Argonaut shell found at Runaway Beach


Report from Kelly Green – Tristan photos from Amanda Swain


What is believed to be a first discovery of an argonaut shell was discovered by Ricky Swain on 27th November 2022 while on Runaway Beach.


Marine expert Sue Scott has identified the shell as as argonaut, which is a type of octopus, this specimen a female having a paper-thin shell to protect its eggs. They are found in tropical and sub tropical Atlantic and Mediterranean waters. No one can remember one being found on Tristan da Cunha before.

             The beautiful argonaut shell.
Artists’ impressions of a female argonaut octopus emerging from its shell.
Female argonauts grow up to 20 cm but males to only 2cm.


The male argonaut is a maximum of 2 cm in size and will breed only once. The female shell grows up to 20 cm and expels from the shoulders a limestone mass forming a spirally twisted shell, into which it lays eggs and also serves as a vessel. The female breeds many times and lives far longer than the paltry male. Unlike most octopuses, argonauts live close to the surface rather than on the seabed. The eggcase contains a bubble of air that the animal captures at the surface of the water and uses for buoyancy. They swim by expelling water through their funnels. Argonauts have very large eyes and small webs between the tentacles.



Of course the word ‘argonaut’ is always linked with the story of Jason and the Argonauts, which is one of the best-known tales of Greek mythology. These Argonauts got their name by combining the name of the ship, Argo, named after its builder, Argus, with the ancient Greek word, “naut,” meaning sailor or voyager.


There is no doubt the argonaut found on Runaway Beach in November 2022 was a marine voyager. The argonaut is also commonly called the paper nautilus in reference to its thin shell and the fact that it is very mobile across the seas.