Evisceration (autotomy)

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Evisceration is a method of autotomy involving the ejection of internal organs used by animals as a defensive strategy. Sea cucumbers (Holothuroidea) eject parts of the gut in order to scare and defend against potential predators such as crabs and fish. The organs are regenerated in a few days by cells in the interior of the sea cucumber. [1] [2]

Contents

Description

When stressed, the sea cucumber faces away from the attacker and contracts its body wall muscles sharply. This causes the wall of the cloaca to tear and the anus to gape. The evisceration process in Eupentacta quinquesemita proceeds as follows: [1] [3] [4]

  1. Three main structures weaken over a period of about 1–3 minutes, become soft and transparent, and eventually separate from their attachments. These are the basal part of the tentacles, the attachment points of the introvert retractor muscles to the longitudinal muscles (there are 10 of these), and the junction of intestine and cloaca. The softening is a state-transformation of the collagen components in the tissue.
  2. Parts eviscerated include the gut, associated haemal vessels, tentacles, and introvert (the dexterous anterior extensible portion of the body wall). The gut tears away from the mesenteries that suspend it within the coelomic cavity.
  3. Most of the gonad stays behind. Only strands of gonad tangled in the gut are eviscerated. The paired respiratory trees and cloaca also remain (although they may be expelled in other species)
  4. The introvert changes from being firm and opaque to being soft and translucent. The body-wall muscles contract and the increased pressure forces coelomic fluid and viscera into the introvert. It enlarges like a balloon and soon ruptures, expelling the fluid and viscera.
  5. This takes about 20 minutes, with final detachment of the tentacles and introvert sometimes taking as long as 12 hours.
  6. The anterior rupture seals, at first by muscular contraction and then by healing as a plug of connective-tissue.

Function

During evisceration in some species, several hundred Cuvierian tubules (part of the respiratory tree) may be expelled. Water from the respiratory tree is forced into these tubules causing a rapid expansion and they elongate by up to 20 times their original length. They have great tensile strength and become sticky when they encounter any object. The adhesive is unique among marine invertebrates and a firm grip is obtained in under ten seconds. The mass of threads can entangle and immobilise potential predators such as small fish or crabs. The threads become detached from the sea cucumber which crawls away. [2] The tubules are readily regenerated, a process that takes about 17 days in Holothuria leucospilota and five weeks in Holothuria forskali . [2] The tubules contain a toxic saponin called holothurin, which is also present in the body wall in some sea cucumber species. [5]

Occurrence

The giant California sea cucumber ( Parastichopus californicus ) will often eviscerate due to rough handling, temperature shock, or other stressful treatments. The event occurs through the anus and the eviscerated parts are mainly the respiratory trees.

Holothuria arenicola is described as a sea cucumber suitable for keeping in aquaria as it does not eviscerate, whereas the "Australian" sea apple (Paracucumaria tricolor) frequently eviscerates. [6]

Similar behaviour

Some starfish evert their stomachs through their mouths to eat their prey. The starfish then retracts its stomach back inside of its body. [7]

Evisceration plays a role in the Theodore Sturgeon short story "The Girl Had Guts" (Venture Science Fiction, January 1957; also appears in his collection "A Touch of Strange"). [8]

Related Research Articles

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An echinoderm is any deuterostomal animal of the phylum Echinodermata, which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as larvae, as adults echinoderms are recognisable by their usually five-pointed radial symmetry, and are found on the sea bed at every ocean depth from the intertidal zone to the abyssal zone. The phylum contains about 7,600 living species, making it the second-largest group of deuterostomes after the chordates, as well as the largest marine-only phylum. The first definitive echinoderms appeared near the start of the Cambrian.

<span class="mw-page-title-main">Sea cucumber</span> Class of echinoderms

Sea cucumbers are echinoderms from the class Holothuroidea. They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. They are found on the sea floor worldwide. The number of known holothurian species worldwide is about 1,786, with the greatest number being in the Asia-Pacific region. Many of these are gathered for human consumption and some species are cultivated in aquaculture systems. The harvested product is variously referred to as trepang, namako, bêche-de-mer, or balate. Sea cucumbers serve a useful role in the marine ecosystem as they help recycle nutrients, breaking down detritus and other organic matter, after which bacteria can continue the decomposition process.

<span class="mw-page-title-main">Holothuriida</span> Clade of sea cucumbers

Holothuriida is an order of sea cucumbers. Taxa within the order Holothuriida were previously classified in the order Aspidochirotida, which was determined to be polyphyletic in 2017. Some taxa were also reclassified into the clades Synallactida and Persiculida.

<i>Holothuria atra</i> Species of sea cucumber

Holothuria atra, commonly known as the black sea cucumber or lollyfish, is a species of marine invertebrate in the family Holothuriidae. It was placed in the subgenus Halodeima by Pearson in 1914, making its full scientific name Holothuria (Halodeima) atra. It is the type species of the subgenus.

The worm pearlfish is an eel-like fish in the family Carapidae.

<i>Holothuria forskali</i> Species of sea cucumber

Holothuria forskali, the black sea cucumber or cotton-spinner is a species of sea cucumber in the family Holothuriidae. It is found at shallow depths in the eastern Atlantic Ocean and the Mediterranean Sea. It was placed in the subgenus Panningothuria by Rowe in 1969 and is the type taxon of the subgenus.

<i>Holothuria scabra</i> Species of sea cucumber

Holothuria scabra, or sandfish, is a species of sea cucumber in the family Holothuriidae. It was placed in the subgenus Metriatyla by Rowe in 1969 and is the type species of the subgenus. Sandfish are harvested and processed into "beche-de-mer" and eaten in China and other Pacific coastal communities.

<i>Colochirus robustus</i> Species of echinoderm

Colochirus robustus, commonly known as the robust sea cucumber or the yellow sea cucumber, is a species of sea cucumber in the family Cucumariidae. It is found in shallow seas in tropical parts of the central Indo-Pacific region. C. robustus belongs to the class Holothuroidea, a group of echinoderms called sea cucumbers and known for unusual behavior including evisceration, asexual reproduction, and regeneration. The robust sea cucumber has a soft body and lacks a spine, but it does have an endoskeleton consisting of microscopic spicules, or ossicles, made of calcium carbonate. C. robustus has a respiratory tree that allows it to extract oxygen for respiration, using the anus to pump water. The robust sea cucumber is an important dietary staple for many East and Southeast Asian populations, and has been used for medicinal purposes for hundreds of years. Recent research suggests that peptides from C. robustus enhance the activity of the immune system.

<i>Pearsonothuria</i> Genus of sea cucumbers

Pearsonothuria is a genus of sea cucumbers in the family Holothuriidae. Pearsonothuria graeffei is the only species in the genus. Graeffe's sea cucumber is found in the tropical Indo-Pacific Ocean and the type locality is Viti Island, Fiji. It is named after Eduard Heinrich Graeffe, Semper's coworker at the Museum Godeffroy.

<i>Holothuria parvula</i> Species of sea cucumber

Holothuria parvula, the golden sea cucumber, is a species of echinoderm in the class Holothuroidea. It was first described by Emil Selenka in 1867 and has since been placed in the subgenus Platyperona, making its full scientific name Holothuria (Platyperona) parvula. It is found in shallow areas of the Caribbean Sea and Gulf of Mexico and is unusual among sea cucumbers in that it can reproduce by breaking in half.

<i>Holothuria leucospilota</i> Species of sea cucumber

Holothuria leucospilota, commonly known as the black sea cucumber or black tarzan, is a species of marine invertebrate in the family Holothuriidae. It is placed in the subgenus Mertensiothuria making its full scientific name Holothuria (Mertensiothuria) leucospilota. It is the type species of the subgenus and is found on the seabed in shallow water in the Indo-Pacific.

<span class="mw-page-title-main">Cuvierian tubules</span> Tubes found in some sea cucumbers

Cuvierian tubules are clusters of fine tubes located at the base of the respiratory tree in some sea cucumbers in the genera Bohadschia, Holothuria and Pearsonothuria, all of which are included in the family Holothuriidae. The tubules can be discharged through the anus when the sea cucumber is stressed. They lengthen when they come into contact with seawater and become adhesive when they encounter objects, functioning as a form of defense against predators or sources of danger. They are named after the French zoologist Georges Cuvier, who first described them.

<span class="mw-page-title-main">Chiridotidae</span> Family of sea cucumbers

Chiridotidae is a family of sea cucumbers found in the order Apodida. Within the family, there are 16 recognized genera all with different ranges of body types and functions. Sea cucumbers play a fundamental role in many marine ecosystems.

Thyonicola americana is a species of parasitic sea snail, a marine gastropod mollusc in the family Eulimidae. It infests the sea cucumbers Eupentacta quinquesemita and Eupentacta pseudoquinquesemita in Puget Sound and other parts of the northeastern Pacific Ocean.

<i>Eupentacta quinquesemita</i> Species of sea cucumber

Eupentacta quinquesemita is a species of sea cucumber, a marine invertebrate with an elongated body, a leathery skin and tentacles surrounding the mouth. It is commonly known as the stiff-footed sea cucumber or white sea cucumber, and occurs on rocky coasts in the northeastern Pacific Ocean.

<i>Holothuria fuscopunctata</i> Species of sea cucumber

Holothuria fuscopunctata, the elephant trunkfish, is a species of sea cucumber in the family Holothuriidae native to shallow water in the tropical Indo-Pacific. It is placed in the subgenus Microthele, making its full name Holothuria (Microthele) fuscopunctata.

<i>Holothuria hilla</i> Species of sea cucumber

Holothuria hilla is a species of sea cucumber in the subgenus Mertensiothuria of the genus Holothuria. Some common names include the contractile sea cucumber, the sand sifting sea cucumber and the tigertail sea cucumber, and in Hawaii it is known as the light spotted sea cucumber. It is found in the Indo-Pacific region and the Red Sea.

<i>Actinopyga varians</i> Species of sea cucumber

Actinopyga varians, the Pacific white-spotted sea cucumber or Hawaiian sea cucumber, is a species of sea cucumber in the family Holothuriidae. It is found in the Pacific Ocean near Hawaii and also in the Indo-Pacific Ocean.

<i>Holothuria pervicax</i> Species of sea cucumber

Holothuria pervicax is a species of sea cucumber in the genus Holothuria. It is commonly called the stubborn sea cucumber due to its inability to be kept alive in captivity. It is commonly found buried beneath rocks on reefs in warm waters.

<i>Holothuria impatiens</i> Species of sea cucumber

Holothuria (Thymiosycia) impatiens, commonly known as the impatient sea cucumber or bottleneck sea cucumber, is a species of sea cucumber in the genus Holothuria, subgenus Thymiosycia.

References

  1. 1 2 Anon. "Learn about sea cucumbers; Defences and predators". Archived from the original on January 11, 2018. Retrieved August 14, 2013.
  2. 1 2 3 Flammang, P.; Ribesse, J. & Jangoux, M. (2002). "Biomechanics of adhesion in sea cucumber cuvierian tubules (Echinodermata, Holothuroidea)". Integrative and Comparative Biology. 42 (6): 1107–15. doi: 10.1093/icb/42.6.1107 . PMID   21680394.
  3. ↑ Byrne, M. (1985). "Evisceration behaviour and the seasonal incidence of evisceration in the Holothurian Eupentacta quinquestemita (Selenka)". Ophelia. 24 (2): 75–90. doi:10.1080/00785236.1985.10426621.
  4. ↑ Byrne, M. (2001). "The morphology of autotomy structures in the sea cucumber Eupentacta quinquesemita before and during evisceration". Journal of Experimental Biology. 204 (Pt 5): 849–863. doi: 10.1242/jeb.204.5.849 . PMID   11171409.
  5. ↑ Ruppert, Edward E.; Fox, Richard, S.; Barnes, Robert D. (2004). Invertebrate Zoology, 7th edition. Cengage Learning. p. 915. ISBN   978-81-315-0104-7.{{cite book}}: CS1 maint: multiple names: authors list (link)
  6. ↑ Fenner, B. "Sea cucumbers: Not a pretty picture". WetWebMedia.com. Retrieved August 14, 2013.
  7. ↑ Carefoot, Tom. "Adult feeding". Sea Stars: Feeding, growth, & regeneration. A Snail's Odyssey. Archived from the original on May 12, 2013. Retrieved August 14, 2013.
  8. ↑ Sturgeon, Theodore (1958). A Touch of Strange. DoubleDay and Company.
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