A sea slug to start your day

 

 

Quick shot of a Wine-plume Dorid nudibranch (Acanthodoris nanaimoensis), photographed on 5 July 2023.

Holiday lights?

  

Cockerell's Dorid (Limacia cockerelli), a beautiful nudibranch photographed by Eric on 25 November 2022.  I've shown this species on the blog before, but this is a much better photo!  Thanks, Eric!

Looking like a sponge

While doing a little tidepooling this morning, I came across several nudibranch egg ribbons attached to the rock:

 

When you find egg ribbons, the nudibranch that laid them is often still in the area, so I started scanning to see if I could locate the species that produced these eggs.

I was looking around, noticing coralline algae, sea squirts, sponges, and not finding any nudibranchs, but then I paused.  Something looked a little different here:

 

Aha!  Two nudibranchs!  They were so transparent and blended in so well with the general background community that I hadn't seen them at first.

Zooming in for a closer look, I realized this isn't a species that we see very often.  Meet Chan's Dorid (Hallaxa chani):

 

Eric got the best picture (above), where you can see the translucent coloration, bumpy dorsal surface, rhinophores (sensory appendages at the front end) with subtle reddish-brown tips, and an unusual gill plume (that to my eye looks like a little pom-pom). 

Hallaxa chani feeds exclusively on the sponge Halisarca.  It has a more northern distribution, and it's apparently relatively rare at the southern end of its range.

Here are a couple more pictures for the record:

 

 

A few tips

Once again, Eric's sharp eyes spotted an interesting nudibranch.  This is the first time we've seen this species in the Bodega Bay area.

 

Before we got a close-up view, we could see the tiny black spots, which made it look like the nudibranch had been sprinkled with black pepper.  This individual was ~10 mm long with its foot extended.

Although the northern range limit of Black-tipped Spiny Dorids (Acanthodoris rhodoceras) is Cape Arago in Oregon, it appears that this species is uncommon north of San Francisco.

Here's a closer view of the tall rhinophores (sensory organs) and the black-tipped papillae:

 

Eric captured some very nice video of this wonderful nudibranch.  Here are a few "tips" regarding what to watch for: (1) close-ups of those fabulous black-tipped papillae, (2) the heart beating where there's brown coloration in the center of the nudibranch, and (3) the circle of gill plumes near the back end.  [Click on the title of the video below the viewer to see a higher resolution version.]

spiny_black-tipped_dorid_sanford from Jackie Sones on Vimeo.

Orange peel

We had a few minutes after finishing some field work at Pinnacle Gulch, so we looked around in the intertidal zone.  A bright orange animal caught my eye:

 

A closer view revealed just how orange this nudibranch was!

 

In the picture above, you can also see relatively long papillae (or projections) that make the nudibranch look fuzzy, white flecks scattered across the surface, dark tips to the rhinophores (the sensory organs), and a hint of the white gill plumes — all important characteristics of an Orange-peel Dorid (Acanthodoris lutea).

The orange color is important to the nudibranch.  It's an example of aposematic coloration, or "warning" coloration — a signal to potential predators that the nudibranch is unpalatable or toxic.

Here's one more image, this time from above.   The water was flowing by at the time, so the rhinophores are leaning to the left.  This shot includes a better view of the extended white gill plumes.

 

Although they're known to occur from Cape Arago, Oregon to northern Baja California, Orange-peel Dorids appear to be uncommon in the Bodega Bay area.  This is the first time we've encountered this species locally.