Tun formation is not a prerequisite for desiccation tolerance in the marine tidal tardigrade Echiniscoides sigismundi

The so-called ‘tun’ state is best known from limno-terrestrial tardigrades and rotifers that rely on this compact body shape for anhydrobiotic survival. Little is known of tun formation in marine species and the evolutionary origin of the state is presently unknown. Here, we investigate desiccation tolerance and tun formation in the marine tidal echiniscoidean tardigrade, Echiniscoides sigismundi (M. Schultze, 1865). Groups of approximately 20 E. sigismundi sampled from Lynæs (Denmark) were dehydrated on filter paper from seawater as well as ultrapurified water and kept for 48 h at 5 °C, after which they were rehydrated in seawater. The activity and behaviour of the tardigrades was examined under a light microscope, whereas scanning electron microscopy was used for high-resolution three-dimensional imaging. When dehydrated from seawater, E. sigismundi enters a tun, however, when exposed to ultrapurified water, the tardigrade swells and becomes incapable of movement, and thus incapable of tun formation. Nonetheless, E. sigismundi tolerates being dehydrated from ultrapurified water, revealing an exceptional and unparalleled resilience towards losing structural integrity. Our results confirm previous investigations, which suggest that tun formation relies on a functional musculature. They further suggest that tun formation may have evolved as a response to elevated external pressure rather than desiccation per se

Osmotic stress tolerance in semi-terrestrial tardigrades

Heidemann, Nanna W. T., Smith, Daniel K., Hygum, Thomas L., Stapane, Lilian, Clausen, Lykke K. B., Jørgensen, Aslak, Helix-Nielsen, Claus, Møbjerg, Nadja (2016): Osmotic stress tolerance in semi-terrestrial tardigrades. Zoological Journal of the Linnean Society 178 (4): 912-918, DOI: 10.1111/zoj.12502, URL: http://dx.doi.org/10.1111/zoj.1250

Comparative Investigation of Copper Tolerance and Identification of Putative Tolerance Related Genes in Tardigrades

Tardigrades are microscopic aquatic animals renowned for their tolerance toward extreme environmental conditions. The current study is the first to investigate their tolerance toward heavy metals and we present a novel tardigrade toxicant tolerance assay based on activity assessments as a measure of survival. Specifically, we compare tolerance toward copper in four species representing different evolutionary lineages, habitats and adaptation strategies, i.e., a marine heterotardigrade, Echiniscoides sigismundi , a limno-terrestrial heterotardigrade, Echiniscus testudo , a limno-terrestrial eutardigrade, Ramazzottius oberhaeuseri , and a marine eutardigrade, Halobiotus crispae . The latter was sampled at a time of year, when the population is predominantly represented by aberrant P1 cysts, while the other species were in normal active states prior to exposure. Based on volume measurements and a general relation between body mass and copper tolerance, expected tardigrade EC50 values were estimated at 0.5–2 μg l −1 . Following 24 h of exposure, tolerance was high with no apparent link to lineage or habitat. EC50s (95% CI), 24 h after exposure, were estimated at 178 (168–186) and 310 (295–328) μg l −1 , respectively, for E. sigismundi and R. oberhaeuseri , whereas E. testudo and H. crispae were less affected. Highest tolerance was observed in H. crispae with a mean ± s.e.m . activity of 77 ± 2% ( n = 3) 24 h after removal from ~3 mg l −1 copper, suggesting that tardigrade cysts have increased tolerance toward toxicants. In order to identify putative tolerance related genes, an E. sigismundi transcriptome was searched for key enzymes involved in osmoregulation, antioxidant defense and copper metabolism. We found high expression of Na/K ATPase and carbonic anhydrase, known targets for copper. Our transcriptome, furthermore, revealed high expression of antioxidant enzymes, copper transporters, ATOX1, and a Cu-ATPase. In summary, our results indicate that tardigrades express well-known key osmoregulatory enzymes, supporting the hypothesis that copper inhibits sodium turnover as demonstrated for other aquatic organisms. Tardigrades, nevertheless, have high tolerance toward the toxicant, which is likely linked to high expression of antioxidant enzymes and an ability to enter dormant states. Tardigrades, furthermore, seem to have a well-developed battery of cuproproteins involved in copper homeostasis, providing basis for active copper sequestering and excretion

Data E sigismundi radiation tolerance_Jönsson et al

Doses of gamma ray are given in the unit "Gray"

Data from: Tolerance to gamma radiation in the marine heterotardigrade, Echiniscoides sigismundi

Tardigrades belong to the most radiation tolerant animals on Earth, as documented by a number of studies using both low-LET and high-LET ionizing radiation. Previous studies have focused on semi-terrestrial species, which are also very tolerant to desiccation. The predominant view on the reason for the high radiation tolerance among these semi-terrestrial species, is that it relies on molecular mechanisms that evolved as adaptations for surviving dehydration. In this study we report the first study on radiation tolerance in a marine tardigrade, Echiniscoides sigismundi. Adult specimens in the hydrated active state were exposed to doses of gamma radiation from 100 to 5000 Gy. The results showed little effect of radiation at 100 and 500 Gy but a clear decline in activity at 1000 Gy and higher. The highest dose survived was 4000 Gy, at which ca. 8% of the tardigrades were active 7 days after irradiation. LD50 in the first 7 days after irradiation was in the range of 1100-1600 Gy. Compared to previous studies on radiation tolerance in semi-terrestrial and limnic tardigrades, Echiniscoides sigismundi seems to have a lower tolerance. However, the species still fits into the category of tardigrades that have high tolerance to both desiccation and radiation, supporting the hypothesis that radiation tolerance is a by-product of adaptative mechanisms to survive desiccation. More studies on radiation tolerance in tardigrade species adapted to permanently wet conditions, both marine and freshwater, are needed to obtain a more comprehensive picture of the patterns of radiation tolerance

Data from: Tolerance to gamma radiation in the marine heterotardigrade, Echiniscoides sigismundi

Tardigrades belong to the most radiation tolerant animals on Earth, as documented by a number of studies using both low-LET and high-LET ionizing radiation. Previous studies have focused on semi-terrestrial species, which are also very tolerant to desiccation. The predominant view on the reason for the high radiation tolerance among these semi-terrestrial species, is that it relies on molecular mechanisms that evolved as adaptations for surviving dehydration. In this study we report the first study on radiation tolerance in a marine tardigrade, Echiniscoides sigismundi. Adult specimens in the hydrated active state were exposed to doses of gamma radiation from 100 to 5000 Gy. The results showed little effect of radiation at 100 and 500 Gy but a clear decline in activity at 1000 Gy and higher. The highest dose survived was 4000 Gy, at which ca. 8% of the tardigrades were active 7 days after irradiation. LD50 in the first 7 days after irradiation was in the range of 1100-1600 Gy. Compared to previous studies on radiation tolerance in semi-terrestrial and limnic tardigrades, Echiniscoides sigismundi seems to have a lower tolerance. However, the species still fits into the category of tardigrades that have high tolerance to both desiccation and radiation, supporting the hypothesis that radiation tolerance is a by-product of adaptative mechanisms to survive desiccation. More studies on radiation tolerance in tardigrade species adapted to permanently wet conditions, both marine and freshwater, are needed to obtain a more comprehensive picture of the patterns of radiation tolerance

Mean proportion of adult <i>Echiniscoides sigismundi</i> showing activity after exposure to different doses of gamma radiation.

<p>The figure shows estimates from four different time points after irradiation, from 24h to 7 days. Error bars represent standard errors of the mean from 3 repeats, each with approx. 20 animals.</p

Figure 1. A in Osmotic stress tolerance in semi-terrestrial tardigrades

Figure 1. A, Light micrograph of Ramazzottius oberhaeuseri. Scale bar = 100 µm. B, Activity in percentage (mean ƚ SEM) of R. oberhaeuseri in experimental series (N = 3–6) with acute exposures to 192 ƚ 1, 463 ƚ 1, 560 ƚ 1 and 758 1 mOsm kg—1 NaCl solutions. The four graph lines (open symbols) the activity in ƚ top express percentage (mean ƚ SEM) of the corresponding control groups (N = 3–6) in purified water. C, Light micrograph of Echiniscus testudo. Scale bar = 100 µm. D, Activity in percentage (mean ƚ SEM) of Echiniscus testudo in experimental series (N = 3–6) with acute exposures to 93 0, 192 1, 281 0 and 463 1 mOsm kg—1 NaCl solutions. The top four graph lines (open ƚ ƚ ƚ ƚ symbols) express the activity in percentage (mean ƚ SEM) of the corresponding control groups (N = 3–6) in purified water. In B and D t = 0 h represents the activity in purified water immediately prior to osmolyte exposure, whereas t = 24 h indicates the activity after exposure to a given test solution for 24 h. The tardigrades were subsequently transferred to purified water and their activity was assessed at t = 26 h, t = 48 h and t = 72 h.Published as part of &lt;i&gt;Heidemann, Nanna W. T., Smith, Daniel K., Hygum, Thomas L., Stapane, Lilian, Clausen, Lykke K. B., Jørgensen, Aslak, Helix-Nielsen, Claus &amp; Møbjerg, Nadja, 2016, Osmotic stress tolerance in semi-terrestrial tardigrades, pp. 912-918 in Zoological Journal of the Linnean Society 178 (4)&lt;/i&gt; on page 915, DOI: 10.1111/zoj.12502, &lt;a href="http://zenodo.org/record/10110738"&gt;http://zenodo.org/record/10110738&lt;/a&gt