Intra-host competition between co-infecting digeneans within a bivalve second intermediate host: Dominance by priority-effect or taking advantage of others?

We experimentally investigated the interactions between two parasites known to manipulate their host's phenotype, the trematodes Acanthoparyphium sp. and Curtuteria australis, which infect the cockle Austrovenus stutchburyi. The larval stages of both species encyst within the tissue of the bivalve's muscular foot, with a preference for the tip of the foot. As more individuals accumulate at that site, they impair the burrowing behaviour of cockles and increase the probability of the parasites' transmission to a bird definitive host. However, individuals at the foot tip are also vulnerable to non-host predators in the form of foot-cropping fish which selectively bite off the foot tip of exposed cockles. Parasites encysted at the foot base are safe from such predators although they do not contribute to altering host behaviour, but nevertheless benefit from host manipulation as all parasites within the cockle are transmitted if it is ingested by a bird. Experimental infection revealed that Acanthoparyphium sp. and C. australis have different encystment patterns within the host, with proportionally fewer Acanthoparyphium metacercariae encysting at the foot tip than C. australis. This indicates that Acanthoparyphium may benefit indirectly from C. australis and incur a lower risk of non-host predation. However, in co-infections, not only did C. australis have higher infectivity than Acanthoparyphium, it also severely affected the latter's infection success. The asymmetrical strategies and interactions between the two species suggest that the advantages obtained from exploiting the host manipulation efforts of another parasite might be offset by traits such as reduced competitiveness in co-infections.     

Separating water‐potential induced swelling and shrinking from measured radial stem variations reveals a cambial growth and osmotic concentration signal

The quantification of cambial growth over short time periods has been hampered by problems to discern between growth and the swelling and shrinking of a tree stem. This paper presents a model, which separates cambial growth and reversible water‐potential induced diurnal changes from simultaneously measured whole stem and xylem radial variations, from field‐measured Scots pine trees in Finland. The modelled growth, which includes osmotic concentration changes, was compared with (direct) dendrometer measurements and microcore samples. In addition, the relationship of modelled growth and dendrometer measurements to environmental factors was analysed. The results showed that the water‐potential induced changes of tree radius were successfully separated from stem growth. Daily growth predicted by the model exhibited a high correlation with the modelled daily changes of osmotic concentration in phloem, and a temperature dependency in early summer. Late‐summer growth saw higher dependency on water availability and temperature. Evaluation of the model against dendrometer measurements showed that the latter masked a true environmental signal in stem growth due to water‐potential induced changes. The model provides better understanding of radial growth physiology and offers potential to examine growth dynamics and changes due to osmotic concentration, and how the environment affects growth.     

Does doping with aluminum alter the effects of ZnO nanoparticles on the metabolism of soil pseudomonads?

Doping of ZnO nanoparticles (NPs) is being used to increase their commercialization in the optical and semiconductor fields. This paper addresses whether doping with Al alters how ZnO NPs at nonlethal levels modifies the metabolism of soil-borne pseudomonads which are beneficial in performing bioremediation or promoting plant growth. The differences in X-ray diffraction (XRD) patterns, observed between commercial ZnO and Al-doped ZnO NPs indicated the aluminum was present as Al NPs. Both particles aggregated in the bacterial growth medium and formed colloids of different surface charges. They had similar effects on bacterial metabolism: rapid, dose-dependent loss in light output indicative of temporary toxicity in a biosensor constructed in Pseudomonas putida KT2440; increased production of a fluorescent pyoverdine-type siderophore, and decreased levels of indole acetic acid and phenazines in Pseudomonas chlororaphis O6. Solubilization of Zn and Al from the NPs contributed to these responses to different extents. These findings indicate that Al-doping of the ZnO NPs did not reduce the ability of the NPs to alter bacterial metabolism in ways that could influence performance of the pseudomonads in their soil environment.     

Impaired intracellular transport of class I MHC antigens as a possible means for adenoviruses to evade immune surveillance

Early region E3 of adenovirus-2 encodes a glycoprotein, E19, that associates with class I MHC antigens. The interaction occurs concomitantly with abrogated terminal glycosylation of class I antigen heavy chains, as shown by pulse-chase and Endo H digestion experiments. Also the viral protein remains in the high mannose form throughout the chase period. These results do not reflect a general impairment of terminal glycosylation of membrane proteins. Immunofluorescence analyses demonstrated that in virally infected cells E19 and class I antigens accumulate in the perinuclear region. Class I antigens gradually disappear from the cell surface. A diminished cell surface expression of class I antigens may be a means by which adenoviruses evade immune surveillance.     

Exploring key issues of aerobic scope interpretation in ectotherms: absolute versus factorial

Aerobic scope represents an animal’s capacity to increase its aerobic metabolic rate above maintenance levels (i.e. the difference between standard (SMR) and maximum (MMR) metabolic rates). Aerobic scope data can be presented in absolute or factorial terms (AAS or FAS, respectively). However, the robustness of these calculations to noise or variability in measures of metabolic rate can influence subsequent interpretations of patterns in the data. We explored this issue using simple models and we compared the predictions from these models to experimental data from the literature. First, we investigated the robustness of aerobic scope calculations as a function of varying SMR when MMR is fixed, and vice versa. While FAS is unexpectedly robust to variability in SMR, even in species with low aerobic scopes, AAS is less sensitive to variation in SMR than is FAS. However, where variation in MMR is the main concern, FAS is more robust than AAS. Our findings highlight the equal importance of minimising variability in MMR, rather than just the variability in SMR, to obtain robust aerobic scope estimates. Second, we analysed metabolic rate accounting for locomotor speed and body mass for swimming fish. The interactions among these factors in relation to AAS and FAS are complex and the appropriate metric is dependent on the specific eco-physiological context of the research question. We conclude with qualified recommendations for using and interpreting AAS and FAS.     

Eight new species of Hieracium sect. Tridentata (Asteraceae) from southern and northern Sweden

Eight new species of Hieracium sect. Tridentata, namely H. antrorsum, H. quercifolium, H. stenianum, H. vestrogothicum, and H. vetlandaënse are described from the Götaland region (southern Sweden), H. grothii from Norrbotten in the Norrland region (northeast Sweden), and H. sparsifolium var. suppansum Johanss. and H. adampliatum var. pilosius Ohlsén are raised to specific rank as H. suppansum and H. gothiciferum respectively.