In Search Of The Sea Urchins

This weekend, the Biol 326 class made the six hour trek out to bamfield marine sciences centre to explore the magical world of (mainly) marine invertebrates in one of the most amazing places on the BC coast. The weekend was filled up with various ocean activities, my personal favourite being dredging. To do this we sailed out on a boat, which was fantastically designed after old school fishing boats, to the open water where we sent down an empty crate and pulled up a plethora of marine invertebrates. Over the course of the entire weekend, since our night time exploration on our first night there, a classmate and I had been desperately trying to find sea urchins. As I’m sure you can imagine, one of the treasures that we dragged up from the ocean depths was a whole bunch of sea urchins. We were overjoyed.

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Sea urchins belong to the phylum Echinodermata, along with sea stars and sea cucumbers. I like to think of them as sea hedgehogs (this is actually where the name urchin comes from, it is an old word for hedgehog), because they are round, covered in spines, and are absolutely adorable. However, urchins are obviously cool for much more than their good looks, they have several unique features that makes them one of the coolest animals out there, my favourite being their tube feet.
While it might first appear that an urchins test (shell) is covered completely in spines and pokey things that hurt or sting, it is actually quite full of these amazing structures called tube feet. Tube feet, are found in other echinoderms as well and is the whole group’s main source of locomotion. Tube feet act like hundreds of little tiny suction cups, that stick out from sea urchin and onto the surface they are crawling over, or food they are eating. The coolest part about them, is that instead of being controlled by nerves and muscles like most animal feet, tube feet (while still containing some muscles) are controlled by something called a water vascular system. With this system, the sea urchin can send water to and from the tube feet, and use the water pressure to move them around. This system also controls spine movement and the movement of pedicellarines, which are claw like projections that can sting their predators and prey. This system is very cool because it acts independently of the urchins nervous system, and still works even when the urchin has died. During our dredge we pulled up a few pieces of an urchins test that still had spines on it, and they would still move around and be stimulated by touching them.
After finally finding sea urchins on our last day of the adventure, we were able to nap happily on our trip home, dreaming of sea hedgehogs.

More sea urchin (and lots of other benthic marine invertebrates) goodness

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