rodent
not annotated - annotated - LINNAEUS only
20980515
Reverse genetics generation of chimeric infectious Junin/Lassa virus is dependent on interaction of homologous glycoprotein stable signal peptide and G2 cytoplasmic domains.
The Arenaviridae are a diverse and globally distributed collection of viruses that are maintained primarily by rodent reservoirs. Junin virus (JUNV) and Lassa virus (LASV) can both cause significant outbreaks of severe and often fatal human disease throughout their respective areas of endemicity. In an effort to improve upon the existing live attenuated JUNV Candid1 vaccine, we generated a genetically homogenous stock of this virus from cDNA copies of the virus S and L segments by using a reverse genetics system. Further, these cDNAs were used in combination with LASV cDNAs to successfully generate two recombinant Candid1 JUNV/LASV chimeric viruses (via envelope glycoprotein [GPC] exchange). It was found that while the GPC extravirion domains were readily exchangeable, homologous stable signal peptide (SSP) and G2 transmembrane and cytoplasmic tail domains were essential for correct GPC maturation and production of infectious chimeric viruses. The switching of the JUNV and LASV G1/G2 ectodomains within the Candid1 vaccine background did not alter the attenuated phenotype of the vaccine strain in a lethal mouse model. These recombinant chimeric viruses shed light on the fundamental requirements of arenavirus GPC maturation and may serve as a strategy for the development of bivalent JUNV and LASV vaccine candidates.
21477201
The importance of marine vs. human-induced subsidies in the maintenance of an expanding mesocarnivore in the arctic tundra.
1. Most studies addressing the causes of the recent increases and expansions of mesopredators in many ecosystems have focused on the top-down, releasing effect of extinctions of large apex predators. However, in the case of the northward expansion of the red fox into the arctic tundra, a bottom-up effect of increased resource availability has been proposed, an effect that can counteract prey shortage in the low phase of the multi-annual rodent cycle. Resource subsidies both with marine and with terrestrial origins could potentially be involved. 2. During different phases of a multi-annual rodent cycle, we investigated the seasonal dynamics and spatial pattern of resource use by red foxes across a coast to inland low arctic tundra gradient, Varanger Peninsula, Norway. We employed two complementary methods of diet analyses: stomach contents and stable isotope analysis. 3. We found that inland red foxes primarily subsisted on reindeer carrions during the low phase of a small rodent population cycle. Lemmings became the most important food item towards the peak phase of the rodent cycle, despite being less abundant than sympatric voles. Isotopic signatures of tissue from both predator and prey also revealed that red foxes near the coast used marine-derived subsidies in the winter, but these allochthonous resources did not spillover to adult foxes living beyond 20-25 km from the coast. 4. Although more needs to be learned about the link between increasing primary productivity due to climatic warming and trophic dynamics in tundra ecosystems, we suggest that changes in reindeer management through a bottom-up effect, at least regionally, may have paved the way towards the establishment of a new mesopredator in the tundra biome.
21521215
Effects of individual condition and habitat quality on natal dispersal behaviour in a small rodent.
1. Individuals should benefit from settling in high-quality habitats, but dispersers born under favourable conditions have a better physical condition and should therefore be more successful at settling in high-quality habitats. 2. We tested these predictions with root voles (Microtus oeconomus) by a manipulation of individual condition through litter-size enlargement and reduction during lactation combined with a manipulation of habitat quality through degradation of the vegetation cover. We accurately monitored movements of 149 juveniles during a settlement and breeding period of 3 months. 3. The litter size treatment had long-lasting effects on body size, life-history traits and home range size, but did not influence dispersal behaviour. 4. Different stages of dispersal were influenced by habitat quality. In low-quality patches, females dispersed earlier, spent more time prospecting their environment before settling, and settlers had a smaller adult body size than in high-quality patches. Preference and competition for high-quality patches is likely adaptive as it increased fitness both in terms of survival and reproduction. 5. We found no interactive effect of individual condition and habitat quality on natal dispersal and habitat selection. 6. These findings suggest that immediate conditions are more important determinants of dispersal decisions than conditions experienced early in life.
21498113
New insights into the excystation process and oocyst morphology of rodent Eimeria species.
In this study, the mechanism of excystation of the rodent parasites Eimeria nieschulzi, from rats, and Eimeria falciformis, from mice, was investigated. In vitro, oocysts of both species are susceptible to the protease pepsin, and sporocysts and sporozoites can be excysted in a similar way. Scanning electron microscopy (SEM) revealed a collapse of the oocysts wall at both polar ends after pepsin treatment. This occurs without any visible damage of the outer wall. Using fluorescence and transmission electron microscopy (TEM) we observed that pepsin enters sporulated oocysts at both polar ends and causes degradation of the inner oocyst wall. Using scanning electron microscopy we could identify two polar caps in both investigated rodent Eimeria species, but only one is harbouring the micropyle. Thus the polar caps are the entry site for the pepsin. Furthermore, we provide evidence that the oocyst cap and micropyle are functionally different structures. This study complements the morphological description of both Eimeria species and is of relevance for other coccidian species.