One time I had a bluegill in my tank that ate a 4" red worm when i dangled it in front of him one day. totally sucked it down. He never spit it out. Two weeks later i noticed something on the bottom of the tank. It was the 4" worm that had passed all the way through his gut, and had turned into a mottled brown color (sort of a nice craw pattern actually). he crapped it out in perfect shape though, including the curl tail still intact.

Gills - you gotta love 'em.

M