This week, our Feature Creature at the Portsmouth tank is of the spiny variety - the green sea urchin! We have at least one little guy in our tank; another, more elusive urchin may be hiding in there too.
Urchins are related to sea stars, sand dollars and sea cucumbers. They have lots of small green spines on the outside of their test, or body - one visitor today called our urchin "the porcupine of the sea." Their tests are round and squat, and all those spines protect the insides, where urchins ingest their food and harbor their eggs.
The mouth of an urchin is located on its underside. From what you can see when you hold one, it looks like a small opening, similar to the mouth of the sea star. But from the inside, it looks strikingly different: there are five "teeth" that come together to munch on algae (particularly kelp). Here's what the teeth, all together called an Aristotle's lantern, look like from inside the urchin's test:
Urchins move around using tiny tube feet, just like seastars do. But whereas seastars' feet are found only on the undersides of their arms, urchins have tube feet all over their bodies - you can watch them all stick out if you hold an urchin under the water for a moment or two!
These funny little creatures are harvested quite frequently from the Gulf of Maine, often to be sold to Asian seafood markets. Found under the name "uni" in Japanese American restaurants, urchin roe and gonads are a delicacy in many Asian countries. There have been recent reports that the urchin population in the area is under threat of overfishing, so it may be best to avoid this on the menu - at least until populations increase again!
Come check out these fascinating animals, and give our one - or two - urchins a name. See you at the tank!
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