Sunday, May 1, 2011

The Nautilus

The Nautilus is basically a living fossil, thought to be around since the triassic period, there is no doubt that this cephalopod is one hardy organism. The Nautilus is only found in the Indo-Pacific area, from the 30 N to 30 S latitude and the 90-185 W longitude. Here, they tend to thrive on the deep slopes of some coral reefs.
The anatomy of a Nautilus is quite different from the anatomy of most other cephalopods. Although it still has a prominent head like the rest of the class, the fact that it has a shell as an outer covering is where the differences begin.
Nautilus’ also typically have more tentacles than other cephalopods, up to 90. These tentacles have no pads or suckers, and just because of their frictional surface, they tend to grab hold of objects. The radula inside the mouth of the organism has 9 teeth and is very large compared to the size of the animal. The “shell” of the nautilus is actually not just a shell the organism found and fit into, but rather an externalized body structure that grows with the animal. The structure is very strong and can withstand pressure down to depths as deep as 2,600 ft. before imploding. As the nautilus grows and matures the shell gains new chambers, called camarae. The divisions are shown by the presence of a septa, with a hole in each for the siphuncle, which controls buoyancy of the organism allowing it to stay upright at all times, which is very evolutionary and convenient.

Nautilus’ eat small fish, shrimp, and other small crustaceans, but due the little amount of energy that it uses swimming because of the jet propultion system it possesses.
This propultion system, other than its hard shell and the ability to pull its head into the shell, is it’s only defense mechanism.
Nautilus’ reproduce by laying eggs. Females attach them to rocks in shallow water. They take 8-12 months to develop, and then hatch. Females spawn once a year and are able to regenerate their gonads.
The male has four modified tentacles called the spadix, which transfers the sperm into the females mantle.

Chambered nautilus (Nautilus pompilius pompilius) responds to underwater vibrations*
Christian P. Soucier1 and Jennifer A. Basil
Evolution, Ecology, and Behavior Program, City University of New York–Graduate Center, Department of Biology, CUNY Brooklyn College, 2900 Bedford Avenue, Brooklyn, New York 11210, U.S.A., and

1 Present Address: 333 East 102nd Street, Suite 726, New York, New York 10029, U.S.A.

The deep-water cephalopod Nautilus pompilius pompilius Linnaeus, 1758 may benefit from detecting potential signals such as mechanical and acoustical stimuli in its dark habitat where visual information is often limited. Here we examined whether specimens of chambered nautilus are capable of responding to waterborne vibration—a sensory mechanism that has yet to be investigated. We measured the ventilation rate of animals responding to a vibrating bead that produced a range of displacements and velocities. We found that nautiluses do indeed respond to underwater acoustical stimuli, decreasing their ventilation in the presence of a vibratory stimulus. Vibrations resulting from large-bead displacements and high source-velocities caused the animals to decrease their ventilation the most. Stimuli <20 cm from the animals caused a further reduction in their ventilation rates than those at greater distances. These nocturnal animals, living in dark conditions where visual information is often limited, may benefit from including vibrations in the suite of stimuli to which they can respond.

Received: October 1, 2006; Accepted: July 30, 2007; Revised: December 17, 2007

This article basically stated that Nautilus are able to respond to vibrations in the water column and by sensing these, their ventilation level goes down. these tests show that the nautilus may be able to detect prey by sensing acoustic vibrations in the water column.

The beautiful shells of these animals are the only thing that pose a threat to the species. they are not deadly and are not a source of food, so hopefully if the shelling is curbed, the nautilus with thrive for 500 million years more!

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