AGA Institute Review of Endoscopic Sedation Cohen, Lawrence B; DeLegge, Mark H; Aisenberg, James ...
Gastroenterology (New York, N.Y. 1943),
08/2007, Letnik:
133, Številka:
2
Journal Article
Bioluminescent glow‐worms (Arachnocampa spp.) capture prey in glue‐coated silk capture threads hung from their nests on damp cave and wet forest substrates. In a dry environment, these animals are ...very susceptible to desiccation as their bodies can become life threateningly dry and their silk has been anecdotally observed to become non‐sticky. Water has a plasticizing effect on the structural proteins of several invertebrate silks, including those used in caddisfly nets, mussel byssus and spider webs. Moreover, water facilitates interfacial adhesion by spreading adhesive biomolecules in functionally analogous velvet worm slime and spider silk glue. We tested the effects of water on the mechanics and adhesion of Arachnocampa tasmaniensis capture threads sampled within damp caves. We found that threads tested at high humidity were three times more compliant and over 10‐fold more extensible than those tested at low humidity (30% RH). We also found the threads to be significantly more adhesive in high humidity with force at detachment increasing two orders of magnitude and work of adhesion increasing by five orders of magnitude compared to threads tested at low humidity. Our results unequivocally demonstrate that A. tasmaniensis capture thread functionality is dependent upon exposure to high humidity. Our results both confirm previous reports and indicate that the foraging habitat of these animals is restricted to caves and cave‐like environments, such as wet forests.
Bioluminescent glow‐worms catch prey using glue‐coated capture silk threads hung vertically from their nests on damp cave and wet forest substrates. We found that threads tensile and adhesion tested at >90% RH (relative humidity) were three times more compliant and over 10‐fold more extensible with work of adhesion increasing by five orders of magnitude compared to threads tested at 30% RH, which were relatively brittle and non‐adhesive. Our results unequivocally demonstrate that A. tasmaniensis capture thread functionality is dependent upon exposure to high humidity which likely indicates that these animals’ foraging habitat is restricted to environments with sufficiently high humidity.
Animal morphological traits may vary across life stages. Web‐building spiders are diverse insectivores that can display ontogenetic shifts in the design and properties of their webs. Nevertheless, we ...know little about how a critical component of their webs, major ampullate silk (MAS), varies in property across life stages, inferably owing to a difficulty in finding suitable model species. The Tasmanian cave spider Hickmania troglodytes presents as a good model as it is long‐lived and grows to a large body size with overlapping generations. We collected MAS from the webs of different‐sized H. troglodytes and performed tensile tests on MAS fibers collected from their webs to search for shifts in properties over life stages. We found that strength and toughness (i.e. ability to deform and absorb energy) of the MAS increased with spider carapace width and body length. We expect that such a shift in silk performance across life stages has distinctive advantages, including enhanced prey capture capabilities, an improvement in the economy of silk production and ability of the web to support the spider's larger body.
Web‐building spiders are diverse insectivores that can display ontogenetic shifts in the design and properties of their webs. Throughout ontogeny, we found that the Tasmanian cave spider Hickmania troglodytes varies in the biomechanical properties of a key component of their webs: major ampullate silk. Increases in the strength and toughness of these silk fibers may have beneficial fitness effects, such as enhanced prey capture capabilities, improvement in the economy of silk production and ability of the web to support the spider's larger body.
Wind has become one of the fastest growing sources of renewable energy worldwide, but widespread and often extensive fatalities of bats have increased concern regarding the impacts of wind energy ...development on bats and other wildlife. We synthesized available information on patterns of bat fatalities from a review of 21 postconstruction fatality studies conducted at 19 facilities in 5 United States regions and one Canadian province. Dominance of migratory, foliage- and tree-roosting lasiurine species (e.g., hoary bat Lasiurus cinereus) killed by turbines was consistent among studies. Bat fatalities, although highly variable and periodic, consistently peaked in late summer and fall, coinciding with migration of lasiurines and other species. A notable exception was documented fatalities of pregnant female Brazilian free-tailed bats (Tadarida brasiliensis) in May and June at a facility in Oklahoma, USA, and female silver-haired bats (Lasionycteris noctivagans) during spring in Tennessee, USA, and Alberta, Canada. Most studies reported that fatalities were distributed randomly across turbines at a site, although the highest number of fatalities was often found near the end of turbine strings. Two studies conducted simultaneously in the same region documented similar timing of fatalities between sites, which suggests broader patterns of collisions dictated by weather, prey abundance, or other factors. None of the studies found differences in bat fatalities between turbines equipped with lighting required by the Federal Aviation Administration and turbines that were unlit. All studies that addressed relationships between bat fatalities and weather patterns found that most bats were killed on nights with low wind speed (<6 m/sec) and that fatalities increased immediately before and after passage of storm fronts. Weather patterns may be predictors of bat activity and fatality; thus, mitigation efforts that focus on these high-risk periods could reduce bat fatality substantially. We caution that estimates of bat fatality are conditioned by length of study and search interval and that they are biased in relation to how searcher efficiency, scavenger removal, and habitat differences were or were not accounted for. Our review will assist managers, biologists, and decision-makers with understanding unifying and unique patterns of bat fatality, biases, and limitations of existing efforts, and it will aid in designing future research needed to develop mitigation strategies for minimizing or eliminating bat fatality at wind facilities.
Spatial analysis that aims to identify site-specific hotspots of collision mortality from birds or bats striking wind turbines can potentially lead to mitigating measures that reduce mortality rates. ...During May–Jul. 2004 and 2005, we studied bird and bat mortality from collisions with wind turbines at a 102 megawatt, 68-turbine wind farm in the southern Great Plains, Oklahoma, USA. Standardized searches around turbine bases yielded 122 total carcasses of which 92 (75%) were found within 20 m of the turbine bases. We identified 111 carcasses of seven species of bats and 11 carcasses of 6 species of birds. Brazilian free-tailed bats (Tadarida brasiliensis) comprised 85% of bat carcasses collected. We corrected turbine collision estimates using searcher efficiency trials and a range of removal (i.e., “scavenging”) rates reported in the literature. Estimated bat turbine collisions ranged from 1.19–1.71 fatalities/turbine (1.03–1.37/megawatt). These data provide some of the first evidence for a steady rate of collision mortality of Brazilian free-tailed bats at a North American wind farm, most likely due to the site's proximity (∼15 km) to a maternity colony. Spatial analyses indicated no consistent pattern in mortality estimates relative to ground cover or topographic position; but collision mortality was higher at several individual turbines, all of which were located near the heads of eroded ravines.
A State-threatened White Sands pupfish (Cyprinodon tularosa) was captured by a fishing spider (genus Dolomedes) in a spring on White Sands Missile Range, New Mexico. Before it was able to consume its ...prey, a predaceous diving beetle (Cybister fimbriolatus) stole the pupfish from the spider's grasp. Depredation of pupfish by these two invertebrates has not previously been documented to our knowledge. Although it is likely not a significant mortality source for pupfish populations, the pupfish is nonetheless a potential food source for Dolomedes and C. fimbriolatus.
With upcoming global wind-energy build-out estimated in millions of units, cumulative environmental impacts must be considered and understood to promote responsible expansion of this renewable energy ...source. In June 2009, 30 wildlife scientists convened in Racine, Wisconsin, USA to identify key research priorities concerning wind energy's potential impacts on migratory wildlife (birds and bats). This working group suggested 4 areas where improved science is most needed to evaluate the impacts of wind-energy development on migrating animals more accurately than can be accomplished today: 1) standardized protocols and definitions; 2) new methods and models for assessing and forecasting risk; 3) documenting lethal and sub-lethal effects at existing wind facilities; and 4) improved facility-site access, data access, and data management for researchers. Focused research based on these priorities will both quantify potential risks associated with wind-energy development and help derive science-based, peerreviewed, best-management practices for existing and future wind projects.
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