For the octopus, reproduction is the ultimate goal in life. Unfortunately for them, however, after achieving their life's mission, they are destined to die.
Courtship begins between two octopuses when the male finds the female after coming across her chemical signals. They then begin determining attraction by using their sense of sight. Males prefer larger females because they produce more eggs which the male can pass his genes on to.
To turn the lady octopus on, he performs flashes of intricate skin displays. The erectile tissue that is located in his arm becomes enlarged as attraction increases. He uses the female octopuses' response to judge her willingness and readiness to proceed. If all is A-OK, the deed will be performed.
However, after the sensual performance, the octopuses part ways. The male departs and they both gain a dementia-like state of existence. The males wander around without a purpose. Moving through the open ocean aimlessly and neglecting to eat, subsequently losing weight and ultimately dying - usually because of starvation or predation.
Females suffer the same affliction, but stick around until their young hatch - after which they usually succumb soon after for the same reasons as the male.