| 1. |
- Czernekova, Michaela, et al.
(författare)
-
A comparative ultrastructure study of storage cells in the eutardigrade Richtersius coronifer in the hydrated state and after desiccation and heating stress
- 2018
-
Ingår i: PLOS ONE. - 1932-6203. ; 13:8
-
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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| 2. |
- Czernekova, Michaela, et al.
(författare)
-
A comparative ultrastructure study of storage cells in the eutardigrade Richtersius coronifer in the hydrated state and after desiccation and heating stress
- 2018
-
Ingår i: PLoS ONE. - : Public Library of Science. - 1932-6203. ; 13:8
-
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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| 3. |
- Czernekova, Michaela, et al.
(författare)
-
Evaluation of extraction methods for quantitative analysis of tardigrade populations in soil and leaf litter
- 2018
-
Ingår i: Pedobiologia. - : Elsevier. - 0031-4056 .- 1873-1511. ; 70, s. 1-5
-
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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| 4. |
- Czernekova, Michaela, et al.
(författare)
-
Evaluation of extraction methods for quantitative analysis of tardigrade populations in soil and leaf litter
- 2018
-
Ingår i: Pedobiologia. - : Urban und Fischer Verlag Jena. - 0031-4056 .- 1873-1511. ; 70, s. 1-5
-
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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| 5. |
- Czernekova, Michaela, et al.
(författare)
-
Experimentally induced repeated anhydrobiosis in the Eutardigrade Richtersius coronifer
- 2016
-
Ingår i: PLOS ONE. - 1932-6203. ; 11:11
-
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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| 6. |
- Czernekova, Michaela, et al.
(författare)
-
Experimentally induced repeated anhydrobiosis in the Eutardigrade Richtersius coronifer
- 2016
-
Ingår i: PLoS ONE. - : Public Library of Science. - 1932-6203. ; 11:11
-
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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| 7. |
- Czernekova, Michaela, et al.
(författare)
-
Mitosis in storage cells of the eutardigrade Richtersius coronifer
- 2016
-
Ingår i: Zoological Journal of the Linnean Society. - 0024-4082 .- 1096-3642. ; 178:4, s. 888-896
-
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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| 8. |
- Czernekova, Michaela, et al.
(författare)
-
Mitosis in storage cells of the eutardigrade Richtersius coronifer
- 2015
-
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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| 9. |
- Czernekova, Michaela, et al.
(författare)
-
Mitosis in storage cells of the eutardigrade Richtersius coronifer
- 2016
-
Ingår i: Zoological Journal of the Linnean Society. - : Oxford University Press. - 0024-4082 .- 1096-3642. ; 178:4, s. 888-896
-
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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| 10. |
- Czernekova, Michaela, et al.
(författare)
-
Mitosis in storage cells of the eutardigrade Richtersius coronifer
- 2015
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)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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