Friday, July 25, 2014

Tiger Cowry

CEP image

Tiger Cowry

These may just look like any cool shell that you find on a reef or on the beach, but they are actually home to the one and only tiger cowry (Cypraea tigris Linnaeus 1758). The cowry is actually a type of ocean snail. They are found throughout the Indo-Pacific, although Hawaii produces the largest tiger cowries worldwide. Like all snails, the shell is actually an external skeleton, they have muscle and skin attached directly to the shell and a special layer of skin lays down new shell as they grow.

 The cowrie's shell starts out looking like a typical shell, growing in a spiral out from small to large, with a wide opening at the end. When the cowry nears adulthood, shell growth changes dramatically. Instead of continuing to add shell to the outer edges of the spiral, the outside of the shell curls in and almost encloses, leaving a tiny slit for the living cowry. Once the shell folds over, the shell starts to harden and begins growing into the shells that are so appealing to the eye.



Image from http://www.divegallery.com/shellfish4.jpgre
You may be wondering what keeps these shells so shiny and in such a nice condition. The snail’s mantle actually comes up over the outside of the shell when they are adults - adding thickness and coincidentally keeping it polished nicely. As you can see in the photo to the right, the mantle of the cowry has folded up and over the outside of the shell. The purpose of the small, white tipped papillae on the mantle are still unclear, but it’s been thought that they aid with absorption of oxygen in the water.
              
 

         

   
Image by Z. Boone
One interesting thing about the Tiger Cowry is that they consume what is believed to be Mycale Spp. as a tasty treat. This is a good thing because this particular sponge is invasive to Hawaii, meaning that is not a natural inhabitant to the area. To the right is a photo I took during a snorkel session of a large Tiger Cowry sitting on a patch of sponge in between a colony of Finger Coral.  

Another interesting piece of information is that because of the beauty of these shells, they have been and still are used as different jewelry pieces. Also, a long time ago, they have been used as currency in some parts of the world.

-Zach


Sources:
http://www.waikikiaquarium.org/experience/animal-guide/invertebrates/molluscs/tiger-cowry/
Hoover, John P. Hawai’i’s Sea Creatures. Revised Edition ed. Honolulu, HI: Mutual Publishing, 1999. 108-21. Print.