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Cryptobiosis
Cryptobiosis is an ametabolic state of life entered by some lower organismsin response to adverse environmental conditions such as desiccation, freezing, and oxygendeficiency. In the cryptobiotic state, all metabolic procedures stop, preventing reproduction, development, and repair. An organismin a cryptobiotic state can essentially live indefinitely until environmental conditions return to being hospitable. When this occurs, the organismwill return to its metabolicstate of life as it was prior to the cryptobiosis.
AnhydrobiosisAnhydrobiosis is the most studied form of cryptobiosis and occurs in situations of extreme desiccation. The term anhydrobiosis derives from the Greek for "life without water" and is most commonly used for the desiccation tolerance observed in certain invertebrate animals such as bdelloid rotifers, tardigrades, brine shrimpsand nematodes. However, other life forms, including resurrection plants, the majority of plant seeds, and many micro-organisms such as bakers' yeast, also exhibit desiccation tolerance. Invertebrates undergoing anhydrobiosis often contract into a smaller shape and some proceed to form a sugarcalled trehalose. Desiccation tolerance in plants is associated with the production of another sugar, sucrose. These sugars are thought to protect the organism from desiccation damage, and studies have shown that anhydrobiotic organisms can survive for decades in the dry state. In some creatures, such as bdelloid rotifers, no trehalose has been found, which has led scientists to propose other mechanisms of anhydrobiosis. A new application, 2004, of anhydrobiosis is being applied to vaccines. The process allows some organisms to survive dried-up by replacing water with a sugar solution that keeps cells in a state of suspended animation until rehydration occurs. In vaccines, the process can produce a dry vaccine that reactivates once it is injected into the body. In theory, dry-vaccine technology could be used on any vaccine, including live vaccines such as the one for measles. It could also potentially be adapted to allow a vaccine's slow release, eliminating the need for boosters. This proposes to eliminate the need for refrigerating vaccines, thus making dry vaccines more widely available throughout the developing world where refrigeration, electricity, and proper storage are less accessible. (source BBC News: [1]) CryobiosisCryobiosis is a form of cryptobiosis that takes place in reaction to decreased temperature. To initiate cryobiosis, the organism freezes all of the water within its cells. This allows the organism to endure the freezing temperatures until more hospitable conditions return. Studies have shown that the longer an organism remains in cryobiosis, the longer it takes for the organism to come out of cryobiosis. This is because the organism must use its own energyto come out of cryobiosis, and the longer it stays in cryobiosis the less energy it has. OsmobiosisOsmobiosis is the least studied of the four types of cryptobiosis. Osmobiosis occurs in response to increased soluteconcentration in the solution the organism lives in. Not much is known for sure, other than that osmobiosis appears to involve a cessation of metabolism. AnoxybiosisAnoxybiosis isn't considered a form of cryptobiosis by some. It takes place in situations lacking oxygen, and involves the organism intaking water and becoming turgid and immobile. Studies have been done about survival rates of organisms during anoxybiosis, but have achieved conflicting results. ExamplesThe most commonly known organismwhich undergoes cryptobiosis is the tardigrade, or water bear. It is the most studied as well, partially because it can undergo all four types of cryptobiosis. While in this state their metabolismlowers to less than 0.01% of what is normal and their water content can drop to 1% of normal. They can withstand extreme temperature, radiation, and pressurewhile in a cryptobiotic state. See also
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Categories: Physiology
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