Beware of cute little monsters: The jelly-dwelling anemone has a spooky secret

Eyes Under Puget Sound - Critter of the Month

Brown and white anemone tentacles radiate out from a red center with bits of white shell stuck to it.

Adult jelly-dwelling anemone, Peachia quinquecapitata, in a West Seattle tide pool. Photo by Minette Layne, from Wikimedia Commons.

Step aside, Alien. Puget Sound has its very own version of this famous parasitic predator, but without the terrifying claws or fangs. Like an eerily adorable child in a horror movie, an innocent-looking exterior hides the sinister intent of this squishy little monster.

Skeletons in the closet

Peachia quinquecapitata sounds like an unassuming name — even charming! But these innocuous anemones have a sordid past, and the road to adulthood is paved with the bodies of those who stood in their way. 

Text reads: Kingdom Animalia, Phylum Cnidaria, Class Anthozoa, Order Actiniaria, Family Haloclavidae, Genus/Species Peachia quinquecapita

Shortly after hatching into the water column, larval Peachia, called planula, are eaten by jellyfish. You'd think this would be the end of the line, but it’s exactly what the baby anemones were hoping for. Instead of getting digested, the planula get comfortable in their hosts’ gastrovascular cavities and help themselves to food particles. Hey, who doesn’t like a safe place to hide, free transportation and a free meal?

Body snatchers

Unfortunately for the hosts, that free meal is just an appetizer. After a few days, the freeloading anemones begin to hunger for the main course — wait for it — the jellyfish’s internal organs. Duhn-duhn-duuuuuuuh! These pint-size parasites start with the reproductive tissue (a single baby Peachia can consume an entire jelly gonad in two days), then move on to other organs for dessert. Yum! 

A clear jellyfish bell with a tiny white anemone stuck to the inside of it, on a black background.

Jellyfish with P. quinquecapitata attached to the inside of its bell. Photo by Matt Goff,

Weird science

This fascinating research on the Peachia life cycle was conducted at Puget Sound’s own Friday Harbor Laboratories, where scientists determined that up to 62% of one host jelly population (Clytia gregaria) was infected with these little leeches each spring. Although the planula may be able to live freely without hosts, when scientists replicated this process in laboratory culture, only the ones that were eaten by jellies survived. An amazing host-swapping behavior was also observed: the anemones were able to fire their stinging cells into new host jellies and make very slow, sticky Spiderman-esque leaps from one bell to the next. 

Peach-colored, trumpet-shaped anemone with clear jellyfish draped over it. Watermark reads, King County.

“Who, me?” The head of this cute little anemone innocently protrudes from under the bell of the jelly it is parasitizing. Photo by Lyndsey Swanson, courtesy of King County.

Beg, steal or burrow

After about a month of eating the unlucky jellies from their insides out, the anemones have had their fill. Remember the scene in Alien where the thing bursts out of the guy’s chest? Well, picture something like that, only way less disgusting. Like swollen ticks, the now fat and happy anemones drop off and go on their merry way, settling down on the sea floor and burrowing the long columns of their bodies into the mud.

Not much is known about the fate of the host jellies, but I am guessing that having your organs munched is probably harmful to your health.

Brown and white anemone tentacles form a circle on top of greenish ocean floor.

P. quinquecapitata adult with banded tentacles fanned out. Photography by Derek Holzapfel,


After spending their childhoods wreaking youthful havoc on other living creatures, Peachia adults assume new peaceful identities as model citizens. Occurring in the shallow subtidal zone of the Pacific Northwest, they spend their time with their 12 tentacles splayed out on the surface, passively waiting for food to drift by. A closer look reveals that their striped pattern is made up of delicate chevrons — very on-trend with the interior decorating crowd.

Forceps pinch a portion of whitish anemone tissue to indicate a 5-lobed structure.

A red circle indicates the fleshy white “fingers” of the conchula in this preserved Peachia specimen.

Living hand to mouth

The taxonomy crowd might appreciate Peachia for a different stand-out feature, called the conchula: a projection near the mouth that functions in feeding, and is unique to this genus. In Peachia quinquecapitata, the conchula is divided into five distinct finger-like lobes, almost like a miniature hand. And I have to hand it to these mini moochers…they definitely get away with biting the hand that feeds them!

Critter of the Month

A smiling woman in a black raincoat poses against a backdrop of gray sky, green rocks, a ferry, and the waters of Friday Harbor.

Dany is a benthic taxonomist, a scientist who identifies and counts the sediment-dwelling organisms in our samples as part of our Marine Sediment Monitoring Program. We track the numbers and types of species we see to detect changes over time and understand the health of Puget Sound.

Dany shares her discoveries by bringing us a benthic Critter of the Month. These posts will give you a peek into the life of Puget Sound’s least-known inhabitants. We’ll share details on identification, habitat, life history, and the role each critter plays in the sediment community. Can't get enough benthos? See photos from our Eyes Under Puget Sound collection on Flickr.