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This is a cg model by David Bodenstein, but it’s the clearest depiction around of the two specialized, fan-like tentacles that actually secrete the “paper” and form the shell.

She can leave the shell if she needs to, but those same two tentacles are usually gripping it tightly. Not only does it offer protection, but it serves as her egg case after she finds a mate. Like most octopuses, she dies after her babies hatch, so she does carry the shell around for the remainder of her life.

She typically swims with her mouth and suckers facing outward, the tips of her tentacles folded behind her into the shell so the whole animal looks like a weird ball of cephalopod.

The male has a tiny baby-like (neotenous?) form, but since octopuses deliver sperm through a single specialized arm, his has to be MUCH longer and larger than all his other arms in order to mate, and it’s usually kept in a weird little bag of skin.

All argonauts of any sex have a wild habit of grabbing on to the top of a jellyfish and either dragging it around with them or riding it, depending on how much bigger the jellyfish is. This not only protects the cephalopod with the jelly’s stinging tentacles, but helps it catch more food; there’s evidence that they use their beak to chew a tiny hole through the jelly’s cap and suck out their stomach contents. It’s kind of like being able to shift into a “parasitic” mode as they please, and kind of like using another animal as both a vehicle and eating utencil.