MARINE NUISANCES – Nautilus: A living fossil


In 1870, a famous French writer published an epic tale of adventure whose influences are still evident in me today. The author was none other than Jules Vernes and the book was “20,000 leagues under the sea”. As the story unfolds the reader is introduced to the reclusive Captain Nemo, a mysterious name which means “manly” in Oromo and “nothing” in Latin and that, in my humble opinion, has been ruined by Disney’s animated studio, Pixar. Captain Nemo pilots an awe-inspiring submarine called the Nautilus a name which is intrinsically linked to my life today.

Apart from the submarine, the nautilus is the most archaic of the Cephalopods, a group which include the Squid, Cuttlefish and Octopus. The name cephalopod comes from the Greek and literally means head (cephalo) foot (poda). Quite unbelievably though, they form part of the Mollusca phyla which include the whelks, nudibranchs, clams and oysters. Their comparably high intelligence is a true testimony to how far they have come.

Their brains are less developed and have different structures to some of their cousins. Scientific studies have shown that they have the ability to retain information in both short-term and long-term memory. However, these studies found that their ability to retain this information long-term was much less developed in nautilus compared with other cephalopods.

The most striking part of the nautilus is its shell which is coiled and has a beautiful pearly sheen to it. Brown bands appear on the top of the shell whilst at the bottom, it is completely white. The most obvious reason for this has been as a form of camouflage, dark when looking directly down on it and light when looking from the depths up. This is further evidenced by the fact that unlike all of its cousins, the nautilus does not change its skin colour.

Their shell does create a problem for them though. They use gas, which they extract from the water around them, to fill up chambered compartments within it, much like a human diver with a BCD. The deeper they travel, the more of this gas is required to keep them neutrally buoyant and here lies the problem; gases compress and liquids don’t. At around 800 metres deep, the crushing pressure is so great that the shell can no longer withstand it and implodes, killing the nautilus. A poor situation to be in if you are a deep-sea dweller.

Humans like to credit themselves with the invention of jet-propulsion but in truth, cephalopods have been using this form of movement for millions of years. They push a huge amount of water out of a siphon with the position of it determining which direction the animal travels in.

Primarily scavengers, today’s nautilus live in deep water where there is little to no light. They tend to eat any detritus that sinks into the depths including the molts of lobsters and crabs and any carrion. Of all the cephalopods, the nautilus has the most basic eyes. Having said that, they do have good vison although they lack a focusing lens like we have.

They also have a specialised parrot like beak which forms its mouth parts. This allows it to take bites out of its prey. With 90 tentacles coming out from the shell, they can also be highly dextrous with prey items.

The nautilus are sexually dimorphic, with males being larger than females. They lay eggs, like all the relatives in the cephalopod class, and can continuously breed over their reproductive lifespan which is circa five years. This is not very long as they only live up to around 20 years old and it is the latter years where they are sexually active. It is this fact that makes them particularly vulnerable as a species as their shells are sought after by collectors.

It is precisely because they have been on this planet for over 500 million years and because of this sensitivity that we should be trying to preserve them. The Mediterranean hosts around three separate species as described by Carl Linnaeus in 1958. It seems clear that we have a responsibility to review their present ecological status and ensure that our activities do not prejudice their continued survival.

One final thought taken from Jules Vernes novel, “Your arguments are rotten at the foundation. You speak in the future, ‘We shall be there! We shall be here!’ I speak in the present, ‘We are here, and we must profit by it.” We have an opportunity to preserve these amazing creatures right now. Conservational efforts based on future actions and possibilities might well come too late. Our oceans are already seeing massive changes driven by climatic action and the outlook does not look great. Our oceans would be in an even poorer state without them.

words | Lewis Stagnetto, The Nautilus Project