When we come across strong sunlight☀️, we cannot forget to put on some sunscreen or a hat👒. Surprisingly, just like us, some marine creatures are unable to withstand the strong sunlight and have developed some interesting protection strategies🛡. The decorator urchin (𝘚𝘢𝘭𝘮𝘢𝘤𝘪𝘴 𝘚𝘱𝘩𝘢𝘦𝘳𝘰𝘪𝘥𝘦𝘴) is one of these species that will cover itself with materials such as empty shells🐚, pieces of algae🌱 or stones, to gain some protection against environmental stresses🤜🏻. Using its spines, the sea urchin will transfer surrounding materials bit by bit onto the top of its body.
According to several studies, this covering behavior observed in the decorator urchin not only provides advantages against strong UV light🕶 but also against wave actions🌊 and limit detection and predation from predators🍽. Simply put, the more coverage an urchin has, the better is the protection against strong wave surges for instance. During strong wave surges, the position of the cover material is also important. As a result, urchin with coverage on the side of their body 💃🏻provides better streamline and add body mass limiting the strong actions of waves. To limit damages, urchins will also decrease their foraging activities thus decreasing potential damages on the precious spines that strong waves could cause🤕. But covering behavior also allows urchins to face lower degrees of stress against UV-light and other predators, but it was observed that adults which are larger and better protected against predators then rely less on coverage than juveniles👨👩👧👦.
There are also species-specific choice differences between decorator urchins and other species of sea urchins. The coverage of flower urchin (𝘛𝘰𝘹𝘰𝘱𝘯𝘦𝘶𝘴𝘵𝘦𝘴 𝘱𝘪𝘭𝘦𝘰𝘭𝘶𝘴) for instance is mainly composed of coral and shells pieces🐚, while the decorated urchins (𝘚. s𝘱𝘩𝘢𝘦𝘳𝘰𝘪𝘥𝘦𝘴) prefer using organic debris to cover themselves with about 50% of the cover materials used being made of algae and seagrass🌿; which conveniently are also part of its diet. Some researchers then hypothesized that beyond being used for protection, this accumulation of seagrass was maybe a mechanism to store food 🛄 - thus the decorated urchin is always ready for a little picnic. It should be noted, however, that 𝘚𝘢𝘭𝘮𝘢𝘤𝘪𝘴 s𝘱𝘩𝘢𝘦𝘳𝘰𝘪𝘥𝘦𝘴 diet is quite diverse and includes seagrass, macroalgae, other sea urchins (𝘉𝘳𝘪𝘴𝘴𝘶𝘴 𝘭𝘢𝘵𝘦𝘤𝘢𝘳𝘪𝘯𝘢𝘵𝘶𝘴 𝘢𝘯𝘥 𝘓𝘰𝘷𝘦𝘯𝘪𝘢 𝘦𝘭𝘰𝘯𝘨𝘢𝘵𝘢), jellyfish, sea pen and more. Quite a voracious little spiky one 😋!
Talking about size, the decorator sea urchin measures about 5 to 8 cm with short, greenish-color spines of a maximum length of 1.5 cm 📏. But don’t let their small size fool you, as they can live up to 20-25 years! Although they are commonly found in Hong Kong shallow water, you will need to pay extra attention to spot them as they usually cover themselves with all sorts of things🙈. Alternatively, you can just come to the Hong Kong Biodiversity Museum to observe them without any coverage on them😳 - let’s be honest it’s much easier.
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