Five incredible facts about the paper nautilus
1. Not a nautilus
The paper nautilus (Argonauta spp.) is actually an octopus.
Also known as an argonaut, they are part of the argonautidae family, unlike real nautiluses, which are cephalopods.
2. The shell
The shell is actually an egg incubator.
Females make it themselves by secreting a form of calcium, creating a paper-like shell (hence the name, paper nautilus).
Once complete, the female lays her eggs inside, then squeezes in herself.
3. Life in the water column
Paper nautiluses live in the water column, just like real natilusus do, but unlike other octopuses who live on the ocean floor.
The shell also acts as a floatation device, sealing in a bubble of air when the paper nautilus visits the water’s surface to take a breath. It can then bob in the water column without having to use much of its own energy.
They are also known to hitch a ride with jellyfish or attach themselves to driftwood.
Paper nautiluses also use jet propulsion to move extremely quickly.
4. Epic size disproportion
Male paper nautilus are less than 2.5cm long, while females grow to more than 37cm.
Females are also 600 times heavier than the males.
5. Losing limbs
When the male and female mate, the male leaves behind an arm!
The penis remains inside the male, with sperm transported to the female along this specially-adapted tentacle.
In this video Dr Julian Finn explains what Argonauts are and some findings that have come out of his PHD research on these fascinating creatures: