Norvo Odan was a male Trill joined to the Odan symbiont. He served as ambassador to the United Federation of Planets while Trill was being considered for membership in the Federation.
After spending three weeks on a Federation starship en route to Earth, and two months on Earth itself, Ambassador Odan regretfully made a recommendation to the Assembly of the Trill Republic that Trill kept the existence of the symbionts a secret. This was because he observed a somewhat parochial attitude towards inter-species relations in some of the Federation's member races. He was concerned for the Trill's safety if certain races thought the Trill humanoids were being controlled by the "aliens" within them. (ST reference: Federation: The First 150 Years)