The influence of behaviour and season on habitat selection by a small mammal

This study examined the selection of habitat by Ningaui yvonneae , a small, nocturnal insectivorous marsupial of semi-arid regions of southern Australia. In addition to idengifying habitat preferences, the study was concerned with idengifying how habitats were used, and for what purpose they were valued. Triodia irritans (hummock grass) was the most preferred habitat component overall. However, other habitat components were found to be of equal or greater preference during certain seasons and for certain behaviours. The importance of considering behaviour in studies of habitat selection was discussed. Habitat selection by N. yvonneae appeared to be influenced by predation risk and energetic reward. The selection for Triodia is thought to be due to its provision of protection and foraging opportunities. However, leaf litter was preferred over Triodia for foraging, possibly because it offered greater energetic returns. To minimise predation risk while in leaf litter, ningauis remained close to Triodia and moved larger prey items to the edge of Triodia for consumption.     

Differential modulation of human epidermal Langerhans cell maturation by ultraviolet B radiation.

UVB irradiation of the skin causes immunosuppression and Ag-specific tolerance in which Langerhans cells (LC) are involved. We tested the effect of UVB on LC that had migrated out of cultured epidermal sheets derived from the skin that was irradiated ex vivo (200, 400, 800, or 1600 J/m2). Two separate subpopulations of LC were distinguished: large-sized LC with high HLA-DR expression, and HLA-DR-low, small LC. UVB stimulated the maturation of the former LC subset as demonstrated by enhanced up-regulation of CD80, CD86, CD54, CD40, and CD83 and reduced CD1a expression in comparison with unirradiated controls. In contrast, the latter LC exhibited little or no up-regulation of these molecules except for high CD1a expression and high binding of annexin V, indicating that they were apoptotic, although their CD95 expression was relatively low. Stimulation of enriched LC with CD40 ligand-transfected cells and IFN-gamma revealed that the release of IL-1beta, IL-6, IL-8, and TNF-alpha was enhanced by UVB. In comparison with HLA-DR-low LC, HLA-DR-high LC were the principal IL-8 producers as demonstrated by intracellular cytokine staining, and they retained more accessory function. There was no detectable secretion of IL-12 p70, and IL-18 production was neither affected by any stimulus nor by UVB. These results suggest a dual action of UVB on LC when irradiated in situ: 1) immunosuppression by preventing maturation and inducing apoptotic cell death in part of LC, and 2) immunopotentiation by enhancing the up-regulation of costimulatory molecules and the production of proinflammatory cytokines in another part.     

Some notes on differential chromosome activity inDrosophila

In the lethal mutantltl ofDrosophila melanogaster, a characteristic pattern of puffs on the right arm of the third chromosome is described. This pattern includes anaerobiosis puffs in some of the lethal larvae. Puffing, and incorporation of radioactive uridine was observed even at advanced stages of disintegration. From the behaviour of the chromosomes it may be concluded that the internal milieu ofltl larvae differs from that of artificially (by ligating) over-aged wild type larvae as well as from that of the imago.     

Etiological aspects of congenital diaphragmatic hernia: results of a case comparison study

We report the results of a parental questionnaire concerning possible etiological and teratological factors, such as exposure to herbicides, in the development of congenital diaphragmatic hernia (CDH). The herbicide Nitrofen interferes with lung development in rats, can induce diaphragmatic hernia and greatly resembles thyroid hormone. No association with the studied teratogens nor with maternal thyroid dysfunction was found. The questionnaire was completed by 33 parents whose baby had CDH, and by 43 couples whose baby had oesophageal atresia. The resemblance of Nitrofen to thyroid hormone, a well-known growth factor for the developing lung, is of particular interest from a pathogenetic point of view in the development of CDH.     

Plastics select for distinct early colonizing microbial populations with reproducible traits across environmental gradients

Little is known about early plastic biofilm assemblage dynamics and successional changes over time. By incubating virgin microplastics along oceanic transects and comparing adhered microbial communities with those of naturally occurring plastic litter at the same locations, we constructed gene catalogues to contrast the metabolic differences between early and mature biofilm communities. Early colonization incubations were reproducibly dominated by Alteromonadaceae and harboured significantly higher proportions of genes associated with adhesion, biofilm formation, chemotaxis, hydrocarbon degradation and motility. Comparative genomic analyses among the Alteromonadaceae metagenome assembled genomes (MAGs) highlighted the importance of the mannose-sensitive hemagglutinin (MSHA) operon, recognized as a key factor for intestinal colonization, for early colonization of hydrophobic plastic surfaces. Synteny alignments of MSHA also demonstrated positive selection for mshA alleles across all MAGs, suggesting that mshA provides a competitive advantage for surface colonization and nutrient acquisition. Large-scale genomic characteristics of early colonizers varied little, despite environmental variability. Mature plastic biofilms were composed of predominantly Rhodobacteraceae and displayed significantly higher proportions of carbohydrate hydrolysis enzymes and genes for photosynthesis and secondary metabolism. Our metagenomic analyses provide insight into early biofilm formation on plastics in the ocean and how early colonizers self-assemble, compared to mature, phylogenetically and metabolically diverse biofilms.     

Female‐biased sex allocation and lack of inbreeding avoidance in Cubitermes termites

Sexually reproducing organisms face a strong selective pressure to find a mate and ensure reproduction. An important criterion during mate‐selection is to avoid closely related individuals and subsequent potential fitness costs of resulting inbred offspring. Inbreeding avoidance can be active through kin recognition during mate choice, or passive through differential male and female‐biased sex ratios, which effectively prevents sib‐mating. In addition, sex allocation, or the resources allotted to male and female offspring, can impact mating and reproductive success. Here, we investigate mate choice, sex ratios, and sex allocation in dispersing reproductives (alates) from colonies of the termite Cubitermes tenuiceps. Termites have a short time to select a mate for life, which should intensify any fitness consequences of inbreeding. However, alates did not actively avoid inbreeding through mate choice via kin recognition based on genetic or environmental cues. Furthermore, the majority of colonies exhibited a female‐biased sex ratio, and none exhibited a male‐bias, indicating that differential bias does not reduce inbreeding. Sex allocation was generally female‐biased, as females also were heavier, but the potential fitness effect of this costly strategy remains unclear. The bacterium Wolbachia, known in other insects to parasitically distort sex allocation toward females, was present within all alates. While Wolbachia is commonly associated with termites, parasitism has yet to be demonstrated, warranting further study of the nature of the symbiosis. Both the apparent lack of inbreeding avoidance and potential maladaptive sex allocation implies possible negative effects on mating and fitness.