I woke up this morning and found one of my Derasa's in the wierdest shape......the left shell was broke in half right down the middle.....right side fully in tact and the front part of the left shell was fine.....but the whole back left side was gone....well it was laying beside the clam......I have never seen anything like this in all my time keeping tanks....has anyone ever seen this or heard of this......it was like something was trying to break it in 4ths.....needless to say clam is dead...I did find a nassuris snail inside of it but I am sure it is because the tissue was so exposed......wierd