Editing Sea cucumber (section)

=== Predators and defensive systems ===
[[Image:Tonna Perdix en train de se nourrir.JPG|thumb|''[[Tonna perdix]]'', a selective predator of tropical sea cucumbers]]
[[File:Sea cucumber defence.JPG|thumb|left|A sea cucumber in [[Mahé, Seychelles]] ejects sticky filaments from the anus in self-defense.]]
Sea cucumbers are often ignored by most of the marine predators because of the toxins they contain (in particular, [[holothurin]]) and because of their often spectacular defensive systems. However, they remain a prey for some highly specialized predators which are not affected by their toxins, such as the big mollusks ''[[Tonna galea]]'' and ''[[Tonna perdix]]'', which paralyzes them using powerful poison before swallowing them completely.<ref>{{cite journal |author1=Philippe Bourjon |author2=Sébastien Vasquez |date=2016 |title=Predation by the gastropod ''Tonna perdix'' (Gastropoda: Tonnoidea) on the holothurian ''Actinopyga echinites'' (Echinodermata: Holothuroidea) on a reef of Réunion |url=http://www.spc.int/DigitalLibrary/Doc/FAME/InfoBull/BDM/36/BDM36_45_Bourjon.pdf |journal=SPC Beche-de-mer Information Bulletin |volume=36 }}</ref>
Some other less specialized and opportunist predators can also prey on sea cucumbers sometimes when they cannot find any better food, such as certain species of fish ([[triggerfish]], [[pufferfish]]) and crustaceans (crabs, lobsters, [[hermit crab]]s).

Some species of coral-reef sea cucumbers within the order [[Aspidochirotida]] can defend themselves by expelling their sticky [[cuvierian tubules]] (enlargements of the respiratory tree that float freely in the [[Body cavity|coelom]]) to entangle potential predators. When startled, these cucumbers may expel some of them through a tear in the wall of the [[cloaca]] in an [[Autotomy|autotomic]] process known as [[Evisceration (autotomy)|evisceration]]. Replacement tubules grow back in one and a half to five weeks, depending on the species.<ref name=PLoSone/><ref>{{cite journal | title = Biomechanics of adhesion in sea cucumber Cuvierian tubules (Echinodermata, Holothuroidea) | journal = Integrative and Comparative Biology | date =2002-12-01 | last = Flammang | first = Patrick |author2=Ribesse, Jerome |author3=Jangoux, Michel | doi=10.1093/icb/42.6.1107|volume=42|issue=6|pages=1107–1115 | pmid = 21680394 |doi-access=free }}</ref> The release of these tubules can also be accompanied by the discharge of a toxic chemical known as [[holothurin]], which has similar properties to soap. This chemical can kill animals in the vicinity and is one more method by which these sedentary animals can defend themselves.<ref name=piper/>