Cryptobiosis

Cryptobiosis

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Encyclopedia
Cryptobiosis is an ametabolic state of life entered by an organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...

 in response to adverse environmental conditions such as desiccation
Desiccation
Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic substance that induces or sustains such a state in its local vicinity in a moderately sealed container.-Science:...

, freezing
Freezing
Freezing or solidification is a phase change in which a liquid turns into a solid when its temperature is lowered below its freezing point. The reverse process is melting....

, and oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 deficiency. In the cryptobiotic state, all metabolic procedures stop, preventing reproduction, development, and repair. An organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...

 in a cryptobiotic state can essentially live indefinitely until environmental conditions return to being hospitable. When this occurs, the organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...

 will return to its metabolic
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

 state of life as it was prior to the cryptobiosis.

Anhydrobiosis


Anhydrobiosis is the most studied form of cryptobiosis and occurs in situations of extreme desiccation
Desiccation
Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic substance that induces or sustains such a state in its local vicinity in a moderately sealed container.-Science:...

. 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 shrimp
Brine shrimp
Artemia is a genus of aquatic crustaceans known as brine shrimp. Artemia, the only genus in the family Artemiidae, has changed little externally since the Triassic period...

, nematodes, and at least one species of chironomid (Polypedilum vanderplanki
Polypedilum vanderplanki
Polypedilum vanderplanki or the sleeping chironomid, is a dipteran in the family Chironomidae. It occurs in northern Nigeria and Uganda where its larvae grow in temporary pools of water that frequently dry out during the lifetime of P. vanderplanki larvae. Under these conditions, the larvae's body...

). However, other life forms, including the resurrection plant
Resurrection plant
A resurrection plant is any plant with the habit of reviving after seeming to be dead or of seeming to revive when being in fact dead.Examples include...

 Craterostigma plantagineum, 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 sugar
Sugar
Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...

 called trehalose
Trehalose
Trehalose, also known as mycose or tremalose, is a natural alpha-linked disaccharide formed by an α,α-1,1-glucoside bond between two α-glucose units. In 1832, H.A.L. Wiggers discovered trehalose in an ergot of rye, and in 1859 Marcellin Berthelot isolated it from trehala manna, a substance made...

. 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
Trehalose
Trehalose, also known as mycose or tremalose, is a natural alpha-linked disaccharide formed by an α,α-1,1-glucoside bond between two α-glucose units. In 1832, H.A.L. Wiggers discovered trehalose in an ergot of rye, and in 1859 Marcellin Berthelot isolated it from trehala manna, a substance made...

 has been found, which has led scientists to propose other mechanisms of anhydrobiosis.

As of 2004, a new application of anhydrobiosis is being applied to vaccine
Vaccine
A vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe or its toxins...

s. The process allows some organisms to survive being dried-up by replacing water with a sugar solution that keeps cells in a state of suspended animation
Suspended animation
Suspended animation is the slowing of life processes by external means without termination. Breathing, heartbeat, and other involuntary functions may still occur, but they can only be detected by artificial means. Extreme cold can be used to precipitate the slowing of an individual's functions; use...

 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.

Based on the principles of anhydrobiosis, lyopreservation
Lyopreservation
Lyopreservation is biomimetic strategy based on anhydrobiosis to preserve cells at ambient temperature. It has been explored as an alternative technique for cryopreservation. The technique has the advantages of being able to preserve biological samples at ambient temperature without the need for...

 has been developed as a technique for preservation of biological samples at ambient temperatures.

Anoxybiosis


Anoxybiosis isn't considered a form of cryptobiosis by some. It takes place in situations lacking oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

, and involves the organism intaking water and becoming turgid and immobile. Studies of the survival rates of organisms during anoxybiosis have given conflicting results.

Chemobiosis


Chemobiosis is the cryptobiotic response to high levels of environmental toxins.

Cryobiosis


Cryobiosis is a form of cryptobiosis that takes place in reaction to decreased temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

. Cryobiosis initiates when the water surrounding the organism's cells has been frozen, stopping molecule mobility and allowing the organism to endure the freezing temperatures until more hospitable conditions return. Organisms capable of enduring these conditions typically feature molecules that facilitate freezing of water in preferential locations while also prohibiting the growth of large ice crystals that could otherwise damage cells.

Osmobiosis


Osmobiosis is the least studied of all types of cryptobiosis. Osmobiosis occurs in response to increased solute
Solution
In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...

 concentration in the solution the organism lives in. Little is known for certain, other than that osmobiosis appears to involve a cessation of metabolism.

Examples


A commonly-known organism that undergoes cryptobiosis is Artemia salina, also known as the brine shrimp
Brine shrimp
Artemia is a genus of aquatic crustaceans known as brine shrimp. Artemia, the only genus in the family Artemiidae, has changed little externally since the Triassic period...

 or by its brand name Sea-monkeys. This species, which can be found in the Makgadikgadi Pans in Botswana
Botswana
Botswana, officially the Republic of Botswana , is a landlocked country located in Southern Africa. The citizens are referred to as "Batswana" . Formerly the British protectorate of Bechuanaland, Botswana adopted its new name after becoming independent within the Commonwealth on 30 September 1966...

, survives over the dry season when the water of the pans evaporates, leaving a virtually desiccated lake bed.

The tardigrade
Tardigrade
Tardigrades form the phylum Tardigrada, part of the superphylum Ecdysozoa. They are microscopic, water-dwelling, segmented animals with eight legs. Tardigrades were first described by Johann August Ephraim Goeze in 1773...

, or water bear, is a widely studied and notable example, partially because it can undergo all five types of cryptobiosis. While in a cryptobiotic state, the tardigrade's metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

 reduces to less than 0.01% of what is normal, and its water content can drop to 1% of normal. It can withstand extreme temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

, radiation
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...

, and pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...

 while in a cryptobiotic state.

Some nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...

s and rotifer
Rotifer
The rotifers make up a phylum of microscopic and near-microscopic pseudocoelomate animals. They were first described by Rev. John Harris in 1696, and other forms were described by Anton van Leeuwenhoek in 1703...

s can also undergo cryptobiosis.

See also

  • Cryptobiotic soil
    Cryptobiotic soil
    A Cryptobiotic soil is a biological soil crust composed of living cyanobacteria, green algae, brown algae, fungi, lichens, and/or mosses. Commonly found in arid regions around the world, cryptobiotic soils go by many names, including cryptogamic, microbiotic, or microphytic soils or crusts...

  • Biostasis
    Biostasis
    Biostasis is the ability of an organism to tolerate environmental changes without having to actively adapt to them. The word is also used as a synonym for cryostasis or cryonics. It is found in organisms that live in habitats that may encounter unfavourable living conditions...

  • Cryonics
    Cryonics
    Cryonics is the low-temperature preservation of humans and animals who can no longer be sustained by contemporary medicine, with the hope that healing and resuscitation may be possible in the future. Cryopreservation of people or large animals is not reversible with current technology...

  • Hibernation
    Hibernation
    Hibernation is a state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and lower metabolic rate. Hibernating animals conserve food, especially during winter when food supplies are limited, tapping energy reserves, body fat, at a slow rate...

  • Lyopreservation
    Lyopreservation
    Lyopreservation is biomimetic strategy based on anhydrobiosis to preserve cells at ambient temperature. It has been explored as an alternative technique for cryopreservation. The technique has the advantages of being able to preserve biological samples at ambient temperature without the need for...


Further Reading

  • David A. Wharton, Life at the Limits: Organisms in Extreme Environments, Cambridge University Press, 2002, hardcover, ISBN 0-521-78212-0
  • Illinois Wesleyan University Tardigrade Facts