MARINELAND, Fla. -

Nellie, the oldest dolphin in human care, died after 61 years living at Marineland, according to a Georgia Aquarium blog.

Marineland was the first oceanarium in the world and said it was proud to share 61 of its 76 years with Nellie. The attraction announced Nellie's death on its website on Thursday, noting she was euthanized earlier this week after her conditioned quickly worsened.

According to the website, Nellie was born at Marineland on Feb. 27, 1953. The legendary dolphin starred in several TV shows filmed at Marineland in the 1950s and was featured in a Timex watch commercial in 1961 that aired on Frank Sinatra's special "Welcome Home Elvis." She became famous for her hula hoop trick.

Jacksonville University adopted Nellie as its mascot and awarded her honorary undergraduate and graduate degrees. Last June, the university bestowed an honorary doctoral degree to Nellie in a presentation as part of Marineland's 75th anniversary.

"She's pretty much the heart of Marineland," JU grad student Kimberly Mann said. "I mean, it will go on without her, but she's the heart and soul of Marineland. So I could just imagine everyone there is very sad right now."

The Georgia Aquarium said Nellie became an icon for the zoological community, living twice the expectancy of female Atlantic bottlenose dolphins living in the ocean.

"She was very sweet and attentive, especially with kids," Mann said. "You could tell that she could tell the difference between the little ones and the adults because she spent extra attention on them."

Marineland calls Nellie's death an unfortunate loss but said her legacy will continue through the memories and inspiration she left behind.

Dr. Quinton White, executive director and professor of biology and marine science at JU, said he was saddened by the news their beloved mascot had passed.

"It was expected, but it's like anytime someone you know is sick and know is going to pass away, you are still sad when they pass away," White said.

Nellie's remarkable resilience exceeded all expectations, as the median life expectancy for dolphins in captivity is less than 30 years and much less than that for dolphins in the wild.

The aquarium wants to celebrate Nellie's life through fan's memories of her. You can share your moments with Nellie through the Marineland Facebook and Twitter pages using #Nellie.

A public celebration of Nellie's life is planned for May 15. More information will be announced on the website, www.marineland.net.