Storage and mobilization of muscle glycogen in exercising horses fed a fat-supplemented diet

In a switchback experiment, six mature mares were fed a control and a fat-supplemented diet while being exercised in a galloping regimen. After three weeks adaptation to each diet, horses performed an exercise test (ET) consisting of four, 600-m gallops. Muscle biopsies were obtained before and after the ET, and blood samples were taken before, during and throughout recovery from the ET. Resting glycogen concentration in the biceps femoris muscle increased (P<.05) from 15.77 mg/g wet tissue when the horses were fed the control diet to 22.89 mg/g when they were fed the fats-supplemented diet. During the ET, the amount of glycogen mobilized by the muscle increased (P<.05) from 6.99 mg/g when the horses were fed the control diet to 13.09 mg/g when they were fed the fat-supplemented diet. When the horses were fed the fat-supplemented diet, they galloped faster (P<.09), at a constant heart rate, during the last two gallops of the ET. Thus, adapting exercising horses to a fat-supplemented diet increased muscle glycogen concentrations, which appeared to enhance their performance past the anaerobic threshold.     

Susceptibility of invasive taxa of European blackberry to rust disease caused by the uredinial stage of Phragmidium violaceum under field conditions in Australia

European blackberry ( Rubus fruticosus agg.) is an aggregate of closely related taxa, with at least 15 taxa naturalized in Australia. Biological control of this Weed of National Significance, using the nonindigenous rust fungus Phragmidium violaceum , is effective when the weather is conducive to multiple cycles of infection, but some blackberry taxa escape severe disease. Thirty-one taxa of naturalized R. fruticosus agg. from southeastern Australia were isolated, their DNA phenotype determined and clones of each taxon inoculated with P. violaceum isolate SA1. Disease development was monitored for at least four generations of uredinia on large potted plants under field conditions. Although variation in mean disease severity appeared continuous over the range of Rubus clones tested, counts of uredinia and telia enabled identification of eight resistant taxa. Fine scale variation in susceptibility to rust disease was observed when different clones of R. leucostachys with the same DNA phenotype were found to express either resistance or susceptibility to P. violaceum (SA1). There were significant differences among 23 Rubus taxa rated as susceptible to rust disease in the mean number of leaves emerging per latent period of uredinia (LELPU). Mean LELPU appeared to account for some of the variation in two measures of mean disease severity observed among susceptible Rubus clones, although the correlation was insignificant (0·10 <  P  > 0·05).     

Use of a trap garden to find additional genetically distinct isolates of the rust fungus <Emphasis Type="Italic">Phragmidium violaceum</Emphasis> to enhance biological control of European blackberry in Australia

Biological control agents can be more effective if their populations are genetically diverse, particularly when the target invasive plant comprises a range of genotypes with different susceptibilities and occurs across various microclimates. We report on the use of an efficient approach to find, in the native range, diverse isolates of a rust fungus for biological control. An outdoor trap garden containing various clones of invasive European blackberry (Rubus fruticosus agg.) collected in Australia, each with a different DNA phenotype, was established in France. Within 4 weeks of establishment, the leaf-rust fungus Phragmidium violaceum was recovered from all clones in the garden. Molecular analyses of eight recovered and purified isolates of the fungus from the garden revealed that they were genetically distinct from each other and from isolates already present in Australia. These garden isolates also represented a subset of the population existing in Europe, when compared to isolates collected about 30 years ago. Two pathogenicity phenotypes were observed among the garden isolates in bioassays consisting of representative blackberry clones from Australia, and together the isolates were capable of infecting all clones. Results from host-specificity tests on key non-target plant species closely related to European blackberry concurred with previous findings that the leaf-rust fungus does not pose a threat to commercial blackberry cultivars and Rubus species native to Australia. The release and establishment of the garden isolates in Australia has potential to increase the genetic diversity and evolutionary potential of the leaf-rust fungus for more effective biological control.     

Irvingia, a forest host of the cocoa black-pod pathogen, Phytophthora megakarya, in Cameroon

Phytophthora megakarya is an increasingly important invasive pathogen of cocoa in West Africa, where it forms part of the black-pod disease complex together with the more widespread, but less aggressive, P. palmivora . Its purported centre of diversity, based on evidence from molecular studies and mating types, lies on the Cameroon–Nigeria border, from where it has spread throughout both countries and more recently into Ghana and the Ivory Coast. A survey undertaken in an ancient primary forest (Korup National Park) in western Cameroon, adjacent to the Nigerian border, identified Irvingia sp., close to I. gabonensis (Irvingiaceae), as a wild host of P. megakarya , using both morphological and molecular characterization. ITS fingerprinting of two additional Phytophthora isolates, obtained during a supplementary survey in central Cameroon, showed identical banding patterns for the isolate from a cocoa pod, whilst the isolate from an unknown forest fruit proved to belong to P. heveae . This is the first authenticated record of P. heveae from the African continent. Subsequent AFLP analysis grouped the two P. megakarya isolates with other Cameroonian isolates held in the CABI Genetic Resource Collection, but separated them from the Ghanaian isolates.     

ASTRONOMY: Don't We Already Know Everything About Polaris?

Recent results on Polaris and other Cepheids, variable stars used as a yardstick for astronomical distances, illustrate some of the new capabilities we have for studying this important class of stars. In her Perspective, Evans charts some of the recent work and highlights some of the surprises that have been revealed, even in objects thought to be basically understood.     

A critical analysis of the direct effects of dredging on fish

Dredging can have significant impacts on aquatic environments, but the direct effects on fish have not been critically evaluated. Here, a meta‐analysis following a conservative approach is used to understand how dredging‐related stressors, including suspended sediment, contaminated sediment, hydraulic entrainment and underwater noise, directly influence the effect size and the response elicited in fish across all aquatic ecosystems and all life‐history stages. This is followed by an in‐depth review summarizing the effects of each dredging‐related stressor on fish. Across all dredging‐related stressors, studies that reported fish mortality had significantly higher effect sizes than those that describe physiological responses, although indicators of dredge impacts should endeavour to detect effects before excessive mortality occurs. Studies examining the effects of contaminated sediment also had significantly higher effect sizes than studies on clean sediment alone or noise, suggesting additive or synergistic impacts from dredging‐related stressors. The early life stages such as eggs and larvae were most likely to suffer lethal impacts, while behavioural effects were more likely to occur in adult catadromous fishes. Both suspended sediment concentration and duration of exposure greatly influenced the type of fish response observed, with both higher concentrations and longer exposure durations associated with fish mortality. The review highlights the need for in situ studies on the effects of dredging on fish which consider the interactive effects of multiple dredging‐related stressors and their impact on sensitive species of ecological and fisheries value. This information will improve the management of dredging projects and ultimately minimize their impacts on fish.