Implosion of living Nautilus under increased pressure

Abstract

In a hyperbaric chamber, a living mature specimen of Nautilus pompilius withstood a hydrostatic pressure of 8.05 MPa (80.5 kg/cm2) equivalent to 785 m deep in the sea. Thereafter it was killed instantly by implosion of the shell. Before implosion, the animal reacted physiologically to increasing pressure. Therefore, the depth of 785 m can be assigned the depth limit of N. pompilius. The result bears on critical interpretations on the paleoecology and paleobiology of extinct nautiloids and ammonoids with similar shells.

Isotope Signature of Ammonoid Shells

“…In fact, depth habitat of modern Nautilus is much shallower than the shell explosion depth (cf. Kanie et al 1980;Saunders and Ward 2010). On the other hand, as shown in exquisite examples on isotopic analyses of modern Nautilus, oxygen isotopic thermometry would enhance our knowledge on ammonoid habitat.…”

“…However, the implosion depth of the shell of living Nautilus does not represent an actual preferred depth of the animal. Direct observations using a remote camera and capture records using baited traps have demonstrated that the optimal habitat depth of Nautilus ranges from 150 and 300 m deep in Palau and between 300 and 500 m deep in Fiji (Saunders 1984;Hayasaka et al 1987;Dunstan et al 2011), whereas the shell implosion depth of Nautilus is comparable to 800 m deep (Kanie et al 1980). Although these analyses in functional morphology gave us many great suggestions for considering ammonoid ecology, reasonable questions unanswered are still left on a table for future discussion.…”

Ammonoid Buoyancy

“…After migrating below a water depth of 250 m, a resting and re-equilibration period at around 200 m becomes necessary which has been documented by Dunstan et al (2011). Note that diving depth of Nautilus is limited by temperature, chamber re-filling and shell implosion with the greatest depth being around 800 m (Kanie et al 1980;Ward et al 1980a).…”

Ammonoid Taphonomy

“…Some experiments have demonstrated that depths of 750-800 m are enough to cause implosion in modern nautili (Denton and Gilpin-Brown 1966;Denton 1973;Saunders and Wehman 1977;Kanie et al 1980;Westermann and Ward 1980;Ward and Martin 1980;Kanie and Hattori 1983;Saunders 1984;Chamberlain and Chamberlain 1985;Westermann 1987, 1988;Dunstan et al 2011). However, sea water floods the empty shell until the cameral gas pressure equals ambient water pressure, and therefore, the phragmocone does not implode, even at great water depths (Boston and Mapes 1991).…”

“…Ammonoid shells became possibly fragmented and broken by various mechanisms during their taphonomic history (especially biostratinomic and early diagenetic processes; e.g., implosion by water pressure, collision during post mortem floating as well as further transport with sediment on the seafloor, sediment loading after Wani (2004) performed experiments mimicking some fragmentation patterns by transport with sediment on the seafloor, sediment loading after burial within sediments, and collision during floating, and considered the breaking patterns by other mechanisms (predation and implosion by water pressure) documented in the literatures (for predation, Haven 1972;Tucker and Mapes 1978;Saunders 1984;Arnold 1985;Ward 1987;Saunders et al 1987Saunders et al , 1991Tanabe et al 1988; for implosion by water pressure, Denton and Gilpin-Brown 1966;Denton 1973;Saunders and Wehman 1977;Kanie et al 1980;Westermann and Ward 1980;Ward and Martin 1980;Kanie and Hattori 1983;Saunders 1984;Chamberlain and Chamberlain 1985;Westermann 1987, 1988). Based on these considerations, Wani (2004) concluded that the fragmentation patterns produced by various mechanisms are distinct and therefore can be differentiated, which would allow the identification of distinct mechanisms responsible for specific fragmentation patterns both in modern nautili and ammonoids.…”