Nudibranchs

You’ve been missing out if you haven’t spent time gazing down into tidepools, patiently scanning them for nudibranchs. Below are a few common nudibranchs I’ve been lucky enough to find and photograph in pools and exposed on rocks on Oregon’s shores. The photos are from the northern Oregon coast unless otherwise noted. My organization follows Lamb and Hanby (2005), and I refer to WoRMS for scientific names, but common names, if I use them, are my choice. The books, field guides, and online resources listed at the bottom of the page cover the nudibranchs shown below and many more.

And now, let’s touch base with a few nudibranch friends.

There are a few similar-looking yellow dorids, and distinguishing between them takes more practice than I have done. So, while recognizing some uncertainty, I think the examples below share more characteristics in common with Doris montereyensis than with any of the alternatives.

Yellow dorid on a rock face, resting on a green sponge while an isopod, probably Idotea, photobombs.
Exposed by low tide near a food source (the sponge, not the isopod!)
Egg ribbon draped on a rock face among several giant green anemones.
Egg ribbon
Yellow dorid exposed on a rock face with a scattering of little brown barnacles, several giant green anemones, and a patch of crustose red.
Exposed in a low intertidal setting


And for a different look, here’s a good-sized yellow dorid (est. 7-8 cm) on an early morning excursion across a sand-filled pool.

Closeup of a yellow dorid (from above) on the sand on the bottom of a clear tidepool.
Trucking across the bottom of a shallow, sand-filled pool
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Diaulula odonoghuei

Beefy little leopards are always a treat, as are their lovely egg ribbon rosettes. You don’t want to be a sponge in their path.

Closeup of a leopard dorid and a sponge the nudibranch has chowed a path through.
It’s safe to say Diaulula odonoghuei eats sponges
Two leopard dorids resting head to head, and their egg ribbons exposed on a rock wall by low tide.
It’s not uncommon to come across head-to-head pairs
A pair of leopard dorids resting head-to-head next to a nearly perfect egg ribbon rosette.
Diaulula odonoghuei and a well-laid rosette
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Acanthodoris nanaimoensis Nanaimo or rufus-tipped dorid

A mottled gray Acanthodoris nanaimoensis oriented head-up on an Alaria blade. Rhinophores up.
Mottled gray Nanaimo on Alaria
Closeup showing body details, color, and pattern.
Red-tipped gills and rhinophores
A light-colored Nanaimo dorid with red-tipped gills and rhinophores, shallow-water trucking over Alaria.
A light-colored version on Alaria
An upside-down Nanaimo dorid riding the surface tension.
Ah, surface tension
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Rostanga pulchra Red sponge dorid

Small and red, they’re easy to miss on the sponges where they spend a lot of time.

Small red nudibranch on a red sponge.
A good place to find Rostanga pulchra is on red sponges
A pair of nudibranchs and three egg coils on a red sponge.
Egg coils, just above a pair of Rostanga pulchra
A pair of nudibranchs and an egg coil blend in on a bed of red sponge.
Blending in
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Doto

I think there’s a good chance the examples shown in this entry are what people call, for now, the orange or hammerhead doto Doto amyra.

Closeup of a solo Doto, probably Doto amyra, the orange or hammerhead doto.
Closeup of a solo Doto, probably Doto amyra, the orange or hammerhead doto.
Closeup of a solo Doto, probably Doto amyra, the orange or hammerhead doto.
Closeup of a solo Doto, probably Doto amyra, the orange or hammerhead doto.


The image below is from my first Doto encounter. Years later, I pretty much hope to never again subject a nudibranch to a petri dish indignity.

Closeup of a solo Doto, probably Doto amyra, the orange or hammerhead doto confined in a petri dish.
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Dirona albolineata White-lined dirona

Medium range view of a single white-lined dirona traversing a red blade (which hosts a collection of tiny snails) in a shallow, sand-filled pool.
Dirona the explorer (perhaps ready for a meal of snails?)
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Antiopella fusca White-and-orange-tipped nudibranch

Closeup on a single Antiopella fusca on a shallowly submerged Alaria blade.
Antiopella fusca on an Alaria blade
Upside-down nudibranch riding surface tension on the surface of a quiet tidepool.
Riding surface tension
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Hermissenda

The beauty in the two panels below is Hermissenda crassicornis. With such a lovely scientific name, a common name is a distraction. On a personal note, it’s the first nudibranch I discovered in a book and the wild.

Close up on a single individual crawling around on some Ahnfeltiopsis in a sand-scoured pool.
Hermissenda crassicornis in a low sand-filled pool (egg ribbon in the upper left-hand corner)
Looking straight down on a single Hermissenda crassicornis through clear water in a shallow pool.
Hermissenda crassicornis making good time over open sand in a low pool


Here’s a different Hermessinda look, one I don’t bump into very often in the northern Oregon tide pools I visit. It resembles what Behrens et al. (2022) call Hermissenda opalescens.

Those cerata tips!
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Coryphella trilineata

Nudibranch in a shallow tidepool
Nudibranch, seemingly dislodged and kind of adrift in the bottom of a shallow sand-filled pool. in a shallow tidepool.
Nudibranch in a shallow tidepool
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Aeolidia

The familiar shag-rug nudibranchs on the northern Oregon coast, Aeolidia papillosa, are part of a geographically wide-ranging complex described in 2016 (click here if you want to dig in). If I understand correctly, the Aeolidia we find in Oregon have been assigned to A. loui, a new species. Behrens et al. (2022) (see references below) give its range from Port Hardy, British Columbia, to Isla de Cedros, Baja California, Mexico. (A hallmark characteristic is warty tubercules on the rhinophores!).

Aeolidia papillosa stretched out over a bed of acorn barnacles in a shallow, still tidepool.
Shag-rug on a barnacle bed
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References

Behrens, D. W., K. Fletcher, A. Hermosillo, and G. C. Jensen. 2022. Nudibranchs and Sea Slugs of the Eastern Pacific. MolaMarine.

Gotshall, D. W. 2005. Guide to Marine Invertebrates, Alaska to Baja California 2nd Edition (Revised). Shoreline Press.

Harbo, R. M. 2011. Whelks to Whales: Coastal Marine Life of the Pacific Northwest. 2nd ed. Harbour Publishing Co.

Kozloff, E. N. 1993. Seashore Life of the Northern Pacific Coast. 3rd ed. University of Washington Press.

Lamb, A. and B. P. Hanby. 2005. Marine Life of the Pacific Northwest. Harbour Publishing.

Sept. J. D. 2019. The New Beachcomber’s Guide to the Pacific Northwest. Harbour Publishing.


Online Resources

Pacific Northwest Shell Club’s Nudibranch page. Accessed March 20, 2025.

Friends of Netarts Bay WEBS Mollusks page. Accessed March 20, 2025.

It’s worth scrolling down to the nudibranchs in Common Sea Life of Southeastern Alaska: A field guide by Aaron Baldwin & Paul Norwood. Accessed March 20, 2025.


Species Accounts

Robbie Wheeling (2002 as edited). Hermissenda crassicornis (Eschscholtz, 1831). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed March 20, 2025.

Cowles, D. (2005). Doris montereyensis (Cooper, 1862). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed March 20, 2025.

Cowles, D. (2007). Acanthodoris nanaimoensis O’Donoghue, 1921. Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed March 20, 2025.

Cowles, D. (2007). Rostanga pulchra MacFarland, 1905. Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed March 20, 2025.

Cowles, D. (2007). Dirona albolineata Mac Farland in Cockerell & Eliot, 1905 (or Eliot, 1905). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed March 20, 2025.

Cowles, D. (2008 as edited). Aeolidia loui Keinberger et al., 2016. Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed January 19, 2023.

Cowles, D. (2018). Hermissenda opalescens (Cooper, 1862). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed March 20, 2025.

Cowles, D. (2019). Diaulula odonoghuei Steinberg 1963. Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed March 20, 2025.


I updated this page on March 20, 2025