Jadzia Dax is a joined Trill. "Jadzia" is the name of the young Trill woman, while "Dax" refers to a slug-like symbiont that resides in her abdomen; Jadzia's actual family name was never revealed on the show. In the novels, her original name is said to be Jadzia Idaris. While Jadzia is 28 years old at the beginning of the series, the creature Dax is roughly 300 years old, having previously been hosted by seven other Trills. As a result, Dax may be considered the oldest crewmate on Deep Space Nine.