Striped mystery revealed

Okay, remember last night's mystery photo?  

Here's another view:

 

Meet Taylor's Sea Hare (Phyllaplysia taylori), a wonderful marine mollusc that lives in local Eelgrass (Zostera marina) beds.

This one washed up along the shoreline of Bodega Harbor, but I moved it to a small pool on the tidal flats:

 

Although this sea hare stands out against the gray/brown background of the mud, they're usually found living on blades of Eelgrass, so the green coloration with black and white stripes is excellent camouflage in its typical habitat.

P.S.  If you're wondering, the flap on the back right side is the opening to the gill cavity.

Hide nor hare

I'm excited to share an update about the identity of last night's mystery object!  Here's a reminder of the object that I wasn't sure about:

 

I had wondered about a bivalve periostracum (the outermost layer)...and also about a snail's operculum (the "trap door"), as had a few other folks.  But I wasn't satisfied with either possibility.

For example, after checking various books, I couldn't find any clam with this shape.  And, although I started looking at snail opercula, and some of them were closer in shape, the material (very thin and flexible), the chalky layer, and an odd twist along one side of the shell, didn't match with any operculum I was familiar with.  Here's a picture of the twist that puzzled me:

 

However, a breakthrough came today via a Twitter exchange!  Annaliese (at Oregon State University) sent out a request for assistance and Rebecca (at the California Academy of Sciences) responded with an identification, including a photo! 

Here's the photo of a dried specimen from the California Academy of Sciences:

 

Compare that with my mystery specimen from Dillon Beach (now dried out, see below):

 

You can see how similar the shape and texture are.

I agree with Rebecca that this is a good match with her sample which is the *internal* shell of a California Sea Hare (Aplysia californica)!  I'll admit that I hadn't known (or had forgotten) that Aplysia had an internal shell, and I've certainly never seen hide nor hare of such a shell.  ;)

I know that this phenomenon might be confusing at first, but there are some snail relatives (like sea hares) that have internal shells that aren't visible from the outside.  Here's a link to a diagram showing the development of a California Sea Hare (see Research study 2).  Note that they have an external shell when very young, but the shell becomes internal in the adults.

Many thanks to Rebecca and Annaliese for solving the mystery!

P.S.  Adult California Sea Hares were observed in Sonoma and Marin counties in 2015 and 2016.  To review what the adults look like, see the posts from 28 September 2016 and 23 May 2015.

Noodles!

Stephanie has been finding these washed up on Dillon Beach.  Do you have a guess about what they are?

 

That's an impressive tangle of "noodles"!

Here's a close-up that might provide some more clues:

 

If you look closely at the individual strands, you'll see small whitish compartments in a regular pattern.  Each of these is a cluster of embryos.  There can be 10s to 100s of embryos per cluster (depending on the size of the female laying the eggs)...and up to ~1 million embryos per string!

Here's another view.  The animal responsible for these will be revealed below the photo: 

 

And the answer is...these are egg strings of a California Sea Hare (Aplysia californica)!

Stephanie also documented a few adults washing up on the beach:

 

The embryos will take a little over 1 week to develop.  Then the free-swimming larvae (veligers) will spend ~1 month in the plankton before undergoing metamorphosis to become tiny sea hares.  

California Sea Hares are uncommon in this region (they're generally a more southern species), so let us know if you spot any and if they're laying eggs.

P.S.  Many thanks to Stephanie for sharing these great photos! 

P.P.S.  For a few other sea hare pictures from Miwok Beach in May 2015, see the post called "Munching at Miwok."

Munching at Miwok

 

Do you recognize this animal?  The picture above is a head-on close-up.

Here's a view from the side (a different individual):

 

Note the two rolled rhinophores (sense organs) sticking up, and the two flap-like oral tentacles extending forward.  The overall coloration is also distinctive — blotches of red, brown, green and gold...and a network of dark lines (reminiscent of the crackle of raku pottery!).

Here's an entire animal viewed from the side:

 

This is a California Sea Hare (Aplysia californica).  We had heard that some had been observed at Miwok Beach (along the Sonoma Coast just north of Bodega Bay), so we stopped there this morning to take a look.

California Sea Hares are rare in northern California.  It's likely their presence here this year is due to the warmer water temperatures during the past year.

Although it's hard to tell from the pictures, they're quite large!  The maximum recorded size is ~75 cm (30 inches) long, and up to 15 lbs (7 kg).  Most are smaller, but still substantial.  The individuals we documented today were ~20-25 cm long.  Here's a picture with my boot for scale (this sea hare had been stranded out of water at low tide, but was just waiting for the tide to return):

 

Why are they called sea hares?  Well, if you return to the first picture of this post, you might be able to see a resemblance between this snail and a hare because of the way the rhinophores look like the tall ears of a hare.  And similar to rabbits, sea hares are herbivores — in this case, grazing on a variety of seaweeds and sometimes seagrass.  Also, although it's probably not related to their name, sea hares move fairly fast relative to other snails.  [If you're wondering, sea hares are gastropods — a group of molluscs that includes snails, limpets, nudibranchs, and sea hares.]

There were at least 50, and perhaps as many as 100 or so, California Sea Hares at Miwok Beach today.  It's not a species we see in this area very often, so if you find them this year, I'd love to hear about it!

 

P.S.  I've heard of reports of California Sea Hares in Tomales Bay this year, but I'm not sure of the exact locations.