Slowest developing animals

A human takes an incredibly long amount of time between birth and sexual maturity and/or full growth. Besides humans what animal takes the longest to become an adult?

The 17-year cicada takes even longer to sexual maturity.

I doubt anything will beat the Greenland Sharkat 150 years.

It has necessitated nearly 43 years for me to attain my wife’s sexual requirements… I may not be through yet.

The 17 year cicada has nothing on us.

The elephant. Born after a 22 month gestation. Reaches adolescence and sexual maturity in its early teens, as humans do, but only starts to mate in adulthood, around ages 18-20.

Ever wondered why you don’t see orange roughy all that much in grocery stores and restaurants any more? Because they can take as long as 30 years to reach sexual maturity.

For reptiles, it’s the tuatara.