| 11. |
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| 12. |
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| 13. |
- Arzel, Céline, et al.
(författare)
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Individual strategies of dabbling ducks : a circum-annual perspectice
- 2003
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Ingår i: Third North American duck symposium. ; , s. 73-
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Konferensbidrag (refereegranskat)abstract
- Very little is still known about the ecology of dabbling ducks on staging areas in spring, despite the fact that this is a crucial period of the year when birds refuel during migration and prepare for subsequent reproduction. This lack of knowledge translates into the current inability to predict the consequences of changes in the environment and harvesting for the population dynamics of ducks. We have launched a joint project to study dabbling ducks in the flyway connecting wintering grounds in France with breeding areas in Sweden. The aim is to study individual dabbling ducks in a circumannual perspective. We are assessing food resource limitation, density-dependent effects and the role of competition by estimating available food, by using a reference functional response curve and by recording the foraging behaviour of wild individual dabbling ducks. We also study survival probability and breeding success, and we will assess inter-individual variation. Birds are captured, weighed, marked and subsequently observed in order to study foraging behaviour and potentially measure the changes in body mass across time through recaptures. Ducks are fitted with nasal marks for individual recognition. Eventually, we will provide a model to predict the number of young that a female duck will produce after simple measurements such as its date of arrival on the breeding grounds and its body-mass at this date. Duckling foraging efficiency and survival will be measured and the relationship with corresponding estimates for their mother will be explored.
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| 14. |
- Arzel, Céline, et al.
(författare)
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Time use and foraging behaviour in pre-breeding dabbling ducks Anas spp. in sub-arctic Norway
- 2015
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Ingår i: Journal of Ornithology. - 2193-7192 .- 2193-7206. ; 156:2, s. 499-513
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Tidskriftsartikel (refereegranskat)abstract
- We studied time budgets and foraging methods in pre-breeding Mallard Anas platyrhynchos, (Eurasian) Teal Anas crecca, Wigeon Anas penelope, Pintail Anas acuta, Shoveler Anas clypeata and Gadwall Anas strepera in subarctic Norway in May. Among all six species studied, foraging accounted for the most common use of time, ranging from 19 % in male Pintail to 40–60 % in female Mallard, Teal, Pintail and Gadwall. Comfort behaviours amounted to 20–34 % of the time budget, and interaction and disturbance were marginal. Vigilance time ranged from 8 % in female Mallard to 20 % in male Pintail. Movement amounted to some 20 % of the time in most species and sexes. In Wigeon, sexes did not differ in time use, whereas in Mallard, Pintail and, in particular, Teal, females foraged more and engaged less in vigilance and interactions than did males. In addition, Teal and Mallard males engaged in the riskier foraging methods less than females, but more in those permitting vigilance. Although overlap in feeding methods was large among these species, Mallard and Teal were generalists, feeding at all depths, Wigeon foraged mainly in shallow water and Pintail foraged essentially in deep water. Our results support the income/capital breeder hypothesis with respect to males only; compared to lighter species, heavier species allocated less time to foraging but more to vigilance. We found no support for the hypothesis that long-distance migrants forage more to compensate for energy loss due to migratory flight. Foraging time in females was related to breeding phenology; early nesters spent more time feeding than later nesters.
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| 15. |
- Barclay, C J, et al.
(författare)
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Efficiency of cross-bridges and mitochondria in mouse cardiac muscle
- 2010
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Ingår i: Muscle biophysics. - : Springer Berlin/Heidelberg. - 9781441963659 - 9781441963666 ; , s. 267-278
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Bokkapitel (refereegranskat)abstract
- The aim of this study was to make cellular-level measurements of the mechanical efficiency of mouse cardiac muscle and to use these measurements to determine (1) the work performed by a cross-bridge in one ATP-splitting cycle and (2) the fraction of the free energy available in metabolic substrates that is transferred by oxidative phosphorylation to free energy in ATP (i.e. mitochondrial thermodynamic efficiency). Experiments were performed using isolated left ventricular mouse papillary muscles (n = 9; studied at 27°C) and the myothermic technique. The production of work and heat was measured during and after 40 contractions at a contraction frequency of 2 Hz. Each contraction consisted of a brief isometric period followed by isovelocity shortening. Work output, heat output and enthalpy output were all independent of shortening velocity. Maximum initial mechanical efficiency (mean ± SEM) was 31.1 ± 1.3% and maximum net mechanical efficiency 16.9 ± 1.5%. It was calculated that the maximum work per cross-bridge cycle was 20 zJ, comparable to values for mouse skeletal muscle, and that mitochondrial thermodynamic efficiency was 72%. Analysis of data in the literature suggests that mitochondrial efficiency of cardiac muscle from other species is also likely to be between 70 and 80%.
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| 16. |
- Bengtsson, Daniel, et al.
(författare)
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Änders rörelser kartlagda
- 2014
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Ingår i: Vår fågelvärld. - 0042-2649. ; 73:5, s. 46-48
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 17. |
- Bertolani, Roberto, et al.
(författare)
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Experiences with dormancy in tardigrades
- 2004
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Ingår i: Journal of limnology. - 1129-5767 .- 1723-8633. ; 63:Suppl. 1, s. 16-25
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Tidskriftsartikel (refereegranskat)abstract
- Tardigrades often colonise extreme habitats, in which they survive using both types of dormancy: quiescence and diapause. Together with nematodes and bdelloid rotifers, tardigrades are known to enter quiescence (with several forms of cryptobiosis: anhydrobiosis, cryobiosis, anoxybiosis, osmobiosis) at any stage of their life cycle, from egg to adult. Entering anhydrobiosis, tardigrades contract their body into a so-called tun, loosing most of their free and bound water (>95%), synthesizing cell protectants (e.g., trehalose, glycerol, heat shock proteins) and strongly reducing or suspending their metabolism. Our research on cryptobiosis focused on some ecological and evolutionary aspects. We evaluated: i) the long-term anhydrobiotic survival by comparing quantitative data on recovery from naturally induced desiccation in several species of tardigrades; ii) differences in survival patterns between species and populations by experimentally inducing anhydrobiosis and cryobiosis; iii) phenotypic factors affecting anhydrobiotic survival. As regards diapause, we considered encystment and eggs. Encystment involves at least the synthesis of new cuticular structures. Morphological changes during cyst formation are more complex than those involved in tun formation. We analyzed more in detail encystment processes, comparing a semiterrestrial with a limnic species. Several inter-specific differences have been identified, other than the production of two types of cysts in the semiterrestrial species. Our analysis of life history traits of a laboratory reared strain of a soil tardigrade revealed a particular hatching phenology that involved the production of both subitaneous and resting eggs. The latter need a cue to hatch (dehydration followed by re-hydration). In addition, the evolutionary meaning of dormancy in tardigrades is discussed
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| 18. |
- Champagnon, Jocelyn, et al.
(författare)
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Assessing the genetic impact of massive restocking on wild mallard
- 2013
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Ingår i: Animal Conservation. - : Wiley: 12 months. - 1367-9430 .- 1469-1795. ; 16:3, s. 295-305
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Tidskriftsartikel (refereegranskat)abstract
- Captive-bred mallards Anas platyrhynchos have been released for hunting purposes at a very large scale in Europe since the mid-1970s. In spite of a potential genetic impact, the actual contribution of restocked mallards to the genome of the target population has received little attention. The genetic structure of modern wild mallards in the Camargue, Southern France, was assessed from two samples: one originating from shot birds in hunting bags and one from presumed wild ducks captured alive in a hunting-free reserve. Reference samples originated from five mallard farms, as well as from museum samples collected before the mid-1970s (i.e. before massive mallard releases started). Our results revealed that the genetic signature of wild wintering mallards has not changed significantly because museum and presumed wild samples from the Camargue hunting-free nature reserve were genetically similar, and clearly differentiated from the farm mallards. This suggests that mallard releases in the Camargue or elsewhere in France, although massive, have not actually translated into complete admixture of wild and captive genomes, most likely due to low survival of released birds once in the wild. Nevertheless, although genetic introgression of the wild population by captive-bred was contained, we found significant rates of hybridization between wild and captive-bred mallards in modern samples. This result suggests that long-term releases of captive-bred mallards, if carried on at such large scale, could compromise irreversibly the genetic structure and composition of European mallards. This work contributes to fill in the gap on the monitoring of the genetic consequences of large-scale game releases for exploitation.
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| 19. |
- Czernekova, Michaela, et al.
(författare)
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A comparative ultrastructure study of storage cells in the eutardigrade Richtersius coronifer in the hydrated state and after desiccation and heating stress
- 2018
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Ingår i: PLOS ONE. - 1932-6203. ; 13:8
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Tidskriftsartikel (refereegranskat)abstract
- Tardigrades represent an invertebrate phylum with no circulatory or respiratory system.Their body cavity is filled with free storage cells of the coelomocyte-type, which are responsible for important physiological functions. We report a study comparing the ultrastructure of storage cells in anhydrobiotic and hydrated specimens of the eutardigrade Richtersius coronifer. We also analysed the effect of temperature stress on storage cell structure. Firstly, we verified two types of ultrastructurally different storage cells, which differ in cellular organelle complexity, amount and content of reserve material and connection to oogenetic stage. Type I cells were found to differ ultrastructurally depending on the oogenetic stage of the animal. The main function of these cells is energy storage. Storage cells of Type I were also observed in the single male that was found among the analysed specimens. The second cell type, Type II, found only in females, represents young undifferentiated cells, possibly stem cells. The two types of cells also differ with respect to the presence of nucleolar vacuoles,which are related to oogenetic stages and to changes in nucleolic activity during oogenesis. Secondly, this study revealed that storage cells are not ultrastructurally affected by six months of desiccation or by heating following this desiccation period. However, heating of the desiccated animals (tuns) tended to reduce animal survival, indicating that longterm desiccation makes these animals more vulnerable to heat stress. We confirmed the degradative pathways during the rehydration process after desiccation and heat stress. Our study is the first to document two ultrastructurally different types of storage cells in tardigrades and reveals new perspectives for further studies of tardigrade storage cells.
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| 20. |
- Czernekova, Michaela, et al.
(författare)
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Evaluation of extraction methods for quantitative analysis of tardigrade populations in soil and leaf litter
- 2018
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Ingår i: Pedobiologia. - : Elsevier. - 0031-4056 .- 1873-1511. ; 70, s. 1-5
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Tidskriftsartikel (refereegranskat)abstract
- Accurate quantitative analysis of soil tardigrades depends on a relevant extraction method. Over the years, a number of different methods have been used, but the efficiency of these methods has rarely been evaluated for soil and leaf litter tardigrades. Four methods of extraction were compared in this study: the light-cooling (L-C) extractor, the high-gradient (H-G), Baermann extractor, the non-gradient (N-G) Baermann extractor and sieves.The results indicate that light and temperature are significant factors influencing tardigrade extraction. The L-C and H-G extractors were more effective than sieves for all substrate categories. These extraction methods (L-C and H-G) therefore seem to be appropriate for quantitative studies of soil and leaf litter tardigrades.
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