Zebra Nerite - Amazing Resurrection!

A couple of months ago I bought 10 mixed nerite snails from EBay, thanks to those who recommended the seller as they are really good value compared to normal nerite prices.

One was a Zebra nerite, which I put into an 80 cm tank. Next day it was attached to the side wall about 10 cms from the top. The following day it was in the same place, and the next day and the next day and .......... to cut a long story short it stayed immobile for 6 weeks. Now I know snails are pretty slow moving, but this was ridiculous. Any animal, even a snail which doesn't move for 6 weeks is pretty likely to be dead. But this nerite was obviously not dead, it was clinging to the side and a snail which had died would have fallen off and be nothing but an empty shell after 6 weeks. Last week, to my surprise, it was no longer in the same place and the following day there it was on the front glass, sliding along quite happily, it's little mouth scraping away at the algae. A week later it's still moving around, quite lively (for a snail).

I'm at a bit of a loss to explain why it stayed motionless for so long and why it suddenly decided to start moving. The only possible answer I can come up with is temperature. I keep this tank fairly cool at 22 - 23^o while last week, sun streaming through the patio doors raised the room, and tank, temperature to about 25. Maybe nerites like it warm and it needed that rise in temperature to stimulate it to get going.

Just another strange story from the mysterious underwater world 

Excuse my ignorance but whats an MTS?

I used the same buyer and have a mysterious black snail that seems to live in the substrate