Editing Echinoderm (section)

===Antipredator defence===
[[File:Centrostephanus coronatus (juvenile).jpg|thumb|Many echinoderms, like this ''[[Centrostephanus coronatus]]'', are defended by sharp spines.]]

Despite their low nutrition value and the abundance of indigestible calcite, echinoderms are preyed upon by many organisms, including [[bony fish]], [[shark]]s, [[eider duck]]s, [[gull]]s, [[crab]]s, [[Gastropoda|gastropod molluscs]], other echinoderms, [[sea otter]]s, [[Arctic fox]]es and humans. Larger starfish prey on smaller ones; the great quantity of eggs and larva that they produce form part of the [[zooplankton]], consumed by many marine creatures. Crinoids, on the other hand, are relatively free from predation.<ref name=Miller>{{harvnb|Miller|1998}}</ref><!--surely we can find a better source than this-->

[[Antipredator defence]]s include the presence of spines, toxins (inherent or delivered through the tube feet), and the discharge of sticky entangling threads by sea cucumbers. Although most echinoderm spines are blunt, those of the [[crown-of-thorns starfish]] are long and sharp and can cause a painful puncture wound as the epithelium covering them contains a toxin.<ref>{{harvnb|Dorit|Walker|Barnes|1991|p=779}}</ref> Because of their catch connective tissue, which can change rapidly from a flaccid to a rigid state, echinoderms are very difficult to dislodge from crevices. Some sea cucumbers have a cluster of [[cuvierian tubules]] which can be ejected as long sticky threads from their anus to entangle and permanently disable an attacker. Sea cucumbers occasionally defend themselves by rupturing their body wall and discharging the gut and internal organs.<ref>{{harvnb|Dorit|Walker|Barnes|1991|pp=789–790}}</ref> Starfish and brittle stars may undergo [[autotomy]] when attacked, detaching an arm; this may distract the predator for long enough for the animal to escape. Some starfish species can swim away from danger.<ref name="Mladenov1989">{{harvnb|Mladenov|Igdoura|Asotra|Burke|1989}}</ref>