Desiccation

Desiccation is the state of extreme dryness, or the process of extreme drying.

A desiccant is a hygroscopic (water-attracting) substance that causes desiccation in a moderately sealed container.

Biology

Desiccation tolerance refers to the ability of an organism to withstand or endure extreme dryness, or drought-like conditions.

Plants and animals living in arid or periodically arid environments such as temporary streams or ponds may face desiccation, therefore physiological or behavioural adaptations are necessary to ensure survival. In particular, insects occupy a wide range of ecologically diverse niches and so have a variety of strategies to avoid desiccation.

Desiccation resistance in insects is generally measured by the change in mass during dry conditions.^[1] The overall mass difference between measurements before and after aridity exposure is attributed to body water loss.

Extreme cases

Cryptobiosis refers to the state of an organism that has no detectable metabolic activity, resulting from extreme and unfavorable environmental conditions.
Anhydrobiosis refers to the state of surviving the loss of (almost) all body water.

Tardigrades

Tardigrades are able to live in environments that would kill most animals.^[2] In 2007, scientists discovered that some tardigrades were able to survive 10 days in outer space.^[3][4] Tardigrades can survive more than ten years without water.^[5]

Rotifers

Rotifers are specialists at living in habitats where water dries up regularly.

The Monogononta, which have males, produce fertilised 'resting eggs' which can resist desiccation (drought) for long periods.^[6]

The Bdelloids, who have no males, contract into an inert form and lose almost all body water, a process known as cryptobiosis. Bdelloids can also survive the dry state for long periods: the longest well-documented dormancy is nine years. After they have dried, they may be revived by adding water.^[7]

References

1. Chown S.L. & Nicolson S.W. (2004). "Insect physiological ecology". New York: Oxford University Press.
2. Neuman, Yair (October 2006). "Cryptobiosis: A new theoretical perspective". Progress in Biophysics and Molecular Biology. 92 (2). Elsevier: 258–267. doi:10.1016/j.pbiomolbio.2005.11.001. PMID 16380155.
3. Jönsson, K. Ingema (9 September 2008). "Tardigrades survive exposure to space in low Earth orbit". Current Biology. 18 (17). Rabbow, Elke; Schill, Ralph O.; Harms-Ringdahl, Mats; Rettberg, Petra. Elsevier Ltd: R729–R731. doi:10.1016/j.cub.2008.06.048. PMID 18786368. S2CID 8566993. Retrieved 1 January 2011.
4. Whalen, Joann K.; Sampedro, Luis (2010). Soil Ecology and Management (illustrated ed.). CABI. pp. 73. ISBN 978-1845935634.
5. Grimaldi, David A.; Engel, Michael S. (2005). Michael S. Engel (ed.). Evolution of the insects. Cambridge Evolution Series (illustrated, reprint ed.). Cambridge University Press. pp. 97. ISBN 0-521-82149-5.
6. Örstan A. 1995. Desiccation survival of the eggs of the rotifer Adineta vaga (Davis 1873). Hydrobiologia 313/314:373-375
7. Kirk, Kevin L. et al. 1999. Physiological responses to variable environments: storage and respiration in starving rotifers. Freshwater Biology 42 637-644.