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Tuesday, May 24, 2016

Swirls on the rocks

Do you have any guesses about the identity of these white swirls?  This photograph is from the rocky intertidal zone on Bodega Head.  The mystery mass was attached to the rock.



After spotting these white swirls, I looked around and found the animal responsible for creating them:



The mystery object above is an egg mass laid by a Shag-Rug Nudibranch (Aeolidia papillosa).  There are three nudibranchs (sea slugs) in the photograph (two on the left and one on the right). 

With their tentacle-like cerata, Shag-Rug Nudibranchs can look very similar to their sea anemone prey.  Here's a different individual photographed in Mendocino County in 2008:


3 comments:

Hollis Bewley said...

The cute little shaggies remind me of mops! :-) It took me a while to realize that they take on the color of their anemone prey: white, tan, pink, brown, etc Your beautiful little guy doesn't show a little green tint if he's been munching on that bad boy on the right or is the anemone just picking up a greenish shade from the light? Or is the green from algae he doesn't absorb? Or does he snack on just the tentacles?

Jackie Sones said...

Good questions, Hollis! I don't know for sure that the nudibranch in the last picture had been eating those greenish anemones. (It could have eaten some others nearby.) But I'm glad that you brought up the fact that the color of the nudibranchs can be related to the color of their prey. Now other people can look for this relationhip if they see Shag-Rug Nudibranchs in tidepools!

John W. Wall said...

Awesome nudibrach -- and egg mass to boot! I was out at Palomarin Beach this morning and wished I still had my 25-year-old self's eyesight. Who knows what marvels I strolled right by.