Among nature’s lazier creations, the humble sea urchin is basically a ball covered in spikes, and a variety of species are found around Malapascua. Sometimes known as the ‘sea hedgehog’ the name ‘urchin’ comes to us from Latin via the Old French ‘herichun’ meaning hedgehog. The resourceful dive instructor can use a field of urchins as the perfect natural tool to conduct an excellent buoyancy session over.
Belonging to the echinoderm family, urchins are cousins of starfish and have the same five fold symmetrical body shape. They also move in the same way as starfish using tube like feet on the bottom of their body. Using hydraulic pressure they are able to pump water in and out of these tiny tube feet and walk in any direction.
The most obvious feature of sea urchins though is the armoury it carries with it. The spines can be highly toxic and cause nasty injuries if contacted, however, these don’t get in the way of a number of specialized predators such as sea otters and triggerfish from enjoying an urchin dinner. If an urchin manages to escape predatory clutches and sickness they can survive for centuries! In addition to the spines, urchins have lots of tiny pincers which are used to groom the spines and keep them clean and needle sharp.
These spines lend themselves to some pretty cool symbiotic relationships with other creatures. Sometimes you will catch sight of a particularly fast urchin scurrying along the sea floor, but on closer inspection it’s being carried by an urchin crab who’s using it as quite a formidable defense against it’s own predators. Collector urchins turn this relationship upside down and hold pieces of broken coral and other things above them as a disguise.
The spines don’t only offer protection to the urchin itself, and other tiny creatures can be found living between them for protection. Notably the zebra urchin crab and the rare Coleman’s shrimp, both pictured, which can both be found on the beautiful fire urchin. Urchin Commensal Shrimp are also commonly sighted on the many urchins around Malapascua You could even find a crab, living on an urchin, being carried by another crab for a ridiculous urchin sandwich!
After a mistranslation of Aristotle’s works, the mouth of an urchin is also known as ‘Aristotle’s lantern’ as urchins supposedly resemble lanterns of his time. It seems lantern designs have improved significantly since then…