The Striking, Brightly-Colored Nudibranchs of Oregon / Washington Coast Tidepools

Published 01/22/21 at 5:56 aM PDT
By Oregon Coast Beach Connection staff

(Oregon Coast) – From the bottom of sea stacks at Bandon or Myers Beach on the southern Oregon coast, to the vast colonies of Bob Creek near Yachats, at Cannon Beach or up on the Washington coast, tidepools are entire other worlds of stunning beauty lying around in this world. They're little ecosytems all their own: full of color, all manner of things poky and gooey, and utterly alien. (All photos courtesy Tiffany Boothe / Seaside Aquarium. Above: opalescent nudibranch / Hermissenda opalescens)

But are you seeing everything?

As colorful as they are, one set of tidepool species sort of hides in plain sight. What are usually just cursory glances at these little environments left off by the tides doesn't tell you everything. One wild little beastie wears not only a myriad of bright, striking shades but incredible and different forms as well.

They're called nudibranchs (the ch is pronounced with a k sound), sometimes known as sea slugs. Some 3,000 different species inhabit the world's oceans and tidepools, ranging in length from 1/8 inch to 12 inches. Around the Pacific Northwest beaches of Oregon and Washington's coastline, there's about 200 different varieties. Some work to hide themselves, others blatantly show off in effort to keep themselves noticed.

There's such a variety of them it's impossible to display all.

Near the border of both the Washington and Oregon coast, Tiffany Boothe of Seaside Aquarium works with them a lot.

“Nudibranchs are marine snails, relatives of limpets and abalone,” Boothe said. “Through evolution they have lost their shell. In fact, the name nudibranch means ‘naked gills,' referring to the fact that their gills are on the outside of the body. While most lack shells some species have a reduced or internal shell.”

Like many other creatures on land and in the sea, if a nudibranch has a bright coloration it's a warning: chomp here and you'll get a mouthful o' nasty and maybe even poison. Scientists often observe fish swallow them and then spit them back out. It takes some time, but many fish learn not to lunch on “that thing” again.

Being a snail they move quite slowly on the bottom of the ocean. Some of these funky creatures have numerous body projections which are called cerata, which increases the overall body surface as well as enhances breathing.

Most if not all species of nudibranchs live in small, special environments particularly suited to them. They often have a narrow range of diet as well as other physological limitations or needs. Boothe said that many aquariums can't house them because of the highly specialized environments needed.

Do they sting? Yes, they do, depending on the species. Boothe said this feels like a bee sting – not too bad. When she handles them it's rare that she's been stung, but it's happened.

That stinging capability takes on a weird twist with the nudibranch.

“Nudibranchs often feed on prey that most sea creatures deem unpalatable, such as hydroids and sea sponges,” Boothe said. “Some nudibranchs, such as the Opalescent (Hermissenda crassicornis), can recycle the stinging cells (called a nematocyst) of its prey to use in its own defense. The cells are often more concentrated in the nudibranchs, and after handling an Opalescent I am often left with a small itchy rash where the nudibranch stung me.”

One major rule – even state law – is do not remove anything from a tidepool. If you're thinking of nabbing one of these vividly-tinged beasties, there's yet another defense. They'll suddenly lose their color or even form if taken out, which comes from their intensely narrow environmental needs. You'll have no show-and-tell if you do.

Boothe said they're more visible during warmer times of the year, but nudibranchs are indeed always around no matter the season. MORE PHOTOS BELOW

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