Nature in general has no shortage of weird, fun creatures, but the ocean really takes the cake. Enter the argonaut: an octopus with an identity crisis. Not only does the argonaut live free-swimming in the open ocean (octopuses almost exclusively live on the seafloor in complex habitats like reefs), it’s also the only octopus species to grow its own shell. The shell is crucial for surviving on the high seas. By ‘gulping’ air into the shell at the surface and trapping it with its body, the argonaut counteracts its own weight to become neutrally buoyant. This makes it easy to maintain its position in the water column without expending a ton of energy – just like a scuba diver.
That’s cool and weird and all, but it gets weirder (radder). All the above applies only to lady argonauts. Male argonauts are wicked tiny (like, less than an inch) and grow a 9th ‘arm’ (not a penis) that they attach sperm to and then detach from their bodies to give to the females. She, of course, stores it in her head cavity with the ones she’s stockpiling from other males. The arm is called a hetocotylus, but what I really want to know is who comes up with this shit? Oh, and afterwards the male probably dies – none have been found alive without their hetocotylus or in the process of growing a new one. That’s a hardcore way to abdicate any fatherly responsibility. Pretty R.A.D., though.