The humble sea cucumber is not a marine creature which gets a lot of love. Although, spend a few minutes reading up on them and you’ll discover they’re quite the creature with plenty of hidden secrets!

Closely related to starfish within the group “Echinoderms”, sea cucumbers have diverged from the 5 fold symmetry of a starfish to a single, cucumber-like, body.

With over 1,250 different species, sea cucumbers can be found from the shallowest of tropical lagoons to the deepest, darkest parts of the ocean.

Sea cucumber at Atmosphere Resort in Dumaguete Philippines

Black spotted sea cucumber with adapted tube feet. Photo: Kirsty Richards

Vacuum cleaners of the ocean

Ever seen links of what looks like sand poop? It’s most likely that these have come from the humble sea cucumber. Selected species have modified tube feet helping them to hoover up sand grains, that are cleaned of any detritus and algae and “pooped” out at the other end as lovely, clean sand.

They breathe through their what?!

Similar to starfish, they breathe using a water vascular system where water is taken into the body, oxygen is extracted using respiratory trees and the de-oxygenated water is pushed out. It just so happens all this takes place using the creature’s anus – they literally breathe through their bums.

Cucumbers & Pearl fish

Several species of Pearl fish are known to have a… “unique” relationship with sea cucumbers. These eel-like fish have found a specific niche and exploited it to the best of their ability – they live, quite literally, up the bum of sea cucumbers. Tracking them down by smell, the fish, helped by it’s lubricated body, wiggles its way into the sea cucumber head first. Worried they may get trapped in there? Well the cucumber still has to breathe!

Leopard sea cucumber with Pearlfish. Photo: Claude Rives from Fishbone

Their best defense against predators?

Any unsuspecting predator trying to pick an easy meal would be surprised at the sea cucumber’s main defense mechanism – they spew out their insides. More specifically, when threatened, they will excrete their respiratory trees – long white and sticky I can only liken them to silly string which are re-grown when lost.

Leopard sea cucumber expels its respiratory trees in defence. Photo: WaterFrame, Alamy

Hot off the press!

Recent research has shown this slow moving creature may not live a sedentary life at all. Some species, when distressed, are able to inflate themselves like a balloon full of water. They release their grip on the seabed, become neutrally buoyant and float away to safety!

So, the next time you’re out diving/snorkeling searching for something ‘cool’, take a moment to appreciate the unappreciated!

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