Effect of ultra-high pressure on small animals, tardigrades and Artemia

Abstract

This research shows that small animals, tardigrades (Milnesium tardigradum) in tun (dehydrated) state and Artemia salina cists (dried eggs) can tolerate the very high hydrostatic pressure of 7.5 GPa. It was really surprising that living organisms can survive after exposure to such a high pressure. We extended these studies to the extremely high pressure of 20 GPa by using a Kawai-type octahedral anvil press. After exposure to this pressure for 30 min, the tardigrades were soaked in pure water and investigated under a microscope. Their bodies regained metabolic state and no serious injury could be seen. But they were not alive. A few of Artemia eggs went part of the way to hatching after soaked in sea water, but they never grew any further. Comparing with the case of blue-green alga, these animals are weaker under ultra-high pressure.

Keywords:

• high pressure biology
• pressure tolerance
• tardigrade
• Milnesium tardigradum
• Artemia salina
• study of matter at extreme conditions

Public Interest Statement

We found that small animals, water bares in dehydrated state and plankton eggs and plant seeds of white clover and moss spores can tolerate the very high pressure of 775,000 atmosphere for at least 1 h. We extended these studies to the extremely high pressure of 200,000 atmosphere. In the bodies of water bares, no serious injury could be seen. But they were not alive. A few of plankton Artemia eggs went part of the way to hatching after being soaked in sea water, but they never grew any further. But, it was really surprising that living organisms can survive or nearly survive after exposure to such ultra-high pressures. This pressure corresponds to that of the depth of 550–600 km below the earth’s surface. The results may give the possibility that a small creature can travel through the space in a large meteorite.

Acknowledgments

Fumihisa Ono wishes his sincere thanks to Dr. Masaya Sougawa for his kind help in generating high pressure. This paper presents a result of a joint research programme carried out at the Institute for Study of the Earth’s Interior, Okayama University.

Additional information

Funding

Funding. The authors received no direct funding for this research.

Notes on contributors

Fumihisa Ono

Fumihisa Ono has been engaged in research study on Physical properties of materials under high pressure. One day, he thought of putting small animals in the high-pressure cell which he has been using, and consulted a biologist. The first candidate was tardigrades in tun state. It was surprising that all of the 20 tardigrades could tolerate the very high pressure of 7.5 GPa for at least 6 h. The study has been extended to other plants and animals by joining Physics and Biology groups. All the specimens investigated so far were found alive after exposure to the high pressure for at least 1 h. Then a big question arose what mechanism made the living creatures so strong against high pressure. To solve this question discussion has been made among Okayama, Rome and Montpellier groups. The pressure has been extended to 20 GPa by joining Misasa group.