Mystery Creature

[Galilean]

I can't figure out what this creature is. My best guess is that it is some kind of ameoba, but I have never seen any ameobas of similar size and structure. Its structure is dendritic like a plant, but it moves very slowly. I have posted this picture of it with a detailed description in the Microphotography section. Hopefully I can afford a better camera before I see it again.

http://reefcentral.com/gallery/showphoto.php?photo=179146&papass=&sort=1&thecat=573

Does anyone know what it is?

[Sk8r]

That's not an amoeba. Digitate hydroid is out, too. Define "moves". Does it wave or does it travel? It's a little skinny for a nudibranch, but they do come in odd forms.

[Galilean]

It moves by sliding the branches along the surface. It can go any direction and is very flexible, but it always retains this highly branched shape. It can't be an ecinoderm, because there is no central disk, the rules out hydriods and medusa forms also. It doesn't have a central column either so it can't be a worm or a nutibranch. All of the red branches have extremely long, thin white branches at the terminal end. But there are also many relatively shorter white branches coming out of the sides randomly. I have never seen any part of the body detach from the surface. It takes all day to move a couple inches, but I have seen one crawl all the way to the top of a ten gallon over the course of a few days. I have them in several different systems.

[graveyardworm]

Does it look anything like the first picture in this article?

http://reefkeeping.com/issues/2003-08/rs/index.php

[LeslieH]

That's a foraminiferan. Do a search - this sort of critter has been in a number of posts. You'll find more detailed information in this article although it doesn't have a picture of this particular form.
http://www.reefkeeping.com/issues/2003-07/rs/index.php

[Galilean]

It could be an unidentified foraminiferan. However, consider the definition below:

(from http://www.reefkeeping.com/issues/2003-07/rs/index.php)

"Although foraminifera are often thought of as simply being amoebas possessing an outside shell, there is more to them than that. Not the least of the problems with such a simplistic approach is that the shell is actually interior to the outer cell membrane that constitutes the outer surface of the organism. Nonetheless, these shells act as support and protection for the majority of the protoplasm that constitutes the foram's body. Three basic shelled foram types may be recognized, defined on the basis of differences in their shell, and recently a few naked forams have been found as well. The naked forams are unusual for a second reason, that being they are found in fresh water. All other forams are marine. Foraminifera with the first skeletal type are called agglutinated or arenaceous forams. They glue sand and other materials together to form an irregular, often star- or tree- shaped structure. These organisms are very common in some coral reefs, particularly in areas where sponges are common. In these areas they may form "spicule trees;" three-dimensional structures made of sponge spicules glued together extending up into the water column. However, these irregular, or agglutinated, forams really come into dominance in the deep seas. Here some species may get large, about the size of dinner plates, perhaps larger. Some species extend up off the bottom as a tree-like shape and have been documented to snare and eat fish or small shrimps. Others form networks of root-like growths that may cover large areas. None of this group has, to the best of my knowledge, been seen in aquaria, and in fact, only a few individuals of these deep- sea groups have ever been seen alive."

It doesn't fit because:
This one is "out of the shell" but not in fresh water.
If I am wrong and it does have a shell, it is not "three-dimensional" and so would not be like the known aborescent foraminiferans. Also the author states "None of this group has, to the best of my knowledge, been seen in aquaria, and in fact, only a few individuals of these deep- sea groups have ever been seen alive."

I've looked into the foraminifera idea before. There are a lot of fossil forms as well, but none really fit the bill. Still this type of ameoba is one of the best options.

[graveyardworm]

I would take Leslie's word for it, if anyone in this forum knows inverts its her.

[LeslieH]

The article is just a partial summary of available information. It contains a lot of good stuff but like all short accounts there's also a lot that isn't in there. Take a look at this article, and particularly at plate 3 figure 6 for something similar to what you have.
http://www.cushmanfoundation.org/awards/students/sabbatini.pdf

Thanks, Dave, but I don't claim to know inverts in depth. There's so much I don't know even about worms, the most wonderful animals in the world!

[Galilean]

Thanks, this is a much more complete description. It is probably some kind of formaminiferan. I still have a few questions though that this article did not answer. I would pressume that the red portion of the body is the test (shell) and the white filaments are pseudopodia. Mine have a very flexible test. Is that normal? All the articles I've read so far seem to suggest that it is a hard, inflexible structure. Also, how would I capture it to look at is under the microscope? It seems like they would be easily destroyed and they are too big for my slides. Some were about a inch in diameter. Can I get it to retract the psedopodia so it is smaller? Could I siphon it up without breaking it? Do they have this structure throughout their life-cycle or do they have a smaller free-swimming form?

Also Leslie did you get my email about the rainbow worm?

[LeslieH]

This group of forams is one I really know very little about. The majority of forams have rigid tests but these & others do have flexible tests or lack them completely. To capture it, hmmm.... I would first try using a pipette or hose to produce a water jet to gently push them off the glass, then siphon it up. If that doesn't work try gently scraping it off with a thin dull- edged implement. I imagine that they do easily break apart but will also readily reform. You said they move? What about taping a microslide in the path of one & just wait for it for move onto the slide? They can retract the pseudopods when touched. Different modes of sexual & asexual reproduction occur in subphylum Sarcodina which includes both naked amebas & forams. Some but not all do have swimming zygotes but I really don't know what happens in this particular form.

Yes, I got your email, thanks. I'm still about 15 emails away from answering it so instead let me say that yes, I would love to see your worm photos. From your description I suspect it's an eunicid or an onuphid.