Brin also believes that aestivation is an exceptionally dangerous strategy.
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Interestingly, Sandberg himself doesn't believe in the aestivation hypothesis, but he says it's important to investigate the possibility.
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At the same time, the aestivation strategy is still something we may want to consider for ourselves in a few billion years, he added.
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Image: Shkadov Thruster L. Blaszkiewicz/CCThe aestivation hypothesis offers a tidy explanation to the Fermi Paradox—the surprising observation that we've never seen signs of aliens—but it's not without problems.
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There are several types of hibernation, which can last an entire season or just a part of a day (this is called "torpor"), and can even happen when the ambient temperature is high (which is called "aestivation").
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New research accepted for publication in the Journal of the British Interplanetary Society suggests that conditions in our current Universe are far too warm for a digital, computer-based civilization, and that it makes sense for such beings to enter into a state of aestivation—hibernation, but in response to excess heat—until the cosmos is much colder in the far, far future.
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Both terrestrial and aquatic animals undergo aestivation. The fossil record suggests that aestivation may have evolved several hundred million years ago.
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Snails may come out of aestivation briefly to feed during dry-season rains, and also may go into aestivation during summer dry spells.
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The bogong moth suffers from predation during both its migration and aestivation. During the spring and autumn migrations, several species of birds, mammals, and even fish have been recorded preying on the moth. Little raven, currawong and Richard's pipit congregations form to feast on bogong moths as they travel from aestivation sites during migration. Aboriginal tribes also traveled to aestivation sites to feast on the dormant moths, and may have searched for these bird congregations to locate these sites.
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Adult alfalfa weevils (Hypera postica) aestivate during the summer in the southeastern United States, during which their metabolism, respiration, and nervous systems show a dampening of activity. Crustacea: An example of a crustacean undergoing aestivation is with the Australian crab Austrothelphusa transversa , which undergoes aestivation underground during the dry season.
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"Morphology and aestivation behaviour in some Madagascan acavid land snails". Biological Journal of the Linnean Society 53(2): 175-187. .
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Gehlbach, F. R., Gordon, R., & Jordan, J. B. (1973). Aestivation of the salamander, Siren intermedia. American Midland Naturalist, 455-463.
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More time is spent in water in overcast, rainy, or misty days. In the southern reaches of their range, as a response to dry, cool conditions that they cannot survive externally, crocodiles may dig and take refuge in tunnels and engage in aestivation. Pooley found in Royal Natal National Park that during aestivation, young crocodiles of total length would dig tunnels around in depth for most, some tunnels measuring more than , the longest there being . Crocodiles in aestivation are totally lethargic, entering a state similar to animals that hibernate.
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The population within each aestivation site fluctuates throughout the summer due to moth mortality and the departure and arrival of moths either migrating further south for aestivation or north to return to breeding grounds. However, this differs from changes during migration periods, when the populations rapidly increase with arrival or decrease with departure. Bogong moths are nocturnal migrants, but the exact mechanism for long-distance navigation is not clear. It is possible that they are oriented by light, as seen in the influence of light intensity on activity during aestivation.
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Isidorella snails are grazers-scrapers and are capable of aestivation. Isidorella may be found in ponds, billabongs, swamps, and sluggish streams and rivers.
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Bogong moths undergo whole scale long-distance migration biannually, in which they can travel up to 965 km (600 miles). The spring migration begins in early September and occurs from the lowlands of Southern Australia south towards the Australian Alps for purposes of reaching aestivation sites. During the summer, the moths remain in their aestivation sites until autumn, when they migrate back towards the breeding grounds of the lowlands as early as February, but primarily in April. The bogong moth utilizes particular aestivation sites repeatedly throughout migrations, as seen with the development of parasites that depend on the regular arrival and departure of the moths from caves.
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1998: 19(2) : 91-93 PDF They aestivate in summer.McCann, C. 1946. Aestivation of the frog Ramanella montana (Jerdon). J. Bombay. Nat. Hist. Soc. :404-406.
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Species native to temperate latitudes typically hibernate to avoid cooler weather, while a few of the tropical species employ aestivation as a method of evading extremes of climate.
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During the spring migration, adult bogong moths can be found in their ideal aestivation sites, which generally consist of cool, dark caves and crevices but can include spaces underneath tors and even fallen tree trunks. Stable temperatures and humidity make these locations ideal for bogong moth aestivation. Crevices regulate their environment through wind flow, and caves generally have more regular temperatures and greater humidity. This reduces water loss in bogong moths during their inactivity.
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In Uganda, lungfish and catfish were mainly fed to the young. The big beak is sometimes used to dig into pond-bottom mud to extract lungfish from their aestivation burrows.
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Because the species is critically endangered, the Perth Zoo began a conservation and breeding program for it. However, zookeepers were unaware of the importance of their aestivation cycle and during the first summer period would perform weekly checks on the animals. This repeated disturbance was detrimental to the health of the animals, with many losing significant weight and some dying. The zookeepers quickly changed their procedures and now leave their captive turtles undisturbed during their aestivation period.
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Newly emerged adults appear from May each year. Adults may enter an aestivation period over Summer after the harvest of mature rape plants. After mating in late summer, some adults will overwinter.
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In March or April the entrances are opened, the burrows cleaned and new construction starts. In late June or July, aestivation occurs and sometimes, especially in dry years, this species goes straight from aestivation to hibernation. During the year it may only be active for 80 to 100 days. As a result of excavating activity over several years, a mound is formed on the surface of the ground, up to eight metres in diameter and 0.6 of a metre in height.
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A. Rhigospira quadrangularis, portion of a plant. Fig. 1, the inflorescence. Fig. 2, a flower: both natural size. Fig. 3, the corolla in bud, showing the pyramidal form of the erect segments in aestivation. Fig.
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The snail's quiescent periods during heat and drought are known as aestivation; its quiescence during winter is known as overwintering. When overwintering, Cornu aspersum avoids the formation of ice in its tissues by altering the osmotic components of its blood (or haemolymph); this permits it to survive temperatures as low as -5 °C (23 °F). During aestivation, the mantle collar has the ability to change its permeability to water. The snail also has an osmoregulatory mechanism that prevents excessive absorption of water during hibernation.
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During the summer, hot temperatures occur and grasses, which are an unfavourable diet for bogong moth larvae, overtake pastures and make up the majority of the plants occupying the pastures. Bogong moths avoid this harsh environment by delaying development during the summer so that their eggs do not hatch in a poorly-suited environment; instead, they migrate to cooler, more suitable areas and delay their development during aestivation until the winter season, when they return to the breeding grounds and winter pasture crops begin to grow again. During aestivation, the bogong moths remain dormant for several months, possibly delaying development due to the lower temperatures. The food they consume during the migration is also dedicated to building fat reserves for aestivation rather than development, as bogong moths must consume more food during the autumn migration before maturation and mating.
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Adults are on wing from early summer. They are dormant for some time to reappear in autumn. It is thought the species migrates from lowland reproduction grounds to alpine aestivation sites. There is one generation per year.
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Only the largest individuals engaging in aestivation leave the burrow to sun on warmest days, otherwise these crocodiles rarely left their burrows. Aestivation has been recorded from May to August. Nile crocodiles usually dive for only a few minutes at a time, but can swim under water up to 30 minutes if threatened, and if they remain fully inactive, they can hold their breath for up to 2 hours (which, as aforementioned, is due to the high levels of lactic acid in their blood). They have a rich vocal range, and good hearing.
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These observations led Thulborn to conclude that Heterodontosaurus must have replaced its entire set of teeth at once on a regular basis. Such a complete replacement could only have been possible within phases of aestivation, when the animal did not feed. Aestivation also complies with the supposed habitat of the animals, which would have been desert-like, including hot dry seasons when food was scarce. CT scan video showing replacement teeth and wear facet orientation in AMNH 24000, a partial skull A comprehensive analysis conducted in 1980 by Hopson questioned Thulborn's ideas.
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Common, I. F. B. (1954). "A study of the ecology of the adult bogong moth, Agrotis infusa (Boisd) (Lepidoptera: Noctuidae), with special reference to its behaviour during migration and aestivation". Australian Journal of Zoology. 2 (2): 223–263.
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During periods when water levels are low, C. expansa will traverse over land to find other water sources. The turtle may also bury itself into mud and enter extended periods of aestivation until rain occurs and water levels increase.
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In the second mode (Johnson's third), migration takes place to a place of hibernation or aestivation where they undergo diapause and the same generation survives to return. The classic example is that of the nymphalid monarch butterfly (Danuas plexippus).
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Boulenger's keelback is oviparous, diurnal and nocturnal. In dry conditions during the summer, it undergoes aestivation. It is active in water bodies in search of its prey, which consist mainly of fish and frogs. It is known to be very aggressive.
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Theba pisana snails aestivating on Foeniculum vulgare in Montbazin, France Aestivation or æstivation (from , summer, but also spelled estivation in American English) is a state of animal dormancy, similar to hibernation, although taking place in the summer rather than the winter. Aestivation is characterized by inactivity and a lowered metabolic rate, that is entered in response to high temperatures and arid conditions. It takes place during times of heat and dryness, the hot dry season, which are often the summer months. Invertebrate and vertebrate animals are known to enter this state to avoid damage from high temperatures and the risk of desiccation.
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Behaviour and daily activity varies greatly across the distribution range. Hibernation occurs in some areas and aestivation in others. This species is diurnal and feeds on the green parts of plants, seeds and roots. The burrows have permanent vertical entrances and temporary slanting ones.
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The threshold temperature is about , higher for smaller individuals and for those from the southern part of the range where the ambient water temperature is higher. This sea cucumber has been known to continue in aestivation in some areas of China for four years.
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Aestivation, also spelled estivation, is an example of consequential dormancy in response to very hot or dry conditions. It is common in invertebrates such as the garden snail and worm but also occurs in other animals such as lungfish, salamanders, desert tortoises, and crocodiles.
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These species are successfully cultivated by specialist growers of terrestrial orchids and are reported to be difficult to grow, being sensitive to rotting and damping off diseases if not properly subjected to a cool and dry aestivation period over the summer months with no water.
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The weevil lays its eggs within seed capsule of the iris, later the larvae feeds on the seed and up to 2 other seeds, and then it pupates. Adult weevils emerge from the seed capsules, fly off for aestivation (summer dormancy) and hibernation within the soil.
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Aggregations of bogong moths in aestivation sites has led to the bioaccumulation of the pollutant in both the surrounding local environment and within predators, particularly in the endangered mountain pygmy-possum. However, no conclusive evidence has directly linked agriculture as the source of arsenic in bogong moths.
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The nematodes are unusual in that they parasitize adult bogong moths instead of the more commonly utilized larval host stage. The nematodes' life cycles demonstrate an adaptation to the migration of the bogong moths, as they are dependent on bogong moths returning to the same aestivation sites.
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Insecta: Lady beetles (Coccinellidae) have been reported to aestivate. Mosquitoes also are reported to undergo aestivation. False honey ants are well known for being winter active and aestivate in temperate climates. Bogong moths will aestivate over the summer to avoid the heat and lack of food sources.
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Two species of mermithid nematodes parasitize the bogong moth during its aestivation: Amphimermis bogongae and Hexamermis cavicola. The parasites are transmitted to bogong moths through water; the early instar larval nematodes reside in the debris of the cave floors of common aestivation sites, and crawl up to reach the moths through trickles of water coming down the walls. Bogong moths are infected upon their arrival within the caves once they drink the water. After a few months, the larval nematodes emerge from the moths, which causes the moth to die, and burrow into the cave floor, where they mature and lay eggs over the winter and wait for the next spring migration of the moths.
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In 2001, a few months after rainfall had washed out debris consisting of dead moths from within the cave, the complete death of local grasses was seen outside of an aestivation site of the bogong moth. Investigation into the causes of the grass mortality showed that the concentration of arsenic in the surrounding areas was much higher than normal, and the source was determined to be the bogong moths. Since the bogong moths do not feed at their aestivation sites, they had absorbed arsenic from lowland feeding sites as larvae and subsequently transported it over long distances into the mountains. Bioaccumulation, the absorption and accumulation of substances by organisms, occurs with arsenic in bogong moths.
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The aestivation hypothesis is a hypothesized solution to the Fermi paradox conceived in 2017 by Anders Sandberg, Stuart Armstrong and Milan M. Ćirković. The hypothesis, published on 27 April 2017, suggests that advanced alien civilizations may be storing energy and aestivating (hibernating in times of heat instead of cold), until the universe cools to better make use of the stored energy to perform tasks. As the universe cools, the potential work producible by stored energy can increase by a multiplier of 1030 per Landauer's principle. If the goal of an advanced civilization is to maximize the number of calculations done, to generate information processing for tasks like mass-producing simulations, then aestivation would be purposeful to achieve this end.
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The type series was collected from under rocks in open, grassy, shallow-soiled plateau at about above sea level. The specimens were collected during the monsoon season. How these caecilians spend the long dry season is unknown but might involve aestivation. Threats to this still little known species are unknown.
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Elachistocleis bicolor are nocturnal and semi-fossorial in their lifestyle. During periods of aestivation, they can be found inside ant and termite nests. Male Elachistocleis bicolor grow to a snout–vent length of and females to . Its name refers to its striking colour pattern with brownish back and yellowish dorsum.
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They have concave sides and correspond with the shape of the wings. The two keel petals are fused at their bases or stuck together to form a boat-shaped structure that encloses the essential flower organs, namely the androecium and gynoecium. Typically these flowers have a vexillary (i.e. descendingly imbricate or overlapping) aestivation.
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Medem (1966) reported the habitat was originally ponds and small brooks within forests, but with the clearing of the woodlands the entire area around the type locality has been transformed into pastures. There, turtles seem to prefer shallow, quiet water bodies, where they fill a bottom-dwelling niche. Aestivation occurs during dry periods.
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Many experts believe that the processes of daily torpor and hibernation form a continuum and utilize similar mechanisms. The equivalent during the summer months is aestivation. Hibernation functions to conserve energy when sufficient food is unavailable. To achieve this energy saving, an endothermic animal decreases its metabolic rate and thereby its body temperature.
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During the dry season, Florida gars burrow into the sediments of the marshes they inhabit and aestivate through the dry season. Aestivation, similar to hibernation in other species, lowers the animal's metabolic rate. This allows the Florida gar to withstand the high temperatures and dry conditions of their habitats during the summer.
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While temporary sites can be used in lower elevations, these sites undergo massive population fluctuations and movements throughout their use. Permanent aestivation sites are generally found in higher altitudes of 1500 metres (4920 ft) or above, with the largest, most stable aggregations found on the summits of mountains such as Mt. Gingera.
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For many amphibians, an annual breeding cycle applies, typically regulated by ambient temperature, precipitation, availability of surface water and food supply. This breeding season is accentuated in temperate regions,W.J. Sutherland, 1996 where prolonged aestivation or hibernation renders many amphibian species inactive for prolonged periods. Breeding habitats are typically ponds and streams.
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During the intermittent dry seasons, the snails, young and adults alike, aestivate ("the warm weather equivalent of hibernation"Gould, S.J., 1985. The Flamingo's Smile; Reflections in Natural History. Norton, New York) on the rocks or in crevices inside the rocks. For aestivation, aggregates are often formed, sometimes reaching sizes of many hundreds of individuals.
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The Cinchoneae are a tribe of flowering plants in the family Rubiaceae containing about 125 species in 9 genera. Representatives are found from Costa Rica to southern tropical America. Species within Cinchoneae are characterized as small trees or shrubs with imbricate or valvate corolla aestivation and often dry capsular fruits. Many species contain alkaloids.
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"Combined morphological and molecular phylogeny of the clusioid clade (Malpighiales) and the placement of the ancient rosid macrofossil Paleoclusia". International Journal of Plant Sciences 174(6):910–936. . There are only a few morphological characters that unite the clusioids with Ochnaceae. The petal aestivation is often contort in the clusioids, and usually so in Ochnaceae.
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Biomphalaria glabrata inhabits small streams, ponds and marshes. These snails can survive in aestivation for a few months when removed from their freshwater habitat or when the habitat dries out. For example, the snail lives in banana plantation drains in Saint Lucia. Biomphalaria glabrata can also survive up to 16 hours in anaerobic water using lactic acid fermentation.
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Critical thermal maximum, in zoology, is the temperature for a given species above which most individuals respond with unorganized locomotion, subjecting the animal to likely death.R.W. McDiarmid, 1999 This concept is particularly relevant in periods of aestivation or quiescence, in which circumstances an organism experiences limited mobility and lacks the ability to seek a microhabitat of reduced thermal stress.
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Spadefoot toads are nocturnal and are rarely seen when it hasn't rained recently. They spend most of the time during the dry season buried in the ground in aestivation. When it rains, they emerge to feed on invertebrates and to breed in vernal pools. They have one of the fastest reproductive cycles of any amphibian species.
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Alcala and Dy-Liacco, p. 141. Desert crocodiles in Mauritania have adapted to their arid environment by staying in caves or burrows in a state of aestivation during the driest periods. When it rains, the reptiles gather at gueltas. American crocodiles basking Dry land is also important as it provides opportunities for basking, nesting, and escaping from temperature extremes.
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In 2013, a well-preserved skeleton of Broomistega was discovered alongside the skeleton of the cynodont Thrinaxodon (a mammal relative) in a cast of a burrow. The individual probably entered the burrow while the cynodont was in a state of aestivation (dormancy), and afterwards a flash flood filled the burrow with sediment to preserve both bodies together.
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The life cycle is completed in 59–65 days at 22–24 °C and 85–86% RH. The Mo sawfly appears to prefer a temperate climate of 21–24 °C, monthly precipitation of 50–150mm and RH of 85–88%. Under some combinations of climatic factors, the Mo sawfly enters diapause and/or aestivation (see below).
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The depression of metabolic rate during aestivation causes a reduction in macromolecule synthesis and degradation. To stabilize 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.
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Gregarious aggregation of bogong moths during aestivation During the spring migration, bogong moths gregariously aggregate with densities reaching 17,000 moths per square metre (10.8 square feet) within caves, crevices, and other areas hidden from the sunlight. The lack of light and relatively constant temperature and humidity makes these spots favourable during aestivation. The first moths that arrive occupy the deepest and darkest locations, using their fore tarsi to grip onto the rock faces, and aggregations form around these initial areas, with moths arriving later settling for less ideal areas with more sunlight, higher temperatures, and decreased humidity. To diminish the amount of light that reaches their light- sensitive eyes, later moths push themselves underneath the wings and abdomens of moths that arrived earlier and place their hind legs on top of the moths beneath them.
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The planktonic larvae develop through several stages before settling on hard surfaces on the seabed, undergoing metamorphosis and becoming juveniles. The Japanese sea cucumber lives in temperate seas. In locations where the water heats up excessively in summer it undergoes aestivation, going into a state of dormancy. In this state, feeding stops, the gut degenerates, the metabolism slows down and weight is lost.
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Jaguars and anacondas are the only other predators of the caimans but they prey only on the smaller specimens. During summer or droughts, the caiman may dig a burrow and go into a form of summer hibernation called aestivation. Female caimans build a large nest in which to lay their eggs. These nests can be more than 1.5 metres wide.
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The slender lungfish has an anguilliform body, much like an eel. The body of the slender lungfish is generally brown; young of the species oftentimes have black spots throughout the body, however adults generally lose these spots as they age. Like all African lungfish the slender lungfish is an obligate air-breather and is capable of aestivation; however, it generally does not aestivate.
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Aestivation has been put forward as the most likely explanation why this therapsid cynodont Thrinaxodon liorhinus shared its burrow with a temnospondyl amphibian, Broomistega putterilli. 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.
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I. iberica is affected by fungal Puccinia iridis. It is also the host plant of Mononychus schoenherrii Kolenati (a weevil that feeds on the seeds of the iris). The weevil lays its eggs within seed capsule of the iris, later the larvae feeds on the seed and then pupates. Adult weevils emerge from the seed capsules, fly off for aestivation (summer dormancy) and hibernation.
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Aestivation only occurs during unusual drought conditions. The Cheat Mountain salamander. The breeding behavior of CMSs has not been directly observed, but most likely occurs on the forest floor. Pairs of males and females have been found together under rocks in both spring and autumn and both sexes during these months are in breeding condition: males with swollen cloacas and squared-off snouts, females with mature follicles.
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They emerge as adults in about one or two weeks. After feeding for a week or two, they may experience aestivation during the remainder of the summer, in which they demonstrate a dampening of their metabolic, respiratory and nervous system activities. In fall, the adults hide in the crowns of alfalfa plants or move onto coarse vegetation in ditches or by fences or in nearby woodland.
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The species rests on the bottom of the water using elongated pelvic and rounded caudal fins. These small and shallow pools may contain a population of around 150 individuals, are generally no larger than 600 square metres, and evaporate in the dry seasons. It is also unusual for its ability to survive desiccation by burrowing into sand, a process of aestivation, when the pools it lives in periodically evaporate.
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Both tadpoles and adults have many senses. Studies support a theory that olfactory sense is important to tadpoles of this species. Adult breeding frogs detect breeding ponds by using auditory cues from other frog calls to gauge distance, size of pool, likelihood of predators and numbers as well as breeding condition of other frogs. Sources say frogs use low frequency sound of rain as a cue to emerge from aestivation.
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The most common sounds made by four-toed hedgehogs are snorts, hisses, and a quiet twittering sound. When attacked, the animal can scream loudly, and males also produce a birdlike call during courtship. Although four-toed hedgehogs do aestivate through the summer, this is not thought to be connected to a rise in temperature, but rather to a lack of available food. Aestivation rarely lasts for more than six weeks.
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The recent rise of average summer temperature resulting from global warming may particularly affect the Mediterranean species. Gümüş et al. (2009) speculated that both the average length of the dry summer period and the absolute temperature are rising, and that the aestivation period of species adapted to the Mediterranean drought is now too long. The animals die from starvation or desiccation, and several species or subspecies may already be approaching the verge of extinction.
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It was further noted that flood levels had previously reached the area, and receded. It is not unusual for riverine species like bowfin to move into backwaters with flood currents, and become trapped when water levels recede. While aestivation is anecdotally documented by multiple researchers, laboratory experiments have suggested instead that bowfin are physiologically incapable of surviving more than three to five days of air exposure. However, no field manipulation has been performed.
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The California red-legged frog may aestivate to conserve energy when its food and water supply is low. The water-holding frog has an aestivation cycle. It buries itself in sandy ground in a secreted, water-tight mucus cocoon during periods of hot, dry weather. Australian Aborigines discovered a means to take advantage of this by digging up one of these frogs and squeezing it, causing the frog to empty its bladder.
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During the cooler dry season the flat-backed spider tortoise enters a stage similar to hibernation known as aestivation, the species buries itself and lies dormant. Mating season usually takes place during the hot/rainy season, and is followed a month later by egg- laying. Females may produce up to three clutches a year, each containing only one relatively large egg. Hatching is therefore timed with the return of the rainy season, when the species is most active.
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Orthalicus reses reses snails are active mainly during the wet season, i.e. May through November, during which time breeding, feeding, and dispersal takes place. Dry periods (December through April) are spent in aestivation, during which time the snail forms a tight sealed barrier between the aperture and a tree trunk or branch. Snails secrete this mucus seal (an epiphragm) that cements their shell to a tree in order to protect them from desiccation during the dry period.
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Prenolepis imparis, male Prenolepis imparis, commonly known as the winter ant, false honey ant, or false honeypot ant, is a species of ant in the genus Prenolepis. The species is found in North America, from Canada to Mexico, nesting deep within the ground. Unusual among ants, Prenolepis imparis prefers lower temperatures, including near freezing, and is only active outside the nest during winter and early spring. Prenolepis imparis enters a hibernation- like state called aestivation during the summer.
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32-45 This is known as aestivation. In the wild, they may burrow very deep; up to 15 m deep and 30 m long. Plants such as grasses and succulents grow around their burrows if kept moist and in nature continue to grow for the tortoise to eat if the soil is replenished with its feces. Sulcata tortoises found in the Sudanese part of their range may reach significantly greater size at maturity than those found in other regions.
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The fish's usual habitats disappear during the dry season, so they burrow into the mud and make a chamber about down, leaving a few holes to the surface for air. During this aestivation, they produce a layer of mucus to seal in moisture, and slow their metabolism down greatly. When the rainy season begins, they come out and begin mating. The parents build a nest for the young, which resemble tadpoles and have four external gills.
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During the last dry season prior to sexual maturation, the subadult snail (the shell of which is already fully developed, albeit thinner than that of an adult) increases the size of its genital organs. Copulation then takes place during the first weeks of autumn rains. Population densities can sometimes be very high, in spite of heavy predation by beetle larvae of the genus Drilus. These insects attack the snails during their aestivation, by perforating the shell and eating the snail inside.
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It is evident from several features of the shell and its internal organization that the shell in this genus is carried with its principal axis transverse to the longitudinal axis of the foot; that is, the spire is directed to the right. The flattened surface of the outer whorl thus rests upon the dorsal surface of the foot or upon the substratum when the animal is in a state of aestivation, a position which they had assumed in both instances.
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Breathing air is primarily of use to fish that inhabit shallow, seasonally variable waters where the water's oxygen concentration may seasonally decline. Fish dependent solely on dissolved oxygen, such as perch and cichlids, quickly suffocate, while air-breathers survive for much longer, in some cases in water that is little more than wet mud. At the most extreme, some air-breathing fish are able to survive in damp burrows for weeks without water, entering a state of aestivation (summertime hibernation) until water returns.
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Larvae of species in the genera Liriomyza and Phytomyza are extremely polyphagous (they attack many different species of plants). A long imaginal aestivation and hibernation period is an uncommon overwintering strategy among agromyzid flies. The shape of the mine is often characteristic of the species and therefore useful for identification. For some of the serpentine leaf miners it is possible to use the mine to indicate the instar of the animal that made it, and in some cases its cause of death.
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Thulborn's aestivation hypothesis was rejected by Hopson due to lack of evidence. In 2006, Butler and colleagues conducted computer tomography scans of the juvenile skull SAM-PK-K10487. To the surprise of these researchers, replacement teeth yet to erupt were present even in this early ontogenetic stage. Despite these findings, the authors argued that tooth replacement must have occurred since the juvenile displayed the same tooth morphology as adult individuals – this morphology would have changed if the tooth simply grew continuously.
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In northern Vietnam, emergence of the adult Mo sawfly occurs twice a year – from spring to early summer (March to May) and from autumn to early winter (late August to early January). Emergence during autumn–winter takes place in waves. The favourable period for the growth of the sawfly is about five months during the spring–summer and about three months during the autumn. The insect undergoes aestivation and/or diapause under certain combinations of climatic factors which are not clearly understood.
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At the most extreme, some air-breathing fish are able to survive in damp burrows for weeks without water, entering a state of aestivation (summertime hibernation) until water returns. Air breathing fish can be divided into obligate air breathers and facultative air breathers. Obligate air breathers, such as the African lungfish, are obligated to breathe air periodically or they suffocate. Facultative air breathers, such as the catfish Hypostomus plecostomus, only breathe air if they need to and can otherwise rely on their gills for oxygen.
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Bogong moth populations are primarily located across southern Australia, west of the Great Dividing Range. The regions contain populations of nonmigratory and migratory moths of this species, distinguished by their differing seasonal presences in each region. The adult bogong moth lays eggs across New South Wales, southern Queensland, and northern parts of Victoria, where larvae hatch and grow until adulthood. During the spring season and subsequent summer aestivation, bogong moths migrate south or east towards the Australian Alps, and can be found in the Australian Capital Territory and Bogong Mountains.
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Various parts of the cerebrum process sensory input, such as smell in the olfactory lobe and sight in the optic lobe, and it is additionally the centre of behaviour and learning. The cerebellum is the center of muscular coordination and the medulla oblongata controls some organ functions including heartbeat and respiration. The brain sends signals through the spinal cord and nerves to regulate activity in the rest of the body. The pineal body, known to regulate sleep patterns in humans, is thought to produce the hormones involved in hibernation and aestivation in amphibians.
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It was thought that heterodontosaurids actually did replace their teeth continually, though more slowly than in other reptiles, but CT scanning of skulls from juvenile and mature Heterodontosaurus shows no replacement teeth. There is currently no evidence that supports the hypothesis of aestivation in heterodontosaurids, but it cannot be rejected, based on the skull scans. While the cheek teeth of heterodontosaurids are clearly adapted for grinding tough plant material, their diet may have been omnivorous. The pointed premaxillary teeth and sharp, curved claws on the forelimbs suggest some degree of predatory behavior.
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The edible bullfrog spends approximately 10 months of the year in aestivation beneath the surface of the soil, only emerging to breed in numbers if sufficiently heavy rain, i.e. more than , falls within a short period. After which male edible bullfrogs call on the flooded grassland and from any small, temporary pools such as included roadside ditches, shallow excavations where the water is shallow, less than in depth and had flooded vegetation. Breeding appears to occur during the day and breeding activity and calling had decreased substantially by midday.
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During this time mudfish will hang quietly at the surface with bubbles of air in their mouths to improve oxygen absorption. Some choose to leave hypoxic water before it dries out, and leave again if pushed back in. While emersed they are aware of their surroundings and are responsive to change in their environment: changing position, moving to damper areas, and congregating. Although they may be found deep below the surface in cavities and root holes, they do not appear to create burrows for the purpose of aestivation, with the exception of N. cleaveri.
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This physical contact and aggregation allow the moths to retain body moisture. When the aestivating moths are disturbed, the moths within the area of disturbance briefly spread out and leave the aggregation, dropping excrement when unsettled before quickly returning to the aggregation and re- positioning themselves. While the moths mostly remain dormant during aestivation, there are some periods of activity within the aggregation which are correlated to changes in light intensity. During dawn and dusk, portions of the population become active, first crawling around and spreading out, and then flying out of their shelter into the open.
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This species is purported to appear in odd places following so called "rain of fish", as they are often observed scattered on the ground in the aftermath of heavy downpours. However, the fish have been transported to these places by flooding. This hardy species can survive dry periods by aestivation in the least amount of moisture in the bottom of a temporary waterbody. It is an omnivorous species which has a diet of consisting largely of aquatic and terrestrial insects, crustaceans and some molluscs, however it will also prey on small fish and consume a small amount of algae and aquatic weeds.
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Hyperolius nitidulus live in an environment with a wet season that can be cold and humid, and an extremely hot and dry season. During the hot and dry season the frog is dependent on water therefore it has special adaptations to survive the extreme climate. Hyperolius nitidulus is known for its unique aestivation behavior during the hot and dry season. During dry season Hyperolius nitidulus do not seek shelter or hide, instead, they fully expose themselves to the sun by sitting on dry plants to reduce rapid water loss and can remain in this sitting position for months without food or water.
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Some combtooth blennies emerge to feed on land, and freshwater eels are able to absorb oxygen through damp skin. Mudskippers can remain out of water for considerable periods, exchanging gases through skin and mucous membranes in the mouth and pharynx. Swamp eels have similar well-vascularised mouth-linings, and can remain out of water for days and go into a resting state (aestivation) in mud. The anabantoids have developed an accessory breathing structure known as the labyrinth organ on the first gill arch and this is used for respiration in air, and airbreathing catfish have a similar suprabranchial organ.
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In the vicinity of the Dead Sea, they usually either burrow to depths of up to 10 cm, or aestivate hidden under stones. All dormant snails of this species can resist ambient temperatures up to 50 °C, but temperatures of 55 °C and above are usually lethal. The soft parts of the animal's body shelter inside the second and the third whorl of its shell, where the temperature can reach up to 50.3 °C. Temperatures of up to 56.2 °C were measured and are known to occur inside the shell's body whorl, which is mostly filled with air during aestivation.
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An apparently lifeless, frozen frog can resume respiration and its heartbeat can restart when conditions warm up. At the other extreme, the striped burrowing frog (Cyclorana alboguttata) regularly aestivates during the hot, dry season in Australia, surviving in a dormant state without access to food and water for nine or ten months of the year. It burrows underground and curls up inside a protective cocoon formed by its shed skin. Researchers at the University of Queensland have found that during aestivation, the metabolism of the frog is altered and the operational efficiency of the mitochondria is increased.
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Bogong moth larvae subsist on winter pasture crops and wild crop weeds such as cape weeds within bogong moth breeding grounds, primarily depending on annual dicotyledons that grow during the winter. Attacks on a wide variety of cultivated crops have been seen, with plants such as Medicago species, wheat, cabbages, cauliflowers, silver beet, peas, and potatoes all recorded being consumed by bogong moth caterpillars. However, the larvae avoid grasses, which overtake pastures during the summer, making summer unfavourable due to lack of larval food sources. Adult bogong moths feed on the nectar of flowers such as Epacris, Grevillea and Eucalyptus while breeding or migrating, but will not actively feed during aestivation.
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Restoration of Pegomastax Most heterodontosaurid fossils are found in geologic formations that represent arid to semi-arid environments, including the Upper Elliot Formation of South Africa and the Purbeck Beds of southern England. It has been suggested that heterodontosaurids underwent seasonal aestivation or hibernation during the driest times of year. Due to the lack of replacement teeth in most heterodontosaurids, it was proposed that the entire set of teeth was replaced during this dormant period, as it seemed that continual and sporadic replacement of teeth would interrupt the function of the tooth row as a single chewing surface. However, this was based on a misunderstanding of heterodontosaurid jaw mechanics.
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A few other fish have structures resembling labyrinth organs in form and function, most notably snakeheads, pikeheads, and the Clariidae catfish family. Breathing air is primarily of use to fish that inhabit shallow, seasonally variable waters where the water's oxygen concentration may seasonally decline. Fish dependent solely on dissolved oxygen, such as perch and cichlids, quickly suffocate, while air-breathers survive for much longer, in some cases in water that is little more than wet mud. At the most extreme, some air-breathing fish are able to survive in damp burrows for weeks without water, entering a state of aestivation (summertime hibernation) until water returns.
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During the active part of their day, such animals maintain normal body temperature and activity levels, but their metabolic rate and body temperature drop during a portion of the day (usually night) to conserve energy. Torpor is often used to help animals survive during periods of colder temperatures, as it allows them to save the energy that would normally be used to maintain a high body temperature. Some animals seasonally go into long periods of inactivity, with reduced body temperature and metabolism, made up of multiple bouts of torpor. This is known as hibernation if it occurs during winter or aestivation if it occurs during the summer.
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The changes in vertebral/rib anatomy that arose in Thrinaxodon permit the animals to a greater range of flexibility, and the ability to place their snout underneath their hindlimbs, an adaptive response to small living quarters, in order to preserve warmth and/or for aestivation purposes. A Thrinaxodon burrow contained an injured temnospondyl, Broomistega. The burrow was scanned using a synchrotron, a tool used to observe the contents of the burrows in this experiment, and not damage the intact specimens. The synchrotron revealed an injured rhinesuchid, Broomistega putterilli, showing signs of broken or damaged limbs and two skull perforations, most likely inflicted by the canines of another carnivore.
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In some areas, the mother crocodiles will only leave the nest if she needs to cool off (thermoregulation) by taking a quick dip or seeking out a patch of shade. Females will not leave nest site even if rocks throw at her back and several authors note her trance-like state while standing near nest, similar to crocodiles in aestivation but not like any other stage in their life-cycle. In such a trance, some mother Nile crocodiles may show no discernable reaction even if pelted with stones. At other times, the female will fiercely attack anything approaching their eggs, sometimes joined by another crocodile which may be the sire of the young.
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Their resistance to both drought and cold has enabled the species to survive introduction from cool, moist conditions of Northern Europe, to Australasia and Southern Africa. In conditions of drought, they simply enter a state of aestivation in the form of diapause in which embryonic development is delayed. The delay lasts till a period of soaking rain sets in or until irrigation begins. During a period of active breeding when plenty of moisture exists, the hatching period is variable; under favourable conditions, most eggs hatch in about 2 weeks, but some take 3 weeks or more, while eggs that have aestivated hatch at various intervals over period around a week to a month or more after wet conditions return.
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From fall to spring the California slender salamander is active on the ground surface, foraging under leaf litter and in tunnels created by a variety of other fauna; however, activity is heightened in intervals of light rain and immediately thereafter. From May to October, aestivation is the norm for this species. Unlike other members of its genus, egg-laying occurs quite early, as soon as December in the southern part of its range. Oviposition is thought to occur primarily in the tunnelsLarry Serpa and Lynn Lozier, Fairfield Osborn Preserve: Natural History and Ecology (1981) of other creatures, but clusters have commonly been found on moist surfaces beneath bark, rocks, or other types of forest detritus.
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The river is thought to have flooded seasonally with the rains, possibly drying up completely between the rainy seasons, and forming new channels on an annual to semi-annual basis. To cope with the dry periods between the seasonal rains, it has been proposed that Limnoscelis might have aestivated during these periods, with the close stratigraphic association of the original specimens found by Baldwin being possible evidence of a communal aestivation den. The environment of Limnoscelis paludis would have likely been dominated by pelycosaurs and other basal synapsids, including Sphenacodon ferox, Ophiacodon mirus, Ophiacodon navajovicus, Clepsydrops vinslovii, Aerosaurus greenleeorum, and Edaphosaurus novomexicanus. Limnoscelis paludis also likely lived alongside other diadectomorphs, including Diadectes lentus, Diasparactus zenos,and Desmatodon hollandi.
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CT image of specimen in burrow Thrinaxodon has been identified as a burrowing cynodont by numerous discoveries in preserved burrow hollows. There is evidence that the burrows are in fact built by the Thrinaxodon to live in them, and they do not simply inhabit leftover burrows by other creatures. Pitted foramina on the snout of Thrinaxodon indicate the likely presence of the sensory organ, whiskers, an adaptation likely used to assist navigation and sensation within burrows. Due to the evolution of a segmented vertebral column into thoracic, lumbar and sacral vertebrae, Thrinaxodon was able to achieve flexibilities that permitted it to comfortably rest within smaller burrows, which may have led to habits such as aestivation or torpor.
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The West African crocodile inhabits much of West and Central Africa, ranging east to South Sudan and Uganda, and south to Democratic Republic of the Congo (in all three countries it may come into contact with Nile crocodiles). Other countries where found include Mauritania, Benin, Liberia, Guinea-Bissau, Nigeria, Niger, Cameroon, Chad, Sierra Leone, Central African Republic, Equatorial Guinea, Senegal, Mali, Guinea, Gambia, Burkina Faso, Ghana, Gabon, Togo, Ivory Coast and Republic of Congo. As late as the 1920s, museums continued to obtain West African crocodile specimens from the southern Nile, but today the species has disappeared from this river. In Mauritania it has adapted to the arid desert environment of the Sahara–Sahel by staying in caves or burrows in a state of aestivation during the driest periods, leading to the alternative common name desert crocodile.
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