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Interesting Flatworm

Today I decided to treat a small outbreak of regular ol’ flatworms in my 20g quarantine tank.  Soon after I dosed the medication, I noticed two fine strings dangling into the current from one of my favorite Rhodactis mushroom corals.  My immediate thought was, “Oh no!  The flatworm toxins are causing my coral to expel zooxanthallae!”  But, as I watched, the strings continued to grow.  Within a few seconds, the strings were each about 4″ long.  Suddenly, what I thought was a piece of the mushroom broke off and drifted along.  This made me very nervous.

Rhodactis Mushroom Coral

Rhodactis Mushroom Coral

Very quickly, I realized this was no piece of coral.  One of the strings grabbed a dead piece of Acropora skeleton and pulled the body in out of the current.  I pulled the critter out and identified it as a flatworm.  However, I’ve never heard or seen a flatworm that used “tentacles” in order to move.  I found that I could get the tentacles to extend by gently swirling the container.  The flatworm would curl up (like below), and then the tentacles would come out.

Flatworm balled up with tentacle extending

Flatworm balled up with tentacle extending

Although the actinics in the photo below make the flatworm appear more bright red than it was in the aquarium, it blended in quite well with the mushroom.

Flatworm extended

Flatworm extended under actinics

Flatworm

Flatworm

I noticed the tentacles also have many little extensions off the sides.  Click the picture for a more detailed shot.  My guess is that these help the flatworm grasp a solid surface when they try to land.

Flatworm with tentacle

Flatworm with tentacle

If you have any information on this flatworm or this type of behavior, please let me know!

2 comments

  1. waaahsabi

    Hi,

    This might perhaps be a Coeloplana sp. or Purse Jelly. I’ve got a few of those living in my Alveopora, and so far all they’re doing is catch stuff floating by using their tentacles. No damage done to corals yet. I don’t have SPS though.

    1. admin

      Hey! I think you hit the nail on the head! Thanks so much!

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