The sinking ark: pollution and the worldwide loss of biodiversity

Humans are making increasing demands on natural ecosystems. One recent study has concluded that our species is consuming or diverting some 40% of the net photosynthetic productivity of our planet. Many habitats are being converted to simpler systems which provide more harvestable goods to people. As a result, genetic diversity, species and whole ecosystems are disappearing; some scientists suggest that as many as 25% of the world's species could be lost in the next several decades.The sinking ark is usually characterized in terms of pollution, habitat loss, poaching, introduced species and illegal trade in wildlife products, but these are symptoms rather than causes. At a more fundamental level, many of the same factors which have enabled pollution to become such a problem have also been responsible for the loss in biodiversity; the most important factor is that the effects of pollutants on biodiversity have been considered an externality, an unintended side effect of industrial activity which brought measurable benefits to people. Development activities which have depleted biodiversity have proven profitable only because the real costs have been hidden.Keeping the ark afloat will require the Five-I Approach: investigation (learning how natural systems function); information (ensuring that the facts are available to inform decisions); incentives (using economic tools to help conserve biodiversity); integration (promoting a cross-sectoral approach to conserving biodiversity); and international support (building productive collaboration for conserving biodiversity).     

Cold shock and heat shock: a comparison of the protection generated by brief pretreatment at less severe temperatures

Abstract Brief exposure to low (0^oC) or high (40^oC) temperature elicits a protective response that prevents injury when the flesh fly, Sarcophaga crassipalpis Macquart, is subjected to more severe cold (-10^oC) or heat (45^oC). Both the low and high temperature responses were found in all developmental stages of the fly, but were most pronounced in the pupal and pharate adult stages. The protective responses generated by brief exposure to 0 or 40^oC appear similar in that both result in a rapid acquisition of cold or heat tolerance and a loss of protection after the flies are returned to 25^oC. The protection generated by chilling is obvious within 10 min of exposure to 0^oC while a 30 min exposure to 40^oC is required to induce the high temperature protection. High temperature protects against cold shock injury within a narrow range (around 36^oC) but we have no evidence that low temperature can protect against heat injury. We previously demonstrated that the rapid increase in cold tolerance correlates with concomitant increases in glycerol concentration, but in this study we found no significant elevation in glycerol in heat-shocked flies. Thus the physiological and biochemical bases for the rapid responses to cold and heat appear to be different.     

Birgean heat budgets and rates of heat uptake in two monomictic lakes

Thermal profile development, rates of heat uptake and annual heat budgets are presented for two monomictic lakes, Whatcom and Washington, in the Puget Sound lowlands of Washington State. The rates of heat gain in the lakes were found to be significantly affected by lake morphometry. In turn, the differing rates of heat gain affected the annual heat budgets.     

Indication for deletion of two introns in theoxi-3 gene of a respiratory-competentSaccharomyces cerevisiae strain

Physical mapping of the mitochondrial DNA of the wild-typeSaccharomyces cerevisiae strainRXII revealed that most of the restriction sites as well as the location of the apocytochromeb gene were identical in comparison with the known maps of the mitochondrial genome in otherSaccharomyces cerevisiae strains. In the middle of theSalI linearized map of theRXII mitochondrial DNA, a deletion was detected which resulted in the loss of twoEcoRI and oneBamHI restriction sites. The corresponding region, however, exists in most other laboratory strains ofSaccharomyces mapped so far. This region overlaps the introns aI2 and aI3 surrounding exon A3 sequences of the subunit 1 of the cytochrome oxidase gene. The nucleotide sequence of the subunit 1 gene showed that theBamHI site was located close to the aI3-A4 intron-exon junction and the distalEcoRI site close to the aI2-A2 boundary. I therefore conclude that these two introns are deleted in the mitochondrial genome of strainRXII. The exon A3 must have been conserved since this strain was respiratory competent. This result, while being a good example of the morphological diversity of a genome with the same function, may contribute to an understanding of the role of introns in the mitochondrial split genes in yeast.     

The influence of invertebrates on the breakdown ofPotamogeton pectinatus L. in a coastal marina (Zandvlei,South Africa)

The influence of invertebrates upon the decomposition ofPotamogeton pectinatus L. in a coastal Marina system was examined over 112 days using litter bags. Invertebrate inclusion bags (2 mm mesh, 5 mm holes) registered a dry mass loss of 1% d^–1, while exclusion litter bags (80 µm mesh) produced a 0.4% mass loss d^–1 (a 2.5 fold difference). Losses of ash and N from inclusion bags were greater than those from exclusion bags (p < 0.05). There was a three fold difference between the two treatments in the time taken for litter to breakdown to half the initial stock: T_1/2 for inclusion bags = 43 d, exclusion bags = 130 d. In both treatments, minerals showed an expected rapid loss, due to leaching, with a subsequent slow increase relative to the dry material remaining. A total of nine invertebrate taxa was recorded from inclusion bags, with a peak biomass of 64 mg g^–1 dry massPotamogeton bag^–1 reached at 64 days after immersion. Grazing amphipods,Melita zeylanica Stebbing andAustrochiltonia subtenuis (Barnard), numerically dominated the litter bag fauna, whileM. zeylanica and nymphs of the zygopteran predatorIschnura senegalensis (Rambur) formed most of the biomass. Scanning Electron Microscopy indicated heavy grazing of micro-organisms by invertebrates, with major qualitative differences occurring 112 days after immersion. Invertebrates significantly accelerated the rate of litter breakdown through their feeding activities, assisting fragmentation and thus contributing to plant losses and also by increasing the surface area for microbial colonisation and attack.     

Aerenchyma and lenticel formation in pine seedlings: A possible avoidance mechanism to anaerobic growth conditions

Seedlings of pond pine ( Pinus serotina Michx.), sand pine [ P. clausa (Engelm.) Sarg.], and loblolly pine ( P. taeda L., wet-site and drought-hardy seed sources) were grown in hydroponic solution culture using a non-circulating, continuously flowing design under anaerobic or aerobic conditions to determine whether flooding tolerance was correlated with enhanced internal root aeration. Transport of atmospheric O₂ from the shoot to the root of anaerobically grown loblolly and pond pine seedlings was demonstrated via rhizosphere oxidation, using both reduced indigo-carmine solution and a polarographic, ensheathing Pt-electrode. Stem and root collar lenticels were the major sites of atmospheric O₂ entry for submerged roots in these seedlings. No O₂ leakage was detected from roots of aerobically grown pine seedlings. Longitudinal and radial pathways for gaseous diffusion via intercellular air spaces in the pericycle and between ray parenchyma cells, respectively, were demonstrated histo-logically in anaerobically grown loblolly and pond pines. Rhizosphere oxidation, and lenticel and aerenchyma development in roots of flood-intolerant sand pine seedlings grown in anaerobic solutions were minimal. Only 15 days of anaerobic growth conditions were necessary to increase internal root porosities of loblolly and pond pine seedlings – although not to the extent found in seedlings treated for 30 or 75 days. Histological results indicated that root tissue in the secondary stage of growth was capable of forming intercellular air spaces, demonstrating a degree of internal plasticity – at least in the more flood-tolerant loblolly and pond pine seedlings.     

Age effects on intracortical microstructure and cortical thickness in adult saddle-back tamarins

Intracortical bone remodeling and cortical thickness data were collected from middiaphyseal thin sections of the humerus, ulna and tibia for 47 specimens ofSaguinus fuscicollis. Individuals were classified into age cohorts: Young Adult, Mid-adult I, Mid-adult II and Old Adult. Correlation analyses revealed significant relationships between age cohort and the number of osteons for the humerus and ulna, and between age cohort and non-Haversian canals for each of the three long bone elements. Significant relationships between age cohort and dimension of cortex size suggested an age-related pattern of cortical shifting in the ulna and older-age bone loss in the tibia.