The paper nautilus is amazingly different to many of its cephalopod cousins, (squid, octopus and cuttlefish). Not only does it pre-digest its prey, the males live to love (briefly …)
Free-floating on the surface of the open oceans, the paper nautilus feeds mostly on prey it can catch within its eight tentacles and manoeuvre into its mouth. Prey includes small molluscs, jellyfish, shells and crustaceans, all of which are injected with a poison from the salivary gland of the paper nautilus – to aid digestion!
Also known as argonauts, these amazing creatures display extreme sexual dimorphism, both in size and longevity. The female is bigger and more sexually active than her male partners.
The females can grow to a size of 10 cm and are iteroparous (can reproduce more than once in a life time). The males barely reach 2-3cm in size and only mate once. The male paper nautilus has no shell; but he does have a modified arm called a hectocotylus in which his sperm is stored. During fertilisation this is inserted into the female paper nautilus, becomes detached within her, and the male subsequently dies.
Scientists in the past were puzzled by the presence of this ‘entity’ within the shell of the female. They assumed it was a parasite – we now know that it is all that is left of her male partner.
Before laying her eggs, the paper nautilus uses her (enlarged) dorsal tentacles to secrete her ‘paper’-thin shell, which can be up to 30 cm in size, and then lives within it. This shell is produced as a brood chamber for her eggs, and when floating in the open ocean the paper nautilus will have her head and tentacles clearly visible, unless disturbed. She can maintain neutral buoyancy by the air that is trapped within this egg case.
Like other cephalopods, the paper nautilus can evade predators by changing its colour to blend in with its background, as well as secreting ink when threatened.
In winter months the paper nautilus float closer to our shores. Their beautifully delicate shells have even been washed ashore on the eastern beaches of Port Phillip – including Ricketts Point Marine Sanctuary at Beaumaris and the beach at Seaford. Keep a look out next time you’re strolling along the beach…
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