Do they mov around or do they die or do they stay still?
Depends on what the stress is...they will most likely try and swim away if they don't like it.  If they're trapped then they'll die if the stress becomes too intense.  Usually we use daphnia as experimental animals when studying effects on heart rates.
You may be aware that whenever the system boots the first things to get started are the SERVICES....these services corresponds to different applications which runs in background...\n\nSo whenever you switch on your system the services starts in background and respective application (which ever is set to start on startup) starts...hence u see the messenger outline...\n\nWhat makes your icons move a little is the restoration of your monitor settings...which the OS does according to the monitor settings and calibrates for a better view...\n\nHope this clarifies your doubt