Tardigrades, also known as water bears or moss piglets, are microscopic invertebrates that are found in almost every corner of the world. They are renowned for their remarkable ability to withstand extreme conditions that would be lethal to most other forms of life, including exposure to radiation, extreme temperatures, desiccation, and even the vacuum of space.
Tardigrades have a cylindrical body that is divided into four segments, each of which has a pair of legs with claws at the end for gripping surfaces. They are typically 0.1 to 1.5 millimeters in length and have a mouth located at the anterior end of their body. They are found in many different habitats, including freshwater, marine environments, and moist terrestrial habitats such as mosses and lichens. One of the most remarkable features of tardigrades is their ability to enter a state of suspended animation known as cryptobiosis, which allows them to survive in extremely harsh environments.
During cryptobiosis, tardigrades lose almost all of their water and become almost completely dehydrated. In this state, they are able to survive for years without water, oxygen, or food. When conditions become favorable again, tardigrades can rehydrate and resume their normal metabolic activities.
Tardigrades have also been shown to be able to survive extreme temperatures, both hot and cold. Some species can survive temperatures as low as -457.6 degrees Fahrenheit (just above absolute zero) and as high as 303.8 degrees Fahrenheit. They are also able to survive exposure to high levels of radiation and can withstand pressures that are thousands of times greater than atmospheric pressure.
The ability of tardigrades to survive in such extreme conditions has attracted the attention of scientists who are interested in understanding the molecular mechanisms that allow these organisms to withstand such stress. Studies have identified several genes and proteins that are involved in protecting tardigrades from environmental stress, including proteins that stabilize their cellular membranes and protect their DNA from damage.
In addition to their scientific importance, tardigrades have captured the public imagination due to their unusual appearance and remarkable abilities. They have been the subject of numerous documentaries, popular science books, and even video games.
- Cryptobiosis is a state of suspended animation that enables certain organisms to survive extreme environmental conditions, such as desiccation, freezing, or exposure to radiation. During cryptobiosis, the metabolism of the organism slows down to a near halt, and all vital functions cease, allowing the organism to remain dormant for prolonged periods until conditions become favorable again for it to resume normal activities. Several groups of organisms, including tardigrades, nematodes, rotifers, and some types of bacteria, are known to be capable of cryptobiosis, and recent research has shed light on some of the molecular processes involved. Understanding the mechanisms of cryptobiosis has practical applications in fields such as biotechnology, agriculture, and medicine, such as developing new methods for preserving cells, tissues, and organs for transplantation, by inducing a state of suspended animation similar to cryptobiosis. [Back]
- Beresheet was a privately-funded Israeli spacecraft developed by the nonprofit organization SpaceIL and Israel Aerospace Industries (IAI) with the aim of landing on the Moon. The spacecraft was launched on February 21, 2019, and although it successfully entered lunar orbit, it experienced technical difficulties during its landing attempt on April 11, 2019, and crashed onto the lunar surface. Despite the mission’s failure to land on the Moon, it was widely celebrated for being the first privately-funded spacecraft to attempt a lunar landing. [Back]
- Guidetti, R., Altiero, T., Rebecchi, L., & Cesari, M. (2011). Tardigrade resistance to space effects: first results of experiments on the LIFE-TARSE mission on FOTON-M3 (September 2007). Astrobiology, 11(7), 651-659.
- Jönsson, K. I., Rabbow, E., Schill, R. O., Harms-Ringdahl, M., & Rettberg, P. (2008). Tardigrades survive exposure to space in low Earth orbit. Current Biology, 18(17), R729-R731.
- Boothby, T. C., Tenlen, J. R., Smith, F. W., Wang, J. R., Patanella, K. A., Osborne Nishimura, E., … & Goldstein, B. (2015). Evidence for extensive horizontal gene transfer from the draft genome of a tardigrade. Proceedings of the National Academy of Sciences, 112(52), 15976-15981.
- Nelson, D. R. (2002). Current status of the tardigrada: evolution and ecology. Integrative and Comparative Biology, 42(3), 652-659.
- Erkut et al., 2011; Jönsson et al., 2008; Horikawa et al., 2012; Boothby et al., 2015; Boothby et al., 2021
- BBC Science Focus