| 1. |
- Jönsson, K. Ingemar, 1959-, et al.
(författare)
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Environmental adaptations : radiation tolerance
- 2019
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Ingår i: Water bears. - : Springer. - 9783319957012 - 9783319957029 ; , s. 311-330
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Several studies in different species have documented that tardigrades are among the most radiation-tolerant animals on Earth, surviving doses of ionizing radiation on the order of kGy. Both low-LET and high-LET radiation have been used with no apparent differences in the tolerance of the animals. Tolerance to ionizing radiation in tardigrades also seems to be independent of whether the animal has entered a dry anhydrobiotic state or is hydrated with normal activity. However, when exposed to UV radiation, desiccated tardigrades show a higher tolerance than hydrated animals. Recent studies in several species have shown that tardigrade embryos have considerably lower tolerance to ionizing radiation compared to adults, and embryos in the early stage of development are clearly more sensitive to radiation than those in the late developmental stage. The molecular mechanisms behind radiation tolerance in tardigrades are still largely unclear, but available evidence suggests that mechanisms related to both the avoidance of DNA damage and the repair of damage are involved.
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| 2. |
- Jönsson, K. Ingemar, 1959-, et al.
(författare)
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The fate of the TARDIS offspring : no intergenerational effects of space exposure
- 2016
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Ingår i: Zoological Journal of the Linnean Society. - 0024-4082 .- 1096-3642. ; 178:4, s. 924-930
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Tidskriftsartikel (refereegranskat)abstract
- In September 2007 tardigrades became the first animal in history to survive the combined effect of exposure to space vacuum, cosmic radiation and ultraviolet radiation in low Earth orbit. The main results from this experiment were reported in 2008, but some of the results have remained unpublished. Here we report that descendant generations of space-exposed tardigrades of the species Milnesium tardigradum did not show reduced performance. This indicates that individual tardigrades that survived the exposure to environmental extremes in space, and were able to reproduce, did not transfer any damage to later generations. Repair of environmentally induced damage may therefore follow a ‘make or break’ rule, such that a damaged animal either fails to repair all damage and dies, or repairs damage successfully and leaves no mutations to descendants. We also report that two additional tardigrade species, Echiniscus testudo and Ramazzottius oberhaeuseri, showed high survival after exposure to space vacuum and cosmic radiation within the TARDIS experiment.
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| 3. |
- Söderquist, Pär
(författare)
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Large-scale releases of native species : the mallard as a predictive model system
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Human alteration of natural systems, and its consequences are of great concern and the impact on global ecosystems is one of the biggest threats that biodiversity stands before. Translocations of invasive species, as well as intraspecific contingents with non-native genotypes, whether they are deliberate or unintentional, are one such alteration and its consequences are continuously being assessed. The mallard (Anas platyrhynchos) is the most numerous and widespread duck in the world and a flagship in wetland conservation. It is also an important game species which is heavily restocked for hunting purposes, especially in Europe where over three million ducklings are released every year. Because of its hunted status, its abundance, and the number of released individuals, it can serve as a model species to study effects of releases, both for conservation and restocking for hunting, on wild populations. In this thesis the status of the mallard was assessed in the Nordic countries and the effects of releases on the wild populations were studied by mining historical ringing data, comparing morphology of present-day wild, farmed, and historical mallards, and analyzing phylogeography of wild and farmed mallards in Europe. The status of the mallard population in the Nordic countries are generally good, however, a joint effort of European countries is needed to monitor and manage the population. A significant difference between wild and farmed mallards concerning longevity, migration, bill morphology and genetic structure was also found, together with signs of cryptic introgression of farmed genotypes in the wild population with potential fitness reduction as a result. The effect is however limited by that only a fraction of released farmed mallards reach the breeding season due to low survival. A natural captive environment is crucial to keep individuals wild-like with high survival rates after release. However, with an introgression of potentially maladapted farmed genotypes leading to a reduction in fitness, a low survival of released mallards would favor the wild population. A legislative change regarding obligation to report numbers, provenance, and release sites of farmed mallard should be considered, together with practical solutions of ringing and genetic monitoring of released mallards.
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| 4. |
- 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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| 5. |
- 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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| 6. |
- 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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| 7. |
- Czernekova, Michaela, et al.
(författare)
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Experimentally induced repeated anhydrobiosis in the Eutardigrade Richtersius coronifer
- 2016
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Ingår i: PLOS ONE. - 1932-6203. ; 11:11
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Tidskriftsartikel (refereegranskat)abstract
- Tardigrades represent one of the main animal groups with anhydrobiotic capacity at any stage of their life cycle. The ability of tardigrades to survive repeated cycles of anhydrobiosis has rarely been studied but is of interest to understand the factors constraining anhydrobiotic survival. The main objective of this study was to investigate the patterns of survival of the eutardigrade Richtersius coronifer under repeated cycles of desiccation, and the potential effect of repeated desiccation on size, shape and number of storage cells. We also analyzed potential change in body size, gut content and frequency of mitotic storage cells. Specimens were kept under non-cultured conditions and desiccated under controlled relative humidity. After each desiccation cycle 10 specimens were selected for analysis of morphometric characteristics and mitosis. The study demonstrates that tardigrades may survive up to 6 repeated desiccations, with declining survival rates with increased numberof desiccations. We found a significantly higher proportion of animals that were unable to contract properly into a tun stage during the desiccation process at the 5th and 6th desiccations. Also total number of storage cells declined at the 5th and 6th desiccations, while no effect on storage cell size was observed. The frequency of mitotic storage cells tended to decline with higher number of desiccation cycles. Our study shows that the number of consecutive cycles of anhydrobiosis that R. coronifer may undergo is limited, with increased inability for tun formation and energetic constraints as possible causal factors.
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| 8. |
- Czernekova, Michaela, et al.
(författare)
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Mitosis in storage cells of the eutardigrade Richtersius coronifer
- 2016
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Ingår i: Zoological Journal of the Linnean Society. - 0024-4082 .- 1096-3642. ; 178:4, s. 888-896
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Tidskriftsartikel (refereegranskat)abstract
- Although tardigrades are sometimes reported as eutelic animals, mitosis has been reported in several somatic tissues of adult eutardigrades. The occurrence of cell division in storage cells is particularly interesting in light of the important role that these cells play in the physiology of tardigrades. We present data on the occurrence of mitosis in storage cells of the eutardigrade Richtersius coronifer (Richters, 1903), and analyse mitotic cells in relation to different body characteristics, including egg development stage, moulting, gut content, body length, number and size of oocytes, and shape and size of the storage cells. Mitosis was present in ~20% of all animals, and was more frequent in juveniles than in adults. The proportion of cells with mitosis (‘mitotic index’) was low: 0.76% in juveniles and 1.47% in adults. In juveniles, none of the measured phenotypic characters had significant predictive power for mitosis, whereas in adult animals in moult or in late egg developmental or post-laying stage were more likely to have mitotic storage cells. The association with the later part of the moulting process was particularly strong. The low mitotic index and the strong association with moulting suggests that mitosis in storage cells may be connected with somatic growth rather than cell renewal, and that the purpose of cell division may relate to a need of more cells to support the enlarged body after moulting. However, the specific life cycle of tardigrades, where energy intake and depletion, egg development, and moulting is highly intertwined and synchronized, make conclusions about the functional role of mitosis in storage cells difficult, however, and more studies are needed to reveal the mechanisms inducing mitosis in these interesting cells.
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| 9. |
- Czernekova, Michaela, et al.
(författare)
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Mitosis in storage cells of the eutardigrade Richtersius coronifer
- 2015
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Konferensbidrag (refereegranskat)abstract
- Tardigrades are often reported as eutelic animals, characterized by a constant cell number after maturity and growing by cell enlargement rather than by increased cell number. However, mitosis has been reported in some of the somatic tissues of adult eutardigrades, including the storage cells, and are therefore not strictly eutelic. Very few studies have investigated the presence of mitosis in tardigrades, and the occurrence of cell division in storage cells is particularly interesting in light of the important role that these cells may play in the physiology and immunology of tardigrades. We present data on the occurrence of mitosis in storage cells of the eutardigrade Richtersius coronifer and provide an analysis of storage cell mitosis in relation to different body characteristics. Specimens were examined for mitotic cells using in toto staining with aceto-lactic orcein, and the same animals were characterized with respect to egg development stage, number of oocytes, gut content, body size, and shape and size of the storage cells. Mitosis was present in ca. 30% of the animals. A large majority (3/4) of the animals with mitotic cells were found in specimens at moulting or directly after egg laying. Amount of gut content was associated with mitosis, with highest mitosis frequency (ca. 50%) in animals with an empty gut. These results for egg developmental stage (incl. moulting) and gut content are however not independent, since gut content generally decrease towards the end of the reproductive cycle. Other measured body characteristics did not influence the frequency of mitosis. In juveniles, mitotic cells were found in about half of the examined specimens. Our results suggest that proliferation of storage cells in R. coronifer is connected to the general life cycle dynamics, and provide a basis for more in depth analyses of the functional role and dynamics of storage cells in tardigrades.
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| 10. |
- Czernekova, Michaela, et al.
(författare)
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Primary Culture of Tardigrade Storage Cells from Richtersius coronifer Richters, 1903
- 2016
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Konferensbidrag (refereegranskat)abstract
- Coelomocytes are macrophage-like cells in the body cavity or the coelomic spaces of many invertebrates and play major roles in their physiology and immunology. Their structure, function and diversity, however, is still poorly understood.Tardigrades are micrometazoans inhabiting a wide variety of environments and with an ability to survive extreme conditions. Coelomocytes (“storage cells”) represent an important part of tardigrade physiology, storing and distributing energy and possibly also having immunological functions. Few studies of tardigrade cell biology have been reported and neither primary nor continuous cell cultures have been established. Tardigrades are normally found and also cultured in an environment rich in microorganisms, some of which may even be of symbiotic value.In this study we have tried to establish a primary culture of storage cells in the eutardigrade Richtersius coronifer. Different cell media and concentrations of fetal bovine serum (FBS) were tested. Extracting cells from the tardigrades in an antiseptical environment is challenging since it has to be done under a microscope and contamination from the tardigrades surface is also a problem. To avoid this we tried culturing with high concentrations of antibiotics and antimycotics. We managed to keep the cells viable for up to 18 days in Grace insect medium with 10 % FBS at 20-22°C. The medium was changed every third day. 10x Antibiotic-Antimycotic and 5x of Penicillin-Streptomycin were used to minimize contamination. These concentrations reduce the bacterial abundance, but contamination with fungi was still an issue. Cell morphology evaluation was performed daily and no obvious toxic effects on the cells was observed. Cell viability and cell division were evaluated with Trypan blue staining and cell counting in a haemocytometer. The results indicate that the cells are viable and that some cell division occurs, however more studies need to be performed to confirm this. Still, this study provides the first evidence that primary cultures of storage cells from tardigrades are possible to establish, but the culturing method has to be refined to avoid contamination.
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