| 1. |
- Bengtsson, Göran, et al.
(författare)
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Patchiness and compensatory growth in a fungus-Collembola system
- 1993
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Ingår i: Oecologia. - 0029-8549. ; 93:2, s. 296-302
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Tidskriftsartikel (refereegranskat)abstract
- The compensatory growth potential of a grazed fungal biomass was mathematically expressed as a function of patchiness in its distribution and demonstrated in an experiment using the fungivorous collembolan Onychiurus armatus and the soil fungi Verticillium bulbillosum and Penicillium spinulosum. The model addresses the regrowth potential in relation to patch fragmentation, travelling time and consumption rate of the collembolan and the mean relative growth rate of the fungus. It suggests that the mean relative growth rate required for regrowth decreases with patch fragmentation and increases with the mean growth rate of the fungus. The experiments were performed with a system of soil-filled vials provided with fungi and collembolans. The size of the vials and the length of the tubes connecting them were varied to give different patch sizes and travelling times. The respiratory activity of fungi after grazing increased as a unit of mycelium was distributed into smaller connected vials. The slow growing species V. bulbillosum showed a greater but delayed response to grazing in comparison with the fast growing P. spinulosum. An increased travelling time delayed the growth response in both species.
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| 2. |
- Bengtsson, Göran, et al.
(författare)
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Selective odor perception in the soil collembola Onychiurus armatus
- 1991
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Ingår i: Journal of Chemical Ecology. - 0098-0331. ; 17:11, s. 2113-2125
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Tidskriftsartikel (refereegranskat)abstract
- The olfactorial response of the fungivorous soil collembolan Onychiurus armatus was examined in a bioassay covering volatile compounds identified in the odor blends of two of its preferred fungal species Monierella isabellina and Verticillium bulbillosum. The odor of the fungi was trapped using activated carbon filters, extracted with diethyl ether, and subjected to GC-MS analysis. About 50% of the compounds resolved by GC were identified by a combination of electron impact and chemical ionization mass spectrometry. In a Y-shaped olfactometer the collembolans were attracted to a variety of common odors, such as CO2 and 2-methyl-1-propanol, and a species-specific odor, such as 1-heptene, and arrested by, for example, decanal and 2-octene. The response was not improved by pairwise combinations of common and specific odors. An amount of 0.5 ng of ethyl acetate or 3 pg of 1-pentanol was sufficient to attract the collembolans. The specific compounds of V. bulbillosum, 1-heptene and 1-octen-3-ol, may be key stimuli explaining why O. armatus prefers V. bulbillosum.
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| 3. |
- Rubio, Carlos A., et al.
(författare)
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Reliability of the reported size of removed colorectal polyps
- 2006
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Ingår i: Anticancer Research. - 0250-7005 .- 1791-7530. ; 26:6C, s. 4895-4899
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Tidskriftsartikel (refereegranskat)abstract
- Background: The size of colorectal polyps is important in the clinical management of these lesions. Aim: To audit the accuracy in calculating the size of polyps by various specialists. Materials and Methods: Eighteen pathologists and four surgeons measured, with a conventional millimetre ruler, the largest diameter of 12 polyp phantoms. The results of two independent measurements (two weeks apart) were compared with the gold standard-size assessed at The Royal Institute of Technology, Sweden. Results: Thirty-one percent (83/264-trial 1) and 33% (88/264-trial 2) of the measurements underestimated or overestimated the gold standard size by > 1 mm. Of the 22 experienced participants, 95% (21/22-trial 1) and 91% (20/22-trial 2) misjudged by > 1 mm the size of one or more polyps. Values given by 13 participants (4.9%) in trial I and by 15 participants (5.7%) in trial 2, differed by ! 4 mm from the gold standard size. In addition, a big difference between the highest and the lowest values was recorded in some polyps (up to 11.4 mm). Those disparate values were regarded as a human error in reading the scale on the ruler. Conclusion: Using a conventional ruler (the tool of pathologists worldwide) unacceptably high intra-observer and inter-observer variations in assessing the size of polyp-phantoms was found. The volume and the shape of devices, as well as human error in reading the scale of the ruler were confounding factors in size assessment. In praxis, the size is crucial in the management of colorectal polyps. Considering the clinical implications of the results obtained, the possibility of developing a method that will allow assessment of the true size of removed clinical polyps is being explored.
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| 4. |
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| 5. |
- Rundgren, Sten
(författare)
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Glacial survival, post-glacial immigration, and a millenium of human impact: On search for a biogeography of Iceland.
- 2007
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Ingår i: Entomologica Scandinavica. Supplementum. - 0105-3574. ; :Suppl. 64, s. 5-44
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Tidskriftsartikel (refereegranskat)abstract
- Northern Europe was capped by ice during Weichsel (Wurm), the maximum of which occurred approximately 18,000 years before present. When in the latter part of the 19(th) century the view of an all-devastating land ice (the tabula rasa hypothesis) was generally adopted by natural scientists, plant biogeographers used a simple model predicting a post-glacial, northwards re-migration of species in continental Europe. Occurrence and distribution of species were the prestige words when the flora and fauna elements of all area were described, and active and passive dispersal by wind, waves and migrating animals were considered. At the turn of the century observations of the distributions of certain plant species in the Scandinavian high mountains did not tally with the accepted tabula rasa and migration hypotheses. As the importance of long-distance dispersal was questioned as a general model to explain the occurrence of species, an alternative hypothesis was proposed that predicted the occurrence of sites (refuges) permitting glacial Survival of species (the refugium hypothesis). As Iceland has been covered by ice - the extent of which is under debate still - and its position in the middle of the Atlantic the occurrence of many species was difficult to explain without resting on the novel hypothesis. The controversy between the Scandinavian advocates of the two alternative hypotheses over time is reflected in the interpretations of field studies focussing oil the occurrence and distribution of the Icelandic biota. Man arrived in Iceland recently, i.e. at the end of the 9(th) century. His appearance and colonization implied that another means of dispersal and establishment of biota had to be considered: man was and,is a conveyor of species to and within the island. Moreover, lie settled, cultivated land, and he and his livestock, often freely grazing, transformed the landscape and affected abundance and distribution of species. To optimize the yield of his farm the farmer made and makes decisions oil a micro-level with bearing upon flora and fauna. But decisions that ultimately affect biota were and are also made on a macro-level e.g. by the Icelandic and foreign Governments (actions against soil erosion, trade barriers, price policy). The context in which decisions are made have to be regarded when we discuss the biogeography of Iceland. Rarely, it is possible to separate the impact of man from that of other agents and to evaluate his effects on the occurrence and distribution of species in most areas. Maybe Iceland is such an area where it would be possible, as man has affected the ecosystems during a rather short period and his doings can be followed in written sources. Such a study requires all integrated scientific approach and is not a matter of a single biologist but a team of skilled scholars and natural scientists.
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| 6. |
- Rundgren, Sten
(författare)
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Lumbricidae in Iceland
- 2007
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Ingår i: Entomologica Scandinavica. Supplementum. - 0105-3574. ; 64, s. 121-159
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Forskningsöversikt (refereegranskat)
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