Chambered Nautilus

• It is one of the few cephalopods that still has an external shell, almost unchanged in 500 million years.
• Unlike other cephalopods, it is long-lived and can breed several times.
• It finds its prey by smell, since its eyesight is rudimentary.
• anatomíaIts logarithmic spiral shell works as a buoyancy chamber, balancing gas and liquid in its internal compartments to control depth.
• historia naturalIt has changed very little in form over the last 500 million years, which is why it is often called a living fossil.
• It is the only living cephalopod with an external shell, and the last representative of a lineage that dominated the seas for hundreds of millions of years.
• Its shell is divided into chambers that it seals off as it grows, and it regulates its buoyancy by adjusting the proportion of gas and liquid inside them through a tube called the siphuncle.
• Its spiral roughly follows a logarithmic progression, and it is one of the shapes most often cited as an example of geometry in nature.
• It has between 60 and 90 tentacles without suckers, which grip by means of sticky grooves, and a primitive eye without a lens that works like a pinhole camera.
• It is long-lived and late-maturing for a cephalopod: it can live twenty years and takes ten or more to mature, against the year or two of an octopus. That makes it very vulnerable to fishing.
• It is intensively exploited for the shell trade, and since 2017 the whole genus has been listed in Appendix II of CITES.

Skeleton type

Invertebrate - no internal skeleton, protected by an external calcareous shell divided into chambers

Habitat & environment

Deep reefs of the tropical Indo-Pacific, between 100 and 700 metres, rising into shallow water at night to feed

Birth weight

Eggs ~3.8 cm long; the newborn's shell ~2.5 cm across

Size at birth

Shell ~2.5 cm across on hatching

Sexual maturity

10-20 years (studies give either 10-15 or 15-20 years depending on the population)

Gestation / incubation

Approximately 1 year (10-12 months) of egg development

Litter / clutch size

10 to 20 eggs a year, laid one at a time

Sources consulted: Encyclopedia of Life; MarineBio; National Marine Sanctuary Foundation; PMC (Osprey Reef demographics study); Center for Biological Diversity; Aquarium La Rochelle; NOAA Fisheries; ScienceInsights