Slug???

[Instant Tang]

I've seen a creature in my tank, in part. He looks sort of like a terrestrial slug, but I've only seen a portion of his body. What I've seen is mostly white, but has some brownish small spots along the edges and down the middle. He's half-cylindrical in shape, smooth, with a rounded end (the only one I've seen so far) that has some small protruding nobs on it. He's bilaterally symetrical. He appears to measure about 3/4" in width and about1-1/2" to 2" in length from what I can tell so far. He's VERY shy of light and hides amongst the rocks...only comes out in the dark.
No shell from what I can tell.
No bright colors.
Does anyone have any advice they can give me? Is he eating corals or are slugs just harmless critters?
I'll try to remove him tomorrow night, just to play it safe.
No pictures of the thing...but I'll get some once I get him out of the tank.

 

[matter1331]

sounds like it coule be a stomatella, here's a pic:
(oh yeah, the 4th picture I believe)

stomatella

 

[Instant Tang]

No, it's not a stomatella. This thing has no shell at all and its' MUCH bigger than my paper shell snails. I've got quite a few stomatella (I hear they're good!) but this thing is a monster compared to the small size of a stomatella...and it doesn't move nearly as fast as a paper shell snail either.
It appears to be about the size of a thumb. Flat on the bottom and "half round" in section. No shell from what I've seen. It's mostly white, with light brown spots on it. At one of the rounded ends (the only one I've seen and I'll call it the head since it's the advancing portion) it has some very small white knobs or bumps, like very, very short antenae.
I hate to tear my aquascape apart to try to capture it if it's harmless. But, if it's a nuisance or eats SPS or sponges, then I won't hesitate to do so. I'm also concerned about toxins, both for me if I grab it with my bare hands, and for the inhabitants of my tank if it decides to let out a blast of neurotoxins or natural antibiotics!
It's very shy and elusive, otherwise I'd snap a picture of the darn thing!
Does anyone know of any pictures online of slugs of various types that I can look at for comparison?
Tanks!

 

[zenya]

Does it appear segmented like? I have a funny feeling that it may be a Chiton or something similar. Chitons like Cryptoplax can get pretty large. This site is dedicated to living Chitons, but it is just a guess on my part.

 

[graveyardworm]

It may also be a polyclad flatworm, this site has an excellent photo gallery.

 

[Instant Tang]

No, it's not segmented, and it's not a flatworm either. It doesn't have the typical anatomy of a flatworm.
It's not flat. It's about 1/4" thick...about 1/2" wide, approximately 1-1/2" to 2" long.
It's mostly white, and has (muscle?) striations that run the longitudinal direction (length of its body)...
It is able to change shape...it's does not have a hard chitoneous shell of any sort. I've seen it move like a slug atop rocks, and I've seen it stretch itself thinner to reach across gaps between rocks.
If it's a nudi, it's a really boring one..though I haven't seen both ends of it yet!
I'll set up my camera tonight so I can catch it if it comes out.

 

[matter1331]

sounds like it could be a nudi, especially if it's stretching to go across rocks. Hopefully you can get a couple of good shots of it.

 

[Instant Tang]

Well, I've gotten up in the middle of the night for three nights now to see if I can get a picture of this thing...and it still eludes me.

I could probably pick it out of a lineup though. Is there a comprehensive nudi photo site?

(gee, that didn't sound quite right)

 

[LeslieH]

The Sea Slug Forum at seaslugforum.net is the biggest slug site around. Try looking at Armina & Dermatobranchus first. If it is a nudi then it's a predator. The question is on what? Some are coral eaters while others go for sponges, hydroides, worms, other nudis, etc. Good luck finding it.

 

[pagojoe]

If you haven't ID'ed this thing yet, I'd suggest giving a serious look at the Cryptoplax species of chitons. Everything you mention sounds like that genus, except for the antenna. If it's not one of the pale Cryptoplax species, the only other thing I can think of that looks like your description and behaves in the way you described is some of the holothurians, or sea cucumbers. This kind of chiton may have the muscle striations you describe, may shy quickly from light, and may flatten or inflate its body. That said, some of the sea cucumbers can do exactly the same thing, and behave the same way. Good luck!

Cheers,



Don