ID of sea urchin hitchhiker?

[Haleyf1024]

I recently noticed a sea urchin that crawls around my live rock (from Florida). It's spikes are short and fat, only about 1/4 - 1/2 an inch long at most. I noticed that when it isn't moving around, he flattens himself againts the rock and leaves the top part of his body exposed (no spikes on it). Any idea what species he is? The urchin is about 1- 1.5 inches in length. I was thinking short spined/rock boring urchin but he doesn't fit exactly with their descriptions. He doesn't hurt anybody or knock any rocks out of place and doesn't venture onto the glass at all. It also isn't purple like many FL urchins, he is only black.

 

[Haleyf1024]

Here's a photo of him:

 

[Calappidae]

Echinometra sp.

Rock boring urchin is quite a widespread name, pretty much everything in Echinometra is named that.

They're all pretty much the same in behavior, reef safe, small, wonderful urchins!

Now that pictures is a little fuzzy for me to see so I could be wrong.. the only potential suspect going by the text would be a Cidarid species which is predatory.

 

[Haleyf1024]

The lights had already switched by the time I remebered to get a photo so they keep coming out blurry. I will try to snap a few clear ones tomorrow during the day. He doesn't bother anyone but I am just curious as to what type he is, as I had never seen an urchin with such tiny spines before I saw him.

 

[Haleyf1024]

This is the best picture I could get because of where he is

 

[Calappidae]

I'm not seeing a close comparison to anything, I'd keep a very close eye on it as it looks a little like a Cidarid species.

It could very possibly be something in the middle of recovery after spine loss making it harder to ID with the short stuby developing spines.

 

[Haleyf1024]

Update: I was watching him for a good 10 minutes as he was moving across the live rock. It seems like he has longer, string like black tentacles that are coming from his body. They don't do much except blow slightly in the current. They DEFINITELY don't look like normal spines, they are a bit thicker than hair and I only noticed, maybe 5 of them? And a few of his spines seem to be longer, maybe 1/2- 3/4 of an inch? The urchin has been in the tank for almost 4 months now with the live rock he used as a free ride lol, so is it possible he is still recovering if he had been hurt during transport? I frequent the store I got him in and they have tiny urchins on most of their Florida live rock, but most appear to be normal long spined urchins. If I had to describe how he flattens himself against the rock, I would say it is like when you roll just the outer edge of a cupcake in sprinkles (if that makes any sense?). A lot on pencil/Cidarid species I am seeing only have a few spines that are longer but my guy has probably 100 if I had to guesstimate. Nobody in my tank has gone missing or is injured, even my zoas and RBTA. Should I be concerned that he can become predatory?

 

[Betta132]

The 'tentacles' are his 'feet', like on starfish. Urchins have them all over.
As long as nothing's going missing and/or being eaten, assume he's harmless and leave him in.
On a slightly related note, can I see a picture of a tiny longspine urchin? Sounds adorable.

 

[Haleyf1024]

I will have to get a picture when I go later this week! The babies really are adorable!

 

[hogfanreefer]

This was a small urchin that I got as a hitch hiker on some Gulf live rock. It was about the size of a nickel when I got it. A few months later it was about 5 inches across.

 

[seymour47]

The urchin with the short, stubby spines looks like a type of pencil urchin to me.

 

[seymour47]

This was a small urchin that I got as a hitch hiker on some Gulf live rock. It was about the size of a nickel when I got it. A few months later it was about 5 inches across.

The lab next to mine has a coral tank and they got some Gulf live rock as well. They had 3 of these spiny urchins tag along with their rock. They grew super fast and are a great addition to the tank. It's a lucky hitch hiker if you ask me.

 

[Haleyf1024]

I was looking at him again today, on his flattened side there is a star shape, made up of 5 lines coming from the middle of his body. In the middle where they meet there is a little + shape. Today he was expelling little brown pellet like things from it. I am assuming this is waste?

 

[Betta132]

Yep. Urchins have their mouths on their undersides, so their butt is straight up in the air.
An urchin is, in body structure, very similar to if you curved a starfish's legs up so that the tips met above its body. They're rather closely related to starfish. The star shape is highly visible on urchin shells (tests) that have lost all the spines.

 

[Oceandvr]

If it's from the west coast of Florida, Gulf of Mexico, it's probably the purple-spined urchin, Arbacia punctulata.