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Classification
Kingdom: Animalia
Phylum: Tardigrada
Class: Eutardigrada
Order: Parachela
Family: Macrobiotidae
Genus: Richtersius
Species: Richtersius Coronifer
Description and habitat
Richtersius coronifer is a species of Tardigrade, more commonly known as water bears. They are tiny animals, too small to be seen with the naked eye. They live in water droplets on moss, and can be found in basically any sample of moss from their home range. Despite their small size, these little guys are found over a very wide range, spanning from Europe across most of northern Asia and even into North America. They have squat, fat, transparent bodies with eight stubby legs sticking of. These legs are tipped with what look like hooked claws, four per leg. They have round mouth that they use for feeding on moss.
Why are These Guys Cool?
Despite their seemingly mundane appearance and lifestyle, Richtersius coronifer is actually a very interesting animal, primarily because of their adaptations to the instability of their moss home. The moss habitat of these tiny herbivores is highly unstable, and prone to drying out for uncertain periods of time. Richtersius coronifer has adapted to this extreme environment in a very extreme way. When their environment dries up, or is threatened in some other way, they enter a state of suspended animation by forming what is called a “tun.” In this tun state, the tardigrade withdraws its legs into its body, and loses most of the water in its cells. In this state they can survive for very long times without any water, allowing them to wait till the moss is wet again.
Richtersius coronifer shows these amazing abilities as well as any tardigrade. Experiments have shown that it can survive temperatures as cold as −196°C when submerged in liquid nitrogen. It can survive at these temperatures for up to 2 hours with no ill effects, and even after 24 hours survival rates are around 97% (Persson 2011). They can also withstand temperatures of 70°C for at least an hour (Ramløv 2001). They can also survive being submerged in 1-hexanol for up to seven days with no ill effects, and had a only a 42% decrease if submerged in 1-butanol for the same period of time (Ramløv 2001). They have also been shown to survive doses of gamma radiation up to 3 kGy (Persson 2011). Samples placed in the vacuum of space were also recovered largely unharmed and proceeded to lay eggs as if nothing odd had happened (Jӧnsson 2008).
Interesting Articles on Richtersius coronifer
The following are some interesting articles about Richtersius coronifer, describing some experiments that have been done to test these little creatures amazing survival abilities.
Cryptobiosis in the Eutardigrade Adorybiotus (Richtersius) coronifer: tolerance of Alcohols, Temperatures, and de novo Protien Syntesis:
This article looked at the ability of Richtersius coronifer to survive exposure to alcohols and high temperatures. In the first part tardigrades were exposed to 96% ethanol, 85% ethanol, 1-butanol, and 1-hexanol. The hexane had no effect on them, while the butanol decreased survival by 42% after 7 days. The Ethanol was found to be lethal, with those exposed to 965 living only hours and those exposed to 85% dead within 10 minutes. They also exposed the tardigrades to temperatures ranging form 50 to 100 degrees census. Up to 70 °C there was no drop in survival. Survival dropped to 20% by 80 °C, and no animal survived 100°C. They also looked at these animals to see if they were synthesizing any proteins wile in the tun state. Samples were dried and then their proteins were extracted and compared to samples taken form active tardigrades. While most proteins were found only in the active form or in both, one protein at 71 kDa was discovered only in the tuns, which suggests it was synthesized in that state.
However the tun is not just a way to wait out a dry spell, it also gives them many other extraordinary abilities. While in the tun state tardigrades can withstand heat, cold, high radiation, high pressure, toxic chemicals, extreme pH, and even the vacuum of space (Persson 2011). What’s more, once conditions are hospitable again, they can often come out of this state almost unaffected, and continue their lives as if nothing happened. Even their eggs are relatively indestructible, though not as much as the adults in their tuns.
Extreme stress tolerance in tardigrades: surviving space conditions in low earth orbit:In this experiment, Richtersius coronifer were exposed to the vacuum of space during a space flight. Canisters containing tuns were placed in tubes and left in the specimen chamber of a scanning electron microscope for 24 hours. They were exposed to pressures of approximately 2.9 × 10−8 Pa during this time, which is essentially a vacuum. Separate experiments were carried out to test their cold tolerance. Samples were placed in liquid nitrogen for 30 minutes, two hours, and 24 hours. After exposure to vacuum the tardigrades were revived with no casualties, and 90% suvrived 21 days, and some lasted as long as 110 days. The frozen ones all survived up to two hours of exposure, and 97% survived 24 hours of exposure. Even those who were exposed for 24 hours survived well for up to 35 days, with the last dying after 88 days. This experiment also looked at the number of eggs lain by each test group, and found that there was no decrease in the number compared to controls, and the ones exposed to vacuum seemed to actually lay more eggs.
Induction of Hsp70 by desiccation, ionizing radiation and heat-shock in the eutardigrade Richtersius coronifer:
This article investigated the roll of the protein Hsp70 in tardigrades ability to withstand desiccation. This protein is involved in helping proteins fold in animals under stress from heat. It was hypothesized that it may also help stabilize tardigrade cells during anhydrobiosis (when they are in their tun state). Six treatment groups were used; unstressed and hydrated animals, animals hydrated after anhydrobiosis one hour after rehydration, hydrated animals one hour after heat shock, anhydrobiotic animals, hydrated animals that were irradiated while in the anhydrobiotic state, and hydrated animals that were irradiated in the active state. All groups showed elevated Hsp70 after treatment, except those that where anhydrobiotic while being treated. This shows that Hsp70 is likely not involved in entering an anhydrobiotic state, though it may be involved in coming out of it. The study also suggested that Hsp70 may be involved in protecting cells from radiation by preventing cell death.
Tardigrades survive exposure to space in a low Earth orbit:
In this article, two species of tardigrades Richtersius coronifer and Milnesium tardigradum were exposed to different conditions in space. Three groups were used, along with a control. One group was exposed to just the vacuum of space and solar/galactic radiation, one was exposed to space and placed under a UVA,B light, and the third was exposed to space and a UVAll light. Both species were revived from and basically unaffected by exposure to the vacuum of space. Only 3 tardigrades were revived from exposure to UVAll and although about 68% exposed to UVA,B were revived, most died fairly quickly afterwards. This experiment shows that tardigrades can survive in very extreme conditions such as the vacuum of space, placing them in a small group of organisms such as bacteria and lichens which are capable of this extreme feat, and making them the first animal to do so.
Work Cited
Jӧnsson, K. I., Beltrán-Pardo E. a., Haghdoost, S. Wojcik, A. Bermúdez-Cruz, M., bernal villegas J. E., Harms-Ringdahl, M.. (2013) Tolerance of gamma-irradiation in eggs of the tardigrade Richtersius coronifer depends on stage of development. Journal of Limnology. 72(1s) 73-79. Doi:10.4081/jlimnol.2013.sl.e9 http://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2013.s1.e9
Jӧnsson, K. I., Schill, R. O.. (2006) Induction of Hsp70 by desiccation, ionizing radiation and heat-shock in Eutardigrade Richtersius coronifer. Comparative biochemistry and Physiology Part B: Biochemicstry and Molecular Biology. 146(4), 456-460. Doi:1016/j.cbpb.2006.10.111 http://www.sciencedirect.com/science/article/pii/S1096495906004362
Jӧnsson, K. I., Rabbow, E., Schill, R. O. Harms-Ringdahl, M., Rettberg P.. (2008) Tardigrades survive exposure to space in low Earth orbit. Current biology. 8(13), R729-731. Doi: 10.1016/j.cub.2008.06.048http://www.sciencedirect.com/science/article/pii/S0960982208008051
Persson D., Halberg K. A., Jørgensen, A., Ricci, C. Møbjerg, N., Kristensen, R. M. (2011) Extreme stress tolerance in tardigrades: surviving space conditions in low earth orbit. Journal of Zoological Systematics and Evolutionary Research. 49(s1) 90-97. DOI: 10.1111/j.1439-0469.2010.00605.x http://onlinelibrary.wiley.com/doi/10.1111/j.1439-0469.2010.00605.x/full
Ramløv, H., Westh, P. (2001). Cryptobiosis in the Eutardigrade Adorybiotus (Richtersius) coronifer: tolerance of Alcohols, Temperatures, and de novo Protien Syntesis. Zoologischer Anzeiger. 240(3-4) 517-523. Doi: 10.1078/0044-5231-00062 http://www.sciencedirect.com/science/article/pii/S0044523104700534
Richtersius coronifer (2015, December 1) http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=711047
Untitled drawing of Richtersius coronifer [online image]. Retrieved from http://www.snipview.com/q/Richtersius_coronifer
Untitled electron micrograph of Richtersius coronifer [online image]. Retrieved from http://img-fotki.yandex.ru/get/5200/katoga.0/0_51079_72790507_L.jpg
Untitled photograph of Richtersius coronifer [online image]. Retrieved from http://cdn-ak.f.st-hatena.com/images/fotolife/h/horikawad/20110509/20110509001733.jpg
Welnichz, W., Grohme, M. A., Kaczmarek, Ł., Schill, R. O., Frohme, M.. (2011) Anhydrobiosis in tardigrades – The last decade. Journal of insect Physiology. 57(5) 577-583. Doi:10.1016/j.jinsphys.2011.03.019 http://www.sciencedirect.com/science/article/pii/S0022191011000874
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