Blondie

  

During a field trip to Tomales Bay on 17 August 2023, Melissa spotted this small yellowish-green sea hare crawling on some eelgrass (Zostera marina).  At first I wasn't sure about the identity of this sea hare, but after looking more closely I believe it's a Hedgpeth's Sea Hare (Elysia hedgpethi).  (Those small bright blue spots helped with the i.d.)

I've mostly encountered this species on rocky shores where they are a deep green color (see "Not a flatworm!" on 25 June 2013 and "Magic cape" on 17 August 2022).  So the paler "blonde" color was confusing until I read that this species can be yellowish or brownish, too.  Is the color driven by what they are eating?  Or related to the condition of the chloroplasts they ingest?

Eric was able to get a few nice video clips, too, so check out the video below.  Watch for the rolled rhinophores, the two dark eye spots behind the rhinophores, the wide flaps held upright on either side of the body, and the scattered blue spots.  [If you can't see the video player in your e-mail, click on the title of the post above to watch the video on the NHBH website.]

Many thanks to Melissa for spotting this sea hare and to Eric for putting together the video!

Magic cape

  

I love seeing this sea hare, especially up close, when you can see the bright blue-green spots (and tiny orange dots, too, if you look carefully).  Meet Hedgpeth's Sea Hare (Elysia hedgpethi)!  [I posted about this species a few years ago — see "Not a flatworm!" on 26 June 2013.]

Last week, my first view of this individual was very different.  Under water, they are transformed into the beautiful sea hare in the first photo. But out of water, they look like a flattened green/black blob on the rock:

 

 

I was curious about finding the sea hare on the rock wall.  In the past I've found them near their food, e.g., a green seaweed called Bryopsis corticulans.  So I started scanning and soon located a clump of Bryopsis:

 

 

 

I kept searching and eventually found even more Bryopsis (below).  And this time there were a couple of patches that looked suspicious.  Can you spot the sea hares in the photo below?

 

 

 

Yes!  There's a large individual on the lower left side, and a smaller individual on the lower right side.  They look so much like the Bryopsis! But you can see that they're a little smoother and shinier.  Here's a closer view of the larger individual:

 

 

Their wonderful green lateral flaps with scattered spots always makes me think of a magic cape!

 

 

 

Photographed in Monterey County on 13 August 2022.

Olive's at the coast

  

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!

 

 

P.S.  With many thanks to Zoe for spotting such a cool little slug! 

 

P.P.S.  Thanks to Jeff for assistance with this identification.

 

P.P.P.S.  For an example of a different species of sap-sucking sea slug, see the post called "One cell at a time" on 23 September 2017.

Rolled red rhinophores

  

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!

Out on the flats

Last September I posted about an interesting "sap-sucking sea slug" called Aplysiopsis enteromorphae.  The photographs accompanying that post were taken in the lab, but recently I encountered this species in the field, so here's a picture from the Bodega Harbor tidal flats:

 

This sea slug was ~20 mm long.  To learn more about this local species, check out the post called "One cell at a time" from 23 September 2017. 

P.S.  Related to last night's post, there are a couple of very small phoronids in the photo above (bottom center and top right).  I didn't notice them when I was trying to photograph Aplysiopsis traveling across the sand.  But when I was reviewing the photos, I saw these tiny phoronids emerging from the sand.  Fun!

One cell at at time

Several days ago, Peter was showing me some algae that he had collected on the tidal flats in Bodega Harbor.  When he picked it up, a small nudibranch-like animal was left behind in the tray.  I was intrigued because it didn't look familiar to me.  

When we looked at the animal under the scope, we realized that it wasn't a nudibranch, but a sacoglossan — a group that is sometimes known as "sap-sucking sea slugs."  From the name, perhaps you can guess that sacoglossans eat algae.

Here's one of the first views we had.  Note the small, black eyes and the large, rolled rhinophores above the eyes:

 

There are many projections called cerata on the back — cylindrical, greenish, with scattered gray flecks and white tips:

 

On the underside, you can see a smooth muscular foot with irregular black splotches (creating a marbled pattern):

 

Meet Aplysiopsis enteromorphae!

While we watched, the most striking thing about this species was its feeding behavior.

Aplysiopsis enteromorphae is known to feed on only a few species of seaweeds.  (This individual was feeding on Chaetomorpha.)  The feeding behavior was described originally by Gonor (1961).  The slug grasps the algal filament with the front of its foot and a pair of oral lobes (see diagram below).  It slices open an algal cell with a single row of teeth on its radula, sucks out the contents, and then repeats this process along the filament.  After the filament passes by the mouth, it's easy to see the now-empty algal cells! 

 

Modified from Gonor, J.J.  1961.  Observations on the biology of Hermaeina smithi, a sacoglossan opisthobranch from the West Coast of North America.  Veliger 4: 85-98.

 This is exactly what we saw:

 

Here's an even closer view.  Look for the solid green algal strand in front of the mouth (at the bottom of the photo), and the nearly-clear algal strand after it leaves the mouth and passes along the foot.  The eaten portion of the strand is a little hard to see because it's almost transparent, but there are a few green cells left:

 

We were curious about whether you could see the slits in the algal cells.  We couldn't with our eyes alone, so we put a strand under a compound microscope (200x magnification), and voilà!  Below, the arrows are pointing to two of the slits:

 

Eric was able to capture a few seconds of feeding behavior on video.  Watch carefully as the slug moves along the single strand of Chaetomorpha — grasping, slitting, and sucking out the contents.

Aplysiopsis enteromorphae from Jackie Sones on Vimeo.

Not a flatworm!

When the low tides are this good, it's sometimes hard to stop looking.  On 23 June, I checked one more site and noticed something unusual.  It was relatively small (~2 cm long), oval, with an undulating edge, and a handsome dark green color.  The shape made me think of a flatworm, but I hadn't seen a local flatworm that color before.

I took a picture and then zoomed in to see more detail.  This is where digital cameras come in handy!  Here's what I saw in the field:

 

The distinct head and tentacles (rolled rhinophores) told me this wasn't a flatworm but rather a gastropod or sea slug.  I knew I hadn't seen this species yet, but I had a guess about what it could be.  I'd been wanting to see one for years!

I brought it into the lab for a few microscope pictures for documentation.  Here's one of the first photographs under magnification:

 

This is a Hedgpeth's Sea Hare (Elysia hedgpethi).  Note the beautiful blue spots scattered across the lateral flaps on either side of the body.  There were tiny orange spots, too, but they're harder to see because of their smaller size.

Hedgpeth's Sea Hares are known to feed on two species of green algae: Codium fragile and Bryopsis corticulans.  The sea hare is able to retain the algal chloroplasts which continue to photosynthesize for at least 10 days after they've been ingested!

Although this individual was quite active under the microscope, I managed a few more pictures:

 

 

I wish I had more time to write about Joel Hedgpeth, for whom this sea hare was named.  I'll have to do that another night.  For now, if you'd like to read more about him, I think you can still access a short NY Times obituary here.  And there's a much more complete article in the Journal of Crustacean Biology here.  Among many (many!) other things, Joel was a marine biologist, a local Santa Rosa resident, editor of Between Pacific Tides, and well known for protesting the PG&E attempt to build a nuclear power plant on Bodega Head.

 

Joel also wrote an Introduction to Seashore Life of the San Francisco Bay Region and the Coast of Northern California.  I laughed when I read this passage about Hedgpeth's Sea Hare in that book: "...at first glance may be confused with a large flatworm, but the rolled structure of the head tentacles clearly separates it from flatworms..."  As mentioned in the very beginning of this post, this was my experience exactly!