Let's go back below the ocean's surface this week. Sea anemones belong to a group of animals that share the common characteristic of having specialized cells containing tiny harpoons that they use to disable their prey. Besides sea anemones, this group includes sea jellies, box jellies, corals, sea pens, and sea anemones.
The white tentacles of the sand rose anemone, while graceful and beautiful to look at, hide the same deadly secret as the tentacles of the deadly box jelly whose sting can kill a human in minutes. Fish eating anemones are not at all as potent as the box jelly, unless you are small fish or a member of the plankton. Then you have little hope of surviving should you come in contact with the tentacles.
Once entangled by the tentacles and paralyzed by the harpoons, the prey is dragged to the center of the oral disk and into the mouth. Another feature of this larger group of animals is that there body plan is that of a simple sack. Thus the "mouth" also serves as the "anus," as all of the waste materials left after any food is digested is simply expelled out the same opening through which it came in.
Sea anemones are named after a group of flowering plants in the Ranunculus family. Flowers of these plants form a somewhat flat disk of petals surrounding the central cluster of pistils and stamens. The disk, central mouth and surrounding tentacles of sea anemones reminded people of these flowers, and thus the name. But clearly, these beautiful "flowers" of the sea are not flowers at all, and can pack a powerful punch when catching prey.
This photo was taken at Santa Rosa Island off the central coast of California. It was photographed with a Canon 10D dSLR and an EF 100mm macro lens set at f/27, 1/60 sec and ISO 100. The camera and lens were in an Ikelite underwater housing and lighting was provided by twin Ikelite DS125 submersible strobes.