Anhydrobiotic tardigrades show higher heat tolerance

What the study found: The study found inducible thermotolerance in the eutardigrade Paramacrobiotus sp., linked to its anhydrobiotic, or dried-out, tun state. Active tardigrades did not survive 45°C for 1 hour, while about 90% of tun-state tardigrades did, and some survived temperatures up to 85°C.
Why the authors say this matters: The authors conclude that modulation of thermal conductivity may be a physical mechanism contributing to heat tolerance in anhydrobiotic tardigrades. They say these findings offer new insight into how these animals survive thermal stress.
What the researchers tested: The researchers compared active and anhydrobiotic tardigrades and measured thermal conductivity with a custom-built vacuum apparatus. They examined whether differences in heat transfer could help explain the tun state’s heat tolerance.
What worked and what didn't: The tun state showed significantly higher thermal resistance than the active form. Active tardigrades did not survive the 45°C, 1-hour exposure, whereas most tun-state animals did; some withstood temperatures up to 85°C.
What to keep in mind: The abstract does not describe additional limitations beyond the scope of the reported comparison. The findings are based on Paramacrobiotus sp. and the conditions tested in this study.

Key points

• Paramacrobiotus sp. showed inducible thermotolerance in its anhydrobiotic tun state.
• About 90% of tun-state tardigrades survived 45°C for 1 hour, while active ones did not.
• Some tun-state tardigrades survived temperatures up to 85°C.
• The researchers measured thermal conductivity using a custom-built vacuum apparatus.
• The authors link higher thermal resistance in the tun state to reduced heat transfer.