Helophyte germination in a Mediterranean salt marsh: Gut‐passage by ducks changes seed response to salinity

Question: In seeds which are regularly consumed by waterbirds in the field, how does gut‐passage modify their response to salinity gradients? Location: Doñana National Park salt marsh, south‐west of Spain. Methods: Seeds of Scirpus litoralis and Scirpus maritimus were collected and force fed to mallards (Anas platyrhynchos). Both the ingested seeds (passage) and non‐ingested seeds (controls) were exposed, in germination chambers, to a salinity range similar to that observed in the field (0–32 dS/m). After 30 days, the total percentage germination, the duration of the dormancy period and the germination speed were computed. The response of the different germination parameters to ingestion and salinity was analyzed using generalized lineal models. Recovery tests on seeds that did not germinate in the various treatments and tests of the effect of ingestion on the intrinsic variability in seed response were also performed. Results: An increase in salinity reduced germinability and increased the length of dormancy, while gut pas sage increased the intrinsic variability of the temporal seed response in both species. In S. litoralis there was a significant interaction between the effects of salinity and passage on germination rate. Passage increased germination rate at low salinities (≤2 dS/m) but decreased it at high salinities (≥4 dS/m). Conclusion: Gut‐passage by ducks significantly changes seed response to salinity. The outcome of plant‐animal interactions can be influenced by environmental gradients. Studies of germination in response to gut passage that do not take such gradients into account may produce misleading results.     

Avian malaria infection intensity influences mosquito feeding patterns

Pathogen-induced host phenotypic changes are widespread phenomena that can dramatically influence host–vector interactions. Enhanced vector attraction to infected hosts has been reported in a variety of host–pathogen systems, and has given rise to the parasite manipulation hypothesis whereby pathogens may adaptively modify host phenotypes to increase transmission from host to host. However, host phenotypic changes do not always favour the transmission of pathogens, as random host choice, reduced host attractiveness and even host avoidance after infection have also been reported. Thus, the effects of hosts’ parasitic infections on vector feeding behaviour and on the likelihood of parasite transmission remain unclear. Here, we experimentally tested how host infection status and infection intensity with avian Plasmodium affect mosquito feeding patterns in house sparrows (Passer domesticus). In separate experiments, mosquitoes were allowed to bite pairs containing (i) one infected and one uninfected bird and (ii) two infected birds, one of which treated with the antimalarial drug, primaquine. We found that mosquitoes fed randomly when exposed to both infected and uninfected birds. However, when mosquitoes were exposed only to infected individuals, they preferred to bite the non-treated birds. These results suggest that the malarial parasite load rather than the infection itself plays a key role in mosquito attraction. Our findings partially support the parasite manipulation hypothesis, which probably operates via a reduction in defensive behaviour, and highlights the importance of considering parasite load in studies on host–vector–pathogen interactions.     

Replicability of dominant bacterial populations after long-term surfactant-enrichment in lab-scale activated sludge

Bacterial communities were examined in replicate lab-scale activated sludge reactors after a period of several months of enrichment with non-ionic nonylphenol ethoxylate (NPE) surfactants. Four sequential batch reactors were fed with synthetic sewage, two of which received additionally NPE. Small subunit rDNA-derived denaturing gel gradient electrophoresis (DGGE) profiles and 16S rDNA clone libraries were dominated by clones of Gammaproteobacteria class. Sequences of the other codominant rDNA phylotypes observed only in DGGE from NPE-amended reactors were, respectively, associated with the Group III of the Acidobacteria phylum. Intriguingly, 16S rRNA content from abundant Gammaproteobacteria cells was unexpectedly low. In addition to Acidobacteria, rRNA-derived DGGE profiles were dominated by members of the order Burkholderiales (of the Betaproteobacteria) and of the genus Sphingomonas (a member of the Alphaproteobacteria). Specific oligonucleotide probes for the selected ribotypes were designed and applied for quantitative real time polymerase chain reaction and fluorescence in situ hybridization, confirming their dominance in treated reactors. The parallel abundance of unique phylotypes in replicate reactors implies a distinctive selection of dominant organisms, which are better adapted to specialized niches in the highly selective environment.     

Sex differences in the stopover ecology of Curlew Sandpipers Calidris ferruginea at a refuelling area during autumn migration

We investigated the stopover patterns of male and female Curlew Sandpipers at a stopover area in northeast Spain. Curlew Sandpipers were trapped and colour-ringed during autumn migration in 1992 and 1993. Stopover length was similar to those reported previously for this and other waders that migrate using a small number of widely separated staging areas, but were greater than stopovers reported for other waders that migrate using a large number of staging areas separated by short distances. The differences in stopover length between the birds using these two strategies could be related to the fuel reserves that have to be accumulated to reach the next staging area. Males stayed longer in the area than females. Seasonal changes in prey availability or sex differences in moulting and migratory patterns do not account for these differences in stopover ecology. Following a time-selected model of optimal migration, sex differences in stopover ecology could be related to a dominance of the larger females over the males or to a higher foraging efficiency or a shorter search and settling time in females. Whether these differences are restricted to the studied area or are widespread in other staging areas used by the species could be important for assessing the possible differences in the migration speed of Curlew Sandpipers. The finding that males leave the breeding grounds 21–35 days before females but arrive at the study area with only a 10-day difference supports the hypothesis that females migrate faster than males at least in the first half of their migration.     

Understanding phenotypic responses to global change

Editor's suggested further reading in BioEssays: Evolution in response to climate change: In pursuit of the missing evidence Abstract How will fish that evolved at constant sub‐zero temperatures cope with global warming? Notothenioids as a case study Abstract     

Antioxidant machinery differs between melanic and light nestlings of two polymorphic raptors

Colour polymorphism results from the expression of multiallelic genes generating phenotypes with very distinctive colourations. Most colour polymorphisms are due to differences in the type or amount of melanins present in each morph, which also differ in several behavioural, morphometric and physiological attributes. Melanin-based colour morphs could also differ in the levels of glutathione (GSH), a key intracellular antioxidant, because of the role of this molecule in melanogenesis. As GSH inhibits the synthesis of eumelanin (i.e. the darkest melanin form), individuals of darker morphs are expected to have lower GSH levels than those of lighter morphs. We tested this prediction in nestlings of two polymorphic raptors, the booted eagle Hieraaetus pennatus and the Eleonora's falcon Falco eleonorae, both of which occur in two morphs differing in the extent of eumelanic plumage. As expected, melanic booted eagle nestlings had lower blood GSH levels than light morph eagle nestlings. In the Eleonora's falcon, however, melanic nestlings only had lower GSH levels after controlling for the levels of other antioxidants. We also found that melanic female eagle nestlings had higher levels of antioxidants other than GSH and were in better body condition than light female eagle nestlings. These findings suggest an adaptive response of melanic nestlings to compensate for reduced GSH levels. Nevertheless, these associations were not found in falcons, indicating species-specific particularities in antioxidant machinery. Our results are consistent with previous work revealing the importance of GSH on the expression of melanic characters that show continuous variation, and suggest that this pathway also applies to discrete colour morphs. We suggest that the need to maintain low GSH levels for eumelanogenesis in dark morph individuals may represent a physiological constraint that helps regulate the evolution and maintenance of polymorphisms.     

Characterization of polymorphic microsatellite markers in the brine shrimp Artemia (Branchiopoda, Anostraca)

The brine shrimp Artemia is a complex genus containing sexual species and parthenogenetic lineages. Artemia franciscana is native to America and its cysts (diapausing eggs) are used worldwide as a food source in aquaculture. As a consequence, this anostracan has become an invasive species in many hypersaline aquatic ecosystems of other continents. Parthenogenetic Artemia lineages occur only in the Old World. Ten and five microsatellite markers were developed to characterize two populations for A. franciscana and two populations for diploid parthenogenetic Artemia, respectively. For A. franciscana the number of alleles ranged from 11 to 58 per locus, while for parthenogens the number of alleles ranged from three to 10. The levels of heterozygosity in A. franciscana and in parthenogens ranged from 0.115 to 0.976 and from 0.000 to 0.971, respectively. These microsatellite loci showed a high population assignment power, which will be useful for future studies of population genetics and invasive processes in Artemia.     

Cost-Minimization Analysis Favours Intravenous Ferric Carboxymaltose over Ferric Sucrose for the Ambulatory Treatment of Severe Iron Deficiency

Objective

Intravenous iron is widely used to treat iron deficiency in day-care units. Ferric carboxymaltose (FCM) allows administration of larger iron doses than iron sucrose (IS) in each infusion (1000 mg vs. 200 mg). As FCM reduces the number of infusions required but is more expensive, we performed a cost-minimization analysis to compare the cost impact of the two drugs.

Materials and Methods

The number of infusions and the iron dose of 111 consecutive patients who received intravenous iron at a gastrointestinal diseases day-care unit from 8/2007 to 7/2008 were retrospectively obtained. Costs of intravenous iron drugs were obtained from the Spanish regulatory agencies. The accounting department of the Hospital determined hospital direct and indirect costs for outpatient iron infusion. Non-hospital direct costs were calculated on the basis of patient interviews. In the pharmacoeconomic model, base case mean costs per patient were calculated for administering 1000 mg of iron per infusion using FCM or 200 mg using IS. Sensitivity analysis and Monte Carlo simulation were performed.

Results

Under baseline assumptions, the estimated cost of iron infusion per patient and year was €304 for IS and €274 for FCM, a difference of €30 in favour of FCM. Adding non-hospital direct costs to the model increased the difference to €67 (€354 for IS vs. €287 for FCM). A Monte Carlo simulation taking into account non-hospital direct costs favoured the use of FCM in 97% of simulations.

Conclusion

In this pharmacoeconomic analysis, FCM infusion reduced the costs of iron infusion at a gastrointestinal day-care unit.