Possible influence of increased riparian activity (stream modification and agricultural intensification) on abundance of South African otters

Otters are threatened by habitat loss and the pollution of their riverine habitat. Environmental impacts on top predators are often the first indication of habitat deterioration. It is rare for predator‐prey‐habitats to be monitored over long time intervals (decades), however necessary that may be. Here, we report on the decline in otter relative abundance in a previously pristine habitat and speculate on its causes. We surveyed sign of coexisting otters (Aonyx capensis and Lutra maculicollis) along a river in Kamberg Nature Reserve in uKhahlamba Drakensberg Park, KwaZulu‐Natal, South Africa. The area, Stillerust, lies downstream of a commercial dairy farm and a rural village–subsistence farming area. Data collected recently were compared with two previous surveys, carried out in 1972–1974 and 1993–1994, and were also compared with a pristine section of river in the nature reserve, upstream of the farming areas. At Stillerust, the number of spraint (scat) sites found, for each otter species, approximated only 25% of those recorded in the earlier studies. In the pristine section of the river, the amount of sign and abundance of otters were similar to those recorded in 1993. Assessments of stream biota and water quality analyses revealed negative changes in the river below the pristine area, down to, and including, Stillerust. Visible signs of pollution were evident. Since the 1970s, the rural village population has increased ca eightfold, and the commercial farm has changed from an extensive livestock enterprize to an intensive dairy farm.     

Stromatoporoid palaeoecology in the Frasnian (Upper Devonian) Belgian platform,and its applications in interpretation of carbonate platform environments

Abstract: Stromatoporoid faunas in the Frasnian of southern Belgium are abundant in the carbonate platform environments present in this area. Stromatoporoids dominate the large skeletal organisms and occur principally in biostromes. The stromatoporoid assemblage is represented by a small number of taxa. Stromatoporoid genera include Actinostroma, Amphipora, Atelodictyon, Clathrocoilona, Salairella, Stachyodes, Stictostroma, Stromatopora and Trupetostroma which are present in environments ranging from the outer, outer intermediate, inner intermediate and inner zones and associated biostromes. Most large skeletal stromatoporoids are low profile, which reinforces the conclusions of previous studies that low‐profile growth forms were the most successful stromatoporoid forms. These low‐profile forms are likely to have been important sediment stabilisers that may have led to expansion of the carbonate factory. Growth forms vary between facies, indicating some degree of environmental control on form; for example, laminar in the intermediate zone, bulbous and domical in the inner and outer zones. Stromatoporoid taxa vary in occurrence across the environmental gradient from shallow to deep. There is some taxonomic control on growth forms, with some taxa showing more variability than others in different environments.     

Miocene intertidal zonation on a volcanically active shoreline: Porto Santo in the Madeira Archipelago,Portugal

Santos, A., Mayoral, E.J., da Silva, C.M., Cachão, M., Johnson, M.E. & Baarli, B.G. Miocene intertidal zonation on a volcanically active shoreline: Porto Santo in the Madeira Archipelago, Portugal. Lethaia, Vol. 44, pp. 26–32. Short‐term biological colonization of rockgrounds on the basaltic shorelines of oceanic islands has, as yet, been poorly explored. A Miocene sea cliff on Ilhéu de Cima off Porto Santo in the Madeira Archipelago of Portugal provides a case study showing intertidal zonation with two types of barnacles, serpulid worm tubes, two coral species, epifaunal bivalves and the trace fossils of endolithic bivalves. Large barnacles (Balanus sp.) and serpulids are limited to the upper 400 mm of a basalt cliff of 1.6 m in height. Small barnacles, possibly of the same species, extend to the base. The upper half includes the corals Isophyllastrea orbignyana and Tarbellastraea reussiana, to which many small, coral‐inhabiting, barnacles (Ceratoconcha costata) are fixed. Borings identified as Gastrochaenolites torpedo appear through the bottom two‐thirds of the cliff face. Rarely, Gastrochaenolites lapidicus is exposed in longitudinal section with borings up to 45 mm deep in solid basalt. Epifaunal bivalves, such as Spondylus sp., are limited to a middle zone. Associated with the sea cliff is an outer platform on which a multitude of T. reussiana colonies occur in growth position. The corals exhibit planar erosion over180 m². The shelf was faulted and cut by a basalt dike prior to the brief recolonization of I. orbignyana, found attached to low fault scarps. Habitation of the sea cliff was facilitated by rising sea level, but abruptly terminated by burial under volcanoclastic ejecta. □Basalt bioerosion, coastal dynamics, Ilhéu de Cima (Porto Santo), Miocene intertidal zonation, volcanogenic perturbations.     

Sedimentology and stromatoporoid palaeoecology of Frasnian (Upper Devonian) carbonate mounds in southern Belgium

Da Silva, A.‐C., Kershaw, S. & Boulvain, F. 2011: Sedimentology and stromatoporoid palaeoecology of Frasnian (Upper Devonian) carbonate mounds in southern Belgium. Lethaia, Vol. 44, pp. 255–274. Stromatoporoids are the most abundant large skeletal organisms in middle Frasnian carbonate mound environments of southern Belgium. They occur in environments ranging from flank and off‐mound, mound core, shallow mound and restricted mound. A detailed log and comprehensive sampling of stromatoporoids in a single section cutting through all middle Frasnian mound levels in La Boverie–Rochefort Quarry, near Rochefort and Dinant reveals a stromatoporoid assemblage comprising 10 genera; 472 samples, containing an overall total of 3079 stromatoporoids (including complete and fragmented specimens) have been studied. The following list gives abundance using numbers of specimens and areas of total stromatoporoid area on outcrop surfaces (% number; % area in cm²): Actinostroma (0.4; 9.2), Amphipora (15.5; 1.7), Atelodictyon (0.2; 4.4), Clathrocoilona (0.3; 0.5), Euryamphipora (13.7; 0.7), Idiostroma (2; 1.9), Salairella (1.2; 9.6), branching Stachyodes (43.2; 59.1), laminar Stachyodes australe (1.9; 1.3), Stictostroma (4.8; 13.1) and Trupetostroma (0.2; 0.8), showing that Stachyodes is approximately half of the total assemblage. Deeper environments contain more abundant low profile forms, shallow water facies contain more domical and bulbous forms; branching forms are ubiquitous. Low profile stromatoporoids are likely to have been important sediment stabilizers that may have led to expansion of the carbonate factory, and they may have therefore contributed to the structural building of the mounds. Stromatoporoid‐coral intergrowths are observed in only Stictostroma suggesting that there is a close biological relationship between them; however, stromatoporoid skeletons in almost all cases appear to be unaffected by the presence of intergrown corals, suggesting they were commensals. □Frasnian, Late Devonian, mounds, palaeoecology, stromatoporoid.     

EBV-specific CD8+ T cells from asymptomatic pediatric thoracic transplant patients carrying chronic high EBV loads display contrasting features: activated phenotype and exhausted function

Serial EBV load monitoring of clinically asymptomatic pediatric thoracic organ transplant patients has identified three groups of children who exhibit undetectable (<100 copies/ml), chronic low (100-16,000 copies/ml), or chronic high (>16,000 copies/ml) EBV loads in peripheral blood. Chronic high EBV load patients have a 45% rate of progression to late-onset posttransplant lymphoproliferative disorders. In this article, we report that asymptomatic patients carrying EBV loads (low and high) expressed increased frequencies of EBV-specific CD8(+) T cells, as compared with patients with undetectable EBV loads. Although patients with low viral load displayed EBV-specific CD8(+) T cells with moderate signs of activation (CD38(+/-)/CD127(+/-)), programmed death 1 upregulation and effective IFN-γ secretion, high EBV load carriers showed significant CD38(+) upregulation, features of cellular exhaustion (programmed death 1(+)/CD127(-)) accompanied by a decline in IFN-γ release. Immunopolarization of EBV-specific CD8(+) T cells was skewed from the expected type 1 (IFN-γ) toward type 0 (IFN-γ/IL-5) in patients, and Tr1 (IL-10) in high load carriers. These results indicate the importance of chronic EBV load and of the levels of antigenic pressure in shaping EBV-specific memory CD8(+) T cells. Concomitant phenotypic and functional EBV monitoring is critical for identifying the complex "functional" versus "exhausted" signature of EBV-specific CD8(+) T cells, with implications for immunologic monitoring in the clinic.     

Selective expression in carotid body type I cells of a single splice variant of the large conductance calcium- and voltage-activated potassium channel confers regulation by AMP-activated protein kinase

Inhibition of large conductance calcium-activated potassium (BKCa) channels mediates, in part, oxygen sensing by carotid body type I cells. However, BKCa channels remain active in cells that do not serve to monitor oxygen supply. Using a novel, bacterially derived AMP-activated protein kinase (AMPK), we show that AMPK phosphorylates and inhibits BKCa channels in a splice variant-specific manner. Inclusion of the stress-regulated exon within BKCa channel α subunits increased the stoichiometry of phosphorylation by AMPK when compared with channels lacking this exon. Surprisingly, however, the increased phosphorylation conferred by the stress-regulated exon abolished BKCa channel inhibition by AMPK. Point mutation of a single serine (Ser-657) within this exon reduced channel phosphorylation and restored channel inhibition by AMPK. Significantly, RT-PCR showed that rat carotid body type I cells express only the variant of BKCa that lacks the stress-regulated exon, and intracellular dialysis of bacterially expressed AMPK markedly attenuated BKCa currents in these cells. Conditional regulation of BKCa channel splice variants by AMPK may therefore determine the response of carotid body type I cells to hypoxia.     

The mitochondrial genome of the soybean cyst nematode, Heterodera glycines

We sequenced the entire coding region of the mitochondrial genome of Heterodera glycines. The sequence obtained comprised 14.9 kb, with PCR evidence indicating that the entire genome comprised a single, circular molecule of approximately 21-22 kb. The genome is the most T-rich nematode mitochondrial genome reported to date, with T representing over half of all nucleotides on the coding strand. The genome also contains the highest number of poly(T) tracts so far reported (to our knowledge), with 60 poly(T) tracts ≥ 12 Ts. All genes are transcribed from the same mitochondrial strand. The organization of the mitochondrial genome of H. glycines shows a number of similarities compared with Radopholus similis, but fewer similarities when compared with Meloidogyne javanica. Very few gene boundaries are shared with Globodera pallida or Globodera rostochiensis. Partial mitochondrial genome sequences were also obtained for Heterodera cardiolata (5.3 kb) and Punctodera chalcoensis (6.8 kb), and these had identical organizations compared with H. glycines. We found PCR evidence of a minicircular mitochondrial genome in P. chalcoensis, but at low levels and lacking a noncoding region. Such circularised genome fragments may be present at low levels in a range of nematodes, with multipartite mitochondrial genomes representing a shift to a condition in which these subgenomic circles predominate.     

内蒙古种子植物新资料

报道了内蒙古1个新分布记录属--莴苣属(Lactuca L.);3个新分布记录种:双穗麻黄 (Ephedra distachya L.)、丝毛蓝刺头(Echinops nanus Bunge)、野莴苣(Lactuca serriola L.).     

Effect of mechanical perturbation on the biomechanics, primary growth and secondary tissue development of inflorescence stems of Arabidopsis thaliana

Background and Aims

Mechanical perturbation is known to inhibit elongation of the inflorescence stem of Arabidopsis thaliana. The phenomenon has been reported widely for both herbaceous and woody plants, and has implications for how plants adjust their size and form to survive in mechanically perturbed environments. While this response is an important aspect of the plant''s architecture, little is known about how mechanical properties of the inflorescence stem are modified or how its primary and secondary tissues respond to mechanical perturbation.

Methods

Plants of the Columbia-0 ecotype were exposed to controlled brushing treatments and then submitted to three-point bending tests to determine stem rigidity and stiffness. Contributions of different tissues to the inflorescence stem geometry were analysed.

Key Results

Perturbed plants showed little difference in stem diameter, were 50 % shorter, 75 % less rigid and 70 % less stiff than controls. Changes in mechanical properties were linked to significant changes in tissue geometry – size and position of the pith, lignified interfascicular tissue and cortex – as well as a reduction in density of lignified cells. Stem mechanical properties were modified by changes in primary tissues and thus differ from changes observed in most woody plants tested with indeterminate growth – even though a vascular cambium is present in the inflorescence axis.

Conclusions

The study suggests that delayed development of key primary developmental features of the stem in this ecotype of Arabidopsis results in a ‘short and flexible’ rather than a ‘short and rigid’ strategy for maintaining upright axes in conditions of severe mechanical perturbation. The mechanism is comparable with more general phenomena in plants where changes in developmental rate can significantly affect the overall growth form of the plant in both ecological and evolutionary contexts.