Friend Feature: 12-Tentacled Parasitic Anemone
Friend Feature: 12-Tentacled Parasitic Anemone, Peachia quinquecapitata
Jelly-dwelling anemone, Peachia quinquecapitata sitting innocently in its burrow on the seafloor. Image copyright by Minette Layne Flickr Creative Commons
Finning along the seafloor near Rosario Beach tidepools on a baby rockfish survey recently, something caught my eye. It was not a fish, but a beautiful sea anemone with its stalk buried in the sand and its twelve, striped tentacles fanned out, waiting innocently for a meal to happen by. What I didn’t know then was that this pretty cnidarian was not so innocent; it hid a secret past. I had just come face to …uh…tentacle-ringed mouth/anus* with the adult stage of an anemone with a sinister youth.
*It’s hard to say “face to face” about an animal whose face is also its bottom. Let’s just say cnidarian bodies are designed like a bag within a bag with the opening at one end. Food comes out the same way it goes in. Suddenly thankful for a one-way gut, anyone?
Introducing the 12-tentacled parasitic anemone, sometimes called the jelly-dwelling anemone. “Jelly-dwelling” gives away that this sea anemone hangs out with or on or even inside a jellyfish, another type of cnidarian. What that name politely leaves out is the part where its juvenile stages eat the jellyfish from the inside out. Furthermore, how did it go from the jellyfish to the sandy home where I found it, minding its own business. So, like any nature detective, I did some investigating.
Juvenile delinquent
It all starts after the larva hatches out of a tiny, spine-covered egg that is drifting in the ocean currents as plankton. Soon the larva, called a planula, is eaten by a jellyfish - just what the planula is hoping for. Instead of becoming a meal, the little deviant spends a bit of time, about 11 days, in the mouth or gut of the unsuspecting jellyfish, growing into a young anemone by stealing bits of food as an appetizer. Then it is ready for the main course - the jelly’s gonads. Yes, it travels from the gut to the reproductive organs and chows down. It takes about two days per gonad (there are four). Then the small anemone moves on to other organs in the jellyfish until it has had its fill. What if it hasn’t had its fill?
Young 12-tentacled parasitic anemones, Peachia quinquecapitata, munching on jellyfish gonads, the thin, vertical, white strips inside the jelly’s bell. Image by Reyn Yoshioka Oregon State University and Friday Harbor Labs.
Jelly Jumping Superpower
If it finishes all of the tasty parts of one jellyfish, the young Peachia can exit, shoot out one of its coiled up, sticky stinging threads, called acontia, latch onto another passing jelly, and swing like a slow motion Tarzan to a fresh food supply. After about a month the jelly-dweller is growing fast from gorging on gonads. It now pops out of what is left of its jellyfish host and sinks gracefully to the seafloor.
No more jelly-dwelling
Once on the ground, the adult 12-tentacled anemone digs its stalk into the sand, ready to leave its wild youth behind. In its adult life, the anemone sits quietly and waits for unsuspecting, small invertebrates to touch its tentacles when, like all cnidarians, it can deliver paralyzing stings from its hundreds of stinging cells (Latin root: cnide = nettle). This makes it easier to push its prey’s limp body into its mouth by contracting its tentacles.
Now that they’ve grown up and settled down, they are ready to start a family. Okay, so they don’t exactly have families, but thanks to their own gonads being tucked safely away from parasitic intruders, they do reproduce. Female Peachia will cast their tiny, spike-covered eggs into the water column, where, with a lot of luck, proximity, timing, and the right tidal currents, they will meet up and be fertilized by sperm cast into the water by nearby males, and continue their vicious cycle in a whole new generation.
Parasites are people too
Though this unusual life cycle seems unsavory to people, we are quite an opinionated species. These beautiful anemones undoubtedly play a very important role in their ecosystem. What would happen, for instance, to their targeted jellyfish species’ population size (total number in an area) if they didn’t have any Peachia in the Sound? As part of this great food web of the Salish Sea, what if all of us humans treated all life as sacred and deserving respect, even when we don’t understand them?
Happy exploring!