Simian Tumour Virus Proliferation in Inoculated <Emphasis Type="Italic">Macaca mulatta</Emphasis>

AN oncorna-type virus (M-PMV) was detected in a spontaneous breast tumour of a female rhesus monkey^1,2. This virus is morphologically and biochemically similar to oncogenic RNA viruses of other species^3–5. Using in vitro tissue culture assays and electron microscopy we have observed proliferation of infectious virus in hyperplastic lymph nodes of M-PMV inoculated infant rhesus monkeys.     

Production of θ Antibody by Mice that Fail to Reject θ-Incompatible Skin Grafts

EVIDENCE that female mice failing to reject male skin grafts are nevertheless producing H-Y antibody indicates that graft survival in this case is not due to failure of the recipient to respond to graft antigens¹. Survival of skin grafts in recipients that are producing specific anti-graft antibody is known in another system: radiation chimaeras of constitution (C57BL × A)→A often fail to reject C57BL skin grafts² although they are producing Sk alloantibody³. Sk alloantigens are limited to epidermal cells and brain and so give rise to skin-selective homograft reactions by radiation chimaeras^2,3.     

The recent diatom history of Loch Leven, Kinross

Diatoms in the top metre of lake sediment have been studied for indications or recent changes in the environment of Loch Leven. The diatoms indicate a eutrophic, alkaline lake with Melosira italica ssp. subarctica, Tabellaria Flocculosa and Stephanodiscus astraea the dominant taxa at the base of the 1-m section. There is then an appeance of Melosira ambigua and Stephanodiscus hantzschii suggesting a richer environment. Post A.D. 1816 changes in taxa suggest possible correlation with the lowering of lake level in 1830 and the dominance of Diatoma elongatum, Cyclotella pseudostelligera, Stephanodiscus astraea var. minutula, S. tenuis, S. hantzschii, and Synedra rumpens and var. soctica in zone 4 agrees with present-day plankton records.     

How protective are refuges? Quantifying algal protection in rock crevices

1. Refuges can be functionally important if they harbour sufficient organisms during disturbance to augment population recovery. I quantified the protection of stream algae in crevice refuges using the applied, severe disturbance of scrubbing. Scrubbing effectively removed visible surface algae, and algae remaining on stones were considered protected. 2. In a field experiment, substrata with different quantities of crevice (glass bottles; greywacke; schist; pumice) were incubated in a channelised stream. The possible influence of growth conditions was investigated concurrently; half of the substrata were suspended in the water column, the rest were placed on the bottom (providing differential access to grazers and exposing them to different flow conditions). 3. Rougher substrata had greater total algal biomass than smoother substrata; this pattern resulted from more algal biomass in crevices of the rougher substrata. Protection from scrubbing ranged from about 5% of total algal biomass on glass and greywacke to 80% on pumice. In contrast, algal biomass removed by scrubbing was similar among the experimental substrata. Suspended substrata had more chironomid grazers than those on the bottom, and also greater algal biomass, possibly because of high algal concentrations in the chironomid retreats. 4. A survey of stones from three rivers supported the experimental results; namely, rough pumice protected more algae from scrubbing than did smoother greywacke. 5. In a separate experimental assay, there was no difference in algal growth on agar plates with and without added powdered rock substrata, suggesting that crevice characteristics and not substratum chemistry produced the differences in algal assemblages between rough and smooth surfaces. 6. Results indicate that rough stream stones may protect sufficient algae to augment their recovery in streams following disturbance.     

Methane bubbles in surface peat cores: in situ measurements

The quantification of greenhouse gas sources and sinks is important to understanding the impact of climate change. Methane (CH₄) is a potent greenhouse gas, which, on a global scale, is released largely as a product of anaerobic microbial decomposition and predominantly from wetlands. A zone of intense CH₄ production just below the water table is thought to contribute significantly to the overall flux from peat bogs. We describe the use of membrane inlet quadrupole mass spectrometry (QMS) to confirm the existence of bubbles, their gaseous concentrations and their localization at a fine spatial resolution within intact peat cores. We use the distribution of the noble gas argon (Ar) and the distinct QMS responses to dissolved and gaseous (bubble) phases to identify trapped bubbles with a resolution of 0.6 mm. Bubbles with CH₄ concentrations of up to 20 kPa were widely distributed in the upper 300 mm of the cores with ～11% of all profiles comprising bubbles. The dissolved concentrations responsible for the bubbles were on average 83±80 μm , indicating lower concentrations relative to other QMS studies. We suggest that if the distinction between dissolved and gaseous phases is not made in studies of CH₄ within peat profiles then the prominence of bubbles is likely to result in overestimates of dissolved CH₄ concentrations. Fluxes of CH₄ from peat as a result of drawdown or other perturbation are likely to be large, rapid and short lived because of bubble burst, and also larger than from peat without bubbles. We suggest that the dynamics of fluxes need to be modelled taking into account both gaseous and dissolved phases. Estimates of potential fluxes that assume CH₄ is dissolved are likely to overestimate fluxes if the gaseous phase has not been taken into account.     

PARALLEL EVOLUTION OF HAND ANATOMY IN KANGAROOS AND VOMBATIFORM MARSUPIALS: FUNCTIONAL AND EVOLUTIONARY IMPLICATIONS

Abstract:  The anatomy of the mammalian hand is exposed to an intriguing interplay between phylogeny and function, and provides insights on phylogenetic affinities as well as locomotory habits of extinct species. Within the marsupial order Diprotodontia, terrestrial plantigrade quadrupedalism evolved twice, in the mostly extinct vombatiforms and in extant macropodoids. To assess the influence of functional and phylogenetic signal on the manus in these two clades, manual anatomy and digital proportions in specimens of eight extinct and three extant vombatiforms were investigated and compared with extant macropodoids and extant possums. The results reveal extensive parallelisms in the carpal region of vombatiforms and macropodoids, including flattened distal metacarpal facets, reduction of the palmar process of the hamatum, reduction of mid-wrist joint curve, extensive hamatum/scaphoid contact, and absence of a lunatum. These transformations appear to be related to stabilization of the wrist for plantigrade locomotion. Vombatiforms are apomorphic in scaphoid and triquetrum anatomy and their metacarpals are much more gracile than in other Diprotodontia. Manual diversity is greater in vombatiforms than in macropodoids, as probably was locomotor diversity. Digital proportions as well as wrist anatomy divide the extinct vombatiforms into species resembling arboreal diprotodontians, whereas others group with terrestrial quadrupedal kangaroos and wombats. The latter is suggested to be owing to plantigrade locomotion and/or large size. Carpal anatomy and digital proportions suggest that a range of earlier diverging vombatiforms may have been arboreal or scansorial. As such, we propose that the ancestor of extant vombatiforms (koalas and wombats) may have been arboreal, an option that deserves consideration in the reconstruction of vombatiform evolution.     

Sticky bivalves from the Mesozoic: clues to the origin of the anomalodesmatan arenophilic system

Arenophilic glands represent the only molluscan example of multicellular organs solely concerned with adhesion of foreign particles to the external surfaces of an organism. The glands are exclusive to the bivalve clade Anomalodesmata, but do not occur in all component taxa, having been declared absent in a number of families, including Pholadomyidae. This paper records and describes for the first time the arenophilic apparatus of Pholadomya candida G. B. Sowerby I, 1823, and demonstrates that secretion from these glands is at times preserved in the fossil record. In P. candida , arenophilic glands in the middle mantle folds discharge their products on top of the shell as the animal grows, forming radial lines of secretion that comprise a meandering main strand and numerous thin threads projecting in tufts. The arrangement is similar to that of other families, corroborating the hypothesis that the glands are a synapomorphy of crown-group anomalodesmatans. Instances of preserved secretion in fossil Pholadomya , ranging in age almost to the initial appearance of the genus in the Late Triassic, suggest that fossilized arenophilic secretion may aid systematic studies of problematic fossil groups traditionally included in Anomalodesmata.     

Gene expression profiling: opening the black box of plant ecosystem responses to global change

The use of genomic techniques to address ecological questions is emerging as the field of genomic ecology. Experimentation under environmentally realistic conditions to investigate the molecular response of plants to meaningful changes in growth conditions and ecological interactions is the defining feature of genomic ecology. Because the impact of global change factors on plant performance are mediated by direct effects at the molecular, biochemical, and physiological scales, gene expression analysis promises important advances in understanding factors that have previously been consigned to the 'black box' of unknown mechanism. Various tools and approaches are available for assessing gene expression in model and nonmodel species as part of global change biology studies. Each approach has its own unique advantages and constraints. A first generation of genomic ecology studies in managed ecosystems and mesocosms have provided a testbed for the approach and have begun to reveal how the experimental design and data analysis of gene expression studies can be tailored for use in an ecological context.     

Quantifying the impact of current and future tropospheric ozone on tree biomass, growth, physiology and biochemistry: a quantitative meta-analysis

The northern hemisphere temperate and boreal forests currently provide an important carbon sink; however, current tropospheric ozone concentrations ([O₃]) and [O₃] projected for later this century are damaging to trees and have the potential to reduce the carbon sink strength of these forests. This meta‐analysis estimated the magnitude of the impacts of current [O₃] and future [O₃] on the biomass, growth, physiology and biochemistry of trees representative of northern hemisphere forests. Current ambient [O₃] (40 ppb on average) significantly reduced the total biomass of trees by 7% compared with trees grown in charcoal‐filtered (CF) controls, which approximate preindustrial [O₃]. Above‐ and belowground productivity were equally affected by ambient [O₃] in these studies. Elevated [O₃] of 64 ppb reduced total biomass by 11% compared with trees grown at ambient [O₃] while elevated [O₃] of 97 ppb reduced total biomass of trees by 17% compared with CF controls. The root‐to‐shoot ratio was significantly reduced by elevated [O₃] indicating greater sensitivity of root biomass to [O₃]. At elevated [O₃], trees had significant reductions in leaf area, Rubisco content and chlorophyll content which may underlie significant reductions in photosynthetic capacity. Trees also had lower transpiration rates, and were shorter in height and had reduced diameter when grown at elevated [O₃]. Further, at elevated [O₃], gymnosperms were significantly less sensitive than angiosperms. There were too few observations of the interaction of [O₃] with elevated [CO₂] and drought to conclusively project how these climate change factors will alter tree responses to [O₃]. Taken together, these results demonstrate that the carbon‐sink strength of northern hemisphere forests is likely reduced by current [O₃] and will be further reduced in future if [O₃] rises. This implies that a key carbon sink currently offsetting a significant portion of global fossil fuel CO₂ emissions could be diminished or lost in the future.     

Differential Responses of Postmetamorphic Amphibians to Cattle Grazing in Wetlands

ABSTRACT Global amphibian declines have been linked to various anthropogenic land uses. Recent studies have documented negative impacts of cropland agriculture and deforestation on amphibians; however, few have examined potential impacts of cattle grazing in wetlands on resident amphibians. Therefore, we measured differences in number of captures and body size of postmetamorphic amphibians, egg mass abundance, and shoreline vegetation structure and composition between 4 wetlands with direct cattle access and 4 wetlands from which cattle were excluded on the Cumberland Plateau in Tennessee, USA. We captured amphibians at wetlands from March to August 2005 and 2006 using pitfall traps. Number of green frog (Rana clamitans) metamorphs captured at nonaccess wetlands was 2.5 times and 9.8 times greater than at wetlands with cattle access in 2005 and 2006, respectively. However, number of American toads (Bufo americanus) captured was 68 times and 76 times greater at cattle-access wetlands in 2005 and 2006, respectively. In general, metamorph body size was negatively correlated with species-specific capture rate. We detected no differences in egg mass abundance between cattle land-use types. Height, percent horizontal cover, and percent vertical cover of shoreline vegetation were 74%,25%, and 84% greater, respectively, in nonaccess wetlands in 2005; vegetation trends were similar in 2006. Our results suggest that cattle impact amphibian populations but effects vary by species. Differences in postmetamorphic capture rate may be related to less emergent vegetation at cattle-access wetlands. Although body size differed between land uses for metamorphs, these trends probably were short-lived, because we did not detect differences in juvenile and adult body size between land uses for most species. Based on our findings, we suggest that fencing cattle from wetlands may be a prudent conservation strategy for some amphibian species (e.g., ranids), whereas other species (e.g., bufonids) may benefit from controlled grazing.