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Animal, Vegetable or Mineral? Mystery Egg 3

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Time for my third blog in the Booth’s Mystery Egg series for Easter.

Having worked at the Booth Museum for several years, I have seen a lot of really bizarre objects behind the scenes, some of which I have taken photos of and others which are just stuck in my mind’s eye. Normally, I would bring these objects out from behind the scenes to show visitors at the museum but under the circumstances  we thought we would write three special additions of our usual Animal, Vegetable or Mineral? quiz online to show you some unusual eggs, made by some pretty incredible animals.

These are all objects we have behind the scenes at the Booth Museum. Here is Mystery Egg number 3 of 3.

Mystery Egg 3

Mystery Egg 3, specimen from the Booth Museum of Natural History

Clue 1

The family of animals that made Mystery Egg 3 have a reputation for being one of the most intelligent invertebrates of the ocean. They are famed escapologists and problem solvers, even giving the Great Houdini a run for his money.

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Clue 2

The species of animal that builds this delicate, almost paper-thin shell sails the seven seas for months on end, just like an adventurer engaged in an epic quest. In fact, if these animals were to star in any movie, it would definitely have to be this one…


And the answer is… Drum roll please!

The Argonaut (Paper nautilus), Argonauta sp.


Female paper nautilus, photo by Bernd Hofmann at de.wikipedia

It’s not all in the name

Nautilus, photo by Manuae CC BY-SA 3.0

Although they are named paper nautiluses, these animals aren’t nautiluses at all (although they are distantly related). They are a group of unusual octopuses who spend their lives bobbing along near the surface of tropical and sub-tropical seas unlike typical octopus who live on the sea floor.

What the shell?

The females are the ones that make the beautiful egg case (pictured above) and measure around 38cm – eight times larger than the males (around 2cm) and 600 times heavier. Not much is yet known about the breeding habits of these adventurous octopuses, but when they mate, the male not only leaves his sperm behind in the female, but his entire hectocotylus.

Nooo, the hectocotylus is not a fancy word for penis as you might expect (it’s true penis is inside its body), but a specialised arm that sperm travels down into the females oviducts, still – poor lad! As you can imagine, when early observers in the 18th century found females with the hectocotylus attached they found it quite bizarre and so naturally, they theorised that it was a type of parasitic worm.

Shell yeah!

When females grow they continuously secrete calcite from the ends of two specialised arms to make a temporary shell. This paper-thin shell functions as an egg case to protect her developing young. When ready, she lays her eggs in the case and cosies up beside them, before continuing on their epic journey floating through the ocean – just like Jason!

The shell of the paper nautilus doesn’t just function as a protective egg case, they are also used as a buoyancy device. In order to keep itself buoyant, the paper nautilus routinely swims to the surface and quaffs large amounts of air into its shell. When it swims back down, it seals off the gas in the shell and dives to a depth where the compressed air counters its own body weight. The paper nautilus then becomes neutrally buoyant, making it much easier to swim around freely. But the paper nautilus doesn’t just aimlessly bob along the current passively waiting for food. Like all octopuses they are carnivores and need to hunt.

This quite gentle looking creature actually has a few hidden weapons up its tentacles, which it uses to catch unsuspecting sea slugs and crustaceans. After grasping the target in its tentacles, the octopus pulls the victim towards its mouth, bites down creating a hole using its hard beak and injects a toxin. The octopus then gauges out the fleshy innards through the hole in the crustaceans shell or scrapes at the soft meat of a sea slug using its radula, a kind of tongue covered with rows of small teeth.

I hope you agree that these creatures are a pretty magnificent animal and although most of their behaviour is yet to be discovered by science, it’s hard to imagine what will top a removable hectocotylus.

You can see a beautiful shell of the Nautilus, the paper nautiluses distant cousin, on display in the Booth Museum when we re-open. In the meantime, look out for an upcoming focus on the Paper Nautilus shell on our Close Look Collections page.

Grace Brindle, Collections Assistant