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Autohaemorrhaging, or reflex bleeding, is the action of animals deliberately ejecting
Autohaemorrhaging, or reflex bleeding, is the action of animals deliberately ejecting blood
Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...
from their bodies. Autohaemorrhaging has been observed as occurring in two variations. In the first form, blood is squirted toward a predator. The blood of these animals usually contains toxic compounds, making the behaviour an effective chemical defence mechanism. In the second form, blood is not squirted, but is slowly emitted from the animal's body. This form appears to serve a deterrent effect, and is used by animals whose blood does not seem to be toxic. Most animals that autohaemorrhage are insects, but some reptiles also display this behaviour.
Some organisms have shown an ability to tailor their autohaemorrhaging response. Armoured crickets will projectile autohaemorrhage over longer distances when attacked from the side, compared to being attacked from an overhead predator.
Insects
Six orders of insects have been observed to utilize this defence mechanism. *Beetle
Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...
s
** Meloidae (blister beetles) – their haemolymph contains cantharidin that they sequester from plants on which they feed.
**Chrysomelidae
The insects of the beetle family Chrysomelidae are commonly known as leaf beetles, and include over 37,000 (and probably at least 50,000) species in more than 2,500 genera, making up one of the largest and most commonly encountered of all beetle ...
, incl. ''Timarcha
''Timarcha'' is a genus of leaf beetles in the family Chrysomelidae, with more than 100 described species in three subgenera. The most widely known species is ''T. tenebricosa'', the bloody-nosed beetle. All species are black, wingless organism ...
'' species - their haemolymph contains anthraquinones.
** Coccinellidae (ladybird, ladybug or lady beetles) – An alkaloid toxin in the haemolymph is exuded through the joints of the exoskeleton
An exoskeleton (from Greek ''éxō'' "outer" and ''skeletós'' "skeleton") is an external skeleton that supports and protects an animal's body, in contrast to an internal skeleton ( endoskeleton) in for example, a human. In usage, some of the ...
, triggered by mechanical stimulation (such as predator attack).
* Hemiptera
**Cercopidae
Cercopidae are the largest family of Cercopoidea, a xylem-feeding insect group, commonly called froghoppers or spittlebugs. They belong to the hemipteran suborder Auchenorrhyncha.
Genera
A-C
*'' Abidama''
*'' Aeneolamia''
*†'' Allocerc ...
– including spittlebugs '' Prosapia bicincta'' and ''Prosapia ignipectus''
* Hymenoptera
** Sawfly larvae
* Lepidoptera
** Tiger moth adults, such as '' Arctia caja'', which mixes haemolymph with glandular products (neurotoxic choline esters).
* Orthoptera
** Bushhoppers, such as '' Dictyophorus spumans'', '' Phymateus viridipes'' and '' Phymateus leprosus'' – their haemolymph contains cardiac glycosides, sequestered from milkweed
''Asclepias'' is a genus of herbaceous, perennial, flowering plants known as milkweeds, named for their latex, a milky substance containing cardiac glycosides termed cardenolides, exuded where cells are damaged. Most species are toxic to hum ...
on which they feed.
** Katydids, including '' Eugaster'' species
** Armoured ground crickets
**'' Enyaliopsis nyala''
* Plecoptera
**Stonefly
Plecoptera is an order of insects, commonly known as stoneflies. Some 3,500 species are described worldwide, with new species still being discovered. Stoneflies are found worldwide, except Antarctica. Stoneflies are believed to be one of the mos ...
larvae
Reptiles
Lizards
* Horned lizards ( Phrynosomatidae). At least six species of horned lizards are able to squirt an aimed stream of blood from the corners of their eyes, up to 5 feet (1.5 m).Snakes
* West Indian wood snake ('' Tropidophis''). Thirteen species have been found to expel blood from the mouth and nostrils while also fully flooding both eyes with blood. * European grass snake ('' Natrix natrix''), which secretes blood from the lining of the mouth while playing dead. * Long-nosed snake (''Rhinocheilus lecontei
''Rhinocheilus'' is a genus of snakes, commonly called the long-nosed snakes, in the family Colubridae. The genus is native to the western United States and Mexico.
Species and subspecies
The genus ''Rhinocheilus'' contains the following specie ...
''), which exudes blood from the cloaca.
* Eastern hognose snake ( ''Heterodon'' ''platirhinos''), which emits blood from the cloacal region.
* Plain-bellied water snake ('' Nerodia erythrogaster''), which releases blood from the mouth.
Consequences of reflexive bleeding
In some cases, the loss of blood can be substantial. Beetles may lose up to 13% of their net body weight as a consequence of expelling haemolymph. Autohaemorrhaging may result in dehydration. The ejection of blood puts organisms at risk of cannibalism from conspecifics.
See also
*Autothysis Autothysis (from the Greek roots ''autos-'' "self" and ''thysia'' "sacrifice") or suicidal altruism is the process where an animal destroys itself via an internal rupturing or explosion of an organ which ruptures the skin. The term was proposed b ...
* Haemorrhage
References
External links
*{{commonscat-inline, Autohaemorrhaging, Autohaemorrhaging Antipredator adaptations Blood Insect physiology