The harmless looking sea cucumber is more deadly than it looks and has an array of tools and weapons to ward off predators
It may be spineless and about as tough as a sausage but the holothuroid sea cucumber Holothuria spp. is full of hidden strengths, says David Butvill.
When pestered by a hungry fish or crab, this squishy invertebrate found worldwide can erect rock-solid armour in seconds. Special compounds in its skin allow it to stiffen (and liquefy) its body wall on demand.
This is particularly useful on a reef – the critter can ooze into a crevice, harden in place and be virtually impossible to extract.
If harassed in open terrain, the sea cucumber may draw from a deeper, nastier place and violently eject its intestine and stomach out of its anus. This distraction buys it time to slip away. The innards are laced with poison, so the slightest nibble by its foe is sure to nip further pursuit in the bud.
But if the attack escalates, the annoyed cucumber finally explodes – literally tearing its body cavity and expelling toxins that can kill most organisms on contact, a chemical onslaught known as the ‘cuke nuke.
It also blasts its adversary with sticky tentacle-like organs called Cuvierian tubules. These unusual tissues, which contain muscle fibre, expand to 20 times their initial size, then tighten as the captive struggles. The hunter is left entangled and anchored in place, if it is not already dead.
The gutless sea cucumber, unable to eat, absorbs nutrients through its skin and immediately starts rebuilding its insides. In about a month, the cuke is whole again – with the inner strength to take on what lies ahead.
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