Notes on animal weight, cameral fluids, swimming speed, and color polymorphism of the cephalopod Nautilus pompilius in the Fiji Islands

Abstract

Forty-six specimens of Nautilus pompilius Linnaeus were captured in depths varying between 100 and 500 m outside of the fringing reef near Suva, Fiji Islands. Thirty-eight of the specimens were male. Air weight per individual varied between 347 and 630 g. Sexual dimorphism in size is indicated, since mature shell modifications (approximated septa, blackened aperture) were present in two females weighing about 350 g (soft parts plus shell) and one weighing slightly over 400 g; the smallest male showing mature shell modifications weighed 496 g. All newly captured specimens were heavier than seawater, with mean weight in seawater of 1.87 g determined for twenty-five specimens. Total volumes of cameral liquid ranged between 13.5 and 0 ml. Thirteen of twenty-five sampled specimens showed less than 1.0 ml of cameral liquid from all chambers. Average cameral liquid osmolarity was lower than that observed in sampled populations of N. macromphalus from New Caledonia and N. pompilius from the Philippine Islands. Maximum swimming rates were 0.25 m/sec. N. pompilius exhibits two common color polymorphs.