Fig 1.
Map of New Caledonia. Star indicates the locality at which the specimens were caught. Circles indicate two stations at which water samples were taken (A); Outer shell of Nautilus macromphalus (AMNH 132380; female) (B); Cross-section of N. macromphalus (AMNH 132380; female) (C); Outer shell of N. macromphalus (AMNH 132423; male) (D); Cross-section of N. macromphalus (AMNH 132423; male) (E). Scale bars = 10 mm. Samples were taken through ontogeny (the earliest formed septum as septum 1). Map was reproduced from OpenStreetMap (© OpenStreetMap contributors).
Fig 2.
Cross-section of Nautilus macromphalus with measured morphological conch parameters.
ww = whorl width, dm = conch diameter, wh = whorl height, ww = whorl width, and vd = distance between the ventral edge of the siphuncle and the ventral edge of the conch.
Fig 3.
Temperature versus depth (A); Salinity versus depth (B); TS diagram (C).
Fig 4.
Oxygen isotope composition (δ18Owater; ‰ SMOW) versus depth.
Fig 5.
δ13C (‰ VPDB) (A); δ18O (‰ VPDB) (B). Filled markers represent the data produced at the University of California, Santa Cruz. Unfilled markers represent the data produced at the University of Michigan.
Fig 6.
Morphological parameters in Nautilus macromphalus.
Septal spacing for AMNH 132380 (female) (A); septal spacing for AMNH 132423 (male) (B); siphuncle position index (= vd/wh) for AMNH 132380 (female) (C); siphuncle position index (= vd/wh) for AMNH 132423 (male) (D); whorl expansion rate [= (dm1/dm2)2] for AMNH 132380 (female) (E); whorl expansion rate [= (dm1/dm2)2] for AMNH 132423 (male) (F); whorl width index (= ww/dm) for AMNH 132423 (male) (G); whorl width index (= ww/dm) for AMNH 132423 (male) (H).
Fig 7.
Calculated δ18Oaragonite vs. depth.
Dashed lines indicate the 95% confidence interval.
Fig 8.
Reconstructed habitat depths of Nautilus macromphalus from New Caledonia.
Filled markers represent the data produced at the University of California, Santa Cruz. Unfilled markers represent the data produced at the University of Michigan. Shaded areas represent the estimated error range calculated with the 95% confidence interval in Fig 7.
Fig 9.
Reconstructed habitat depth of Nautilus pompilius from the Philippines and Fiji.
Depth vs. septal number in the Philippines (A) and Fiji (B), based on the δ18Oar vs. depth relationships. Data from Oba et al. [16] and Hayasaka et al. [43, 44].
Fig 10.
Reconstructed fraction of metabolic carbon in Nautilus macromphalus.
Shaded areas indicate the estimated uncertainty in Cmeta given the average ±1sd of δ13Cmeta (-17 ± 2‰).
Table 1.
Comparison of the onset of maturity and changes in isotope composition of the septa.
Table 2.
Spearman’s rank correlation coefficients between morphological parameters septal spacing and siphuncle position index (SPI) and isotopic values (δ18O and δ13C).