Naked in the tidepools

January 17, 2013

Arguably the most colorful critters in the Bay Area are the ones you’re likely to overlook.

That’s because nudibranchs, affectionately called “nudis,” dwell in tidal pools along the coast. Unless you stick your nose down close, you’re liable to miss them. But that would be a shame. Just take a look at these guys/girls (they’re hermaphrodites). Aren’t they about the best bit of eye candy you can hope for in nature?

And they’re pretty amazing to boot. Nudibranchs (Latin for ‘naked gills’) are soft-bodied gastropods that are in the same phylum as mollusks, only they’ve evolved to disgard their shells shortly after the larval stage and then wander essentially naked. But nudibranchs have found other defense mechanisms — they either hide in plain sight by mimicking their surroundings, or they show off colors as a sign of poison.

There are some 3,000 species worldwide and they’re very versatile, inhabiting every ocean, including the waters around Antarctica and to depths greater than 2,000 feet. As carnivores, they slowly ply their habitat with their two highly sensitive tentacles, called rhinophores, and feed on algae, sponges, anemones, corals, barnacles and even other nudis. Some of their prey is poisonous, but no matter for the nudi- it stores the poison or anemone stingers in its own body and gives it to an unsuspecting predator if it gets eaten.

Some nudis can even take in plant cells and reuse the photosynthesis-creating chloroplasts to make food for themselves. It’s no wonders nudis have taken over the world.

With seasonally low tides, now’s the time to put on your galoshes and head out to one of the Bay Area’s great tidepooling spots and observe our local nudibranchs.

And in the meantime, enjoy the images that nature photographer Matt Knoth snapped of nudibranchs at the Fitzgerald Marine Reserve and Pillar Point near Half Moon Bay. For more images of Knoth’s work, check out his Flickr page.



About the Author

Alison Hawkes was a Bay Nature editor from 2011-2017. Before Bay Nature she worked in journalism for more than a decade as a former newspaper reporter turned radio producer turned web editor with each rendition bringing her closer to her dream of covering environmental issues. She co-founded Way Out West, a site dedicated to covering Bay Area environmental news.