pulicaria.

Perfluorooctane sulfonate (PFOS) is an anthropogenic compound found in trace amounts in many environmental compartments far from areas of production. This, along with the highly persistent nature of PFOS, presents a concern for possible effects in aquatic ecosystems. The objective of this study was to determine the toxicity of PFOS in representative freshwater organisms. Toxicity testing using standard laboratory protocols was performed on the green algae Selenastrum capricornutum and Chlorella vulgaris, the floating macrophyte Lemna gibba, and the invertebrates Daphnia magna and Daphnia pulicaria. No observable effect concentration (NOEC) values were generated from the most sensitive endpoints for all organisms. Autotroph inhibition of growth NOEC values were 5.3, 8.2, and 6.6 mg/L for S. capricornutum, C. vulgaris, and L. gibba, respectively. The 48-h immobility NOEC values for D. magna and D. pulicaria were 0.8 and 13.6 mg/L, respectively. In comparison to immobility, the 21-day lethality NOEC for D. magna was 5.3 mg/L. Based on effect (immobility) values, the most sensitive of all test organisms was D. magna. The most sensitive organism based on 50% inhibition of growth (IC(50)) was L. gibba, with an IC(50) value of 31.1 mg/L determined from wet weight. This is 4.3 times less than the LC(50) for D. pulicaria, which was 134 mg/L. Significant adverse effects (p < or = 0.05) were observed for all organisms in concentrations >134 mg/L. The results indicate that under laboratory conditions PFOS is acutely toxic to freshwater organisms at concentrations at or near 100 mg/L. Based on known environmental concentrations of PFOS, which occur in the low ng/L to low microg/L range, there is no apparent risk to freshwater systems. However, further work is required to investigate long-term effects in these and other freshwater organisms.

Alkanesulfonic Acids↗
PubMed2001

The use of biomarkers in Daphnia magna toxicity testing V. In vivo alterations in the carbohydrate metabolism of Daphnia magna exposed to sublethal concentrations of mercury and lindane.

Aspects of the carbohydrate metabolism of Daphnia magna exposed for 48 and 96 h to sublethal concentrations of mercury and lindane were investigated. General as well as toxicant-specific perturbations in the intermediary metabolism were observed. Both model toxicants caused an increase in glycolytic and hexose-monophosphate shunt activity. Mercury exposure increased lactate dehydrogenase and isocitrate activity (only after 96 h), while lindane exposure, on the contrary, inhibited the cellular lactate formation and increased the Krebs' cycle activity (only after 48 h). Daphnids exposed to sublethal mercury concentrations clearly exhibited increased glycogenolytic activity, while in lindane-exposed organisms mainly glycogen phosphorylase inhibition was detected. The short-term enzyme-based effect levels (48--96 h LOEC and EC(10) values) were compared with the effects on the population dynamics. This evaluation for both model toxicants suggests that threshold levels (LOEC or EC(10) values) based on pyruvate kinase activity after 48 and 96 h of exposure could be potential early warning signals for long-term effects. A set of enzymatic endpoints, based on the intermediary metabolism, is suggested to characterize the metabolic state of the daphnids.

Animals↗
PubMed2003

Inducible defences in Daphnia depend on latent alarm signals from conspecific prey activated in predators.

Some water fleas (Daphnia spp.) undergo phenotypic changes when exposed to chemical signals from predators. The chemical signals have been assumed to be of predator origin (i.e. kairomones), since juices of crushed Daphnia have been found ineffective. We speculated that latent alarm signals could be present in Daphnia, to be activated in predators following ingestion. Accordingly, fish predators were fed earthworms for 10 weeks to remove Daphnia remains from their gastro-intestinal tracts. Following another 6 days of earthworm feeding, water conditioned by fish induced no morphological changes in D. galeata. When fish were alternatively fed Daphnia for 6 days, changes were induced with fish-conditioned water. Extracts made from intestines of earthworm-fed fish, homogenized with earthworms, gave no morphological changes, but intestines of the same origin homogenized with Daphnia did. Similar results were found when earthworms and Daphnia were homogenized with fish liver. Freshly frozen extracts of homogenized Daphnia gave no detectable changes at first instar stage in test animals, whereas extracts of Daphnia that had been kept at room temperature did induce such changes. Our results suggest that Daphnia respond to latent conspecific alarm signals (i.e. 'dormant' pheromones) that are activated by intestinal or bacterial enzymes in predators or in the water.

Aggression↗
PubMed2001

Effects of cell-bound microcystins on survival and feeding of Daphnia spp.

The influence of cell-bound microcystins on the survival time and feeding rates of six Daphnia clones belonging to five common species was studied. To do this, the effects of the microcystin-producing Microcystis strain PCC7806 and its mutant, which has been genetically engineered to knock out microcystin synthesis, were compared. Additionally, the relationship between microcystin ingestion rate by the Daphnia clones and Daphnia survival time was analyzed. Microcystins ingested with Microcystis cells were poisonous to all Daphnia clones tested. The median survival time of the animals was closely correlated to their microcystin ingestion rate. It was therefore suggested that differences in survival among Daphnia clones were due to variations in microcystin intake rather than due to differences in susceptibility to the toxins. The correlation between median survival time and microcystin ingestion rate could be described by a reciprocal power function. Feeding experiments showed that, independent of the occurrence of microcystins, cells of wild-type PCC7806 and its mutant are able to inhibit the feeding activity of Daphnia. Both variants of PCC7806 were thus ingested at low rates. In summary, our findings strongly suggest that (i) sensitivity to the toxic effect of cell-bound microcystins is typical for Daphnia spp., (ii) Daphnia spp. and clones may have a comparable sensitivity to microcystins ingested with food particles, (iii) Daphnia spp. may be unable to distinguish between microcystin-producing and -lacking cells, and (iv) the strength of the toxic effect can be predicted from the microcystin ingestion rate of the animals.

Animals↗
PubMed2003

Effects of microcystin-free and microcystin-containing strains of the cyanobacterium Microcystis aeruginosa on growth of the grazer Daphnia magna.

Harmful effects of the common bloom-forming cyanobacterium Microcystis aeruginosa on the grazer Daphnia have been explained from morphological features, nutritional insufficiency, and the production of toxins called microcystins. The effects of four M. aeruginosa strains, including one free of microcystins, on the growth of Daphnia magna were examined. Population growth was measured in Daphnia fed each M. aeruginosa strain alone and fed mixtures of each strain with the green alga Scenedesmus obliquus to avoid nutritional deficiency. The presence of Microcystis in the food resulted in decreased Daphnia population growth rates. A significant correlation (P < 0.001) was found between the amount of microcystins (MC) in the food and the population growth rate, but growth inhibition in Daphnia fed with the MC-free strain could not be explained by the toxicity of the microcystins. Inasmuch as there was greater reduction in growth of the Daphnia fed mixtures of the MC-free strain with Scenedesmus than of the Daphnia fed only the same amount of Scenedesmus as in the mixtures, other factors associated with this Microcystis strain must have inhibited growth. However, morphology and nutritional insufficiency could be excluded as causal factors. The strong relationship between Daphnia feeding activity and population growth suggests that feeding inhibition may have caused the observed detrimental effects on the animals.

Animals↗
PubMed2005

Chronic toxicity and responses of several important enzymes in Daphnia magna on exposure to sublethal microcystin-LR.

In the current study, the toxicological mechanisms of microcystin-LR and its disadvantageous effects on Daphnia magna were examined. Survival rate, number of newborn, activity of several important enzymes [glutathione S-transferase (GST), lactate dehydrogenase (LDH), phosphatases, and glutathione], accumulated microcystins, and ultrastructural changes in different organs of Daphnia were monitored over the course of 21-day chronic tests. The results indicated that low concentrations of dissolved microcystin had no harmful effect on Daphnia. On the contrary, stimulatory effects were detected. In the presence of toxin at high dosage and for long-term exposure, GST and glutathione levels decreased significantly. The decreased enzyme activity in the antioxidant system probably was caused by detoxification reactions with toxins. And these processes of detoxification at the beginning of chronic tests may enable phosphatases in Daphnia magna to withstand inhibition by the toxins. At the same time, we also found that the LDH activity in test animals increased with exposure to microcystin-LR, indicating that adverse effects occurred in Daphnia. With microcystin given at a higher dosage or for a longer exposure, the effect on Daphnia magna was fatal. In the meantime, microcystin began to accumulate in Daphnia magna, and phosphatase activity started to be inhibited. From the ultrastructure results of cells in D. magna, we obtained new information: the alimentary canal may be the target organ affected by exposure of microcystins to D. magna. The results of the current study also suggested that the oxidative damage and PPI (protein phosphatase inhibition) mechanisms of vertebrates also are adapted to Daphnia.

Adaptation, Physiological↗
PubMed2004

Spatial avoidance of littoral and pelagic invertebrate predators by Daphnia.

Studies on spatial avoidance behaviour of predators by prey often ignored the fact that prey typically face multiple predators which themselves interact and show a spatial pattern in abundance and predation rates (PRs). In a series of laboratory experiments, we investigated predation risk (PRI) and horizontal migration of the cladoceran Daphnia magna between open water and vegetation in response to two important invertebrate predators with a contrasting spatial distribution: pelagic Choaborus and vegetation-associated Ischnura. As expected, PRI by Chaoborus was higher in open water due to higher numbers and higher PRs of Chaoborus, while for Ischnura, PRI was highest in the vegetation due to higher densities, despite lower PRs of Ischnura. In accordance with this, Daphnia moved into the vegetation in the presence of the pelagic Chaoborus alone. In the presence of Ischnura alone, however, Daphnia showed no response. We hypothesize this may be the result of a constitutive behaviour of Daphnia to avoid pelagic fish, which impedes a response to the open water. In the combined predator treatment, Daphnia migrated to the open water zone. The increased risk of predation in the vegetation, due to a facilitating effect of Chaoborus on Ischnura PRs is believed to have caused this migration of the Daphnia. This response of Daphnia declined through time and Daphnia moved toward the vegetation. A decline in the activity of the Ischnura larvae through time may have switched the risk balance in favour of the vegetation environment.

Animals↗
PubMed2000

Behaviour plasticity without learning: phenotypic and genetic variation of naïve Daphnia in an ecological trade-off.

The swimming behaviour of adult Daphnia largely governs their depth, which has a direct effect on both individual foraging success and predation avoidance. We treated individual swimming behaviour as a threshold character and used directional changes in average clonal depth within experimental tubes as a test for character plasticity. We compared the swimming behaviours of two cohabiting, phenotypically similar Daphnia (Daphnia galeata and Daphnia galeata-Daphnia rosea hybrid) to determine (1) whether there is inherited variation (H(2)) for different traits (responses to hunger and predator cues); (2) whether changes in genetic parameters (norm of reaction and character state) across four environments could be simulated by combinations of the presence or absence of a predator cue and high or low hunger levels; and (3) whether these Daphnia would respond to directional selection, particularly in a trade-off environment (high hunger and predator cue treatments). Responses of both D. galeata and the D. galeata-rosea hybrid to hunger and a predator cue and the trade-off environment were plastic. Daphnia galeata expressed significant genetic variation within (H(2)) and between environments (heritability of plasticity). Both the character state and norm of reaction estimates of heritable variation in the hybrid were close to zero. Genetic correlations were positive and stable across six environmental pairs in Daphnia galeata. Most hybrid genetic correlations were not significant. The phenotypic distributions of both D. galeata and the hybrid were bimodal in the trade-off environment. The D. galeata distribution was partly due to between-clone variation and the hybrid distribution was almost entirely due to within-clone variation. Genetic variation expressed by D. galeata in the trade-off environment appears to depend on both clone by environment interactions and stable inherited differences. These results indicate that while plastic phenotypic responses cause a similar opportunity for selection in D. galeata and the hybrid, their responses to selection would be different in the trade-off and in related environments. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2004

Embryological aspects of inducible morphological defenses in Daphnia.

Many cases of predator-induced morphological plasticity in daphnids are well studied examples of inducible defenses. However, little is known about the early development of these sometimes conspicuous traits. We compared for the first time in five different Daphnia species the embryonic development of predator-induced and noninduced animals using scanning electron microscopy (SEM). We observed significant morphological changes in the last embryonic stage in helmet formation in Daphnia cucullata and in neck-pedestal development in Daphnia pulex. In contrast, no morphological changes could be found during embryogenesis between induced and noninduced Daphnia lumholtzi, D. longicephala, and D. ambigua. Strategies for initiating the defensive traits differ among Daphnia species because of trade-offs between environmental requirements and developmental constraints. Some general features of Daphnia embryonic development are described using SEM. All Daphnia embryos have to shed at least three different membranes before leaving the brood pouch of the mother. After the embryos shed the third membrane, chemosensillae that are likely able to detect predator-released chemicals are exposed to the olfactory environment.

Animals↗
PubMed2001

Accumulation of cyanobacterial hepatotoxins by Daphnia in some Egyptian irrigation canals.

In this study, microcosm experiments were run in the laboratory to test the possibility of feeding of Daphnia parvula on toxic Microcystis aeruginosa in some Egyptian irrigation canal at Sohag city. The results demonstrated that Daphnia has a priority of feeding on green algae and the diatom Melosira granulata over toxic M. aeruginosa during the first 10 days. Thereafter, when the green algae and diatom were depleted from the water, Daphnia started to feed on toxic Microcystis. This presumably indicates that Daphnia feeds facultatively on toxic cyanobacteria under the conditions of depletion of edible food. Additionally, the results indicated that Daphnia accumulates the Microcystis toxins "microcystins" in its body with a level of 1.78 microg toxin/25 daphnids. No release of toxin into the water was detected during the experimental period. This emphasizes that the disappearance of toxic Microcystis was due to the feeding by Daphnia, not to death or cell lysis. Such an accumulation of cyanobacterial hepatotoxins in the primary consumers (Daphnia) should be taken into consideration when zooplankton are used in the biomanipulation of toxic phytoplankton.

Agriculture↗
PubMed2005

Toxicity identification evaluation of five metals performed with two organisms (Daphnia magna and Lactuca sativa).

When trying to identify the main toxicants in effluents, natural waters, sediments, soil leachates, and leachates from products, the Toxicity Identification Evaluation (TIE) procedure has proven useful. To enhance the use of this procedure for soil, sewage, and sediment samples, we wanted to evaluate this TIE procedure, regarding metal toxicity, for the 96-h root elongation test performed with Lactuca sativa (lettuce) seeds. We also wanted to evaluate the effect of TIE treatment on the toxicity of Mn and Fe to Daphnia magna. Bioassays were performed with Daphnia magna (48-h immobility) and lettuce seeds (96-h root elongation) to determine the effect concentrations for both organisms of Ag, Cu, Fe, Mn, and Zn. The TIE was then performed at the determined Daphnia 48-h EC(84) and Lactuca 96-h EC(50) for each metal. Our results showed that the order of the metal toxicity was Ag>Cu>Zn>Fe>Mn, for Daphnia and Ag = Zn = Fe = Cu > Mn for lettuce seeds. We also found that toxicity of the metals for Daphnia magna was reduced according to the prevailing knowledge regarding Cu, Zn, and Ag. However, the toxicity of Ag and Cu for Daphnia was also reduced by filtration through a C18 resin. Toxicity of Mn and Fe was reduced by filtration through a CM resin and increase of pH. For lettuce seeds, toxicity of the metals was reduced by the same treatments as for Daphnia magna with the exception of EDTA addition, which did not affect Cu toxicity to lettuce seeds. No effects were found for filtration through a C18 resin. We suggest that the TIE procedure using lettuce seeds can be used in toxicity identification of metals. However, the effects of pH manipulations were often stronger with lettuce and should be interpreted with care.

Animals↗
PubMed2005

Life history consequences of sterol availability in the aquatic keystone species Daphnia.

The absence of essential biochemical nutrients, such as polyunsaturated fatty acids or sterols, has been considered as a mechanism determining trophic interactions between the herbivore Daphnia and its phytoplankton food source. Here, we experimentally quantify the sensitivity of two Daphnia species to decreasing amounts of dietary sterols by measuring variations in life history traits. The two species Daphnia magna and D. galeata were fed different mixtures of the sterol-containing green alga Scenedesmus obliquus and the sterol-free cyanobacterium Synechococcus elongatus; a higher proportion of Synechococcus in the food is equivalent to a decrease in dietary sterols. To address the significance of sterol limitation, the Daphnia species were also fed Synechococcus supplemented with cholesterol. In both species, somatic and population growth rates, maternal dry mass, the number of viable offspring, and the probability of survival were significantly reduced with the lower availability of sterols. A high correlation between the sterol content of the mixed diet and the somatic and population growth rates was found, and growth on cholesterol-supplemented Synechococcus fitted well into this correlation. Somatic growth of first-clutch neonates grown on 100% Synechococcus exhibited a pattern similar to that of somatic growth of their mothers grown on the different food regimes, which demonstrated the significance of maternal effects for sterol-limited population growth. Daphnia galeata had a twofold higher incipient limiting sterol level than D. magna, which indicated interspecific differences in sterol requirements between the two Daphnia species. The results suggest a strong impact of dietary sterols on life history traits and therefore, population dynamics of the keystone species Daphnia.

Analysis of Variance↗
PubMed1998

QSAR study of the toxicity of benzoic acids to Vibrio fischeri, Daphnia magna and carp.

The toxicities of benzoic acids to Vibrio fischeri, Daphnia magna and carp were measured. The results showed that the toxicity to V. fischeri and Daphnia decreased in the order of bromo > chloro > fluoro approximately equal to aminobenzoic acids. The toxicity of substituted benzoic acids to carp and Daphnia was much lower that to V. fischeri. The results also showed that the toxicity of benzoic acids to Daphnia decreased as the pH increased. It is suggested that ionized and non-ionized forms have different toxic responses. The non-ionized form may play an important role in toxicity because the toxicity of benzoic acids to Daphnia greatly decreases as the pH increases. The toxicity of benzoic acids to Daphnia may operate through non-polar narcosis, based on the regression results between the toxicities and partition coefficients (log P) and apparent partition coefficients (log D). However, toxicity cannot be predicted from non-polar baseline models because the ionized and non-ionized form of benzoic acids have different contributions to toxicity. Compared with the single descriptors, the prediction of toxicity of the benzoic acids was improved remarkably by using log P with pKa and log P with ELUMO. For the toxicity of benzoic acids to V. fischeri, it is suggested that the toxic mechanism may be different from the mechanism in Daphnia and carp. A probable reason is that V. fischeri is a unicellular organism with low lipid content, and hence both ionized and non-ionized forms of benzoic acids can easily cross the cell membrane and contribute to toxicity.

Animals↗
PubMed2007

Toxicity and biouptake of lead and arsenic by Daphnia pulex.

Acute and chronic toxicity studies were conducted on Daphnia pulex using synthetic lead and arsenic water samples. For acute studies, solutions with 0.25, 0.5, 1.0, 2.0, 5.0 mg/L lead and arsenic along with a control were used. The chronic studies were conducted for 21 days using 0.25, 0.5, 1.0 mg/L lead and arsenic solutions along with a control. Results indicated that the LC50 (48 hour) was 4.0 and 3.4 mg/L for lead and arsenic, respectively. Results from chronic studies suggest that the exposure to lead solutions significantly (P < 0.05) impaired the reproduction rates of Daphnia at the 1 mg/L concentration. However, the reproduction rates were enhanced at low concentrations of arsenic (up to 0.5 mg/L). A second chronic study was conducted to confirm this finding. Results from the second study indicated that lead exhibited significantly higher (P < 0.05) toxicity at 0.5 mg/L concentration, while reproduction rates in all concentrations of arsenic solutions were not significantly different from the controls. Metal analysis on exposed Daphnia, following nitric acid digestion procedures, indicated that Daphnia bio-accumulated 75.3-97.2% of the lead added to the experimental containers. This high lead biouptake coupled with the fast growth, high reproduction rates, and short life cycle all suggest that a Daphnia-based remediation (growth and partial harvest) may a viable treatment alternative that is worth considering. However, further field studies have to be conducted to verify this alternative. Biouptake or sequestration by Daphnia of arsenic at all tested concentrations was negligible, thereby, suggesting selective uptake or sequestration by daphnia under the tested pH and temperature conditions.

Animals↗