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I have a Derassa I am trying to save for a friend. He has a yellow tang that was eating it's shell (or at least the slime coat), mantle, foot, and hinge.

The problem is that the hinge is now totally gone, when you pick it up it is like you are holding 2 pennies, the sides move independent of each other (really creepy feeling).

The clam is still able to open and close, and when firmly shut all the way (shell interlocked) feels normal, but not when loosely closed or open, and it sits sort of off kilter.

The clam opens in my tank, doesn't gape, and extends it's mantle and except for sitting crooked (2 sides of the shell not aligned) it looks good, my question is can this clam live without it's hinge? Can it regrow it's hinge? Or is this clam doomed?

Thanks,
Whiskey
 

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Are you certain that the Yellow Tang did this? I have one in my tank with a deresa clam. That is scary.:(
 

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Discussion Starter #4
Oh, we are sure! We watched it happen many times. He has been trying to get this fish out of his tank for weeks. He has tried traps, nets, small fish hooks, but the fish is too smart.

I also have a yellow tang, and he is not a problem, but the one my friend has is a terror!

Whiskey
 

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Sometime tangs learn to acquire a taste for the zooxanthellae in the clam's mantle, as well as the meat itself.

Most likely you're speaking about the byssal threads that attach the clam to the substrate, as there is not an external ligament that holds the bivalve together. It will regrow in most well-nourished specimens once there is a good location chosen with a firm rocky substrate under the clam. Take a suitable piece of live rock, get a general idea of how big the clam is, and dremmel out a good hole for the clam to attach inside. You will want enough room for the clam to fully open and extend it's mantel, but not so big that it falls over; deep enough to offer some side support, but not so deep that the clam is lost in the hole. These clams will modify their hole as they grow older by using their byssal threads to hold them in place while they "pump" the sides of the shell against the soft rock, wearing it away over time and enlarging the hole.


HTH
 

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Hard to see it in this pic, I am getting ready to do another one when I get back from my roadtrip this week, I'll do a step-by-step to show you how to do it for a clam.
 

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Discussion Starter #8
tdwyatt said:
Sometime tangs learn to acquire a taste for the zooxanthellae in the clam's mantle, as well as the meat itself.

Most likely you're speaking about the byssal threads that attach the clam to the substrate, as there is not an external ligament that holds the bivalve together. It will regrow in most well-nourished specimens once there is a good location chosen with a firm rocky substrate under the clam. Take a suitable piece of live rock, get a general idea of how big the clam is, and dremmel out a good hole for the clam to attach inside. You will want enough room for the clam to fully open and extend it's mantel, but not so big that it falls over; deep enough to offer some side support, but not so deep that the clam is lost in the hole. These clams will modify their hole as they grow older by using their byssal threads to hold them in place while they "pump" the sides of the shell against the soft rock, wearing it away over time and enlarging the hole.


HTH
That is not exactally what I am talking about, remember this is a derassa clam, an they loose their biassal gland as they grow, and depend on their weight to hold them down. On the base of their shell there is something that attaches the 2 sides of the shell together. On this clam that is completally gone, the 2 sides are independent of each other. My Derassa has this, when you pick the clam up it feels like one peice, but his does not, when you pick his clam up the shell squishes around and each side moves up and down. It is very hard to explain, but if you picked it up it would be odvious that something is wrong.

That rock idea is a great one though, I bet a Maxima, or, Crochea would love you for it.

Thanks,
Whiskey
 

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I have maxima, squamosa, and crocea on rocks, they all are happy. I'd give the rock a try, it would probably help support the shell and if there is any ability for it to heal itself it will be able to use its energy for the healing instead of trying to keep its shell from falling apart. Just a thought.
 

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jeeze!

How BIG is this Derasa??? They will still be able to attack to the substrate so long as they are juvies (less than 5 yrs old unless they are quite heavy...) I would hope this is not a case of a torn byssal gland/organ, it (the byssal gland) is attached by four muscles (two pair) inside the shell in much the same manner that gimbals are suspended: the larger pair is attached to the shell directly below the pallial line next to the adductor muscle, and the second pair stretchges from the back of the byssal gland to the bottom of both halves of the shells formin the connective art of the hinge at the cardinal teeth. The organ itself is quite mobile within the shell due to it's method of attachment, allowing the clam to extend it outside the shell and excrete the byssal liquid to form the attachment threads. This is the primary means of sealing the shell against the outside, including potential predators, as well as preventing lifting due to current. The specimens usually have to get pretty big, or have had the byssal organ damaged or torn by intentional attempts to pull the specimen from an attachment, rather than cutting the byssal threads at the substrate. I'll try to find some reference on how big is too big to consider attachment by byssal threads, but unless your specimen is really big (maybe in the >12-15 kg range) or damaged or malnourished, then it should still be able to put down a bysal attachment.

If the shell is lose, I would be a bit suspect of a tear. These can heal over time, but will be a slow process, prolly requiring additional feeding along with good light and water parameters. I will dig for more info for you.


Sorry to hear this, hope this helps some.
 

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Discussion Starter #11
This derassa is about the same size as mine (~6 inches), but he has had his for nearly 4 times as long as me (about 4 years) and he bought his bigger than I bought mine.

I would bet you are right, some kind of tear associated with the tang's constant harassment, or the tang getting it's mouth inside the clam's shell through the byassal opening. (yellow tangs have that snout) This clam when picked on would often end up on it's side so I would not be surprised.

In my tank the clam still looks good, it is opening fully, it has repaired most of the damaged mantle, and it is starting to repair the chipped parts of it's shell, so I am holding out hope.

Thanks,
Whiskey
 

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Wiskey said:
...still looks good, it is opening fully, it has repaired most of the damaged mantle, and it is starting to repair the chipped parts of it's shell, so I am holding out hope...
???


What happened that the shell is chipped? Was this clam dropped on dry land? Was is cut and/or hammered from its old placement? This may point to other issues of a different nature as far as the problems with the byssal ligament, but may be superfluous if the clam is recovering anyway...


How much of the history re: the chipping do you know?
 

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Discussion Starter #13
No, it wasn't dropped, the shell was from the tang too. They were picking on it, and the sharp point at the mantle's edge was chued down, leaving a somewhat jagged edge. Actually the top edge of the shell looks very odd now, because it is about 1/8 thick due to the shell being picked at rather than a sharp edge like a clam normally has.

Whiskey
 

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Wiskey said:
No, it wasn't dropped, the shell was from the tang too. They were picking on it, and the sharp point at the mantle's edge was chued down, leaving a somewhat jagged edge. Actually the top edge of the shell looks very odd now, because it is about 1/8 thick due to the shell being picked at rather than a sharp edge like a clam normally has.

Whiskey
hmmm... what other fishes are in the tank? Pix of the damage please?
 

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Discussion Starter #15
Other fish? Hmm, I might not get them all but these are the ones I remember he has.

Yellow tang
Yellow eye tang
Lubix Fairy wrasse
Firefish
Mandern

I tried to get pics of the damage, but because the mantle covers the top of the shell it is impossible to get a shot that would show you anything.

Thanks,
Whiskey
 

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So how is this clam doing? any more pix in general?
 

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If the hinge portion is not growing back i would grab a zip tye and clip it so it forms 2 flat strips, then glue it across the bottom to the 2 shell halves to create a synthetic hinge. I hope he can grow it back somehow.
 

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Discussion Starter #18
tdwyatt said:
So how is this clam doing? any more pix in general?
The clam is doing great! Good mantle extension, very healthy looking, just a little cockeyed. He is starting to smooth out the top of the shell, the mantle looks perfect, and it almost looks like nothing ever happened. I think he should start growing soon, he has managed to wedge himself between a rock and my front glass and then attached to a sand dollar I had in there for him to attach to.

The hinge thing is still going on, though he doesn't seem to effected.

Whiskey
 

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Discussion Starter #19
Twitterbait said:
If the hinge portion is not growing back i would grab a zip tye and clip it so it forms 2 flat strips, then glue it across the bottom to the 2 shell halves to create a synthetic hinge. I hope he can grow it back somehow.
I am just worried that this might impair his ability to open and close properly.

Whiskey
 

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no need to create a synthetic hinge, which might impare function later down the road if the clam continues to grow. if the muscle is permanently damaged, ift may not be an issue so lng as the clam has a permanent home in a rock or a positioin as you've descrbed.

Youre at that "watch and see" point in the development now. So long as it continues to grow and does not have to move, it will be fine.
 
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