Chamber refilling in Nautilus

Freshly captured Nautilus macromphalus were observed to place new cameral liquid into emptied or partially emptied chambers, both at the surface and at 250 m, in response to sudden buoyancy increase. The sudden addition of buoyancy was accomplished either through removal of cameral liquid from chambers, removal of shell material from the apertural region of the body chamber, or by cementing buoyant corks on the sides of the shell. A maximal refilling rate of 100 μl/h was observed. The osmolality of refilled cameral liquid was observed to match closely the osmolality of the original cameral liquid. The refilling mechanism allows Nautilus to regain neutral buoyancy after sudden buoyancy gain, such as could be expected to occur from shell loss due to predatory attack on the Nautilus, or from shell breakage.