Not sure if you can do this or not but have you tried selecting the edge loop and doing a detach surface?

One sure way to do it but probably not the best or quickest would be to cut the sphere in half (cut face, detach faces, etc - whatever you prefer) and then only merge the vertices on the half that's not going to be opened.

I'm not skilled with UV's yet so I don't know if or how they'll be effected.