The masses

Back in September, while doing a shorebird survey in Bodega Harbor, a couple of different egg masses on the tidal flats caught my eye.

They attracted my attention not only because they were so noticeable, but also because I have been doing shorebird surveys in the same area for over 10 years now and I didn't recall seeing these egg masses before.

One was bright yellow and wrapped around algae or seagrass:

 

The other was bright white, shaped like a corkscrew, and embedded in the sand:

 

I finally tracked down the snail making the yellow egg masses.  It was a bubble snail, Haminoea vesicula.  Here are two images to help you visualize how the yellow egg masses consist of rows of developing embryos:

 

 

I showed examples of adult bubble snails on 4 June 2015, so check out those pictures here.

I kept meaning to return to find out which species had produced the white corkscrew egg masses, but hadn't found the time.  Today Jeff helped me out — he identified the distinctive egg masses as belonging to Rictaxis punctocaelatus.

Below are two close-ups of these spiraled egg masses: 

 

 

I haven't seen adult Rictaxis yet (it's been on my wish list!), but if you'd like to see examples of these wonderful local gastropods, check out pictures here.

Inhaling bubbles

Here's a close-up mystery photo (below).  Can you guess what type of animal this is?

 

It might be tricky unless you're familiar with it.

Here's the entire animal:

 

Meet Navanax inermis.  Although it looks very similar to a nudibranch, Navanax is in a related but different group (Order Cephalaspidea, Family Aglajidae) that includes headshield slugs and bubble snails.

I didn't get a great picture of it, but animals in this group have a well-developed cephalic shield — note the broad head on the left end — that aids in plowing through the sand.  Most have shells, but the shells may be reduced and internal, which makes them hard to see on live animals.  And many have wing-like parapodia that can be folded up over their backs.

Grace spotted Navanax in Bodega Harbor on 4 June 2015.  I'm glad she mentioned that she had found something interesting, because this is an unusual record for this area.  Bodega Harbor is the northern range limit for this species.  In fact, many books still describe the range limit as either Monterey or Bolinas.  But there are local Navanax records from the 1970s (see The Natural Resources of Bodega Harbor by Standing et al., 1975) and Bodega Harbor is also listed as the northern limit in The Light & Smith Manual (2007).

Navanax is known to be a voracious predator.  They eat bubble snails and nudibranchs.

Grace has noticed that one of the bubble snails (Haminoea vesicula) is common in Bodega Harbor right now.  If you haven't seen a bubble snail, here are two quick photos (the second shows the bubble-like shell for which the group is named).

 

 

If you want to see something really impressive, watch Jeff's video of Navanax inhaling a bubble snail.

I don't know how many Navanax are in Bodega Harbor right now.  If you see any, I'd love to hear about it!