Sweeper Tentacles and Coral Placement

ascheff · 2 Dec 2014

Hi guys,

I want to understand coral's sweeper tentacles and how they affect coral placement.

I got a Wellso Folded Brain Coral (Trachyphyllia radiata) just over three weeks ago, and it's doing great. It is about the size of my closed fist, but also inflates itself every now and again to probably double that size. The thing is, its sweeper tentacles are about 20cm long, which is quite long considering my tank isn't very big. He extends them all day and night.

Does this mean I can't have any other coral (or other sessile invertebrate) closer to it than it's sweeper tentacles can reach? Are some corals more sensitive to stings than others? Can corals get used to the sting of its neighbours? I often see photos of other reef tanks where corals are very close together.

Liveaquaria lists this coral as semi-aggressive, also saying the space needed between it and neighbouring corals are because it is sensitive to the sting of other corals.

Here it is, the sweepers can be seen top left against the dark background:

459b · 2 Dec 2014

That looks like slime/waste.
In terms of aggressive coral, brains aren't too bad. What other corals are you wanting to pace near it?

jimilutz · 2 Dec 2014

You sure it's a sweeper and not a vermetid snail living under the coral. I have never seen sweepers on a brain.

viper357 · 2 Dec 2014

Trachy's don't have sweeper tentacles like that, I've seen this before, but for the life of me I can't remember what they are called, lol, it's some type of jellyfish like creature that hosts with the brain corals, I can recall the word "comb" I think. Those long stringy things are in fact part of the jellyfish like creature, it has a few of them thus the 'comb' name I think, but they are quite harmless. Let me have a google and see if I can find it.

viper357 · 2 Dec 2014

jimilutz said:
You sure it's a sweeper and not a vermetid snail living under the coral.

It could be that too.

viper357 · 2 Dec 2014

Found it, it could be a ctenophore, a comb jellyfish. Here's something similar - Trachyphyllia LONG SWEEPERS

ascheff · 3 Dec 2014

459b said:
looks like slime/waste

I don't think so - it has a definite ordered structure (which you can't really see in the photo) and the way it it extends and retracts also has an ordered time cycle

459b said:
What other corals are you wanting to pace near it?

My rocks form an open sandy "bay" area, and the brain currently shares this area with two plate corals and a sea fan, all in fairly close proximity. The one plate tends to move around at times, and got quite close to the brain yesterday, which got me worried, as it's moving doesn't seem very controlled (it inflates and lets the current move it). I also want to add a Squamosa clam to the same open area.

jimilutz said:
living under the coral

What I thought was tentacles seems to rather come from tiny openings in the actual fleshy body of the coral. They are very thin and my eyes not that great, so I might be wrong.

viper357 said:
"comb"

This is probably the best description for it. It has one very long string, which is about 20cm long, and out of it for most of its length there are shorter perpendicular sections about 1cm long coming from it.

viper357 said:
a ctenophore, a comb jellyfish

I think this is it, very interesting, thank you. This is what I love most about the hobby - discovering and learning.

459b said:
In terms of aggressive coral, brains aren't too bad

This is a relief. It was my understanding when I got it that they are not too aggressive.

viper357 said:
they are quite harmless

Also a relief, but I'll still keep him away from my sea fan, as those tentacles are quite sticky and might get tangled in the fan. I saw it get caught on a shrimp antenna yesterday, and the shrimp had to pull a bit to free himself.

Thanks for all the inputs guys.

Here's a photo of the brain inflated:

At least now I can move him away from the rock a bit, without being too worried about the space between it and the other corals.

ascheff · 3 Dec 2014

@viper357

You were spot-on with your identification. After quite a bit of searching and some reading I believe it's indeed a type of comb jelly.

It seems although they are not unknown, they appear to be quite rare in aquariums, or at least unnoticed.

Here is another link: Comb jellies reported for the first time growing underneath mushroom plate corals

There is an especially nice photo posted in the comments. Mine also lives on my coral, but are translucent so appear as part of the coral, at least before I knew what I was looking at.

Here is a short video of mine, showing it "fishing" in the current:

viper357 · 3 Dec 2014

Good to hear you've ID'd it. Cool video :thumbup: