Please help me identify this "wormlike" creature

[mixalis]

Several months ago I spotted an odd wormlike creature in my tank. I could never get a clear enough view of it to get a photo (still can't). It sticks the front part of its body out from among the rocks and withdraws very quickly at the slightest movement. In fact, the periodic quick drawing back modus seems to be part of its behavior.

I hadn't seen the thing for a while until last evening. It has grown from small bristleworm size to about average earthworm size. The best I can describe it is as follows: Color--grayish green. Length: unknown as I have never seen the entire thing. Appearance: Looks very much like a centipede. It appears to be segmented with lots of tiny legs. It MAY have a pair of mandibles. It also appears to have 2 sets of antennae. Behavior: Appears to forage among the rocks. Very "skittish." Seems to like to create little barriers of sand/crushed shell, etc. that are cemented together to form a "lair."

I know that it's difficult to positively identify this thing without a visual, but I'm hoping that someone will recognize some of these traits and be able to provide me a general direction in which to pursue identification.

Thanks much! :)

[rshimek]

Hi,

Your animal is a type of bristle worm. We scientists call these animals "polychaetes" and there have been about 10,000 different types described and named.

With out a picture, I can't definitively tell you what it is, but it sounds like it might be scavenging worm in the group that includes the common clam or sand worms sold for bait along many sea coasts; these worms are called "Nereids." Alternatively, it may be an eunicid, these are mostly predatory and some qet quite large, however, they tend to be less reclusive than what you have described and often different colored.

I think your will be largely harmless, but you might wish to keep it in mind as a potential predator if it get much larger.

:D

[mixalis]

Thanks very much for the reply!

Now I'm worried. Perhaps needlessly. I've observed. Hopefully it's a scavenger and not a predator. last night, I noticed that it appeared to want to wander out of its lair after I had fed the tank. I tried to get a picture, but the thing is so incredibly skittish that even a common bristleworm or amphipod moving nearby will cause it to withdraw quickly before I can get a shot.

If it was one of the predatory species, it would likely not be frightened by these other denizens I would assume. I've noticed no odd deaths or coral damage, and if it feeds on 'pods it hasn't made much of a dent in the population. :)

[brandon429]

me too, I was just trying to catch an eyeshot of my same animal today. skittish is an understatement---it withdraws when I even move my eyeball while looking at it---no joke. it is SUPER sensitive I would be interested to study its photo/movement receptor setup... highly effective for whatever means it uses...

brandon429

[mixalis]

skittish is an understatement---it withdraws when I even move my eyeball while looking at it---no joke. it is SUPER sensitive

Odd that you should say that! It really is quite amazing. I didn't mention it because I thought folks would scoff, but it really does seem *that* sensitive. I swear, if I move my eyeballs to track it, it notices. ;) Forget trying to get a digicam shot of it.

I did notice that it definitely seems to have 4 antennae. Two appear to grow from the back of the head, and two forward.

Does your's cement little pieces of rock and shell together to form barriers?

[brandon429]

yes my animal does that too and does have multiple antennae--looks like cousin of a bristleworm but alot meaner looking (insert anthropomorphism here) if I was a miniature scuba diver and i came across that in the reef I think i would have a heart attack and die. due to the scaling of my tiny reef it makes that beastie look mean! i think the one I have is 2-3 inches long, gigantic compared to all other 'pods 'llids who are micro in size.

yes he would rearrange things all the time. For a while he had me wondering if button polyp frags were motile by some means, they would move across the tank overnite. I call him my reef dragon he is scarrrry

[rshimek]

Hi Folks,

Many tube dwelling worms have the withdrawl response you have noted, it is a good survival response when you are basically fish food.

They cement sand grains together to make tubes which are lined with a hardened mucus material.

Many of these worms are surprisingly intelligent, and definitely can learn about their surroundings. Some of them are quite long lived as well.

The presence of four antennae is somewhat distinctive and make them almost certainly scavengers or algae eaters rather than predatory. Take a good close look the next time you get a chance and see if there is smaller fifth antenna arising from the center of the "forehead." If you can verify that there is no such structure your worm is not likely predatory. If there is, it may well be predatory.

Predatory worms are no big deal in our tanks - virtually every animal in our systems are predators - and if they are well fed they are no more a threat to other animals than are most fish or other inverts.

:D