Anemones Are Not Your Enemies

If you’re lucky enough to live on the Key Peninsula, you probably have the chance to visit Puget Sound beaches more often than the average person. Walking the beach at camp as a kid, I always wondered about the strange squishy round things with a hole in the middle that I saw in the sand. I remember thinking that they were clam siphons because they gushed out water when poked, but I was wrong.

Those squishy round things do not look like much when the tide is low. But when the tide comes in and they are submerged, they open up into something flower-like: the notoriously hard-to-pronounce anemone (not “an enemy”). I usually describe them to kids who are seeing them for the first time as “Nemo’s house,” and they immediately make the association with the “Finding Nemo” movies. The most common species found on local beaches are called Anthopleura elegantissima, also known as elegant or pink-tipped green anemones.

While they may be elegant, anemones—like their jellyfish relatives—are also hungry carnivores. Anemones, jellyfish and corals all belong to the phylum Cnidaria (the “C” is silent) which are characterized by cells called nematocysts that are used for capturing prey through stinging. 

I am cautious about kids getting stung by jellies, but I encourage campers to touch the tentacles of anemones because their sting is so weak that to a human’s thick skin it feels like stickiness rather than pain. The sting does pack a punch for the anemones’ prey, however, paralyzing small crabs, mussels and fish that it swallows intact. The hole in the center of the anemone plays multiple roles; food goes in there and indigestible waste comes back out. If you look closely, you may find an anemone with an empty crab or mussel shell in its “mouth.”

Anemones are either male and female, and the “mouth” is also where sperm and eggs are released into the water in the hope that they will join and settle on a suitable surface—rocks, pilings and even shells or sand dollars. However, A. elegantissima is also known as the aggregating anemone for its ability to reproduce asexually, or clone itself. This is done through binary fission, in which the anemone will pull itself apart over the course of a few days in a process that looks a lot like cell division. Next time you’re walking down the beach, look for anemones that are oval-shaped, or even starting to look like a figure-eight. These may be in the process of cloning themselves.

A. elegantissima will use this fast reproductive technique to form colonies of genetically identical clones. I’ve seen hundreds in dense clusters in certain areas of the beach, often all attached to the same large rock. However, when one cluster comes into contact with another genetically distinct clone colony, anemones act to defend their territory. Anemones on the front lines use specialized tentacles called acrorhagi to clobber and sting each other until one side retreats. This fighting is only done when the anemones are underwater, since they need water to swell their acrorhagi in preparation for battle. It is difficult for the casual beachgoer to witness these “clone wars,” but we can observe the aftermath: an anemone-free no-man’s land that forms between the two colonies.

Anemones, like all aquatic non-mammals, breathe dissolved oxygen from the water, not the air. This is complicated when the tide is out and anemones are left high and dry. To survive, anemones curl their tentacles inwards into their less attractive form, trapping some water to continue breathing until the tide covers them again. I recommend gently touching the anemones’ tentacles to watch the water squirt out. 

Next time you walk the Key Peninsula beaches and see those nondescript circles in the sand, you’ll know that there is a lot more there than meets the eye: a dramatic struggle to survive, reproduce and win the “clone wars.”

Nancyrose Houston is the Outdoor Environmental Education Director at Sound View Camp.

Nature Overlooked