The male octopus literally rips off its arm and gives it to the female so that she can fertilise her eggs at a later date. It’s the ultimate “go f**k yourself”!
In the world of octopi sex is a very weird thing. A male octopus has a special sex arm called a hectocotylus. This is approximately a metre long and rather than covered in suckers contains rows of sperm. When mating, some species of octopi remove the hectocotylus from their body and give it to the female, she will then store it in her mantle until she needs it to fertilise her eggs. In other species, the male doesn’t remove his sex arm he simply inserts it into her.
Soon after donating his sperm (and arm) the male octopus will die. The female doesn’t have much longer to live either, as she is also programmed to die soon after her eggs have hatched.