Close-up of the gill plume of the nudibranch sometimes known as a Sea Lemon (Peltodoris nobilis). Note the extensive branching to increase surface area for respiration.
Evidence suggests that nudibranchs evolved from gastropod ancestors that
lost their coiled shell and original internal gills. Dorid nudibranchs
like this one secondarily evolved an external gill plume for
respiration.
A ribbon of rose-colored embryos!
We were working on a few tasks in the rocky intertidal zone last night (28 January 2025) when Eric came across a Hopkins' Rose Nudibranch (Ceratodoris rosacea) that had recently laid a beautiful string of embryos.
Although we could have missed them in the past, we can't recall finding the embryos of this primarily southern species in Northern California before, so it was an interesting observation for us.
Here's a quick shot of the nudibranch with both its prey (the pink bryozoan, Integripelta bilabiata) and the ribbon of embryos:
A beautiful nudibranch for you -- Colorful Dirona (Dirona picta) photographed by Eric a few days ago. I love the green and blue highlights! [You can click on the image for a larger version.]
P.S. I'm not sure about the meaning of the name Dirona? I read that the first part of the word might refer to the Welsh sêr , or "star," hence the name of this post (but more naming research would be needed!).
Camouflage week continues!
You might recall that back on 14 July 2024, I introduced this amazing nudibranch, Corambe pacifica. I also mentioned that I needed to get a better photo. Well, here you go! And, lucky us...Eric was also able to record some beautiful video clips.
Things to look for:
- how well the color and patterning of the nudibranch match the bryozoan in the background
- two rhinophores (sense organs) near the leading edge (viewed from above, they look like a pair of white spots)
- a small notch along the back edge of the nudibranch
- when viewed up close, sometimes you can catch a glimpse of the branched gills inside the notch (more about the gills in a future post!)
Here's the video clip (below). [If you can't see the video player in the e-mail message, just click on the title of the post above to go directly to the NHBH web page.]
Stay tuned for more about Corambe pacifica.
And thanks to Eric for the great video!
I've heard of several observations in Sonoma County this summer, but this is the first Hopkins' Rose nudibranch (Ceratodoris rosacea) I've seen this year. Thanks so much to Chris for spotting it!
This is a species that can appear in Northern California during and after El Niño events, so it's possible we're seeing a somewhat lagged response to warmer water conditions during the past year.
Back in late June, someone kindly alerted me to the presence of some Onchidoris bilamellata over at Doran Beach. I swung by and took a few quick photos. I still need to go back to see if I might be able to get some better pictures, but I thought I'd share this one for now.
Onchidoris is unusual among nudibranchs in that it feeds on barnacles (!). The mottled brown-and-white nudibranch is in the top center of the photo. In the bottom right you can also see a nice chiton (note the shell plates) next to the barnacles.
I wrote about Onchidoris ~8 years ago, so for some more photos and a little more info, check out the post called "The barnacle-eaters" on 24 June 2014.
Three-lined Nudibranch (Coryphella trilineata) strolling among a forest of Orange Hydroid (Garveia annulata) polyps. Photographed in the low intertidal zone on 14 July 2022.
P.S. I couldn't help hearing the Robert Frost poem when I looked at this photo, but instead of "The woods are lovely, dark and deep..." I heard hydroids instead of woods!
A little surprising, but Abby observed this Hopkins' Rose nudibranch (Okenia rosacea) near Dillon Beach on 16 July 2022. The last time this species appeared in this area was during the marine heatwaves of 2014-2016. With seawater temperatures so cold this year, I wouldn't have had this nudibranch on my radar, but so it goes! If you come across this species this year, I'd love to hear about any additional sightings.
And here's another nice nudibranch sighting: Eric spotted this gorgeous Diamondback Tritonia (Tritonia festiva) this past weekend:
Eric's class was conducting a nudibranch survey recently, and thanks to Zoe's sharp eyes we were introduced to an interesting sea slug — meet Olive's Sapsucker (Hermaea oliviae)! This is the first time we've encountered this species.
It's easy to understand why this sea slug isn't seen that often. They're tiny — this one was only ~5 mm long. And they look a lot like the algae they eat — in this case, Polysiphonia (perhaps Polysiphonia hendryi).
Sacoglossan slugs look similar to nudibranchs, but note the rolled (rather than rounded) rhinophores (the sensory structures that look like tentacles in front of the eyes).
Here's the entire animal (below). It was fun to see them cruising around!
We often see Shag-Rug Nudibranchs (Aeolidia loui) eating Aggregating Sea Anemones (Anthopleura elegantissima), but I haven't observed them eating Brooding Sea Anemones (Epiactis prolifera) as often.
Below is an even closer view. Epiactis broods its young around the base of the column, so those little dots of various sizes are juvenile sea anemones. This view made me wonder if the nudibranch eats the young anemones?
Opalescent Nudibranch (Hermissenda opalescens), photographed in a tidepool on 28 March 2022
Whew! We're finishing up field work soon, but after a quick lunch along San Diego Bay today we found a large piece of Giant Kelp (Macrocystis pyrifera) washed up along the shoreline and noticed a couple of nice invertebrates on the drift kelp:
The "disappearing" nudibranch Corambe sp. on a bryozoan colony (Membranipora sp.). Look closely to spot the circular shape of the nudibranch. They're incredibly well camouflaged, with white lines and brown splotches to match the bryozoan (which is the nudibranch's prey).
I've written about Corambe before, so for more info check out the post called "Ay, Corambe!" from 20 September 2013 and "A story with a point" from 17 August 2014. The latter post has a link to Eric's excellent Corambe video — worth watching!
A wonderful close-up of Aplysiopsis enteromorphae, a sap-sucking sea slug found locally in Bodega Bay last week. I wrote about this species several years ago, so to learn more about them you can check out the post called "One cell at a time" from 23 September 2017.
P.S. The rhinophores are sense organs — in this species they are rolled into a tube (they're the prominent tentacle-like structures extending out in front of the eyes), and in this individual they are a striking reddish color.
P.P.S. Thanks to Jacquie for spotting this well-camouflaged sea slug!
