Volvation (from

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

''volvere'' "roll", and the suffix ''-(a)tion''; sometimes called enrollment or conglobation), is a defensive behavior in certain

animals Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and go through an ontogenetic stage in ...

, in which the animal rolls its own body into a ball, presenting only the hardest parts of its

integument In biology, an integument is the tissue surrounding an organism's body or an organ within, such as skin, a husk, shell, germ or rind. Etymology The term is derived from ''integumentum'', which is Latin for "a covering". In a transferred, or ...

(the animal's "armor"), or its spines to

predators Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

. Among

armadillos Armadillos (meaning "little armored ones" in Spanish) are New World placental mammals in the order Cingulata. The Chlamyphoridae and Dasypodidae are the only surviving families in the order, which is part of the superorder Xenarthra, along ...

, only species in the genus

Tolypeutes The genus ''Tolypeutes'' contains the two species of three-banded armadillos. They are restricted to open and semi-open habitats in South America. Of the several armadillo genera, only ''Tolypeutes'' rely heavily on their armor for protection. W ...

(South American three-banded armadillos) are able to roll into a defensive ball; the

nine-banded armadillo The nine-banded armadillo (''Dasypus novemcinctus''), also known as the nine-banded long-nosed armadillo or common long-nosed armadillo, is a mammal found in North, Central, and South America, making it the most widespread of the armadillos. I ...

and other species have too many plates.. Volvation is used by

earthworms An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. T ...

during periods of extreme heat or

drought A drought is defined as drier than normal conditions.Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D. Jiang, A. Khan, W. Pokam Mba, D. Rosenfeld, J. Tierney, an ...

. Among pill millipedes, volvation is both a protection against external threats and against

dehydration In physiology, dehydration is a lack of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mil ...

. Pillbugs curl themselves into "pills" not only for defense, but also to conserve moisture while resting or sleeping, because they must keep their pseudotrachaea ("gills") wet. Volvation is particularly well evolved in subterranean isopods, but only '' Caecosphaeroma burgundum'' is able to roll up into a hermetic sphere without any outward projections, and thus "approaches perfection in volvation". In vertebrates, an animal's decision to volvate is mediated by the

periaqueductal gray The periaqueductal gray (PAG, also known as the central gray) is a brain region that plays a critical role in autonomic function, motivated behavior and behavioural responses to threatening stimuli. PAG is also the primary control center for d ...

region."...the affective region called the periaqueductal gray signals the motor panic actions of fleeting, curling one's body into a ball for protection, sweating, and so on."

Gallery

Erinaceus-europaeus 2.jpg, The

European hedgehog The European hedgehog (''Erinaceus europaeus''), also known as the West European hedgehog or common hedgehog, is a hedgehog species native to Europe from Iberia and Italy northwards into Scandinavia and westwards into the British Isles.Harris, ...

(''Erinaceus europaeus''). Tatou en boule.JPG, The

Southern three-banded armadillo The southern three-banded armadillo (''Tolypeutes matacus''), also known as La Plata three-banded armadillo or Azara's domed armadillo, is an armadillo species from South America. It is found in parts of southwestern Brazil, northern Argentina, ...

(''Tolypeutes matacus''). Pangolin defending itself from lions (Gir Forest, Gujarat, India).jpg, An

Indian pangolin The Indian pangolin (''Manis crassicaudata''), also called thick-tailed pangolin and scaly anteater is a pangolin native to the Indian subcontinent. Like other pangolins, it has large, overlapping scales on its body which act as armour. The colo ...

(''Manis crassicaudata'') defending itself against

Asiatic lions The Asiatic lion is a population of ''Panthera leo leo'' that today survives in the wild only in India. Since the turn of the 20th century, its range has been restricted to Gir National Park and the surrounding areas in the Indian state of Gujarat ...

(''Panthera leo persica''). Lesser Hedgehog-tenrecs (Echinops telfairi) (10292363783).jpg, Two

lesser hedgehog tenrec The lesser hedgehog tenrec (''Echinops telfairi'') is a species of mammal in the family Tenrecidae. It is the only species in the genus ''Echinops'' and is named in honour of Charles Telfair. It is endemic to Madagascar. Its natural habitats ...

s (''Echinops telfairi''). Echidna, Exmouth.jpg,

Short-beaked echidna The short-beaked echidna (''Tachyglossus aculeatus''), also called the short-nosed echidna, is one of four living species of echidna and the only member of the genus ''Tachyglossus''. It is covered in fur and spines and has a distinctive snout ...

(''Tachyglossus aculeatus'') curling into a ball. BallPythonWithClutch.jpg, The

ball python The ball python (''Python regius''), also called the royal python, is a python species native to West and Central Africa, where it lives in grasslands, shrublands and open forests. This nonvenomous constrictor is the smallest of the African p ...

(''Python regius'') curls into a ball when stressed or frightened. Ouroborus cataphractus02.jpg, The armadillo girdled lizard (''Ouroborus cataphractus''). Armadillidium vulgare 000.jpg, The common pillbug (''Armadillidium vulgare'') is named after the pill it resembles when curled up. Phacops-enrolled.jpg, '' Phacops rana'', a

trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the ...

from the

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

period. Tachypodoiulus niger 2.jpg, '' Tachypodoiulus niger'', a

millipede Millipedes are a group of arthropods that are characterised by having two pairs of jointed legs on most body segments; they are known scientifically as the class Diplopoda, the name derived from this feature. Each double-legged segment is a res ...

, with legs on the inside and head in the center. Glomeris marginata Pill Millipede Unrolling.jpg, Stages of a

pill millipede Pill millipedes are any members of two living (and one extinct) orders of millipedes, often grouped together into a single superorder, Oniscomorpha. The name Oniscomorpha refers to the millipedes' resemblance to certain woodlice (Oniscidea), als ...

(''Glomeris marginata'') unrolling. Ethology Predation Antipredator adaptations

References

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Gallery

See also

References