Colochirus quadrangularis is called the Thorny sea cucumber. From its appearance it could also be described as pink warty sea cucumber. But that is the common name for another species, that might be found right next to ours, Cercodemas anceps. When you think about it, it makes sense. A wart is smaller than a thorn, so C. anceps has a smoother surface. Both are pink though, so confusion is programmed.
It is really helpful to use the scientific names to avoid confusion. This is true for more or less any species of animals or plants. Different cultures also have different common names for animals.
The title I chose for this post seems to be a commonly used one for the topic. See this page for further explanations on scientific names of living beings. Often the scientific names have similar parts, or somehow have parts that sound similar to commonly used names. Even though I don’t know what is quadrangular in our species (I guess the overall body shape), the fact that the name has a meaning makes it easier to recognize it. Pronunciation of scientific names is another game…
C. quadrangularis and C. anceps are both in the family Cucumariidae (together with sea apples, guess the shape!). The closest relatives would be the sea urchins (class Echinoidea), both in the subphylum Echinozoa. Sea cucumbers form the class Holothuroidea. In 2013 a marine biodiversity workshop was done in Singapore. Here only one undetermined, and also pink Colochirus species was found. I wonder if that later turned out to be C. quadrangularis? It has been mentioned by other sources years earlier. They also did not mention C. anceps. Anyway, it is amazing to see how many people care about sea cucumbers!
What we have is a pickle-sized cucumber in amazing colors! Here someone really tried to make sea cucumbers look good, and it worked. Neon pink and yellow is a nice combination.
Usually not much action is to be expected from these marine animals. C. quadrangularis though can be seen using their feeding tentacles. That also helps to locate the front of these marine birds of paradise. I was surprised that there are only 1700 species of sea cucumbers known so far. Also I am not used to the wide distribution of marine species compared to terrestrial species. Our Pink thorny sea cucumber can be found from East Africa to North Australia.
Three cucumbers at approx. 13m depth. Note the feeding tentacles of the one at the bottom. The other two pulled their tentacles in as I approached.
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