The argonaut shell: gas-mediated buoyancy control in a pelagic octopus
Julian K Finn, Mark D Norman
Proceedings of the Royal Society B | ROYAL SOC | Published : 2010
Argonauts (Cephalopoda: Argonautidae) are a group of rarely encountered open-ocean pelagic octopuses with benthic ancestry. Female argonauts inhabit a brittle 'paper nautilus' shell, the role of which has puzzled naturalists for millennia. The primary role attributed to the shell has been as a receptacle for egg deposition and brooding. Our observations of wild argonauts have revealed that the thin calcareous shell also functions as a hydrostatic structure, employed by the female argonaut to precisely control buoyancy at varying depths. Female argonauts use the shell to 'gulp' a measured volume of air at the sea surface, seal off the captured gas using flanged arms and forcefully dive to a d..View full abstract
We thank Koji Nakamura, Nobuhito Yamashita, Yasushi Okumura, Masahiko Sakata, Hideki Abe and the fishermen of Noi and Okidomari Harbour for assistance in Japan. We also thank Dr F. G. Hochberg, Professor Chung-Cheng Lu, Dr Michael Vecchione, Professor Richard E. Young and two anonymous reviewers for their comments on versions of this manuscript. This work was supported by the Hermon Slade Foundation, Australian Biological Resources Study, American Malacological Society, Malacological Society of London, Linnean Society of New South Wales and Museum Victoria.