Search results for "daphnia"
showing 10 items of 134 documents
Sex Allocation Theory for Facultatively Sexual Organisms Inhabiting Seasonal Environments: The Importance of Bet Hedging
2018
Adaptive explanations for dormancy often invoke bet hedging, where reduced mean fitness can be adaptive if it associates with reduced fitness variance. Sex allocation theory typically ignores variance effects and focuses on mean fitness. For many cyclical parthenogens, these themes become linked, as only sexually produced eggs undergo the dormancy needed to survive harsh conditions. We ask how sex allocation and the timing of sex evolve when this constraint exists in the form of a trade-off between asexual reproduction and sexual production of dormant eggs-the former being crucial for within-season success and the latter for survival across seasons. We show that male production can be tempo…
Daphnia females adjust sex allocation in response to current sex ratio and density
2018
Cyclical parthenogenesis presents an interesting challenge for the study of sex allocation, as individuals’ allocation decisions involve both the choice between sexual and asexual reproduction, and the choice between sons and daughters. Male production is therefore expected to depend on ecological and evolutionary drivers of overall investment in sex, and those influencing male reproductive value during sexual periods. We manipulated experimental populations, and made repeated observations of natural populations over their growing season, to disentangle effects of population density and the timing of sex from effects of adult sex ratio on sex allocation in cyclically parthenogenetic Daphnia…
Invertebrate community responses to emerging water pollutants in Iberian river basins
2014
Abstract Chemical pollution is one of the greatest threats to freshwater ecosystems, especially in Mediterranean watersheds, characterized by periodical low flows that may exacerbate chemical exposure. Different groups of emerging pollutants have been detected in these basins during the last decade. This study aims to identify the relationships between the presence and levels of prioritary and emerging pollutants (pesticides, pharmaceutical active compounds—PhACs, Endocrine Disrupting Compounds EDCs and Perfluorinated Compounds—PFCs) and the invertebrate community in four Mediterranean basins: the Ebro, the Llobregat, the Jucar and the Guadalquivir. Structural (species composition and densi…
Modeling the mobility of glyphosate from two contrasting agricultural soils in laboratory column experiments
2019
Glyphosate (GLP) currently is one of the most widely used herbicides worldwide. The persistence of GLP and its major metabolite, aminomethylphosphonic acid (AMPA) in the environment has been described by other authors. This study was aimed at comparing the GLP and AMPA behavior in sandy and loamy sand soils after spiking with enhanced (445 µg g−1) concentrations of GLP in herbicide KLINIK® (Nufarm, Austria) and bioaugmentation followed by 40 days weathering and a consistent three-stage leaching in a laboratory column experiment. Soil samples were obtained from mineral topsoil (0–10 cm) within former agricultural lands where soil parent material was formed by glacigenic deposits. The total a…
Diet estimation and comparison of fatty acid-based diet modelling methods
2019
Trophic interactions have been a popular research subject among ecologists for decades because understanding the structure of food webs is essential in understanding consumer-resource interactions and complex ecosystems. Consumer diet estimation with biological tracer-based mixing models is an important and recently rapidly developing tool for deciphering aquatic food webs. Bayesian frameworks have been introduced to estimate diets accurately with stable isotope proportions. The low quantity of different stable isotope tracers, however, limits greatly the diet estimation accuracy of complex consumer diets. Therefore, fatty acids have been used as biological tracers to multiply the quantity …
DifferingDaphnia magnaassimilation efficiencies for terrestrial, bacterial, and algal carbon and fatty acids
2014
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) a…
Kvaternizēto amonija sāļu noteikšana šķīdumos pēc organomālu apstrādes
2017
Kvaternizēto amonija sāļu noteikšana šķīdumos pēc organomālu apstrādes. Pāls M., zinātniskais vadītājs Dr. ķīm. Nakurte I., Bakalaura darbs, 33 lappuses, 17 attēli, 8 tabulas, 24 literatūras avoti. Latviešu valodā. Literatūras apskatā apkopota informācija par organomāliem un to īpašībām, kā arī organomālu iegūšanas metodēm un to iespējamo pielietojumu. Aprakstīta kvaternizēto amonija sāļu ietekme uz vidi un to noteikšanas metodes. Bakalaura darba praktiskajā daļā veikta AEŠH-MS metodes pielāgošana, lai analizētu kvaternizēto amonija sāļu koncentrāciju dažādos organomālu un organomālus saturošu materiālu skalojumos. Noteikta kvaternizēto amonija sāļu toksicitāte, izmantojot akūtas toksicitāt…
Laboratory investigation into the development of resistance of Daphnia magna to the herbicide molinate.
2003
Daphnia magna (F0 generation) was exposed to different sublethal molinate concentrations (0, 3.77, 4.71, 6.28, 9.42, and 18.85 mg/L) during 21 days. Chronic toxicity tests, using the same herbicide concentrations, were also carried out during 21 days using neonates of F1 first brood (F1-1st) and F1 third brood (F1-3rd) offspring generations from the parentals (F0) preexposed to the herbicide. Finally, offspring (from F1-1st and F1-3rd broods) were transferred to herbicide-free medium during a 21-day recovery period. The alga Nannochloris oculata (5 x 10(5) cells/mL) was used as food in all the experiments. The effect of molinate on survival, reproduction, and growth was monitored for the se…
Caloric content of Daphnia magna as reflect of propanil stress during a short-term exposure and its relationship to long-term responses
2013
The present study investigates energy stores changes in the aquatic invertebrate Daphnia magna following a 5-d exposure to propanil. Juveniles of D. magna were exposed to sublethal propanil concentrations (0.07, 0.10, 0.21 and 0.55 mgl(-1)) which were used previously to test their effect on reproduction, growth and survival (21 days test) of D. magna. Glycogen, total lipids, proteins, and dry weight were determined in control and exposed daphnids at 24, 48, 72, 96 and 120 h. Data were used to calculate caloric content as biomarker of propanil exposure. Results showed a depletion of energy reserves in D. magna exposed to the herbicide. At 120 h of exposure to the highest propanil concentrati…
Photoinduced toxicity of retene to Daphnia magna under enhanced UV-B radiation.
2001
Abstract The effects of UV radiation on the acute toxicity of retene (7-isopropyl-1-methylphenanthrene) to Daphnia magna Straus were studied. Dehydroabietic acid (DHAA) from which retene is formed in the vicinity of pulp and paper industry was also studied. Pyrene, anthracene, and phenanthrene were used as model PAH compounds. The time taken for immobilization (ET50) was monitored under biologically effective UV-B dose rates of 240, 365, 565, and 650 mW m−2 (UV-A and visible light also present). Median effective concentrations (EC50) were determined after a 15-min UV exposure (565 mW m−2) followed by 24 h in the dark. Retene ( 10–320 μg l −1 ) was not acutely toxic in the dark. The inductio…