good urchin or bad? picture included

[wwinters]

After reading all the posts on the gen. disc. board I thought I should
probably take this guy out till someone could tell me if he will eat my softies
or if the worse it could do was knock over my rocks and eat some calorous algae.

He is dark purple and shaped like a ball that has been squished flat just a little. it has thick short spikes along the sides and thin tentacle like things on the sides and bottom. The top is smooth and velvety with a 5 point star pattern in the middle that is a slightly different velvet purple color. It is about the size of a nickle and I think came a a hitchhiker on my vanis or vanuatu rocks from Jeff's

It spends most of it's time in crevices of my live rock.

[ August 12, 2001: Message edited by: wwinters ]

 

[horge]

Hi ww,

Probably Echinometra oblonga, but either my monitor needs changing or that pic wayyy too dark

It is one of the most impressive rock-boring urchins around. It depends really, how you want to view it, but in my book it's a good thing to have in the tank. Not as effcient and broad-spectrum an herbivore as, but definitely safer than, a Diadema setosum.

hth,

horge

 

[wwinters]

Thanks the picture colors not at all what he looked like. I tried to lighten it up in photoshop to get the color closer but the picture of him is still to dark.

I will happily put him back in the tank.

 

[davelin315]

Looking at my National Audubon Society Field Guide to North American Seashore Creatures, it looks like one of 3 species of urchin: 1. Atlantic Purple Sea Urchin - Arbacia punctulata 2. Rock Boring Urchin - Echinometra lu****er 3. Purple Sea Urchin - Strongylocentrotus purpuratus.

1. Spines are longitudinally grooved, cylindrical, and can reach 1", and the top is nearly free of spines. It has 4 plates on its anus (bet you wanted to look at your urchins butt and study it, didn't you?). It is oval shaped, with purplish brown, reddish gray, or black spines, black skin. Range is from Cape Cod to Florida, Texas, Yucatan, Cuba, Jamaica, West Indies, Trinidad. It says this species is omnivorous and will eat algae, sponges, coral polyps, mussels, sand dollars, and dead or dying urchins or other animals.

2. Skin is reddish brown or brownish black, tinged with purple or green, the spines are light green, violet, light or dark reddish brown, and it is somewhat oval. Its anus has multiple plates of varying size, and many small spines around it. Range is Florida to Texas and Mexico, Bermuda, Jamaica, West Indies to Brazil. It says it bores into the rock and creates a burrow, no comments on what it eats.

3. Adults are vivid purple, juveniles are greenish, up to 4" wide, 1 3/4" high. Domed above and flattened beneath, with many scalelike plates around its anus. Range is from British Columbia to Baja California. It is another rock boring urchin, no comments on what it eats.

Hopefully, you can figure out which one it is from above. If you know where your liverock came from, this will help, since #3 is only from the pacific ocean, while the #1 and #2 are found in the Atlantic and various tropical islands. Also, you can take a look at your urchins butt, and see how many plates it has. This is usually pretty simple to do if it crawls on your glass at all. I currently have a low opinion of urchins, and have only one in my tank, a shingle urchin, but I'm not even sure if he's reef safe.

 

[horge]

For those trying to perform identification diagnostics on urchins...


The mouth is on the animal's underside,
but the anus is up on central topside.

horge

 

[tilly]

Off the subject a little...but still urchin related..... Does anyone have experience with a pencil urchin in their tank? I bought one after finding 4 or 5 sources stating they were reef safe. Now I'm hearing they will eat corraline algea and corals. I'd like to hear from people who have actually had them in their reef tanks.
Thanks, Tilly

 

[Fredfish]

Tilly,
Accorting to Ron Schemik they are all predatory!! There is an article on urchins by him in the Aquarium Frontiers archives

Fred

 

[danmhippo]

Dave:
You have an undulated trigger with urchin coexisting peacefully????? I am surprised that the urchin is still alive with agility to get to the clam meat faster than the trigger!!

Ahem....Ahem....I think you got some explaining to do!

 

[davelin315]

In my experience (IME for future reference in case you didn't know, it took me a few weeks until somebody finally told me what it meant), pencil urchins, so called "collector" urchins or "decorator" or "pin cushion", long spines, and all the rest are predatory omnivores. They will eat anything they can find, and will scavenge, too. Tonight, in fact, I tossed a dead crocea clam (damn xenia keeps on overgrowing the things and choking them out) into my pond where the urchins have been banished to. The first one to make a meal out of it was not the undulated trigger that lives there, nor the copepods, amphipods, and worms that reside in the substrate, but the pin cushion urchin which is pretty similar to the blue tuxedo urchin that so many are so fond of. By the way, my pencil urchin got banished not when I caught him eating xenias, but when I caught him eating one of my starfish.

 

[davelin315]

The undulated is keeping my filter alive (and also a rescued fish) and he lives with 3 urchins and also a few clumps of xenia in a pond. I am as surprised as you were that he has not taken a bite out of one of the urchins. When I put him in the pond, the first thing he did was start blowing sand around and eating bristle worms. Now, he is very fat, and spends a lot of time in a large rock formation on one end of the pond. Swims around until I come down to look, and then he darts away to the rock pile.