Sea Cucumber
Breathes through its anus — and ejects its own organs as a weapon
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Superpower
When threatened, many sea cucumbers eject their internal organs through their body wall (or anus) in a process called evisceration. Some species eject Cuvierian tubules — sticky white threads that expand dramatically on contact with seawater, entangling and immobilizing the attacker. The sea cucumber then regenerates the ejected organs over the following 1–5 weeks. Separately: most sea cucumbers breathe by drawing water in and out through their anus, which contains internal 'respiratory trees' — the primary gas exchange organ of the animal.
Overview
Sea cucumbers are echinoderms — relatives of sea urchins and starfish — found on the seafloor worldwide and representing a crucial link in ocean nutrient cycling. They process sediment by eating it and excreting clean sand, and their bodies contain holothurin, a compound with anti-tumor and antifungal properties that is currently being studied for pharmaceutical applications. There are over 1,700 species. Some deep-sea species are bioluminescent; some can liquefy their own bodies to squeeze through narrow gaps, then resolidify on the other side.
Found in
Seafloors worldwide at every depth, from intertidal rock pools to abyssal trenches at 5,000m. Particularly abundant in tropical shallow-water environments. Some species are harvested commercially as trepang (bêche-de-mer) and used in cooking.
Things worth knowing
- 1
Sea cucumbers can liquefy their own connective tissue — a process called 'catch connective tissue' — allowing them to squeeze through openings far smaller than their resting body size, then resolidify on the other side.
- 2
Some pearlfish (Carapidae) live exclusively inside the body cavity of sea cucumbers, entering and exiting through the anus. The sea cucumber appears unable to evict them.
- 3
Holothurin, a compound extracted from sea cucumbers, has demonstrated anti-tumor, antifungal, and anticoagulant properties in laboratory studies. Multiple pharmaceutical companies are investigating it.
- 4
The eviscerated organs of sea cucumbers can continue functioning outside the body for hours — ejected respiratory trees have been observed still contracting after separation.
- 5
Some species of sea cucumber reproduce by fission — literally splitting themselves in half lengthwise, with each half regenerating into a complete animal.