Bobbitt worm?

[Flameback Pair]

I have a very fat, and long bristle worm in my tank. I hope this the won't turn into a Bobbitt worm. Can anyone tell me if Bobbitt worms start out looking like bristle worms then metamorph?

 

[JoJosReef]

I have a very fat, and long bristle worm in my tank. I hope this the won't turn into a Bobbitt worm. Can anyone tell me if Bobbitt worms start out looking like bristle worms then metamorph?

They do not. Bobbitt worms start out looking like Bobbitt worms. It's unlikely you'd have a true Bobbitt worm in your tank, although there are many species of Eunice worms (of which the Bobbitt is one) that can end up in your tank. Luckily most of them are not the fearsome ambush predator that you see on videos snatching fish to an early grave. They can still be opportunistic, but are often observed as detritivores, picking at things on the rocks. You will usually see them only briefly unless you are watching after lights out with a red flashlight (they can't see red well). They are very skittish and will retract back into their holes with lightning speed.

You can ID the Eunice worms by looking for 5 antennae pointed straight forward from the head in a star shaped pattern. Often you see the top three antennae first, because the bottom two are situated lower on the head. If there are 4 antennae, two on either side of the head curved backwards, that may be a Dorvillidae worm (not bad) and not a Eunice worm (generally disliked, whether deserved or not). Neither of these are bristleworms as they are commonly called, which are a different genus (Polydora). Eunice worms also often have a light band across their "neck" right behind the head. They have lots of bristly appendages called parapodia, like a bristleworm. If you see a worm sticking out of a rock that looks smooth and often paler, that could be a peanut worm, an annelid worm in the class Sipuncula and generally considered harmless if not beneficial.

Pics of your worm would help!

*This reply was not AI generated unless you consider my brain and googling skills both artificial and intelligent.

 

[Flameback Pair]

Thanks @JoJosReef for the detailed answer. This is a month old image that doesn't show any scale of size. Although it was retracted into a crevice and was about as big around as my little finger. That's Reef rubble in the foreground.

 

[JoJosReef]

That's a sizeable bristleworm! Some people hate them. Some don't mind them. Maybe a few love them. They certainly put in work cleaning up the tank. Just make sure they aren't taking residence inside any of your meatier LPS.

Thanks @JoJosReef for the detailed answer. This is a month old image that doesn't show any scale of size. Although it was retracted into a crevice and was about as big around as my little finger. That's Reef rubble in the foreground.