高水圧下におけるオウムガイの呼吸と殻破壊実験  [in Japanese] Respiration and Shell Implosion of Living Nautilus under Increased Hydrostatic Pressure  [in Japanese]

In a hyperbaric chamber, living mature specimens of Nautilus pompilius withstood the hydrostatic pressure of 8.31 MPa (84.7 kg/cm^2) equipvalent to 827 m-depth in the sea and 7.89 MPa (80.5 kg/cm^2) equivalent to 785 m-depth, respectively, before it was killed instantly by implosion, the animals reacted physiologically to increasing pressure including increased partial pressure of oxygen with the compression rate (0.0981 MPa/min). This suggests that Nautilus undergoes severe stress during rapid descent and ascent through the water column. The shell implosion was caused by maximum strain-shortening (1.3% of the length). The shell implosion under pressure seems to have occurred at an old air chamber or siphuncular tube but not at the last septum of the phragmocone. Consequently, the depth of approximately 800 m is considered to be the maximal depth that N. pompilius is durable. The result will be usable for interpretations on paleobiology of extinct nautiloids and ammonoids which have similar shells and siphuncular tube system as living Nautilus.