Tuesday, December 7, 2010

ABC Wednesday: U is for Urchin

A sea urchin has attached itself to the glass of its tank with the help of its tube feet. If you ever have the chance to encounter one in the wild or in a touch pool at the zoo, hold your hand close to it and it will explore your fingers with those feet (it tickles a bit). Here's a closeup The feet are used for walking and for passing food along to the mouth, the round thing you can see just in the middle. It's called an Aristotele's Lantern, because he described it and compared it to a lantern.

The name comes from an old name for hedgehogs, urcheon. They are related to sea stars and sea cucumbers and feed on algae, sea weed and other plants. If you live near the ocean or have spent a vacation there, you may have found the skeleton (called a test) of a sea urchin:
(source: Wikipedia
Or you found a sand dollar, the test of various sea urchin species that are extremely flattened to accommodate their burrowing lifestyle.

The spines of a sea urchin can be very painful when you step on an urchin or when it's attacked by a predator, like a Sea Otter, but otherwise they are harmless to humans. Some urchins have very broad spines that they use like feet, some can dig with them. Apart from the spines, sea urchins have so-called pedicellaria, small pinchers between the spines that are used to clean the surface of the urchin and, with some species, they contain a toxin in case of attack.
Here's a very cool BBC video on sea urchins, including a closeup of an eating sea urching and a mass of live sanddollars:

click here if video doesn't work.

What else does U stand for ? Find out with ABC Wedneyday


Roger Owen Green said...

interesting creature I've heard of but don't think much about, i must confess.

ROG, ABC Wednesday team

Jingle said...

love your u take.

Sylvia K said...

Such an interesting post for the day! I always learn something when I visit your blog and that's always good! Hope your week is going well! Enjoy!


photowannabe said...

Fascinating information on a very unique creature.
Thanks for posting it.

Tumblewords: said...

I remember seeing many of these when I lived near the ocean and near large aquariums. They are absolutely fascinating. Excellent U post!

Reader Wil said...

This is animal I didn't know, although we had found some fossils of sea urchins in Danmark. Thank you for this interesting post! The video with David Attenborough is great! Thank you!

RuneE said...

A highly stinging U! Just ask anyone who fishes with nets...

Pam said...

A wonderful U word. Urchin's are so interesting to watch in their natural habitat. I have a few shells in my collection of things from the sea.


Anonymous said...

What a great post and I LOVE that you love rodents. So many people don't. If you are ever interested, I host a meme called Nature Notes on Wed/Thurs that only a few people participate in who are nature lovers, but you are welcome.

I forgot to label my hawk as a sharp-shinned. I have both sharpies and coopers hawks stalking the bird feeders on occasion.... Michelle

Anonymous said...

I forgot to add that with sharp-shinned and coopers hawks the eye color changes with age – from yellow to deep red...Michelle

Barbara said...

Fascinating things - I had no idea where the name came from.

Jay at The Depp Effect said...

Wow, that documentary was fascinating! I loved seeing the starfish all speeded up - you really appreciate what active animals they are, don't you? And the sand dollars! I don't think I've ever seen a live one before.

Great post!

Francisca said...

What an interesting post about sea urchins! I know a number of people who like to get them from the sea and eat the insides... but I crunch up my face when they do that... not my cuppa tea.