Bioverfügbarkeit, Bioakkumulation und Toxizität der Platingruppenelemente Pt, Pd und Rh in aquatischen Organismen

Bioverfügbarkeit, Bioakkumulation und Toxizität der Platingruppenelemente Pt, Pd und Rh in aquatischen Organismen Förderkennzeichen (BWBÖ 99008) Bernd Sures, Sonja Zimmermann: Zoologisches Institut I, Ökologie-Parasitologie, Geb. 30.43, Universität Karlsruhe, 76128 Karlsruhe Zusammenfassung Seit Beginn der 80iger Jahre werden in Deutschland durch den Einsatz von Autoabgas-katalysatoren in zunehmendem Umfang die katalytisch wirksamen Platingruppenelemente (PGE) Platin, Palladium und Rhodium emittiert. Jedoch ist bisher unklar, ob diese Metalle für die aquatische Biosphäre verfügbar sind, folglich aufgenommen und akkumuliert werden können. Ziel des hier vorgestellten Forschungsvorhabens ist es, mit verschiedenen aquatischen Organismen zunächst die Frage der Bioverfügbarkeit der Kfz-bürtigen PGE zu klären. Im Rahmen dieses Projektes konnte nun erstmalig nachgewiesen werden, dass das bisher aufgrund der schwierigen Spurenanalytik kaum untersuchte Pd bioverfügbar ist. Nach nur vierwöchiger Exposition von Aalen in Hälterungswasser mit Straßensediment (10 kg/100 l) fand sich in der Leber exponierter Aale eine mittlere Pd-Konzentration von 0,18 ± 0,05 ng/g (FS). Sobald die z.Z. noch laufenden Expositionsversuche abgeschlossen sind, lässt sich auch für Pt und Rh die Frage der Bioverfügbarkeit quantifizieren und das Ausmaß der PGE Akkumulation einschätzen. Summary Following the introduction of automobile catalysts in the middle of the 80th there is an increasing emission of the platinum-group-elements (PGE) platinum, palladium and rhodium. Still, it remains unclear if these metals are bioavailable for aquatic organisms and to which extent they become accumulated by the biosphere. To answer these questions experimental studies were conducted with aquatic animals maintained in water containing road dust (10 kg/100 l). Results from a four weeks exposure study revealed for the first time an uptake of automobile catalyst emitted Pd by European eels which showed a mean liver Pd concentration of 0.18 ± 0.05 ng/g (wet weight). By the end of the present exposure studies also the bioavailability of Pt and Rh as well as the degree of the PGE accumulation will become clear

Aufnahme und Anreicherung KFZ-bürtiger Platingruppenelemente durch Fische, ihre Endoparasiten und Muscheln

Zusammenfassung Die Aufnahme und Anreicherung der KFZ-bürtigen Platingruppenelemente (PGE) Pt, Pd und Rh durch aquatische Tiere wurde an Dreikantmuscheln sowie an Aalen und Barben einschließlich ihrer Darmparasiten untersucht. Hierzu wurden die Testorganismen in Wasser mit Straßenstaub einer stark befahrenen Straße oder mit Autokatalysatormaterial über mehrere Wochen exponiert. Im Rahmen dieses Projektes konnte erstmalig nachgewiesen werden, daß alle drei Metalle durch aquatische Organismen aufgenommen und angereichert werden. Dabei fand sich für Pd die höchste Bioverfügbarkeit, gefolgt von Pt und Rh. Weiterhin geht aus unseren Untersuchungen hervor, daß natürliche Wasserinhaltsstoffe die Aufnahme der PGE durch die Muscheln erhöhen. Nachweisbare PGE-Konzentrationen in den nicht exponierten Kontrollmuscheln, die dem Freiland entnommen wurden, zeigen die zunehmende Bedeutung dieser Metallemissionen für die Biosphäre. Summary The uptake and accumulation of the traffic related platinum group elements (PGE) Pt, Pd and Rh by the aquatic fauna was investigated. Zebra mussels as well as eel and barbel, both infected with intestinal parasites, were maintained in water containing either road dust or ground catalytic converter material. These exposure studies revealed that all three catalyst emitted metals were accumulated by aquatic organisms. The highest bioavailability was found for Pd followed by Pt and Rh. Presence of humic substances in the water enhances the uptake of metals by the mussels. Interestingly, also some of the unexposed animals contained PGE concentrations above the detection limit. This demonstrates the increasing relevance of traffic related metals for the biosphere

Assessing prior knowledge types as predictors of academic achievement in the introductory phase of biology and physics study programmes using logistic regression

Background: Increasingly, high dropout rates in science courses at colleges and universities have led to discussions of causes and potential support measures of students. Students’ prior knowledge is repeatedly mentioned as the best predictor of academic achievement. Theory describes four hierarchically ordered types of prior knowledge, from declarative knowledge of facts to procedural application of knowledge. This study explores the relevance of these four prior knowledge types to academic achievement in the introductory phase of the two science subjects, biology and physics. Results: We assessed the knowledge types at the beginning and student achievement (measured by course completion) at the end of the first study year. We applied logistic regression models to evaluate the relationship between the knowledge types and academic achievement. First, we controlled for a well-established predictor of academic achievement (high school grade point average). Second, we added the knowledge types as predictors. For biology, we found that only knowledge about principles and concepts was a significant predictor in the first year. For physics, knowledge about concepts and principles as well as the ability to apply knowledge to problems was related to academic achievement. Conclusion: Our results concerning the knowledge types, which are of special relevance in biology and physics studies, could lead to effective measures, e.g. for identifying at-risk students and course guidance. Furthermore, the results provide a profound starting point for controlled intervention studies that systematically foster the identified relevant knowledge types in each subject and aim at a theory- and empirical-based optimization of pre- and introductory courses

Larval trematode communities in Radix auricularia and Lymnaea stagnalis in a reservoir system of the Ruhr River

<p>Abstract</p> <p>Background</p> <p>Analysis of the data available from traditional faunistic approaches to mollusc-trematode systems covering large spatial and/or temporal scales in Europe convinced us that a parasite community approach in well-defined aquatic ecosystems is essential for the substantial advancement of our understanding of the parasite response to anthropogenic pressures in urbanised areas which are typical on a European scale. Here we describe communities of larval trematodes in two lymnaeid species, <it>Radix auricularia </it>and <it>Lymnaea stagnalis </it>in four man-made interconnected reservoirs of the Ruhr River (Germany) focusing on among- and within-reservoir variations in parasite prevalence and component community composition and structure.</p> <p>Results</p> <p>The mature reservoir system on the Ruhr River provides an excellent environment for the development of species-rich and abundant trematode communities in <it>Radix auricularia </it>(12 species) and <it>Lymnaea stagnalis </it>(6 species). The lake-adapted <it>R. auricularia </it>dominated numerically over <it>L. stagnalis </it>and played a major role in the trematode transmission in the reservoir system. Both host-parasite systems were dominated by bird parasites (13 out of 15 species) characteristic for eutrophic water bodies. In addition to snail size, two environmental variables, the oxygen content and pH of the water, were identified as important determinants of the probability of infection. Between-reservoir comparisons indicated an advanced eutrophication at Baldeneysee and Hengsteysee and the small-scale within-reservoir variations of component communities provided evidence that larval trematodes may have reflected spatial bird aggregations (infection 'hot spots'). Two life history groupings of dominant species, the 'cyprinid' and 'anatid' parasites, that depict two aspects of progressive eutrophication in this mature reservoir system, were identified.</p> <p>Conclusions</p> <p>We conclude that trematode communities in the lake-adapted <it>R. auricularia </it>are better suited for monitoring the effect of environmental change on host-parasite associations in the reservoir system on the Ruhr River and other similar systems due to the important role of this host in trematode transmission in lakes. Whereas variations in trematode community diversity and abundance may indicate the degree of eutrophication on a larger scale (among reservoirs), the infection rates of the two life history groups of dominant species, the 'cyprinid' and 'anatid' assemblages, may be particularly useful in depicting environmental variability, eutrophication effects and infection 'hot spots' on smaller spatial scales.</p

New cryptic species of the ‘revolutum’ group of Echinostoma (Digenea: Echinostomatidae) revealed by molecular and morphological data

BACKGROUND: The digenean species of Echinostoma (Echinostomatidae) with 37 collar spines that comprise the so-called ‘revolutum’ species complex, qualify as cryptic due to the interspecific homogeneity of characters used to differentiate species. Only five species were considered valid in the most recent revision of the group but recent molecular studies have demonstrated a higher diversity within the group. In a study of the digeneans parasitising molluscs in central and northern Europe we found that Radix auricularia, R. peregra and Stagnicola palustris were infected with larval stages of two cryptic species of the ‘revolutum’ complex, one resembling E. revolutum and one undescribed species, Echinostoma sp. IG. This paper provides morphological and molecular evidence for their delimitation. METHODS: Totals of 2,030 R. auricularia, 357 R. peregra and 577 S. palustris were collected in seven reservoirs of the River Ruhr catchment area in Germany and a total of 573 R. peregra was collected in five lakes in Iceland. Cercariae were examined and identified live and fixed in molecular grade ethanol for DNA isolation and in hot/cold 4% formaldehyde solution for obtaining measurements from fixed materials. Partial fragments of the mitochondrial gene nicotinamide adenine dinucleotide dehydrogenase subunit 1 (nad1) were amplified for 14 isolates. RESULTS: Detailed examination of cercarial morphology allowed us to differentiate the cercariae of the two Echinostoma spp. of the ‘revolutum’ species complex. A total of 14 partial nad1 sequences was generated and aligned with selected published sequences for eight species of the ‘revolutum’ species complex. Both NJ and BI analyses resulted in consensus trees with similar topologies in which the isolates from Europe formed strongly supported reciprocally monophyletic lineages. The analyses also provided evidence that North American isolates identified as E. revolutum represent another cryptic species of the ‘revolutum’ species complex. CONCLUSION: Our findings highlight the need for further analyses of patterns of interspecific variation based on molecular and morphological evidence to enhance the re-evaluation of the species and advance our understanding of the relationships within the ‘revolutum’ group of Echinostoma

Nematode eel parasite found inside acanthocephalan cysts - a "Trojan horse" strategy?

BackgroundThe invasive eel parasite Anguillicoloides crassus (syn. Anguillicola crassus) is considered one of the major causes for the decline of the European eel (Anguilla anguilla) panmictic population. It impairs the swim bladder function and reduces swimming performance of its host. The life cycle of this parasite involves different intermediate and paratenic hosts. Despite an efficient immune system of the paratenic fish hosts acting against infections with A. crassus, levels of parasitized eels remain high in European river systems. Recently, the round goby Neogobius melanostomus (Gobiidae) has become dominant in many rivers in Europe and is still spreading at a rapid pace. This highly invasive species might potentially act as an important, so far neglected paratenic fish host for A. crassus.MethodsBased on own observations and earlier single sightings of A. crassus in N. melanostomus, 60 fresh individuals of N. melanostomus were caught in the Rhine River and examined to assess the infection levels with metazoan parasites, especially A. crassus. Glycerin preparations were used for parasite identification.ResultsThe parasite most frequently found in N. melanostomus was the acanthocephalan Pomphorhynchus sp. (subadult stage) which occurred mainly encysted in the mesenteries and liver. Every third gobiid (P = 31.7%) was infected by A. crassus larvae (L3) which exclusively occurred inside the acanthocephalan cysts. No intact or degenerated larvae of A. crassus were detected elsewhere in the goby, neither in the body cavity and mesenteries nor in other organs. Affected cysts contained the acanthocephalan larvae and 1-12 (mI =3) living A. crassus larvae. Additionally, encysted larvae of the nematode Raphidascaris acus were detected in the gobies, but only in the body cavity and not inside the acanthocephalan cysts.ConclusionsBased on our observations, we suggest that A. crassus might actively bypass the immune response of N. melanostomus by invading the cysts of acanthocephalan parasites of the genus Pomphorhynchus using them as "Trojan horses". Providing that eels prey on the highly abundant round goby and that the latter transfers viable infective larvae of A. crassus, the new paratenic host might have a strong impact on the epidemiology of A. crassu

Eye fluke infection changes diet composition in juvenile European perch (Perca fluviatilis)

Intraspecific diet specialization, usually driven by resource availability, competition and predation, is common in natural populations. However, the role of parasites on diet specialization of their hosts has rarely been studied. Eye flukes can impair vision ability of their hosts and have been associated with alterations of fish feeding behavior. Here it was assessed whether European perch (Perca fluviatilis) alter their diet composition as a consequence of infection with eye flukes. Young-of-the-year (YOY) perch from temperate Lake Müggelsee (Berlin, Germany) were sampled in two years, eye flukes counted and fish diet was evaluated using both stomach content and stable isotope analyses. Perch diet was dominated by zooplankton and benthic macroinvertebrates. Both methods indicated that with increasing eye fluke infection intensity fish had a more selective diet, feeding mainly on the benthic macroinvertebrate Dikerogammarus villosus, while less intensively infected fish appeared to be generalist feeders showing no preference for any particular prey type. Our results show that infection with eye flukes can indirectly affect interaction of the host with lower trophic levels by altering the diet composition and highlight the underestimated role of parasites in food web studies.Leibniz-AssociationPeer Reviewe

Heat sensitivity of first host and cercariae may restrict parasite transmission in a warming sea

To predict global warming impacts on parasitism, we should describe the thermal tolerance of all players in host–parasite systems. Complex life-cycle parasites such as trematodes are of particular interest since they can drive complex ecological changes. This study evaluates the net response to temperature of the infective larval stage of Himasthla elongata, a parasite inhabiting the southwestern Baltic Sea. The thermal sensitivity of (i) the infected and uninfected first intermediate host (Littorina littorea) and (ii) the cercarial emergence, survival, self-propelling, encystment, and infection capacity to the second intermediate host (Mytilus edulis sensu lato) were examined. We found that infection by the trematode rendered the gastropod more susceptible to elevated temperatures representing warm summer events in the region. At 22 °C, cercarial emergence and infectivity were at their optimum while cercarial survival was shortened, narrowing the time window for successful mussel infection. Faster out-of-host encystment occurred at increasing temperatures. After correcting the cercarial emergence and infectivity for the temperature-specific gastropod survival, we found that warming induces net adverse effects on the trematode transmission to the bivalve host. The findings suggest that gastropod and cercariae mortality, as a tradeoff for the emergence and infectivity, will hamper the possibility for trematodes to flourish in a warming ocean

Photoluminescence of Fully Inorganic Colloidal Gold Nanocluster and Their Manipulation Using Surface Charge Effects

International audienceFully inorganic, colloidal gold nanoclusters (NCs) constitute a new class of nanomaterials that are clearly distinguishable from their commonly studied metal–organic ligand-capped counterparts. As their synthesis by chemical methods is challenging, details about their optical properties remain widely unknown. In this work, laser fragmentation in liquids is performed to produce fully inorganic and size-controlled colloidal gold NCs with monomodal particle size distributions and an fcc-like structure. Results reveal that these NCs exhibit highly pronounced photoluminescence with quantum yields of 2%. The emission behavior of small (2–2.5 nm) and ultrasmall (<1 nm) NCs is significantly different and dominated by either core- or surface-based emission states. It is further verified that emission intensities are a function of the surface charge density, which is easily controllable by the pH of the surrounding medium. This experimentally observed correlation between surface charge and photoluminescence emission intensity is confirmed by density functional theoretical simulations, demonstrating that fully inorganic NCs provide an appropriate material to bridge the gap between experimental and computational studies of NCs. The presented study deepens the understanding of electronic structures in fully inorganic colloidal gold NCs and how to systematically tune their optical properties via surface charge density and particle size