Myrianida pachycera is a polychaete worm with a very strange reproductive cycle.
It begins with an adult reproducing asexually by budding, forming a crazy tail of growing wormlings.
As the youngsters become full grown they detach, swim to the water’s surface, release either eggs or sperm and then die.
The eggs hatch and the new worms soon descend to grow a whole new tail of sexual wormlings.
Like some kind of ascetic, you can have life, or you can have sex. You can’t have both.