HELP...Urchin!

[Monique]

Please help me....I was given a gift of a sea urchin, (if you can believe it), and I can't find anything about it in my references....it's mostly black, with black needles, or spines.....about 5 inches long.....do these guys need any special feeding of treatment? so far, all I got was they make good algae grazers......thanks.

[Flatfish]

Many urchins have a taste for coralline algae. Mine prefers the back glass where I don't scrape the coralline off. It only comes out as night and will leave tracks in the coralline. That's how I know it's still around. Some will munch the coralline off the rock or munch the LR itself.

If you have a healthy tank with LR and a lot of misc growth it will be just fine on it's own. I've never has to directly feed mine.

Since there are so many, many urchins some one may be more familiar with yours and may have more specific advice.

Cheers!

[Mrs Smith]

Hey there!

Your "gift" sounds like a black spiny urchin. These guys are really good hair algae grazers, but do tend to bulldoze things when they get big. Yes, it will eat your coralline, which may be good or bad, depending on your situation. (Helps spread it around vs eats it all)

We have two of these guys, but they are both pretty small. They don't tend to wander far from their home rock, but do get around. At first, they ate and ate and ate (a couple of hours) and then just sat and sat and sat. (a couple of weeks, seemed like.)

They might be a Diadema sp, but I don't honestly know. Just ignore him - they're low maintenance.(no special food or treatment to worry about.) Until he starts knocking stuff over. Then he might have to go, but it's up to you.

PS. Try to keep track of where he is in relation to you. Yeah, he's pretty obvious, but I've bumped into ours and while they don't really hurt, they could if you hit hard enough.

JME,
Danielle

[jjharrisx4]

Urchins are really cool!

One thing to be careful of is that (I believe) all urchins are venemous. You don't want to have those long spines poke you and break off. Bad mojo!

[Stang69]

As posted above most urchins will eat coraline but IMO they are merely seeding more growth. Keep an eye on them when they do get big ya may as well Print in big yellow letters " Catipillar" On the side they are like dosers.


Jeff

[mapster]

jjharrisx4,

If it is a long spined urchin (Ill post a pic so you can tell), Ive had one for about 4 months. They are good algea eaters, the only care they will need in good water parameters (what doesn't) and a steady diet of algea. If your tank does not have enough algea you could use Nori sheets (seaweed used for sushi) as a substitute. Rubber banded to a rock and placed in the tank is one way of doing this.

Like other have said, when they get bigger, they will knock stuff over. In four months mine has at least doubled in size. Ive read they they can reach 15" in diameter (including spines). I dont know if they can reach that size in captivity but if they even get close they would be destructive in a small to med sized tank.

As well as being clumsy, their spine can also puncture corals and fingers. Be carefull and never handle it.

Over all, I love my long spined urchin, but eventually it will have to be removed from my main tank.

HTH, sorry for blabbing on.

[Monique]

Wow, thanks for the info, guys.....when I tried to look it up, I got worried when I couldn't find anything......Like maybe it was a big no-no........I feel better now...thanks.

[tdwyatt]

Originally posted by Monique
...when I tried to look it up, I got worried when I couldn't find anything......

Hello Monique, you might try using some of the following keywords in your searches: Diadema, West Indian Urchins, Class Echinoidea, Echinoderms, heart urchins. The sea urchins are of Class Echinoidea, all are free-moving echinoderms which include the sea urchins, heart urchins, and the sand dollars.

Echinoidea is a Latin term meaning "like a hedgehog (porcupine)", or course, referring to the movable spines covering their bodies. The echinoid body does not possess arms, rather the circular oval structure is a result of the fusion of the skeletal ossicles to form a solid case called the test. They display both circular (radial) symmetry and, especially those spp. that live on soft substrates, a secondary bilateral symmetry. Around 950 species have been described. I have had Caribbean specimens that have attained the 15 inch diameter easily within a 2 year period.

Their grazing improves coverage and proliferation by coralline algae by 2 means. Firstly, in order for the coralline to spread rapidly, it must have a means of broadcasting rather than depending on colonial spread at the margins for it's growth. Most coralline algae have a means of doing this, but it is best attained by the messy eating habits of the Echinoids (Regular Echinoids are the sea urchins). Secondly, coralline does not compete well for substrate space when the substrate is covered by filamentatious algae. Many Echinoids are quite effective in consuming algae down to the bare substrate, which allows the coralline to colonize and cover the solid substrates. Diadema spp. in particular are prodigious at consuming algae, and algae comprises the majority of their diet. The effect of this grazing can be seen in the results that followed the population crash of Diadema antillarum (prolly what you have) in the Caribbean in 1983. This resulted in increases in average algal mat thickness from 1 to 2 mm to 20 to 30 mm in one season (this may have been the ultimate cause of the dramatic losses at that time of Acroporoids in the Caribbean as well).

Sea urchins feed with a highly specialized scraping apparatus known as Aristotle's lantern. It is composed of 5 large pyramids, calcareous plates shaped like an arrowhead, with the points pointing toward the center of the oral opening. These pyramids are arranged radially with the sides of each arrowhead attached to the next with a set of transverse muscles. Along the length of the inner side of each pyramid is a calcareous band that extends beyond the tip of the pyramid and forms a tooth. This tooth projects outside the lantern and act as the grazing surfaces responsible for the actual removal of food materials from the substrate. These bands grow quite quickly, in some species, new tooth material is produced at the rate of 1 to 1.5 mm each week. Other apparati are involved in some more specialized feeders, but for the most part, this is the means by which these urchins scrape the substrate for their food. Diadema spp prefer filamentatious algae, but will consume coralline to some extent as green algae becomes scarce. The net effect will be to have a net growth in coralline coverage unless the tank is too small to provide adequate nutrition for the specimen you have.

As an added benefit, if you decide to have a tank to raise Bangaii cardinal fish in, these make excellent aids for keeping the fry alive once the male expels them from the oral pouches.

Hope this helps, biggest problem you will have is the physical space and the occasional rearrangement of the rockwork. Be very careful of the spines, these spines are hollow, some species of urchins possess poison spines on their aboral surface. Diadema spp. spines are hollow, brittle, and provided with an irritant (not a poison). These spines can be rapidly moved and pointed toward a perceived threat (just pass a shadow over one of them and watch the reaction). The outer surface is covered with circlets of small barbs directed toward the point of the needle. They easily inflict painful wounds if they should puncture an unwary Aquarist.

Again, I hope this helps, enjoy your fascinating creature.

[Monique]

Wow, thanks for the info, tdwyatt.....it was really helpful.

[tdwyatt]

There are several spp. iomported from the Caribbean and the indo-pacific, one of the really coool ones has several jewel blue eyespots on the aboral surface f the test. These really show up well with actinic light, and appear to glow in the midst of a thorn thicket. Here's to the health of your Diadema!!!

[hesaias]

Another black urchin is a rock boring urchin (Echinometra sp.). They have white circles around the base of thier spines. Ive heard they can cause LR collapses, but Mine never did. The only thing it did was bury itself in a hole in the rock. Kinda seclusive, but cool.