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| 13. |
- Nilsson, Erika, et al.
(författare)
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Facilitation and interference among three predators affect their consumption of a stream-dwelling mayfly
- 2006
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Ingår i: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 51:8, s. 1507-1514
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Tidskriftsartikel (refereegranskat)abstract
- 1. We experimentally tested if a multiplicative risk model accurately predicted the consumption of a common mayfly at risk of predation from three predator species in New Zealand streams. Deviations between model predictions and experimental observations were interpreted as indicators of ecologically important interactions between predators. 2. The predators included a drift-feeding fish [brown trout (T), Salmo trutta], a benthivorous fish [galaxiid (G), koaro, Galaxias brevipennis] and a benthic predatory stonefly (S; Stenoperla sp.) with Deleatidium sp. mayflies as prey. Eight treatments with all predator species combinations and a predator-free control were used. Experiments were performed in aquaria with cobbles as predator refuges for mayflies and we measured the proportion of prey consumed after 6 h for both day and night trials. 3. Trout consumed a higher proportion of prey than other predators. For the two predator treatments we found less than expected prey consumption in the galaxiid + trout treatment (G + T) for both day and night trials, whereas a higher than expected proportion of prey was consumed during night time in the stonefly + trout (S + T) treatment. 4. The results indicate interference (G + T) and facilitation (S + T) between predators depending on predator identity and time of day. Thus, to make accurate predictions of interspecific interactions, it is necessary to consider the ecology of individual species and how differences influence the direction and magnitude of interactions.
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| 14. |
- Olsson, Karin, et al.
(författare)
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Does natural acidity mediate interactions between introduced brown trout, native fish, crayfish and other invertebrates in West Coast New Zealand streams?
- 2006
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Ingår i: Biological Conservation. - : Elsevier BV. - 1873-2917 .- 0006-3207. ; 130:2, s. 255-267
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Tidskriftsartikel (refereegranskat)abstract
- The presence of introduced brown trout (Salmo trutta) on the distribution of native crayfish (Paranephrops planifrons), native galaxiid fishes (Galaxias spp.) and invertebrate fauna was investigated in 18 West Coast New Zealand streams (8 with trout and 10 without trout) differing in chemical characteristics. Gut contents of trout, crayfish and eels were also examined to evaluate whether competition or predation could be linked to the patterns found. Abundances of crayfish and galaxiids were significantly lower in streams with trout, but in streams without trout, substrate size was one of the most important factors determining crayfish abundance. In contrast to crayfish, other macroinvertebrates were more abundant in trout streams than streams without trout and significantly more taxa were found in streams with trout. Macroinvertebrate abundance was related to environmental factors, such as pH, substrate, depth and total nitrogen. Gut content analysis showed an overlap in diet (mostly invertebrates) between trout and eels. Crayfish, however, had a more omnivorous diet where detritus was the most frequently occurring food material. Differences in chemical characteristics marked the streams with and without trout. Thus, trout were not present in streams with pH < 6.0. Crayfish and galaxiids were present in streams with pH ranging from 4.1 to 7.9, and those with pH < 6.0 may function as trout-free refuges where larger populations of these species may persist. However, other macroinvertebrate taxa may be more negatively affected by acidification than by trout. By protecting naturally acidic, brown water streams, New Zealand crayfish and galaxiid fish populations can be conserved within geographic areas where trout are present.
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| 15. |
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| 16. |
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| 17. |
- Thompson, Hilaire J., et al.
(författare)
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Tissue sparing and functional recovery following experimental traumatic brain injury is provided by treatment with an anti-myelin-associated glycoprotein antibody
- 2006
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Ingår i: European Journal of Neuroscience. - : Wiley. - 0953-816X .- 1460-9568. ; 24:11, s. 3063-3072
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Tidskriftsartikel (refereegranskat)abstract
- Axonal injury is a hallmark of traumatic brain injury (TBI) and is associated with a poor clinical outcome. Following central nervous system injury, axons regenerate poorly, in part due to the presence of molecules associated with myelin that inhibit axonal outgrowth, including myelin-associated glycoprotein (MAG). The involvement of MAG in neurobehavioral deficits and tissue loss following experimental TBI remains unexplored and was evaluated in the current study using an MAG-specific monoclonal antibody (mAb). Anesthetized rats (n = 102) were subjected to either lateral fluid percussion brain injury (n = 59) or sham injury (n = 43). In surviving animals, beginning at 1 h post-injury, 8.64 mu g anti-MAG mAb (n = 33 injured, n = 21 sham) or control IgG (n = 26 injured, n = 22 sham) was infused intracerebroventricularly for 72 h. One group of these rats (n = 14 sham, n = 11 injured) was killed at 72 h post-injury for verification of drug diffusion and MAG immunohistochemistry. All other animals were evaluated up to 8 weeks post-injury using tests for neurologic motor, sensory and cognitive function. Hemispheric tissue loss was also evaluated at 8 weeks post-injury. At 72 h post-injury, increased immunoreactivity for MAG was seen in the ipsilateral cortex, thalamus and hippocampus of brain-injured animals, and anti-MAG mAb was detectable in the hippocampus, fimbria and ventricles. Brain-injured animals receiving anti-MAG mAb showed significantly improved recovery of sensorimotor function at 6 and 8 weeks (P < 0.01) post-injury when compared with brain-injured IgG-treated animals. Additionally, at 8 weeks post-injury, the anti-MAG mAb-treated brain-injured animals demonstrated significantly improved cognitive function and reduced hemispheric tissue loss (P < 0.05) when compared with their brain-injured controls. These results indicate that MAG may contribute to the pathophysiology of experimental TBI and treatment strategies that target MAG may be suitable for further evaluation.
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