In all shell families there is some distinguishing mark or trait that sets them apart from others. In the case of the Tonnidae family they are light weight, have a large opening, and give the appearance of being extra fragile. They may look fragile but they are not for once again nature has come up with a way to fortify their shell. If you rub your hand over the shell you will immediately notice raised ridges. It is the ridges that give the shell greater strength. The best comparison to how this adds to strength is to look at the Old Gray House tin roof that has remained there for over a hundred years. It is not a smooth sheet of metal but it has V-style ridges or corrugation. The tun shell is corrugated and it is that corrugation that accounts for the strength of the shell.
It is not often we find members of the Tonnidae family on the Hatteras Beach. Occasionally I do find small ones even though their distribution is as a general rule confined to tropical waters. Probably the reason for this is that they lay huge ribbons of eggs on the sandy bottoms of the ocean which produce thousands of free floating larvae throughout the oceans of the world. As time goes on if the climate changes continue to occur world wide as predicted, who knows what new type of shells might appear on our beaches.
When it comes to feeding the tun shell is not a gentle creature. It is carnivorous and enjoys a good meal of sea urchins, fish, sea cucumbers and crustaceans. The animal
Inside the shell is not blessed with the defense mechanism of most mollusks. It does not have a trap door or operculum. The animalís foot is longer than the shell and it emits a mucous to help it glide along. It is usually found in a sandy area at the edge of coral reefs.
One use I have found for the giant tun is to hang it in a shell hanger with an artificial plant in it. The one you will see as you enter the Gray House has been a huge attention getter over the years.