When you picture a hedgehog, typically your mind conjures up images of a little brown desert animal. With soft small eyes, a little snout, and tiny little feet, the last thing you think of is salt water, spikes, and ancient writings from Aristotle. But it’s true; there is another type of hedgehog that often goes unnoticed – the Sea Hedgehog (known more commonly as an urchin).
The red and green sea urchin (aka Strongylocentrotus purpuratus & Strongylocentrotus droebachiensis for our scientific readers) are the most common species found in shallow waters on the BC coast. Urchins typically live in kelp forests and can be spotted slowly crawling along the rocky sea floor. When you see this animal under water the first thing that will strike you is the long thin spines protruding from its outer calcium carbonate shell. These thin body spears are super pointy and sharp on top; they even have a little claw near the top of the spine to help clean the urchin’s body. Underneath this spiky shell is a strange sight. If you flip an urchin over you will see a single mouth surrounded by five pairs of suction cupping tube feet and five large individual teeth. For those history buffs out there, the mouth of the sea urchin is formally known as “Aristotle’s Lantern” (know that’s a mouthful!). In ancient times burning candles would be surrounded by five pieces of horn in efforts to prevent the flame from being blown out as they were carried. Known famously for his philosophical writings, Aristotle was fascinated with animals and also wrote and drew sketches of the sea urchin, describing the mouth as one of these lanterns. Hundreds of years later, the term “Aristotle’s Lantern” has still stuck. Who knew! One of the most interesting factoids about an urchin’s teeth is that they are self-sharpening and self- repairing when broken (no dentist needed!). Structured as a complex dental apparatus, the five teeth of an urchin are primarily used to scrape algae from rocks for food. But urchins are omnivorous and also eat small ocean organisms as they float by.
Sea Otters are a natural predator of the urchin, diving for them and bringing them to the surface to be cracked open so the high nutrient roe inside can be eaten. But otters are not the only predator that has taken a liking to the insides of our spiny Salt Water Hedgehog. Urchins are harvested annually by BC scuba divers between September and March for sale to restaurants as a lightly salted delicacy. As one of the longest living creatures on earth (with some red urchins living over 200 years), these small, round, and spiky animals form an important part of the marine ecosystem by promoting the growth of kelp forests and algae.
With over 700 species of urchins in our world’s oceans, even if you don’t live on the North Island, you’ll probably have lots of opportunities to search out and see this amazing little animal yourself in all its variances and biological differences around the globe. Unfortunately, unlike the urchin, we all still need our check up’s with the local dentist.
Bryce Casavant is a former BC Conservation Officer and currently a Doctoral Candidate with Royal Roads University. He writes for the Eagle from his home on Vancouver Island.