This is an Argonaut, also known as a paper nautilus. The creature that lives inside this precious shell is a type of octopus. Photo: Steven Kuiter
The female Argonauts make a paper-thin shell to protect and incubate her eggs, in this image the eggs are ready to hatch! Photo: Rudie Kuiter
A two to three centimetre male Argonaut catching a ride with a Lion’s Mane jellyfish. Photo: Steven Kuiter.
Welcome to the Marine Mili series, a regular column about all things marine! During this series I aim to inspire people to want to protect our oceans and all the marine life that call our oceans home. Hopefully after reading each column, you would have learnt something new, including what we can do to help protect and preserve our oceans. You can follow me and my journey on my Instagram page: _marine_mili.
This week, I want to talk about Argonauts, another fascinating sea creature.
An Argonaut is also known as a paper nautilus, however, the only true nautilus is the pearly or chambered nautilus.
Their delicate, paper-thin spiral shells can be found washed up on beaches.
The creature that lives inside this precious shell is actually a type of octopus.
Unlike the shells of other mollusks, the Argonaut shell is actually an egg case, not a permanent part of the animal's body.
The female Argonauts make this paper-thin shell to protect and incubate her eggs, while also controlling where she swims in the water column.
Females make their shell using two of their elongated tentacles to secrete a calcite substance.
Males don’t have a shell, however they do have an arm called the hectocotylus which is where their sperm is stored, and how they transfer sperm to the female.
Believe it or not, female Argonaut can grow between 30-40 centimetres while the males can only grow between two and three centimetres. Females can also be up to 600 times heavier than the males.
Males can only mate once and shortly after he has mated and lost his arm (that transfers sperm), he will die. This is an inevitable part of the reproduction cycle of Argonauts.
As the males are so small, they don’t have any natural defences.
To stay safe, they usually hitch a ride with jellyfish which will also deter predators. This works for both creatures, as the Argonaut leads the jellyfish to bustling feeding areas to help the jellyfish grow and get to a practical size.
This species can be found in Southern Ocean temperate waters, meaning mild conditions.
They can be seen in Port Phillip Bay and Western Port Bay.
