| 1. |
- Tabiri, S, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 2. |
- Bravo, L, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 3. |
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| 4. |
- Vogel, Jacob W., et al.
(författare)
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Four distinct trajectories of tau deposition identified in Alzheimer’s disease
- 2021
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Ingår i: Nature Medicine. - : Springer Science and Business Media LLC. - 1078-8956 .- 1546-170X. ; 27:5, s. 871-881
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Tidskriftsartikel (refereegranskat)abstract
- Alzheimer’s disease (AD) is characterized by the spread of tau pathology throughout the cerebral cortex. This spreading pattern was thought to be fairly consistent across individuals, although recent work has demonstrated substantial variability in the population with AD. Using tau-positron emission tomography scans from 1,612 individuals, we identified 4 distinct spatiotemporal trajectories of tau pathology, ranging in prevalence from 18 to 33%. We replicated previously described limbic-predominant and medial temporal lobe-sparing patterns, while also discovering posterior and lateral temporal patterns resembling atypical clinical variants of AD. These ‘subtypes’ were stable during longitudinal follow-up and were replicated in a separate sample using a different radiotracer. The subtypes presented with distinct demographic and cognitive profiles and differing longitudinal outcomes. Additionally, network diffusion models implied that pathology originates and spreads through distinct corticolimbic networks in the different subtypes. Together, our results suggest that variation in tau pathology is common and systematic, perhaps warranting a re-examination of the notion of ‘typical AD’ and a revisiting of tau pathological staging. © 2021, The Author(s), under exclusive licence to Springer Nature America, Inc.
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| 5. |
- Thoma, B, et al.
(författare)
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An international, interprofessional investigation of the self-reported podcast listening habits of emergency clinicians: A METRIQ Study
- 2020
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Ingår i: CJEM. - : Springer Science and Business Media LLC. - 1481-8043 .- 1481-8035. ; 22:1, s. 112-117
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Tidskriftsartikel (refereegranskat)abstract
- ObjectivesPodcasts are increasingly being used for medical education. A deeper understanding of usage patterns would inform both producers and researchers of medical podcasts. We aimed to determine how and why podcasts are used by emergency medicine and critical care clinicians.MethodsAn international interprofessional sample (medical students, residents, physicians, nurses, physician assistants, and paramedics) was recruited through direct contact and a multimodal social media (Twitter and Facebook) campaign. Each participant completed a survey outlining how and why they utilize medical podcasts. Recruitment materials included an infographic and study website.Results390 participants from 33 countries and 4 professions (medicine, nursing, paramedicine, physician assistant) completed the survey. Participants most frequently listened to medical podcasts to review new literature (75.8%), learn core material (75.1%), and refresh memory (71.8%). The majority (62.6%) were aware of the ability to listen at increased speeds, but most (76.9%) listened at 1.0 x (normal) speed. All but 25 (6.4%) participants concurrently performed other tasks while listening. Driving (72.3%), exercising (39.7%), and completing chores (39.2%) were the most common. A minority of participants used active learning techniques such as pausing, rewinding, and replaying segments of the podcast. Very few listened to podcasts multiple times.ConclusionsAn international cohort of emergency clinicians use medical podcasts predominantly for learning. Their listening habits (rarely employing active learning strategies and frequently performing concurrent tasks) may not support this goal. Further exploration of the impact of these activities on learning from podcasts is warranted.
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| 6. |
- Zhou, XP, et al.
(författare)
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Non-coding variability at the APOE locus contributes to the Alzheimer's risk
- 2019
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Ingår i: Nature communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 10:1, s. 3310-
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Tidskriftsartikel (refereegranskat)abstract
- Alzheimer’s disease (AD) is a leading cause of mortality in the elderly. While the coding change of APOE-ε4 is a key risk factor for late-onset AD and has been believed to be the only risk factor in the APOE locus, it does not fully explain the risk effect conferred by the locus. Here, we report the identification of AD causal variants in PVRL2 and APOC1 regions in proximity to APOE and define common risk haplotypes independent of APOE-ε4 coding change. These risk haplotypes are associated with changes of AD-related endophenotypes including cognitive performance, and altered expression of APOE and its nearby genes in the human brain and blood. High-throughput genome-wide chromosome conformation capture analysis further supports the roles of these risk haplotypes in modulating chromatin states and gene expression in the brain. Our findings provide compelling evidence for additional risk factors in the APOE locus that contribute to AD pathogenesis.
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| 7. |
- Baden, Susanne P., 1952, et al.
(författare)
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Between-individual variation in haemocyanin concentrations in the Norway lobster Nephrops norvegicus following exposure to hypoxia and manganese
- 2003
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Ingår i: Marine Biology. - 0025-3162. ; 143:2, s. 267-273
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Tidskriftsartikel (refereegranskat)abstract
- Environmental hypoxia and the release of reduced manganese (Mn) are often combined stress factors in marine sediments. Previous investigations have shown that hypoxia induces variable responses in the concentration of the respiratory pigment haemocyanin (Hc) of crustaceans. A recent study demonstrated that the magnitude and direction of the changes was dependent on the initial level of Hc in individuals of the Norway lobster Nephrops norvegicus. The changes also took place within 24 h rather than days as suggested by previous studies. In this present study we investigated changes of Hc in individual N. norvegicus in uncontaminated sea water after exposure to and release from realistic hypoxic stress (PO2 = 6.0 kPa). Furthermore we investigated how concomitant exposure to realistic concentrations of manganese (20 mg 1(-1)) modified the responses we observed. We confirmed a between-individual variation in response and a change in Hc towards an optimum level after hypoxia, but also showed that changes that took place post-hypoxic exposure occurred over a timescale similar to that of the hypoxic response itself. Manganese exposure resulted in no significant changes in Hc whereas Mn exposure combined with hypoxia resulted in a significant decrease (15%) in all individuals independent of initial Hc. N. norvegicus was thus unable to compensate for the effects of hypoxia by synthesis of Hc after exposure to naturally occurring Mn concentrations.
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| 8. |
- Bednarsek, N., et al.
(författare)
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Synthesis of Thresholds of Ocean Acidification Impacts on Echinoderms
- 2021
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Ingår i: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Assessing the vulnerability of marine invertebrates to ocean acidification (OA) requires an understanding of critical thresholds at which developmental, physiological, and behavioral traits are affected. To identify relevant thresholds for echinoderms, we undertook a three-step data synthesis, focused on California Current Ecosystem (CCE) species. First, literature characterizing echinoderm responses to OA was compiled, creating a dataset comprised of >12,000 datapoints from 41 studies. Analysis of this data set demonstrated responses related to physiology, behavior, growth and development, and increased mortality in the larval and adult stages to low pH exposure. Second, statistical analyses were conducted on selected pathways to identify OA thresholds specific to duration, taxa, and depth-related life stage. Exposure to reduced pH led to impaired responses across a range of physiology, behavior, growth and development, and mortality endpoints for both larval and adult stages. Third, through discussions and synthesis, the expert panel identified a set of eight duration-dependent, life stage, and habitat-dependent pH thresholds and assigned each a confidence score based on quantity and agreement of evidence. The thresholds for these effects ranged within pH from 7.20 to 7.74 and duration from 7 to 30 days, all of which were characterized with either medium or low confidence. These thresholds yielded a risk range from early warning to lethal impacts, providing the foundation for consistent interpretation of OA monitoring data or numerical ocean model simulations to support climate change marine vulnerability assessments and evaluation of ocean management strategies. As a demonstration, two echinoderm thresholds were applied to simulations of a CCE numerical model to visualize the effects of current state of pH conditions on potential habitat.
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| 9. |
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| 10. |
- Jacobson, A, et al.
(författare)
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Expression of human hyaluronan synthases in response to external stimuli.
- 2000
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Ingår i: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 348 Pt 1, s. 29-35
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Tidskriftsartikel (refereegranskat)abstract
- In the present study we have investigated the expression of mRNAs for hyaluronan synthase isoforms (HAS1, HAS2 and HAS3) in different cells in response to various stimuli. Human mesothelial cells, which synthesize large amounts of hyaluronan, express mRNAs encoding all three HAS isoforms, whereas their transformed counterparts, mesothelioma cells, which produce only minute amounts of hyaluronan, express only HAS3 mRNA. Human lung fibroblasts and the glioma cell line U-118 MG express only the HAS2 and HAS3 genes. The expression of the transcripts was higher in subconfluent than in confluent cultures and was well correlated with the production of hyaluronan by the cells. Stimulation of mesothelial cells with platelet-derived growth factor-BB induced an up-regulation of mRNA for HAS2 to a maximum after 6 h of stimulation; HAS1 and HAS3 genes were only induced slightly. Transforming growth factor-beta1 reduced HAS2 mRNA slightly, and hydrocortisone reduced it strongly, within 6 h of stimulation in mesothelial cell cultures but did not significantly affect the expression of mRNAs for HAS1 and HAS3. Induction of HAS1 and HAS2 protein levels in response to the stimuli above correlated with HAS transcript levels. Thus the expression of the three HAS isoforms is more prominent in growing cells than in resting cells and is differentially regulated by various stimuli suggesting distinct functional roles of the three proteins.
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| 11. |
- Spicer, T. M., et al.
(författare)
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Spatial mapping of torques within a spin Hall nano-oscillator
- 2018
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Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 98:21
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Tidskriftsartikel (refereegranskat)abstract
- Time-resolved scanning Kerr microscopy (TRSKM) was used to study precessional magnetization dynamics induced by a radio frequency (RF) current within a Al2O3/Py(5 nm)/Pt(6 nm)/Au(150 nm) spin Hall nano-oscillator structure. The Au layer was formed into two needle-shaped electrical contacts that concentrated the current in the center of a Py/Pt mesa of 4 mu m diameter. Due to the spin Hall effect, current within the Pt layer drives a spin current into the Py layer, exerting a spin transfer torque (STT). By injecting RF current and exploiting the phase sensitivity of TRSKM and the symmetry of the device structure, the STT and Oersted field torques have been separated and spatially mapped. The STT and torque due to the in-plane Oersted field are observed to exhibit minima at the device center that is ascribed to spreading of RF current that is not observed for DC current. Torques associated with the RF current may destabilize the position of the self-localized bullet mode excited by the DC current and inhibit injection locking. The present study demonstrates the need to characterize both DC and RF current distributions carefully.
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| 12. |
- Spicer, T. M., et al.
(författare)
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Time resolved imaging of the non-linear bullet mode within an injection-locked nano-contact spin Hall nano-oscillator
- 2018
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 113:19
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Tidskriftsartikel (refereegranskat)abstract
- Time-resolved scanning Kerr microscopy (TRSKM) has been used to image precessional magnetization dynamics excited by a DC current within a nano-contact (NC) spin Hall nanooscillator (SHNO). Injection of a radio frequency (RF) current was used to phase lock the SHNO to TRSKM. The out of plane magnetization was detected by means of the polar magneto optical Kerr effect (MOKE). However, longitudinal MOKE images were dominated by an artifact arising from the edges of the Au NCs. Time resolved imaging revealed the simultaneous excitation of a nonlinear "bullet" mode at the centre of the device, once the DC current exceeded a threshold value, and ferromagnetic resonance (FMR) induced by the RF current. However, the FMR response observed for sub-critical DC current values exhibits an amplitude minimum at the centre, which is attributed to spreading of the RF spin current due to the reactance of the device structure. This FMR response can be subtracted to yield images of the bullet mode. As the DC current is increased above threshold, the bullet mode appears to increase in size, suggesting increased translational motion. The reduced spatial overlap of the bullet and FMR modes, and this putative translational motion, may impede the injection locking and contribute to the reduced locking range observed within NC-SHNO devices. This illustrates a more general need to control the geometry of an injection-locked oscillator so that the autonomous dynamics of the oscillator exhibit strong spatial overlap with those resulting from the injected signal. Published by AIP Publishing.
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| 13. |
- Arachchige, Erandi C.W.Subasinghe, et al.
(författare)
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A global assessment of the species composition and effectiveness of watermelon pollinators and the management strategies to inform effective pollination service delivery
- 2023
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Ingår i: Basic and Applied Ecology. - : Elsevier BV. - 1439-1791. ; 66, s. 50-62
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Forskningsöversikt (refereegranskat)abstract
- For most food crops the identity and efficiency of pollinators across key growing regions remains a significant knowledge gap that needs to be addressed before we can develop crop-specific approaches for pollination service delivery. Here, we conducted a systematic literature review and meta-analysis on watermelon (Citrullus lanatus (Thunb. Matsum. & Nakai)), a globally important fruit crop, to identify the floral visitors and their efficiency across different growing regions. We found that 265 insect species visit watermelon flowers (including 5 orders, 18 families and 75 genera) across 17 countries and 6 continents. Bees and flies were the most abundant flower visitors overall, but show distinct regional differences. Honey bees were the majority visitor in 53% of growing regions (range: 0 – 94%), whilst wild bee species were more abundant in 42% of regions (range: 3.4 – 100%). Honey bees and other bees were equally effective at depositing pollen on stigmas, but varied in effectiveness for fruit set and seed set. Pollination data from global studies appear to be limited for the largest-scale watermelon producers, namely: China, Turkey, and India, with the majority (56%) of data available from North America. This synthesis identified four key themes for improving pollination in watermelon: increasing honey bee densities on crops where local polices and environmental conditions are suitable; introducing other managed pollinators; identifying key wild pollinator taxa to encourage within crops; and improving local and landscape management practices to support pollinators.
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| 14. |
- Arnberg, M., et al.
(författare)
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Effects of oil and global environmental drivers on two keystone marine invertebrates
- 2018
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Ocean warming (OW) and acidification (OA) are key features of global change and are predicted to have negative consequences for marine species and ecosystems. At a smaller scale increasing oil and gas activities at northern high latitudes could lead to greater risk of petroleum pollution, potentially exacerbating the effects of such global stressors. However, knowledge of combined effects is limited. This study employed a scenario-based, collapsed design to investigate the impact of one local acute stressor (North Sea crude oil) and two chronic global drivers (pH for OA and temperature for OW), alone or in combination on aspects of the biology of larval stages of two key invertebrates: the northern shrimp (Pandalus borealis) and the green sea urchin (Strongylocentrotus droebachiensis). Both local and global drivers had negative effects on survival, development and growth of the larval stages. These effects were species- and stage-dependent. No statistical interactions were observed between local and global drivers and the combined effects of the two drivers were approximately equal to the sum of their separate effects. This study highlights the importance of adjusting regulation associated with oil spill prevention to maximize the resilience of marine organisms to predicted future global conditions. © 2018, The Author(s).
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| 15. |
- Daly, Robert J., et al.
(författare)
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A palynological study of an extinct arctic ecosystem from the Palaeocene of Northern Alaska
- 2011
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Ingår i: Review of Palaeobotany and Palynology. - : Elsevier BV. - 0034-6667. ; 166:1-2, s. 107-116
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Tidskriftsartikel (refereegranskat)abstract
- The Palaeocene arctic supported a vegetation type quite distinct from the tundra and polar desert of today. Here we demonstrate, through the palynological record, the structure of this extinct vegetation and its dynamics over this period. The Late Palaeocene coal-bearing units of the Sagwon Bluffs on Alaska's North Slope (present latitude 69 degrees N) are predominantly fine-grained, non-marine and rich in palynomorph-bearing sediments. From the analysed palynological assemblage we were able to demonstrate, using 'Detrended Correspondence Analysis' (DCA) and 'Fuzzy c-Means Cluster Analysis' (FCM), 1) a complex heterogeneous ecosystem, 2) its major successional states, and 3) its development over an extended period. The climax state of the floodplain was dominated by flood-tolerant, deciduous conifers such as Metasequoia. A more heterogeneous mid-successional assemblage is represented by angiosperm and gymnosperm co-dominance with an angiosperm dominance of Corylus, while early-successional ecological groups, dominated by ferns and bryophytes, are considered to represent riparian and post-disturbance niches. The structure of this vegetation does not remain static over the course of the stratigraphic interval represented. We observe a particularly dramatic ecological change for instance, following the deposition of a large conglomeratic unit. It is hypothesized that this corresponds to altered drainage and/or precipitation on the North Slope. The vegetation examined herein shows marked similarities to that of other palaeobotanical studies from various sites of similar age at high northern latitudes. It is hence considered to represent an extensive and long-lived circumpolar arctic biome. (C) 2011 Elsevier B.V. All rights reserved.
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| 16. |
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| 17. |
- Ellis, Robert P., et al.
(författare)
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Does sex really matter? Explaining intraspecies variation in ocean acidification responses
- 2017
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Ingår i: Biology Letters. - : The Royal Society. - 1744-9561 .- 1744-957X. ; 13:2
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Tidskriftsartikel (refereegranskat)abstract
- Ocean acidification (OA) poses a major threat to marine ecosystems globally, having significant ecological and economic importance. The number and complexity of experiments examining the effects of OA has substantially increased over the past decade, in an attempt to address multi-stressor interactions and long-term responses in an increasing range of aquatic organisms. However, differences in the response of males and females to elevated pCO2 have been investigated in fewer than 4% of studies to date, often being precluded by the difficulty of determining sex non-destructively, particularly in early life stages. Herewe highlight that sex can significantly impact organismresponses to OA, differentially affecting physiology, reproduction, biochemistry and ultimately survival. What is more, these impacts do not always conform to ecological theory based on differential resource allocation towards reproduction, which would predict females to be more sensitive to OA owing to the higher production cost of eggs compared with sperm. Therefore, non-sex-specific studies may overlook subtle but ecologically significant differences in the responses of males and females to OA, with consequences for forecasting the fate of natural populations in a near-future ocean.
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| 18. |
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| 19. |
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| 20. |
- Kuang Soh, Wuu, et al.
(författare)
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Rising CO2 drives divergence in water use efficiency of evergreen and deciduous plants
- 2019
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 5:12
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Tidskriftsartikel (refereegranskat)abstract
- Intrinsic water use efficiency (iWUE), defined as the ratio of photosynthesis to stomatal conductance, is a key variable in plant physiology and ecology. Yet, how rising atmospheric CO2 concentration affects iWUE at broad species and ecosystem scales is poorly understood. In a field-based study of 244 woody angiosperm species across eight biomes over the past 25 years of increasing atmospheric CO2 (similar to 45 ppm), we show that iWUE in evergreen species has increased more rapidly than in deciduous species. Specifically, the difference in iWUE gain between evergreen and deciduous taxa diverges along a mean annual temperature gradient from tropical to boreal forests and follows similar observed trends in leaf functional traits such as leaf mass per area. Synthesis of multiple lines of evidence supports our findings. This study provides timely insights into the impact of Anthropocene climate change on forest ecosystems and will aid the development of next-generation trait-based vegetation models.
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| 21. |
- Murray, Michelle, et al.
(författare)
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Convergence in Maximum Stomatal Conductance of C-3 Woody Angiosperms in Natural Ecosystems Across Bioclimatic Zones
- 2019
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Ingår i: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Stomatal conductance (g(s)) in terrestrial vegetation regulates the uptake of atmospheric carbon dioxide for photosynthesis and water loss through transpiration, closely linking the biosphere and atmosphere and influencing climate. Yet, the range and pattern of g(s) in plants from natural ecosystems across broad geographic, climatic, and taxonomic ranges remains poorly quantified. Furthermore, attempts to characterize g(s) on such scales have predominantly relied upon meta-analyses compiling data from many different studies. This approach may be inherently problematic as it combines data collected using unstandardized protocols, sometimes over decadal time spans, and from different habitat groups. Using a standardized protocol, we measured leaf-level g(s) using porometry in 218 C-3 woody angiosperm species in natural ecosystems representing seven bioclimatic zones. The resulting dataset of 4273 g(s) measurements, which we call STraits (Stomatal Traits), was used to determine patterns in maximum g(s) (g(smax)) across bioclimatic zones and whether there was similarity in the mean g(smax) of C3 woody angiosperms across ecosystem types. We also tested for differential g(smax) in two broadly defined habitat groups - open-canopy and understory-subcanopy - within and across bioclimatic zones. We found strong convergence in mean g(smax) of C3 woody angiosperms in the understory-subcanopy habitats across six bioclimatic zones, but not in open-canopy habitats. Mean g(smax) in open-canopy habitats (266 +/- 100 mmol m(-2) s(-1)) was significantly higher than in understory-subcanopy habitats (233 +/- 86 mmol m(-2) s(-1)). There was also a central tendency in the overall dataset to operate toward a g(smax) of similar to 250 mmol m(-2) s(-1). We suggest that the observed convergence in mean g(smax) of C3 woody angiosperms in the understory-subcanopy is due to a buffering of g(smax) against macroclimate effects which will lead to differential response of C3 woody angiosperm vegetation in these two habitats to future global change. Therefore, it will be important for future studies of g(smax) to categorize vegetation according to habitat group.
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| 22. |
- Spicer, J. I., et al.
(författare)
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Developmental changes in the responses of O-2 uptake and ventilation to acutely declining O-2 tensions in larval krill Meganyctiphanes norvegica
- 2003
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Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 295:2, s. 207-218
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Tidskriftsartikel (refereegranskat)abstract
- The effect of exposure to acutely declining oxygen tensions on O-2 uptake (Mo-2) and ventilation has been investigated in different larval stages of Northern krill Meganyctiphanes norvegica (calytopis III/ early furcilia I, late furcilia I, furcilia III and V). An ability to regulate Mo-2 during acutely declining P-O2 began to appear about furcilia III (critical O-2 tension or P-c = 15.4 +/- 0.73 kPa) and had improved by furcilia V (P-c= 12.6 +/- 0.39 kPa). Hypoxia-related hyperventilation was achieved by an increase in pleopod (but not thoracic limb) activity (P-c similar to 11 kPa), a sensitivity which also appeared at, or just before, furcilia V even though an earlier stage (furcilia III) had a full compliment of functional setose pleopods. While this regulatory ability appeared as the gills were beginning to form, furcilia V is still early in gill ontogeny compared with adults. Preexposure to very moderate hypoxia (60% and 70% O-2 (saturation) of furcilia III and V resulted in substantial mortality, but where it did not (furcilia V, 80% O-2 saturation), there was no effect of keeping krill at this P-O2 on either M-O2 or ventilation, suggesting that the development of respiratory regulation in M. norvegica is not open to environmental influence in the same way as for other crustaceans. We suggest that ontogeny of pleopod control provides furcilia V+ with both a stronger means of propulsion, allowing the ontogeny of DVM but also with an ability to regulate M-O2 during exposure to acutely declining P(O2)s. The onset of respiratory regulation (furcilia V) preceded the onset of DVM (furcilia VI+). As pleopod ontogeny is associated intimately with the ontogeny of DVM and respiratory regulation, in the Gullmarsfjord this co-occurrence is fortuitous as krill can be required during DVM to migrate into hypoxic water which they are not equipped to deal with, in physiological terms, before furcilia V. (C) 2003 Elsevier B.V. All rights reserved.
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| 23. |
- Spicer, J. I., et al.
(författare)
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Diel vertical migration and the haemocyanin of krill Meganyctiphanes norvegica
- 2002
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Ingår i: Marine Ecology-Progress Series. - 0171-8630. ; 238, s. 153-162
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Tidskriftsartikel (refereegranskat)abstract
- Changes in environmental factors (PO2, temperature, salinity and food availability) influence the concentration of the respiratory pigment haemocyanin ([Hc]) present in many crustaceans. We investigated the possibility that [Hc] and HcO(2) affinity altered during the diel vertical migration (DVM) of Nordic krill Meganyctiphanes norvegica in the Gullmarsfjord, Sweden. The [Hc] decreased with increasing depth, for individuals both trawled and caged at different depths. Laboratory experiments indicated that this pattern could not be explained by differences in PO2, temperature or salinity. Alternatively, starvation had a significant effect on [Hc] over the course of a few h (less than or equal to10), i.e. a much shorter time scale than found for other crustacean species. Starved individuals showed a dramatic decrease in [Hc] compared with fed individuals. This decrease was exacerbated by an increase in temperature. We suggest that when M norvegica migrates into deep water during the day, for whatever reason (predator avoidance or reduced prey abundance, or reduced ability to locate and capture prey), they cannot secure enough energy to meet routine metabolic demands; they therefore break down Hc and use it as an energy source. We conclude that there is likely to be a trade-off between the respiratory function of Hc and its importance in nutrition when krill migrate into deeper, nutritionally poorer waters during their DVM.
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| 24. |
- Spicer, J. I., et al.
(författare)
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Does the development of respiratory regulation always accompany the transition from pelagic larvae to benthic fossorial postlarvae in the Norway lobster Nephrops norvegicus (L.)?
- 2003
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Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 295:2, s. 219-243
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Tidskriftsartikel (refereegranskat)abstract
- The ability to regulate O-2 uptake during exposure to acutely declining PO2S co-occurred with metamorphosis from a planktonic to a benthic existence in the Norway lobster Nephrops norvegicus when cultured under normoxic conditions in the laboratory. The onset of this regulation appears to be related to the presence of a hypoxia-related hyperventilation of extrabranchial exchange surfaces (telson/uropods) by the pleopods and a shift from a low to a high He O-2 affinity. This co-occured with a dramatic calcification of the exoskeleton at metamorphosis, which will restrict gas exchange over the general body surface. Evidence marshalled here points to a shift from a pleopod-based, hypoxia-related, hyperventilation of the uropods/telson as gas exchange surfaces to, in later postlarval stages, a scaphognathitc-based response, where the gills are the main areas for gas exchange. This is the first time that experimental evidence has been put forward for the use of uropods/telson by larval lobsters as extrabranchial gas exchange surfaces. Pre-exposure of larval and postlarval N. norvegicus to reduced P-O2, both in the laboratory and in the field, resulted in the "adult" pattern of M-O2, regulation present during exposure to declining P-O2 being established before metamorphosis. Bringing the ontogeny of this regulation forward in the development itinerary was to some extent a result of a shift from a low to a high He O-2 affinity well before metamorphosis and an increase in the magnitude of the hypoxia-related hyperventilatory response in the planktonic larval stages. Thus, the development of respiratory regulation does not always accompany the transition from pelagic larvae to benthic fossorial larvae in N. norvegicus as its onset can be influenced prevailing O-2 conditions, both in the laboratory and the field. (C) 2003 Elsevier B.V. All rights reserved.
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| 25. |
- Spicer, J. I., et al.
(författare)
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Metabolic responses to low salinity of the shipworm Teredo navalis (L.)
- 2003
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Ingår i: Sarsia. - 0036-4827. ; 88:4, s. 302-305
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Tidskriftsartikel (refereegranskat)abstract
- It has long been thought that shipworms are sensitive to salinity changes, but few studies have investigated this possibility. The oxygen uptake of excised gill tissue from individuals of a population of the shipworm Teredo navalis from southwest Sweden decreased with decreasing salinity. The greatest fall occurred between S = 4 and 8 PSU. Excised gill tissue showed little effect of salinity on ciliary beat rate at S greater than or equal to 3-4 PSU, but below this beating ceased. Individuals withdrew their siphons and sealed their bur-rows at S = 4-8 PSU. Burrows could remain closed at S < 4 PSU for at least 6 days at 22 degreesC. Siphons re-emerged within minutes of a return to S > 4 PSU. We conclude that a salinity range of 4-8 PSU is critical for this population of T. navalis. This fits well with information on salinity tolerance from other populations of this species.
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