Aestivation
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Aestivation (
Invertebrate and vertebrate animals are known to enter this state to avoid damage from high temperatures and the risk of desiccation. Both terrestrial and aquatic animals undergo aestivation. Fossil records suggest that aestivation may have evolved several hundred million years ago.
Physiology
Organisms that aestivate appear to be in a fairly "light" state of dormancy, as their physiological state can be rapidly reversed, and the organism can quickly return to a normal state. A study done on Otala lactea, a snail native to parts of Europe and Northern Africa, shows that they can wake from their dormant state within ten minutes of being introduced to a wetter environment.
The primary physiological and biochemical concerns for an aestivating animal are to conserve energy, retain water in the body, ration the use of stored energy, handle the nitrogenous end products, and stabilize bodily organs, cells, and macromolecules. This can be quite a task as hot temperatures and arid conditions may last for months, in some cases for years. The depression of metabolic rate during aestivation causes a reduction in macromolecule synthesis and degradation. To stabilise the macromolecules, aestivators will enhance antioxidant defenses and elevate chaperone proteins. This is a widely used strategy across all forms of hypometabolism. These physiological and biochemical concerns appear to be the core elements of hypometabolism throughout the animal kingdom. In other words, animals which aestivate appear to go through nearly the same physiological processes as animals that hibernate.[2]
Invertebrates
Mollusca
Gastropoda: some air-breathing land snails, including species in the genera Helix, Cernuella, Theba, Helicella, Achatina and Otala, commonly aestivate during periods of heat. Some species move into shaded vegetation or rubble. Others climb up tall plants, including crop species as well as bushes and trees, and will also climb human-made structures such as posts, fences, etc.
Their habit of climbing vegetation to aestivate has caused more than one introduced snail species to be declared an agricultural nuisance.
To seal the opening to their shell to prevent water loss, pulmonate land snails secrete a membrane of dried mucus called an epiphragm. In certain species, such as Helix pomatia, this barrier is reinforced with calcium carbonate, and thus it superficially resembles an operculum, except that it has a tiny hole to allow some oxygen exchange.[citation needed]
There is a decrease in
Arthropoda
Crustacea: An example of a crustacean undergoing aestivation is with the Australian crab Austrothelphusa transversa , which undergoes aestivation underground during the dry season.[10]
Vertebrates
Reptiles and amphibians
Non-mammalian animals that aestivate include North American desert tortoises, crocodiles, and salamanders. Some amphibians (e.g. the cane toad and greater siren) aestivate during the hot dry season by moving underground where it is cooler and more humid. The California red-legged frog may aestivate to conserve energy when its food and water supply is low.[12]
The
The
Fish
Mammals
Although relatively uncommon, a small number of mammals aestivate.
See also
- Critical thermal maximum
- Hibernation induction trigger
- Siesta
- Torpor
References
- ISBN 978-0-444-52949-7.
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- doi:10.1071/ZO97009.
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- Audubon Guides. Archived from the originalon 21 November 2018. Retrieved 5 September 2012.
- ^ Pough, F. H.; Andrews, R. M.; Cadle, J. E.; Crump, M. L.; Savitzky, A. H.; Wells, K. D. (2001). Herpetology, second edition. Upper Saddle River, New Jersey: Prentice Hall.
- ^ Burbrige, Andrew; Kuchling, Gerald (2004). Western swamp tortoise (Pseudemydura umbrina) recovery plan (PDF) (3 ed.). Perth, Western Australia: Dept. of Conservation and Land Management. Retrieved 26 November 2015.
- PMID 4411892.
- JSTOR 986798.
- ISBN 978-0-8014-3913-1.
- S2CID 4366123.
- ^ "East African Hedgehog". Oakland Zoo. Archived from the original on 7 August 2016. Retrieved 5 September 2012.
Further reading
- Navas, Carlos Arturo; Carvalho, José Eduardo (2009). Aestivation: Molecular and Physiological Aspects. Springer. ISBN 978-3-642-02420-7.