The host body shared the generations of experiences amassed by the worm and the worm was guaranteed a nurturing host body to continue its journey through the ages.
Space station Captain Benjamin Sisko (Avery Brooks) called Jadzia Dax "Old Man" because in a former incarnation the Trill's host body was a male warrior.
Her symbiont worm was transplanted into Ezri Dax (Nicole de Boer), a student psychiatrist.