Moon Jelly

The jellyfish is translucent, usually about 25–40 cm (10–16 in) in diameter, and can be recognized by its four horseshoe-shaped gonads, easily seen through the top of the bell.
A recent study has found that A. aurita are capable of lifecycle reversal where individuals grow younger instead of older, akin to the "immortal jellyfish" Turritopsis dohrnii.