Something living on and eating coralline algae

[superusername]

Has anyone seen these before? Small spots grow on the coralline algae and appear to consumer the nearby algae forming a bullseye-like circle. They seem like they might occasionally move, given the trail of spots tracked below. I can't find any documentation indicating what they are.

Starting image:

1 week after starting image:

4 weeks after starting image:

In other spots, the progress has been much more rapid:

Starting image:

1 week after starting image:

4 weeks after starting image:

Can anyone help identify this? Fortunately it does not seem to have affected anything other than coralline (so far).

 

[wkscott]

Do you have an urchin in the tank? They love coraline. Some limpets will also eat it.

 

[superusername]

No, I don't have an urchin, and as far as I know, I don't have limpets either. These photos are not just the marks of bites, I believe they are also the animals themselves. The little dark spot in the center of the bullseye is what's causing the white rings around them. Once they move on, they leave just the white circular spot behind.

In the photos of the torch coral branches, you can see how one specimen moves down and to the left from the growth border of the coralline algae. The original spots eventually get grown over by the coralline, but you can still make it the trail of white spots where it had previously been. They seem to move only one every few days.

 

[wkscott]

I've see what you mean now. I've been keeping marine tanks for 40 years now and have never seen this before. Let's refer. #reefsquad

 

[reefwiser]

Have you taken one of the rocks out and with a sharp knife see if the area of the spot can be lifted off the rock?
There are all kinds of animals in the sea that have never been named or documented.
I use a Ogle Mesoscope when I find animals like this in my tank.

 

[tupes]

I would also say try to scrape the rock to see if the brown spots come off. Then maybe see if you have someone close bybthat has a microscope to try and see what it is.

 

[Elegance Coral]

looks like newly settled vermetid snails to me.........

 

[terrell wohlrab]

i also have these spots on the bottom parts of my coral (torch) they have been there for some time,

 

[Lionfish Lair]

Can you maybe scrape some off so we can see what's underneath there? You may not be able to get one off intact, but you should be able to see if one likes like a limpet.

 

[superusername]

I chipped a piece of rock off that had one on it. They are tiny, maybe a millimeter in diameter, and I've yet to see one larger. I tried scraping the spot off the rock with tweezers but crushed it. Perhaps a limpet or snail of some sort is a good lead. It's hard to say with such a tiny thing, but it felt like a shell on top and softer flesh underneath. I'll have to try again with a razor.

Gonna see if I can find someone in NYC that has a microscope this weekend.

(Oh, and that Ogle Mesoscope looks like a lot of fun!)

 

[Lionfish Lair]

I think they are little limpets from what I see when I blow them up in photoshop. That's why I suspected you'd crush them trying to get them off. Baby limpets are hard to remove without crushing them. They stick on super well and their shells are very niche. I was doing it the other day as I had a million babies appear in a tank. I killed a lot :-(

If you want to stick some in the mail, I would gladly at them under my scope.

 

[superusername]

So do you think baby limpets or some type of dwarf limpet? They don't seem to be growing past about 1.5mm diameter.

Sadly the Ogles Mesoscope appears to be discontinued or is at least unavailable. Thanks for the offer, and I might mail you some in the future, but I think I found someone whose microscope I can use locally. I'll post pics when I get to use it.

 

[superusername]

OK, so these things continue to progress, so I have a bit of a photo-dump to catch up here:

First, looking at the torch, the spots continue to move and reproduce, but not as aggressively as in other spots. However, I've yet to see any that have grown in size larger than these.

In other areas, the coralline has gotten more thoroughly consumed

I was finally able to get some under a microscope.
Some look like aliens!

 

[saltyfilmfolks]

Oh those are beauties! Great pics.
Wow a barnacle or snail?
Do you ever see how they move? Mouthparts or mucus?

 

[reefwiser]

Every interesting. They don't over time grow any larger than these images. Just move and eat the coralline. One of the problems with ID'ing these small animals is that the ocean is so vast that researchers just never get down to these small animals. They are still finding new fish species. So we in aquariums really get a chance to really learn about these small animals that come in on live rock or corals.
They are just now doing studies on Zoa's and mapping out that genome. If that tell's you anything. I will post the images on the coral research mailing list to see if anyone there has any ideas.

 

[Elegance Coral]

I still say, vermetid snails. Especially after that last set of pic's.

 

[lauderdalestunner]

You might want to find a predator take care of some of your overpopulation issues maybe a possum wrasse and or a sapphire damsel might help? I have limpets in my overflow but non in the display from what I can see. Just an idea, hopefully you can get them under control. Good luck

 

[Tahoe61]

They almost look like a type of Foraminiferans. Renee will be thrilled with the images.

 

[superusername]

After more researching, I'm increasingly persuaded that foraminiferans may be right.

This page of Adobe stock images has some amazing photos, and some do look like similar forms.

As I've been paying close attention to these specimens in the tank, I've also noticed what a wide variety of coralline types there are. Some types such as this one characterized by a waxy appearance and white growth edges don't seem to harbor there little creatures at all.

Also the coralline that is closer to burgundy color doesn't have any. Apart from those spots, these seem to have found their way everywhere.

 

[superusername]

Quick update...

Here's the first example (right in the center behind the setosa frag) I've found that seems to have grown any larger than the typical 1mm diameter, or at least it is creating a larger than normal white spot around itself. But given how long they've now been in the system, I'm surprised I haven't seen any grow larger.

And here's a quick update on the torch. You can see how quickly they decimate some types of coralline (the quicker growing kind near the top left), and how the darker slower growing type towards the bottom is not as thoroughly consumed: