What is this critter?

[bitstream]

It’s attached to a zoa colony in my QT. It survived CoralRx and hydrogen peroxide. I’ve tried grabbing it with tweezers twice but it’s super tiny and retracts into its hidey hole faster than Usain Bolt.

Last time I tried grabbing it, it went into hiding for 5 days.

 

[TX_REEF]

Kinda looks like a feather duster worm? Is it causing problems?

 

[JoJosReef]

@vetteguy53081 @ISpeakForTheSeas
Any idea here? I know zoa spiders exist but never seen them and understand they aren't easy to deal with. Or is this some other critter?

Best to be on the safe side...

 

[bitstream]

Kinda looks like a feather duster worm? Is it causing problems?

No issues that I can see. It’s a new coral from a LFS that has been in my quarantine tank for a week.

 

[bitstream]

@vetteguy53081 @ISpeakForTheSeas
Any idea here? I know zoa spiders exist but never seen them and understand they aren't easy to deal with. Or is this some other critter?

Best to be on the safe side...

It’s weird in that it hides in a little hole in the rock and when it does appear, it just sticks out, but never moves anywhere.

I took a redditor’s suggestion and super glued the spot it comes out of. Either that’s gonna kill it or it’ll wiggle its way out from another spot. Better safe than sorry!

Still curious to know what this is. Based on my research so far, I can’t say definitively.

 

[ISpeakForTheSeas]

@vetteguy53081 @ISpeakForTheSeas
Any idea here? I know zoa spiders exist but never seen them and understand they aren't easy to deal with. Or is this some other critter?

Probably not a zoanthid eating spider in this case, but I can't see clearly enough to feel confident with an ID at the moment.

 

[bitstream]

Probably not a zoanthid eating spider in this case, but I can't see clearly enough to feel confident with an ID at the moment.

That’s the best picture I can get — it’s with 5x zoom and a DeepSee. The thing is super tiny.

 

[vetteguy53081]

@vetteguy53081 @ISpeakForTheSeas
Any idea here? I know zoa spiders exist but never seen them and understand they aren't easy to deal with. Or is this some other critter?

Best to be on the safe side...

If its moving, may very well be a zoa eating spider which typically buries itself within the zoa polyp. Other possibility is a hydroid

 

[ISpeakForTheSeas]

That’s the best picture I can get — it’s with 5x zoom and a DeepSee. The thing is super tiny.

Yeah, it's not easy getting pics of stuff that small. Can you describe the critter and its hole more at all? (For examples, does it look like a crustacean? Is the hole a tube? Is the hole hard like barnacle shell? How does the critter move - does it open/close, expand/contract, extend/retract, etc.?)

As is, it kind of does look like a little feather duster or barnacle - are the little appendages sticking out in the pics leg-like, tentacle-like, or feather-like?

 

[bitstream]

If its moving, may very well be a zoa eating spider which typically buries itself within the zoa polyp. Other possibility is a hydroid

It just sticks out And retracts. I’ve never seen it move…

 

[bitstream]

Yeah, it's not easy getting pics of stuff that small. Can you describe the critter and its hole more at all? (For examples, does it look like a crustacean? Is the hole a tube? Is the hole hard like barnacle shell? How does the critter move - does it open/close, expand/contract, extend/retract, etc.?)

As is, it kind of does look like a little feather duster or barnacle - are the little appendages sticking out in the pics leg-like, tentacle-like, or feather-like?

The zoas are on a rounded piece of rock that someone cut with a band saw and then glued to a frag disc. The hole is probably 2mm by 1mm right next to the base of a polyp.

All I see is that little feathery looking part stick out but can’t make out what the body looks like. What I can say is that it’s either brown or black, with no other colors at all. It only sticks out about 2mm and any agitation causes it to immediately retract into the hole and disappear completely for days at a time.

Looking at pics online, it doesn’t seem to have enough “feathers” to be a feather duster, nor does it look like any of the worms some have suggested it might be. Given that it has about 7 “arms” attached to some kind of base and that the zoas dont seem to be bothered at all, I am doubting it’s a spider or Zola eating nudibranch. Today when I was closely inspecting the area where this thing resides (now covered with glue), I saw what looked like a strand with about a half dozen tiny eggs on it. Whether that is related to this thing is also anybody’s guess.

For now, I’ve glued the hole and am going to inspect several times daily to see if it or anything similar reappears elsewhere.

 

[vetteguy53081]

Great

It just sticks out And retracts. I’ve never seen it move…

Great - sounds like what a hydroid would do

 

[bitstream]

Great

Great - sounds like what a hydroid would do

I looked at pictures of hydroids and it’s not an exact match, but probably the best bet so far given that this thing doesn’t seem to move about.

Fingers crossed that gluing it kills it off and that no others appear. I’ll have to research the lifecycle of these things to determine how long to leave the coral in quarantine.

 

[bitstream]

The interesting bit I’m reading is that folks say hydrogen peroxide kills hydroids, but this thing survived not only a peroxide dip, but a secondary direct injection of peroxide into the hole with a pipette.

 

[vetteguy53081]

Gluing will kill it
Other possibility is Medusa worm

 

[EeyoreIsMySpiritAnimal]

Might have been a barnacle... When it popped in and out, was it like it was waving at you?

 

[bitstream]

Might have been a barnacle... When it popped in and out, was it like it was waving at you?

No, not waving at all.

 

[bitstream]

I did some more digging and this could very well have been a baby aiptasia. The behavior is spot on in terms of it retracting and disappearing. Photos some other folks posted of baby aiptasia look virtually identical.