On the buoyancy of the pearly Nautilus

Abstract Fourteen freshly captured Nautilus macromphalus were weighed in seawater, and all were found to be negatively buoyant (heavier than seawater), with a mean weight of 1.76 g. Maximum rates of cameral liquid removal from chambers artificially filled with seawater were 1.0 ml/chamber/day at the surface. Specimens made artificially buoyant by the removal of cameral fluid, and maintained at 60 m or less, were unable to regain normal, slightly negative buoyancy through admission of new liquid into the emptied chambers via the siphuncle. Specimens maintained at depths of greater than 150 m all showed new cameral liquid in the previously emptied chambers. Because of the relatively slow rate of cameral liquid removal from the chambers, and seeming inability of Nautilu to place cameral liquid into emptied chambers in shallow water, we conclude that the phragnocone‐cameral liquid system is utilized for long term buoyancy adjustments rather than short term changes which might aid vertical ascent or descent.