Cool critter of the month: the chambered nautilus (Nautilus pompilius)

Phylum: Mollusca Family: Nautilidae

Where do they live? These ocean dwellers can be found throughout the Pacific and Indian Oceans.  As it turns out, there are two sub-species of (Nautilus pompilius).  Nautilus pompilius polpilius is the larger of the two subspecies.  These guys can be found in the Andaman Sea down to Western Australia in the Indian Ocean, and from southern Japan down to Northern Australia in the Pacific.  Nautilus pompilius suluensis has a much more restricted range, staying in the Sulu Sea between Malaysia and the Philippines.

Why are they awesome? Back in prehistoric times, there were an estimated 10,000 species of nautilus swimming about the ocean.  Today there are but six species, and the chambered nautilus is the largest, and also the most common.  These strange looking critters haven’t really changed that much in the past 400 million years, giving it the title of a ‘living fossil’.  These guys may not look like they are well adapted to swimming about the ocean, but like many cephalopods they use “jet propulsion”, pulling water into the mantle cavity and expelling it out through a siphon at high pressure, and in the direction desired by the animal.  For buoyancy they make use of an argon-nitrogen mixture, and a liquid saline solution stored within closed chambers of their shell.  These critters have the ability to change the ratio of gas to liquid, which allows it to move up, down, or “float” in the water column*.  If that’s not cool enough for you, here are a couple of open access papers on these amazing creatures:

I’m stuck on you Nautilus are, like their cephalopod brethren, scavengers and predators.  And like their fellow cephalopods, they have tentacles.  Unlike the other cephalopods their tentacles do not have hooks or suckers in which to ensnare their prey.  Instead they produce a special glue that lets them pick up food, attach themselves to substrate – or even other nautilus for mating.  Janek von Byern from the University of Vienna and fellow researchers wanted to have a look at the gland system that produces this sticky substance.  They found that the glue primarily consists of neutral mucopolysaccharidesis.  Super sticky stuff.  Which presents an issue for the nautilus – releasing their grip.  The authors note that this is likely a slow, mechanical process.  In essence, they have to peel their tentacles off whatever they are stuck to.  Have a read of their paper – which is accompanied by some very nice images of the glands.

From dusk till dawn Nautilus are known to undergo diurnal migration.  During the day, they stay at depth but at night head up to the surface, at around 200 meters at night.  Well that’s what we thought was standard until Andrew Dunstan from the University of Queensland and colleagues took a closer look chambered nautilus living at Osprey Reef in the Coral Sea, Australia.  Tagging 11 individuals and using remotely operated vehicles (ROVs) to watch additional nautilus (48 in total), the researchers found variation in their daily vertical movement.  During the daytime, it seems that they either stay “in virtual stasis” at around 160 – 225 metres depth, or head down deeper (489 – 700 metres) to actively forage for food.  During the night, they found the nautilus underwent virtually continuous movement between 130 and 700 metres.  It seems some things aren’t quite as straight forward as we may first think.  Have a read of their paper (and see a photo of a tagged nautilus)

Image:  This image was taken by Hans Hillewaert and kindly licensed under CC BY-SA 4.0 via Wikimedia Commons.  Thanks Hans!

*Want to see a video of a nautilus swimming?  Have a look at this short (under 3 minutes) one taken by +cmcandles