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Maxima Clam Questions

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This is not my first clam, but I have some questions about things I've not seen before, or maybe just not paid attention to. 

 

Since added to my tank, it has been super happy, open mantle, etc. However, there has been a snail that has been grooming it's shell for the past couple days, and it's causing the clam to not open up all the way, and then on the snail is usually a hermit that comes along and bothers it. I went to pull the snail off the clam shell, and the clams foot was tightly gripped to the holder I have it placed on. The snail keeps finding it's way back to the clam shell, and last night a hermit was on the snail. I went to pull the hermit off the snail, and the whole clam, hermit, snail came off the holder. I looked and the foot was completely receded into the shell, same with the mantle. Today, it's open again, snail found it, so it's not fully open, but I don't want to touch it and disturb it again. 

 

Seeing as the clam is still being super reactive 48 hours later to touch/light/movement, I'm presuming it's fine, although I've never seen a clam recede it's foot into it's shell, is this something that they can do?

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No clam experts, huh? 

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The foot is mobile and both extensible and retractable. That's one way they can move small distances, dig, and set down roots (establish themselves). Unless the foot is torn or damaged, it's probably fine. A retracted mantle is often a sign of disease or irritation. The snail may be just going after algae growing on the shell - probably nothing to be concerned about as long as it's not a parasitic snail (which it doesn't sound like it is). Since maxima clams are both filter feeders and photosynthetic (and can survive exclusively on photosynthesis per James Fatherree), a mantle that's retracted for a long time can ultimately lead to the clam wasting away. I suspect that the clam is just irritated, not that it's sick given your first post.

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By the way, maxima clams normally attach to a surface using what's called Byssal threads that are secreted by the foot. While the foot can retract, the threads are normally not motile (but they can stretch some). For the foot to retract and come off the surface would require it to lose the threads (which it can do) or, if it was a relatively new placement, it may not yet have formed the threads. If it had formed these threads, you may see a remnant left behind on the surface that it was adhered to at one time. If there weren't many threads or if they were very short, you might not even see anything at all.

 

A damaged/torn foot, though, can be fatal in the long-term.

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No expert here, but if you didn't tear out the byssal organ and just tore the threads then it should be fine. I would think that by now you should see some new threads. Is this the case?

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Thanks Tom. I was familiar with the byssal threads, and I have the same suspicions as you, the snail is just cleaning the algae. I just couldn't find an answer on if a Maxima could recede it's foot into it's shell. I moved the snail in question to the sump, just because it's been irritating the clam for a few days now, and I'll give the clam a few days to see if I can get it to full open again. You can see the snail in the picture, this is before it reached the top of the mantle. 

 

44583599580_4fa5b432fb_z.jpgDSC_0877-3

 

3 minutes ago, WheresTheReef said:

No expert here, but if you didn't tear out the byssal organ and just tore the threads then it should be fine. I would think that by now you should see some new threads. Is this the case?

 

I did not, there was nothing left behind, I didn't even tear the foot. It just completely receded with nothing left behind. I'm not keen on finding out if it's attached again or not because I don't want to bother it. I plan on giving it some time. 

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The foot is actually a muscle (or a group of muscles) in bivalves. The Byssal organ (aka byssus) secretes the threads and is attached to the foot. So, mechanically, the foot is built to be able to move, retract and extend. If an attached clam is forcefully removed, the byssus or the foot can be torn out of the clam. I suspect that this leaves it vulnerable to infection. The threads themselves are not alive, though, and can be (and often are) cut with a razor as one option when we're forced to remove an attached clam.

 

The following picture (taken from the web) shows you the basic anatomy of a mussel, not a Tridacna maxima but another bivalve so they are generally similar.

 

bivalve-byssal.jpg

 

I have a suspicion that your clam, if it had attached itself, decided that it was not happy where it was because of the manipulation and irritation and decided to pull up stakes.

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19 minutes ago, Origami said:

The foot is actually a muscle (or a group of muscles) in bivalves. The Byssal organ (aka byssus) secretes the threads and is attached to the foot. So, mechanically, the foot is built to be able to move, retract and extend. If an attached clam is forcefully removed, the byssus or the foot can be torn out of the clam. I suspect that this leaves it vulnerable to infection. The threads themselves are not alive, though, and can be (and often are) cut with a razor as one option when we're forced to remove an attached clam.

 

The following picture (taken from the web) shows you the basic anatomy of a mussel, not a Tridacna maxima but another bivalve so they are generally similar.

 

bivalve-byssal.jpg

 

I have a suspicion that your clam, if it had attached itself, decided that it was not happy where it was because of the manipulation and irritation and decided to pull up stakes.

 

Super helpful, thanks! I think the foot was down, the byssal threads were not dropped yet. I shouldn't have messed with it, oh well. It still is not opening all the way, but goes a little bit further every day. It is very close to some mushrooms, I can't help but wonder if they might be irritating it. 

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The guy i got my clam from said certain snails-forgot the name, it’s on the tip of my tongue- will wedge themselves into the shell and the clam will try to close but the snail will eat the mantle. It’s those snails that come out of the sand when you feed and have the little trunks. Now I don’t know how true it is but he was selling a bunch of large healthy clams.


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Pyramellid snails can wedge themselves in the folds of the shell and will prey on the clam, but it looks like his was just a really annoying astrea snail that took a liking to the algae on the shell.

 

The pyramellid snails are pretty small.

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Pyramellid snails can wedge themselves in the folds of the shell and will prey on the clam, but it looks like his was just a really annoying astrea snail that took a liking to the algae on the shell.
 
The pyramellid snails are pretty small.


Yup, really annoying astrea for sure! I’m familiar with the pyramellid, and don’t have any!


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Careful, a receded foot is not a great sign.  They can pull their foot back into their body but if there is a gaping hole, it's kind of similar to gaping in the mantle and is never a good sign.  The mantle coming back out is a good sign but keep a close eye on the snail, are you sure you have no predators in there?  Seems kind of bad that the byssal threads tore to me, tridacnids to the best of my knowledge don't often do this and it's more of a factor of something else doing it to them (or at the very least causing them to do it which I would not think a simple snail on the shell would do).

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1 hour ago, davelin315 said:

Careful, a receded foot is not a great sign.  They can pull their foot back into their body but if there is a gaping hole, it's kind of similar to gaping in the mantle and is never a good sign.  The mantle coming back out is a good sign but keep a close eye on the snail, are you sure you have no predators in there?  Seems kind of bad that the byssal threads tore to me, tridacnids to the best of my knowledge don't often do this and it's more of a factor of something else doing it to them (or at the very least causing them to do it which I would not think a simple snail on the shell would do).

Bears watching, but he did say that he pulled on the clam when trying to remove the snail (astrea?). That, along with other frequent irritants, may have caused it to decide this wasn't a good place to be. If the clam is starting to come back out, I'd wait but watch closely. As you've probably seen, they can decline quickly once they begin to retract and stay that way. Then, before you know it, you're left with a near-empty, gaping shell.

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