Why did my snail dump its shell and go topless?

[Swfiend]

Why did this one drop its shell? It progressed around the tank just fine for a couple days or a week but my wrasse finally noticed an easy meal and munched it but is there any reason it would drop its shell?

 

[zoolan70]

It was dying or something hammered it and the foot became disconnected from the shell and it fell off. Snails aren't like hermits...they can't go back in once they fall out.

 

[Swfiend]

It was dying or something hammered it and the foot became disconnected from the shell and it fell off. Snails aren't like hermits...they can't go back in once they fall out.

I’m curious what caused it though since it seemed completely fine still eating grazing and moving about the tank just fine. If my wrasse hadn’t spotted it I don’t believe it would have died. I watched the wrasse swim over and eat it as it was moving along

 

[Dburr1014]

I have never seen anything like that.
@ISpeakForTheSeas

 

[ISpeakForTheSeas]

It's referred to as Mantle Collapse; the only reasons I've heard for snails dropping their shells are disease (illness, parasites, etc.), injury, and possibly somethings like toxins or environmental conditions - in almost every case I've heard of, the shell dropping off is an indication that the snail is going to die soon.

That said, I have heard that Mantle Collapse can be healed with land snails (though this is highly disputed, as people dispute if these cases were truly Mantle Collapse, or if they were cases of Mantle Tears or Puffy Mantles), but I've never heard of it being healed with aquatic snails.

The cases that I've heard of recoveries with:
https://petsnails.proboards.com/thread/18414/positive-outcomes-mantle-collapse-updated


Edit: Looks like the FB link failed, but here's the info of the article:
"MANTLE COLLAPSE IN SNAILS

GEORGE SEBASTIAN NEUFELD·SATURDAY, JULY 22, 2017·"

 

[Swfiend]

Sofar this was the only snail to have had an issue so hopefully not a parasite or infection. I have roughly 120 different types of snails through out the system. I am dosing h202 but would assume if that was the root cause more snails would be dead/dying or similar shell drop. Maybe the wrasse had already picked at the mantle causing the drop…

 

[ISpeakForTheSeas]

Sofar this was the only snail to have had an issue so hopefully not a parasite or infection. I have roughly 120 different types of snails through out the system. I am dosing h202 but would assume if that was the root cause more snails would be dead/dying or similar shell drop. Maybe the wrasse had already picked at the mantle causing the drop…

From what I've seen, these tend to be limited occurrences in our tanks, so I wouldn't expect other snails to have this issue (if they do, then you may have a serious problem). The other cases I've seen of this in saltwater snails:
https://www.reef2reef.com/threads/turbo-snail-lost-its-shell.993058/https://www.reef2reef.com/threads/nassarius-snail-out-ouf-shell-any-chance.934761/