Reproduction Of Daphnia Pulex Research Articles

Photoperiod-dependent effects of zinc oxide nanoparticles on the growth and reproduction of Daphnia pulex

The discharge of metal nanoparticles into the water inevitably poses a threat to aquatic organisms and the balance of the aquatic ecosystem. Photoperiod is one of the most important ecological factors for the development of cladocerans. In addition, different light conditions can also affect the toxicity of metal nanoparticles. In this study, we studied the effects of four photoperiods (8L/16D, 10L/14D, 14L/10D, and 16L/8D) combined with three concentrations of ZnO NPs (0 mg L−1, 0.05 mg L−1, and 0.10 mg L−1) on the growth and reproduction of Daphnia pulex. With the increase of photoperiod, the maternal body size and growth rate increased first and then decreased; the first time to reproduction was advanced, and broods and the total offspring also increased. Under the influence of ZnO NPs, growth rate and reproductive capacity were inhibited. The photoperiod 8L/16D and 16L/8D interacted with ZnO NPs on the growth of D. pulex, which significantly decreased the growth rate. Besides, the interaction between photoperiod 8L/16D and ZnO NPs decreased the reproduction ability of D. pulex. These results suggest that the effects of zinc oxide nanoparticles on the growth and reproduction of D. pulex is photoperiod dependent, which is useful for assessing the risk of pollutants to cladoceras under different light conditions.

Effects of environmental concentrations of 6PPD and its quinone metabolite on the growth and reproduction of freshwater cladoceran

The widespread occurrence and accumulation of N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) and its quinone metabolite, 6PPD quinone (6PPD-Q), have been globally recognized as a critical environmental issue. However, knowledge on the adverse effects of 6PPD and 6PPD-Q on freshwater invertebrates is limited. This study investigated the effects of 6PPD and its oxidative byproduct, 6PPD-Q, on the growth and reproduction of Daphnia pulex. Through 21-day exposure experiments, we measured the uptake of 0.1, 1, and 10 μg/L 6PPD and 6PPD-Q by D. pulex and assessed the effects on growth and fecundity of D. pulex. While 6PPD and 6PPD-Q did not affect the mortality rate of D. pulex, 6PPD-Q exposure inhibited the growth of D. pulex, indicating potential ecological risks. In particular, the reproductive capacity of D. pulex remained unaffected across the tested concentrations of 6PPD and 6PPD-Q, suggesting specific toxicological pathways that warrant further investigation. This study underscored the importance of evaluating the sublethal effects of emerging contaminants such as 6PPD and 6PPD-Q on aquatic invertebrates, and highlighted the need for comprehensive risk assessments to better understand their environmental impacts.

Effects of P70 S6 kinase on the ageing process and reproduction of Daphnia pulex (Branchiopoda, Anomopoda)

Abstract Daphnia pulex is a natural food widely used in aquaculture, and S6K plays an important role in protein translation and ageing. To explore the function of S6K in the ageing process of D. pulex, we cloned and analysed the full-length cDNA of S6K. With the growth of D. pulex, the expression of S6K mRNA first increased, then peaked at 10 days, and then decreased. Western blot analysis showed that the S6K protein expression increased from 1 to 5 days of age, but did not change significantly from 5 to 25 days of age. RNAi knockdown of S6K, reduced the expression of S6K mRNA and S6K protein, and it causes changes in other genes associated with ageing in both sexes. S6K may be involved in reproductive transformation, affecting reproductive capacity, thus significantly affecting the ageing of D. pulex. miRNA with potential regulation of the S6K gene were screened by the bioinformatics method and validated using a dual luciferase reporter gene system. This study deepens our understanding of the mechanisms of ageing in D. pulex and expands our understanding of the role of S6K in the ageing process.

Combined effects of the pesticide spinetoram and the cyanobacterium Microcystis on the water flea Daphnia pulex.

Spinetoram is one of the most worldwidely used pesticides for its high insecticidal efficacy and low human toxicity. Following the large usage of spinetoram, the ecotoxicity and environmental risks to aquatic ecosystems have call for urgent study. In the present study, we investigated the combined effects of spinetoram and the harmful alga Microcystis aeruginosa in freshwater, on survival and reproduction of Daphnia pulex. Acute toxicity test of spinetoram resulted in negative effects on survival, with a 48-h LC50 value of 37.71μg L-1. Under the long-time exposure to environmentally relevant concentrations (0.18 and 0.35μg L-1) of spinetoram and a low composition of Microcystis (30%) in the diet, D. pulex showed both shorter longevity and lower fecundity; the time to first brood also increased. At population level, carrying capacity was highly decreased by spinetoram and Microcystis, whereas a significant decrease of intrinsic growth rate was observed at 0.35μg L-1 spinetoram with 30% Microcystis as food. The present study highlighted that pesticide spinetoram had highly toxic effects on D. pulex and could reduce the tolerance of D. pulex to M. aeruginosa, causing great effects on D. pulex population in natural waterbodies.

Development of an adverse outcome pathway for nanoplastic toxicity in Daphnia pulex using proteomics

Nanoplastics are a growing environmental and public health concern. However, the toxic mechanisms of nanoplastics are poorly understood. Here, we evaluated the effects of spherical polystyrene nanoplastics on reproduction of Daphnia pulex and analyzed the proteome of whole animals followed by molecular and biochemical analyses for the development of an adverse outcome pathway (AOP) for these contaminants of emerging concern. Animals were exposed to polystyrene nanoplastics (0, 0.1, 0.5, 1 and 2 mg/L) via water for 21 days. Nanoplastics negatively impacted cumulative offspring production. A total of 327 differentially expressed proteins (DEPs) were identified in response to nanoplastics which were further validated from gene expression and enzyme activity data. Based on these results, we propose an AOP for nanoplastics, including radical oxygen species production and oxidative stress as the molecular initiating event (MIE); followed by changes in specific signaling pathways (Jak-STAT, mTOR and FoxO) and in the metabolism of glutathione, protein, lipids, and molting proteins; with an end result of growth inhibition and decrease reproductive output. This study serves as a foundation for the development of a mechanistic understanding of nanoplastic toxicity in crustaceans and perhaps other aquatic organisms.

Reproduction of Daphnia pulex in a Northern Italy pond

This paper reports on the occurrence of Daphnia pulex in a small fishless water body of Northern Italy (Bodrio del pastore III) and describes its population dynamics. Bodrio is a typical water body originated by erosion from the old Po river-bed surface. During a three year study (2011-2013), D. pulex population showed an increase in density from spring to early summer, it declined in July-August and did not recover, presumably from ephippia, until the following spring. The seasonal dynamics was related to the species thermal tolerance and to invertebrate predation by Chaoborus that resulted in juvenile high mortality and in adaptive predator-avoidance cyclomorphosis. Seasonal variation was observed in the frequency of individuals, most juveniles, showing neckteeth. D. pulex population reproduces by cyclical parthenogenesis and showed a very early investment in sexual reproduction, independent of population density. Males and ephippial females appeared at the beginning of growth season before the density peak according to a typical feature of Daphnia populations from temporary habitats. This suggests a lower influence of the environmental factors on sex determination compared to populations inhabiting more permanent habitats. Lineages that produce males and ephippial females early in the season had lower growth rate than parthenogenetic ones but may preserve from selection pressure by predators a significant percentage of genetic variation linked to sex allocation so that evolution proceeds toward earlier and increased sexual reproduction. Our results suggest further investigation to verify whether the current population is the last remnant of a once much larger metapopulation eventually reduced by anthropogenic disturbances or if it represents the invasion of North American strains.

Combined exposure to cyanobacteria and carbaryl results in antagonistic effects on the reproduction of daphnia pulex

In aquatic ecosystems, Daphnia are exposed to a wide variety of natural and chemical stressors that can cause interactive effects resulting in an increased impact on aquatic ecosystems. The authors therefore investigated the interactive effects of harmful cyanobacteria (cyanoHABs) with carbaryl in Daphnia pulex, because cyanobacteria have become an important concern for aquatic ecosystems. Daphnia were exposed for 21 d to 4 selected cyanobacteria (Aphanizomenon sp., Cylindrospermopsis raciborskii, Microcystis aeruginosa, and Oscillatoria sp), carbaryl, and all binary combinations of carbaryl and each individual cyanobacterium. Results were analyzed with both the independent action and the concentration addition model. The estimated median effect concentration (EC50) for carbaryl was comparable between the experiments, ranging from 2.28 µg/L to 5.94 µg/L. The EC50 for cyanobacteria ranged from 13.45% of the total diet ratio for Microcystis to 66.69% of the diet ratio for Oscillatoria. In combination with carbaryl, the response of Daphnia to 3 of the 4 cyanobacteria demonstrated antagonistic deviation patterns (p < 0.05). Exposure to combinations of carbaryl and Cylindrospermopsis did not result in statistically significant deviations from both reference models. The results may have important implications for pesticide risk assessment, underlining the impact of interactive effects on aquatic organisms. Based on these results, the authors suggest that both the independent action and the concentration addition model can serve as a protective approach in risk assessment of carbaryl in the presence of cyanobacterial blooms.

Chronic effects of the herbicide diuron on freshwater cladocerans, amphipods, midges, minnows, worms, and snails.

The chronic effects of the herbicide diuron on survival and reproduction of Daphnia pulex, and survival and growth of the amphipod Hyalella azteca, the midge Chironomus tentans, juvenile and embryo/larval fathead minnows, Pimephales promelas, annelid worms, Lumbriculus variegatus, and snails, Physa gyrina, were determined in laboratory static and static-renewal tests. D. pulex 96-h and 7-day LC50 values were 17.9 and 7.1 mg/L; 7-day LOAEL and NOAEL values based on mortality and reproduction were 7.7 and 4.0 mg/L. H. azteca 96-h and 10-day LC50 values were 19.4 and 18.4 mg/L; 10-day LOAEL and NOAEL values based on survival and reduced weight were 15.7 and 7.9 mg/L. C. tentans 10-day LC50 value was 3.3 mg/L; 10-day LOAEL and NOAEL values based on growth were 7.1 and 3.4 mg/L, and 3.4 and 1.9 mg/L based on mortality. Juvenile fathead minnows had a 10-day LC50 of 27.1 mg/L and 10-day LOAEL and NOAEL values based on growth of 3.4 and <3.4 mg/L. The fathead minnow embryo-larval test had a 7-day LC50 value of 11.7 mg/L and 7-day LOAEL and NOAEL values based on reduced growth of 8.3 and 4.2 mg/L. L. variegatus had 10-day LOAEL and NOAEL values based on reduced weight of 3.5 and 1.8 mg/L. P. gyrina had 10-day LOAEL and NOAEL values based on reduced weight of 22.8 and 13.4 mg/L. Laboratory effects concentrations were higher that those found in normal field application situations, except in areas of localized pooling after recent herbicide applications, indicating that there would probably be little harm to these fish and invertebrates from diuron exposure in the field.

Effects of Microcystis aeruginosa exposure and nutritional status on the reproduction of Daphnia pulex

Effects of <i>Microcystis aeruginosa</i> exposure and nutritional status on the reproduction of <i>Daphnia pulex</i>

Sublethal effects of treated liquid effluent from a petroleum refinery. V. Reproduction of Daphnia pulex and overall evaluation

The 48-h LC 50 of treated refinery effluent for 2-day-old Daphnia pulex was 76% effluent. The 14-day LC 50 was 6.4% effluent and this was a threshold value for mortality. For reproductive failure, the 14-day EC 50 was 3.1% effluent, and the EC 5 of 0.52% effluent was considered to approximate the threshold of sublethal effect. Daphnia reproduction was the most sensitive response in a series of studies that included fish growth, reproduction, locomotion, and respiration. Results are considered representative for a well-treated effluent from a petroleum refinery. The 48-h lethal test with D. pulex would be a useful tool for monitoring or assessing such effluents, since it is simple, small-scale, quick, and about 2.6 times as sensitive as a lethal test with trout.

The Effects of Suspended Silt on Feeding and Reproduction of Daphnia pulex

This paper reports the effect of suspended silt on the feeding and reproduction of Daphnia pulex and the impact of suspended silt and clay on freshwater zooplankton community structure. The effects of suspended silt and clay on the filtering and assimilation rates of Daphnia pulex were determined using a 14C radiotracer method. Both filtering and assimilation rates are severely depressed at even low concentrations of suspended silt and clay. Life table studies also showed population growth rate of zooplankton was significantly diminished by suspended silts and clays. The relative abundance of zooplankton varied markedly between two lakes of differing turbidity levels, the more turbid lake having a higher relative abundance of large zooplankton species. Suspended silt and clay reduced zooplankton feeding and production but probably influenced zooplankton community structure by impairing the ability of visually feeding planktivorous fish to locate their prey. INTRODUCTION Zooplankton play a pivotal role in the transfer of energy in food chains of ponds, lakes and oceans. These small herbivores feed on diffuse plant resources, thereby repackaging energy into a much more concentrated form which can be used by carnivores. There have been many studies of the feeding ecology of zooplankton (Ryther, 1954; Rigler, 1961; Burns and Rigler, 1967; Hall et al., 1976; Porter et al., 1982) and the forces which limit zooplankton populations. Still, there is debate on the relative importance of competition among zooplankton for limited food resources vs. planktivory as the dominant force limiting zooplankton population densities and structuring zooplankton communities (Brooks and Dodson, 1965; Hall et al., 1970; Lynch, 1979; Neill and Peacock, 1980; Zaret, 1980). This debate arises anew when considering turbid lakes characteristic of midwestern and southeastern North America. Such lakes often have large zooplankton in relatively high densities and such large zooplankton could result from interaction with suspended silts and clays in at least two ways. First, dissolved organic matter adsorbed to silt particles ingested by filter-feeding zooplankton could supply added nutrition sources (Marzolf, 1965). Second, suspended silt particles may serve as a refuge for zooplankton from planktivorous fish which locate prey visually (Vinyard and O'Brien, 1976; Gardner, 1981). Vinyard and O'Brien (1976) and Wright (1981) showed that increasing turbidity impairs the ability of planktivorous fish to locate prey. Buck (1956) reported production of redear sunfish (Lepomis microlophus) in low turbidity ponds was 300 times greater than in ponds with high turbidity. While the effects of turbidity on predaceous fish are documented, similar data for herbivorous zooplankton are not available. The purpose of this study is to determine the effects of suspended silt and clay on filtering rates, assimilation efficiencies, population growth and community structure of zooplankton. METHODS Algal cultures used in filtering rate and assimilation efficiency determinations were 1 Current address: Department of Environmental Science and Engineering, University of California at Los Angeles, Los Angeles, California.

Oxygen consumption of zooplankton as affected by laboratory and field cadmium exposures.

Virtually none of the many studies of the responses of aquatic organisms to heavy metals has involved organism response to heavy metals under natural, whole system exposure. The ability of laboratory studies to simulate and predict actual field conditions and responses remains questionable. The effects of cadmium exposure on zooplankton has been measured in laboratory studies and in enclosures placed in the field. However, studies involving zooplankton subjected to field exposure of cadmium are lacking. The objectives of this experiment were to measure oxygen consumption, survivorship, and reproduction of Daphnia pulex and Simocephalus serrulatus in response to low level cadmium exposure, in both laboratory and field situations. This design makes possible the comparisons of 1) laboratory and field exposures, and 2) responses of 2 common freshwater zooplankton species.

Longevity and reproduction of Daphnia pulex (de Geer) exposed to cadmium-contaminated food or water

The effect of cadmium on the survival and reproductive capacity of Daphnia pulex was determined. Cadmium was present either in the water at chronic (1–30 μg Cd/litre) and acute (40–90 μg Cd/litre) levels or in the algal food source, Chlorella pyrenoidosa. The average longevity of D. pulex was not affected by exposure to 1 μg Cd/litre but it was reduced in a dose-dependent manner between 5 and 30 μg Cd/litre. Exposure to cadmium had no effect on the number of days to onset or frequency of reproduction but it did cause a reduction in the percentage of adults producing young, the number of broods per adult, the number of young per brood, the number of progeny per adult, the intrinsic rate of natural increase ( r), and the mean generation time ( T). Cadmium-laden Chlorella caused the same effects as did exposure to 1 μg Cd/litre.

Effects of sublethal concentrations of the herbicide Atrazin on Growth and reproduction of Daphnia pulex.

Data on sublethal effects of pesticides on fresh water fauna are rare. This is possibly due to there being up till now no generally accepted standard methods for the measurement of such effects. Although generally accepted methods are used to measure acute toxicity, comparisons of studies carried out on concentrations where mortality cannot be applied as a criterion are not very meaningful, because widely differing parameters together with a whole variety of methods are in use. In view of this obvious need to establish the ecologically relevant effects of substances which are capable of contaminating the environment, it has become urgently necessary to standardize the criteria and methods used for this purpose. Particularly relevant ecologically are the effects on growth and reproduction as even small changes in these parameters can disturb the balance in a biocoenosis quite drastically. In this paper we present results of investigations into the possibilities of measuring such effects on Daphnia Dulex-sanA animal commonly used for toxicological testing. test substance a herbicide was chosen because little is known either about the distribution of these pesticides throughout the environment or the effects on organisms other than plants, although the application of herbicides plays an ever increasing role.