Definitely not a bristleworm….

[BubbleBuddy]

Found this in my filter fleece today. Not sure what type of worm. Broke into 3 pieces when I removed it from the fleece and all pieces have formed new worms.

Believe it came from some chaeto I picked up from a LFS a few weeks ago. No other additions in the last year.

 

[CoralB]

I want to tag along to see if anyone knows . That’s looks interesting

 

[keagan]

Ribbon worm (Nemertea). They sometimes reproduce asexually by fragmentation, it doesn't require injury to cause it to split into pieces. If you have a picture of the "head" of the worm under water it'll help a lot in identification. It could be a peanut worm (Sipunculan) based on morphology but what you described (it splitting into three and regenerating) makes me confident its a ribbon worm

 

[BubbleBuddy]

Ribbon worm (Nemertea). They sometimes reproduce asexually by fragmentation, it doesn't require injury to cause it to split into pieces. If you have a picture of the "head" of the worm under water it'll help a lot in identification. It could be a peanut worm (Sipunculan) based on morphology but what you described (it splitting into three and regenerating) makes me confident its a ribbon worm

I’m not sure which is the original head segment but I’m assuming the red dot segment was it. Second and third images show what is likely a new head.

It doesn’t seem to flatten completely out when moving and the segments pulsate.

 

[CoralB]

I’m not sure which is the original head segment but I’m assuming the red dot segment was it. Second and third images show what is likely a new head.

It doesn’t seem to flatten completely out when moving and the segments pulsate.

And this is how nightmares are formed !

 

[PolypPocket]

Cool! Looks like the middle one?

 

[keagan]

I’m not sure which is the original head segment but I’m assuming the red dot segment was it. Second and third images show what is likely a new head.

It doesn’t seem to flatten completely out when moving and the segments pulsate.

I'm now 100% sure that's a ribbon worm based on the mucus trail, the movement you described, regenerating, and the morphology. There's a lot of newly discovered ribbon worms and a lot of species in general (over 1300) so I will try to narrow the I.D down further but beyond phylum I'm not confident I'll be correct. I love ribbon worms so Ill do a bit of reading and try to narrow that I.D a bit further just keep in mind I'll likely get a species level guess wrong.

If you want nightmares Google ribbon worm proboscis

**I should've added I can't believe I forgot because this is really important. They have dangerous toxins in their mucus secretion don't touch it with bare hands!!**

 

[BubbleBuddy]

I’m not sure which is the original head segment but I’m assuming the red dot segment was it. Second and third images show what is likely a new head.

It doesn’t seem to flatten completely out when moving and the segments pulsate.

I'm now 100% sure that's a ribbon worm based on the mucus trail, the movement you described, regenerating, and the morphology. There's a lot of newly discovered ribbon worms and a lot of species in general (over 1300) so I will try to narrow the I.D down further but beyond phylum I'm not confident I'll be correct. This is really interesting, I love ribbon worms so Ill do a bit of reading and try to narrow that I.D a bit further just keep in mind I'll likely get a species level guess wrong.

If you want nightmares Google ribbon worm proboscis

I’m glad I wear gloves when working in the sump. Thought I only had to worry about bobbit and fireworms. New fear unlocked!