Monday, 14 March 2011

Chambered Nautilus

Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Order: Nautilida
Family: Nautilidae
Genus: Nautilus
Species: Nautilus pompilius
Common names: Chambered Nautilus

The strange looking Chambered Nautilus is the most famous, large and common species of nautilus. It’s a mollusc and a close relative of the octopus, snail, squid and clam. It is considered to be a living fossil since it has remained virtually unchanged for the past 400 million years. The chambered nautilus can be found in tropical waters that extend from the Andaman Sea east to Fiji and from southern Japan to the Great Barrier Reef. This weird creature's habitat usually lies in locations where the coral reef slopes go down into deep waters.

Chambered Nautilus Description
This creature can grow up to 20 cm (8 inches)in total length. Nautilusses have smooth and white shells accompanied by brownish stripes. It is the only cephalopod with a fully developed shell for protection. Like other cephalopodes it uses jet propulsion managing to attain speeds of two knots or even more. Near the tentacles there is a small tube called siphon. The siphon expels water under pressure propeling the nautilus in the opposite direction at the speed mentioned before. The shell is made off many individual chambers. Each and every chamber is individually sealed and contains a certain amount of gas. This feature provides the animal with buoyancy. Density is regulated by injecting or removing fluid into the chambers through a system of tubes. The hard shell is also used as a means of protection.

The chambered nautilus has way more tentacles compared to other molluscs and to be more specific it has around 90 tentacles. These tentacles are arranged into two circles and have no suction cups These tentacles are used to catch shrimp, fish and small crustaceans, which the animal crushes with its powerful beak. Nautiluses are active predators, however their siphon system is very energy-efficient and as a result they need to eat only once a month.

The chambered nautilus has a very poor eyesight since the large eyes contain no lenses. Actually the eyes have just a tiny hole to allow light enter the eye.The average life span of the nautilus is believed to be about 20 years, which is unusually long for a member of the cephalopod family.
Close up image of the Chambered Nautilus Head
Chambered Nautilus Predators
Despite its hard shell, Nautilus pompilius has many natural enemies that can easily crack it, including the following:
  • Octopuses 
  • Sharks 
  • Triggerfish 
  • Turtles
Chambered Nautilus Behavior
During the day, the chambered nautilus prefers to stay in dark and cool waters at depths varying from 900 to 2,000 feet (275 to 610 metres) in order to avoid predators. At night they usually ascend to swallower depths of 300 to 500 feet (90 to 150 metres) for feeding purposes.
After reaching sexual maturity nautiluses reproduce once every year.
The spadix (the male sexual organ which is formed by four modified and fused tentacles) is used for passing the sperm to the female during mating. Astonishingly the mating procedure can last as long as 24 hours. About a dozen eggs are fertilized after mating has occurred. The female will then deposit them one at a time or in small groups throughout the whole year. These eggs are among the largest ones produced by vertebrates and are 1,2 inches in length. It can take 9 to twelve months for the eggs to fully develop and hatch. It should be noted that nautilus eggs have never been observed in the wild thus little is known about the environment where they are laid and hatched! Hatchlings measure about an inch in diameter and their shell has seven chambers. The young ones drift and feed on plankton and other small prey as they grow. As they get bigger and bigger, new chambers are added to the shell. Every new chamber is a little bigger compared to the last one thus allowing the opening of the shell to gradually grow larger.

Video showing the way the Chambered Nautilus swims

Chambered Nautilus Diet
Adults nautiluses feed on dead crabs, fish and shrimp, and also the exoskeletons of molting crustaceans. Newly hatched nautiluses as mentioned before, feed on small shrimp, plankton and other small prey.

It is believed that the Chambered Nautilus uses its smell to locate food.

Chambered Nautilus Subspecies
There are two known subspecies of the Chambered Nautilus:
  • Nautilus pompilius pompilius 
  • Nautilus pompilius suluensis 
N. p. pompilius is the most common and widespread subspecies. It is also called “Emperor Nautilus” due to its large size. Its natural habitat covers the Andaman Sea east to Fiji and southern Japan south to the Great Barrier Reef. Remarkably large specimens with a shell diameter of up to 268 mm (10.3 inches) have been reported from Indonesia and northern Australia. This giant nautilus was firstly described as Nautilus repertus, however most scientists believe that it is not a separate species.

N. p. suluensis is much smaller in size, found only to the Sulu Sea in the southwestern Philippines. The largest specimen ever recorded had a shell diameter of 148 mm (5,5 inches)

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