>Argonauts are a type of octopus. While the female of the species gets a pretty shell, male Argonauts get a more extreme adaptation. They have a special arm, which they use to transfer their sperm to the female. This arm has its own tail and organs of sensation to guide it to the female. The arm detaches from the octopus, and swims towards the female before pumping sperm into her. The male, essentially, has sex in absentia. https://imgur.com/gallery/Axcdx