Architeuthis Buoyancy and Feeding

By Dr. Steve O'Shea

Note: Steve welcomes discussion in TONMO's Architeuthidae forum.

Earth and Oceanic Sciences Research Institute
Auckland University of Technology
Private Bag 92 006
Auckland, New Zealand


Here we present a little scientific evidence supporting our contention that Architeuthis is a rather passive beast, rather than aggressive hunter, much like the Humboldt squid. Within its tissues Architeuthis balances the ration of ammonium ions to sodium ions to achieve buoyancy. The sodium ion (Na+) has a relative atomic mass of 23 amu, while the ammonium ion (NH4+) has a relative atomic mass of 18 amu; ammonium ions are therefore lighter than sodium ions. Tissues taken from various parts of a fresh Architeuthis individual, from the tip of the mantle through to the tips of the arms, manifest variations in ammonium- and sodium-ion levels (Figures 1, 2). The ratio of ammonium to sodium has a maximum in the mantle and a minimum at the arm tip — it is not constant throughout the tissues. This implies that (the adult) Architeuthis suspends itself in the water column at an oblique angle, rather than on the horizontal plane. The animal’s fins and mantle would be up, its arms down, and the two long tentacles would drop almost vertically, clasped together, with their distal, expanded clubs acting as tongs would do, plucking prey from the water column many metres away.

A crude test for the presence of ammonia in Architeuthis tissues has been detailed elsewhere online, but the technique entails cutting a small piece (~ 1 cm...
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About the Author
Steve O'Shea
Steve is an expert in the systematics and biogeography of cephalopods, and joined the staff in June 2002. He can be seen on the Discovery Channel documentary, Chasing Giants: On the Trail of the Giant Squid. For more information, see his Autobiography and Select Bibliography (2003). Dr. O'Shea lives in New Zealand.


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