Untangling the diversity of ribbon worms

  

Such a nice mosaic of local ribbon worms!  [You can click on the image for a sharper version.]

Eric and Maddy (partnering with Christina and Svetlana) worked on a project documenting and discovering the diversity of nemerteans, commonly known as ribbon worms, in Bodega Bay.  Their results were recently published in ZooKeys and a story about their findings is now available in Bay Nature magazine.

For the Bay Nature article, click here.

For the ZooKeys article (scientific publication, with pdf version available), click here. 

Remarkably, their research found 11 ribbon worm species that are new to science!  Nice work, everyone, on documenting this understudied group and opening our eyes to the diversity around us.

In action

Back in February, Eric found this wonderful ribbon worm, Micrura verrilli.  The nemertean was ~12 cm long and observed among sea squirts in the low intertidal zone.  The best part is, he captured some video footage and edited it into a clip that we're excited to share. 

First, here are two still photos:

 

I don't know why this species has such a colorful orange tip at the anterior end.  Do you have any ideas?

 

And now for the video.  It's always fun watching a nemertean in action.  [If you can't see the video player in your e-mail, click on the title of the post above to go to the NHBH web site.]

 P.S.  Thanks, Eric, for sharing this great footage!

P.P.S.  Hello to nemertean fans, Maddy and Serena and Amelia!  ;)

Tales from Poseidon

This past summer, Maddy worked on a project at the marine lab to document as many local species of ribbon worms (nemerteans) as she could find in the Bodega Bay area.  Gabriel, Alisha, and Sarah helped with the search and scooped up a few bags of sediments from the shallow subtidal zone off Doran Beach.  Within those sediments was a very interesting nemertean that we had not seen before. 

Below is a photo of the whole ribbon worm.  When contracted, the worm had a stout and short body, only about 12 mm long: 

 

 

At the pointy tip of its head, it has two conspicuous eyespots (called ocelli). They're tiny, so look closely.  [They're easier to see in the video clip below.]

 

Compared to most other ribbon worms, one of the most unusual aspects of this worm is its habit of drawing the tip of its head back into its body, which forms a “collar” of tissue that surrounds the retracted head:

 

Like other ribbon worms that belong to this taxonomic order (called hoplonemerteans) the proboscis that snares its prey was armed with a sharp stylet that helps in prey capture.  In the photo below you can see the central stylet that fits into a holder (called a basis), which looks a bit like the handle of a screwdriver:

 

Remarkably, if a nemertean’s stylet is lost or damaged, it is replaced with a new one that is moved into the holder!  In the photo above, you can see two accessory pouches (one on the left and one on the right), each holding 3 new stylets.

When we looked through the taxonomic guides, all of these characteristics seemed to be a good match for Poseidonemertes collaris.  This species was first described from specimens collected in intertidal sandy mud in Bodega Harbor in the early 1980s (Roe and Wickham 1984).

Some nemertean species are difficult to identify from their appearances, so as part of Maddy’s project, she sent small tissue samples off to Oregon for DNA sampling.   When the DNA sequences and analyses came back this week, our colleague Svetlana had a surprise for us.  Although this ribbon worm is closely related to Poseidonemertes collaris, the DNA sequences are distinct enough that this is likely a new, previously undescribed species of Poseidonemertes!

Eric was able to capture some video of this fascinating ribbon worm.  In the video, you will see the worm crawling.  Then (at about 35 seconds) watch for close-ups showing the characteristic behavior of the animal quickly retracting the tip of its head.  [If you're reading this in an e-mail and you can't see the video below, click on the title of this post to go to the web page to watch it.]

You might be wondering how this unusual ribbon worm got the name Poseidonemertes? Although we assume the name is associated with Poseidon, we have been unable to find more details regarding how this group of nemerteans came to be associated with the Greek god of the sea and earthquakes.

Many thanks to Maddy, Gabriel, Alisha, Sarah, Eric, and Svetlana for finding and documenting this fascinating worm.

Reference:  Roe, P. and D.E. Wickham. 1984.  Poseidonemertes collaris, n. sp. (Nemertea: Amphiporidae) from California, with notes on its biology.  Proceedings of the Biological Society of Washington 97: 60-70.

Orange through and through

 

Eric spotted this interesting ribbon worm, or nemertean, on two different days in the field during the last couple of months.  We hadn't noticed this species before, so we took a few photographs for the record.  The individual above is from Bodega Head.

Here's another example from a tidepool on the Big Sur coast:

 

We had trouble identifying this ribbon worm, so Eric reached out to Svetlana Maslakova at the Oregon Institute of Marine Biology.  She identified it as Cephalothrix sp. (possibly in the cryptic species complex Cephalothrix "simula").

Eric filmed the individual from Bodega Head, so we've included a short video clip below.  [If you're reading this via e-mail and don't see the video player, click on the title of the blog post above to see the video on the website.]

It's always fun to add a new species to the Bodega Head marine invertebrate list.

P.S.  Many thanks to Svetlana for sharing her ribbon worm expertise!

A close call

After finishing our surveys this morning, we walked past a few boulders with large aggregations of Sand Castle Worms (Phragmatopoma californica).  (For a sense of scale, the mounds were ~5 feet across.)

 

When we looked more closely, Eric noticed some Purple Ribbon Worms (Paranemertes peregrina) hunting among the worm tubes:

 

 

We could see the ribbon worms extending into the openings of the tubes (they're active predators), but we didn't know if the ribbon worms were interested in the Sand Castle Worms themselves or other animals that might be living among the tubes?  We suspected the latter, but we weren't certain, so we kept watching for a few minutes:

 

And then we saw this:

 

This ribbon worm had just everted its proboscis in an attempt to capture the small polychaete worm that had emerged from a tube.  (The smaller worm is not a Sand Castle Worm, but a different species that was justing hanging out in a tube.)  The ribbon worm's proboscis is stored internally, but when contact is made with potential prey, it's everted dramatically and used like a lasso.  There's a stylet (a short spine) at the tip of the proboscis.  The ribbon worm can injure the prey with the stylet and also release a neurotoxin to paralyze it.  After that it swallows the prey whole!  In this case, the little worm evaded the lasso and escaped unharmed.

I'm glad we stopped to appreciate the Sand Castle Worm tubes.  It was fascinating to watch these ribbon worms hunting!

A fine line

 

 

It's hard for me to resist posting pictures of ribbon worms.  This is a close-up of a Six-lined Ribbon Worm (Tubulanus sexlineatus).  Here's the entire animal:

 

Photographed in the low intertidal zone on 16 June 2018.

P.S.  For more photos of this species, check out the post called "All lined up" on 20 March 2015.

 

Orange you glad?

About 5 years ago, I posted some photos of this distinctive nemertean, so some of you might remember Verrill's Ribbon Worm (Micrura verrilli).  We've only encountered this species a few times, so we were happy to see it again.

Today (4 May 2018) Eric noticed it inside a Giant Kelp (Macrocystis pyrifera) holdfast washed up on the beach.  I only had time to take a quick snapshot, but I thought it would be a worthwhile record to document.

For the older post and a little more information (and some nice photos), see "A colorful tip" from 16 March 2013.

S-t-r-e-t-c-h-i-n-g o-u-t

 

So the other day, I was watching this beautiful Six-lined Ribbon Worm (Tubulanus sexlineatus).  It was gliding over a patch of orange sea squirts.  

Along with being curious about what the ribbon worm was up to, I started wondering how long it was.  So I scanned left:

 

And then I scanned to the left some more:

 

And then I scanned to the left some more, and realized that I was looking at a very long ribbon worm.  This might be hard, but can you find additional lengths of the ribbon worm behind the main section?  [You can click on the image below for a slightly larger version.]

 

Given the scale of the photo, I know this is challenging.  Here are some arrows to help you (the rightmost arrow is the head and the leftmost arrow is the last part of the ribbon worm that I could find):

 

And here's a close-up of the lower left corner of the photo to make it easier to spot the left-hand sections of the ribbon worm:

 

 

I estimated that the portions of this Six-lined Ribbon Worm that I could see, from the head to where I could no longer follow it, added up to a length of ~50 cm (~20 inches).  It turns out that this species of nemertean is described as being ~20 cm long, but it can stretch to lengths of over 1 meter!

And since you stayed with me, below is a bonus shot — just enjoying the patterning of the ribbon worm against a colorful backdrop:

 

P.S.  If you're interested, there are some wonderful microscope images of this species in the post called "All lined up" on 20 March 2015.

 

Red ribbon

 

That's a tail-end view (above).

Here's a little bit more (the red animal weaving diagonally across the photo below):

 

And the next picture shows the entire animal (contracted):

 

Although I've shown a few different nemerteans (ribbon worms) on the blog, these are my first pictures of a beautiful species called Cerebratulus montgomeryi.  The impressive length, the rich red color, and the white tip on the head (to the right) are helpful field marks.  (This individual was photographed in the low intertidal zone on Bodega Head on 7 July 2016.)

P.S.  For views of other local nemerteans, see Tubulanus sexlineatus, Micrura verrilli, and Micrura wilsoni.

P.P.S.  Hi, Serena!

Blue ribbon

Okay, do you remember the mystery photos from last night?

 

Some of you might have noticed in the Comments section that Matt won the prize — he guessed correctly that these patches are dense concentrations of pelagic barnacle cyprids.  Recall that cyprids are the final larval stage that settles out of the plankton.  In this case, these are the cyprids of a pelagic gooseneck barnacle called Lepas sp. 

Here's a close-up of the cyprids under a microscope:

 

After settling on a floating substrate, the cyprids will undergo metamorphosis into juvenile barnacles.  A few of them had already done so:

 

I wanted to post these pictures on the blog because there have been amazing numbers of Lepas cyprids this year — more than any other year since I've been observing floating objects washing ashore in Bodega Bay.  I've wondered if it could be related to the warm water temperatures last year, but we can't be certain.

What's perhaps even more fun, though, is that when I went to take these documentary pictures, I noticed a few other things among the cyprids!

 

At first I thought this was just a blue tentacle (perhaps from Velella)...but then it started moving...and then I noticed the eye spots at the anterior (front) end.  A tiny blue ribbon worm!  I'd never seen a blue ribbon worm before.

One time the ribbon worm left one patch of cyprids and crossed the great divide to another patch of cyprids.  If anyone has thoughts about the identity of this ribbon worm, I'd love to hear more.

 

When I was scanning the cyprids, I also noticed quite a few small light brown spots.  If you look very carefully, you'll see them in the lower left corner of the next photo, nestled among the cyprids:

 

When I zoomed in, I could see that these brown spots were moving, that they had dark eyespots, and that they might have some sort of paired structures forming on their heads (see small bumps in image below).

 

Although I'm uncertain, my best guess for these little brown blobs is that they could be very young pelagic nudibranchs (Fiona pinnata).  I've written about Fiona before (see post on 19 October 2012), but I've never seen one this small, hence my uncertainty.  What do you think?  Do you have a different guess?

The Sea Palm and Lepas cyprids reminded us of a valuable lesson — it's always worth taking a closer look!

All lined up

Some of you already know how much I like nemerteans, or ribbon worms.  We've been hoping to find this species for a while so we could introduce it on the blog.  It's relatively uncommon though, so you don't see it as often as you'd like.

 

Six-lined Ribbon Worms (Tubulanus sexlineatus) live in transparent tubes under rocks and among algae and mussels.  This one was photographed out of its tube for the sake of highlighting its wonderful patterning.

In the picture above, that's the head on the left side.  There's one narrow white band near the leading edge, and then at least four thicker white bands after that.  Following these first five bands, the white bands become much closer together (see images below).

The "six lines" for which this species are named are the very narrow white stripes running down the length of the body from the head to the tip.  Several are visible on the dorsal (upper) surface, and a few are on the ventral (lower) surface.

When stretched out, this ribbon worm is quite long — I estimated about 30 cm.  (Some individuals may reach 1 meter or more!)  When looking at the center of the ribbon worm, at first I had trouble identifying the upper and lower surface.  I could see a difference — one had white speckles and the other was more uniformly brown (see next picture), but I wasn't sure which was which. 

 

I had to go back to the head and trace the upper and lower surfaces, and finally figured out that the upper surface is the speckled one.  Now you can identify both in the next two pictures, even as the ribbon worm is twisting:

 

 

Many books and images on the Internet show the head and middle portion of Six-lined Ribbon Worms, but I've hardly seen any pictures of the posterior end.  Here's a picture of the all white tip!

I'm including one more picture of this beautiful ribbon worm (although it would be easy to show many more!).  It's fun to think about the color patterning of this species.  Why does it have so many stripes and bands?  Does it help blend in with light and shadow?  Is it distracting to potential predators?  Is it disruptive coloration (breaking up the outline of the animal to confuse predators)?  Do you have other ideas?

 

A ribbon worm in your cap!

 

Thanks to Carol, we finally got to see a pilidium!  This is the larval stage of a nemertean, or ribbon worm.  It was in a plankton sample collected about 1 kilometer off Bodega Head.

Here's a view of the basic anatomy: 

 

 Modified from A Guide to Marine Coastal Plankton and Marine Invertebrate Larvae (Second Edition) by Smith and Johnson (1996)

Amazingly, the juvenile ribbon worm develops inside this larva that looks like a little hat.  Pilidium comes from the word pileos for "felt cap."

The pilidium is a very graceful swimmer and it also has a fascinating feeding behavior.  It uses both long cilia and flexing movements of its lobes (the "ear flaps") to direct water currents and food particles towards its mouth.  Here's a picture of the cilia along the edges of the lobes.

 

Once the juvenile ribbon worm is ready, it breaks out of the episphere, consumes the larval body, and crawls away.  In this case, we got lucky, because the development of the swimming stage was nearly complete.

One day after we looked at it, we noticed that the "cap" looked smaller.  And the next day, the juvenile ribbon worm had emerged!

Below are pictures of the tiny ribbon worm.  The first image shows the entire ribbon worm not long after metamorphosis.  The second image includes a ruler for scale (with millimeter marks).

 

 

Can you believe how small it is?

Eric was fortunate to capture a few moments in the life of this pilidium and juvenile ribbon worm on film:

Nemertean pilidium from Jackie Sones on Vimeo.

We're not sure which species of ribbon worm this is. In fact, most pilidium larvae haven't been matched to their ribbon worm adults!  But note that this juvenile ribbon worm has a caudal cirrus, the narrow extension at the tail end.  Not all ribbon worms have caudal cirri, but the two ribbon worms I've shown on the blog do — Micrura verrilli and Micrura wilsoni. 

Coming to you from Westfield, MA

 

This is an interesting nemertean, or ribbon worm, that Eric found in a kelp holdfast a couple of weeks ago.  When fully extended, it was ~8 cm long.

The first features we noticed were the chocolate brown coloration, the cream-colored rings, and the bright white borders to the head.  

When viewed from the side, we were impressed with this ribbon worm's extremely long cephalic grooves (see below) — look for the slit or furrow along the lower edge.

 

At the posterior end there was a long appendage called a caudal cirrus (next picture).

 

After looking at all of these features and checking The Light and Smith Manual (2007), we were pretty sure this was Micrura wilsoni.  We looked for photographs online to confirm, but unfortunately couldn't find any pictures.  Eventually we located a copy of Wesley Coe's Nemerteans of the West and Northwest Coasts of North America (1905) with its wonderful set of color plates.

And there was Micrura wilsoni on Plate 3! 

 

Modified from Coe, W.R. (1905). Nemerteans of the West and Northwest Coasts of North America.  Bulletin of the Museum of Comparative Zoology 47: 1-319.

If you look closely at the drawing above, you can see a red spot at the back edge of the head.  We wondered what that was, so we read the species description.  Coe and the illustrator were highlighting the rosy-colored brain of Micrura wilsoni!  Could we see the brain in this individual?  Sure enough, in the right light, a reddish glow was visible (see below).

 

A few more fun things about Micrura wilsoni —

Sometimes it would contract and look somewhat like a leech:

 

Other times it would move via peristalsis — a series of wave-like muscle contractions: 

 

We wondered who Micrura wilsoni was named after.  Surprisingly, there's a connection to western Massachusetts!  Coe says: 

"The species is named in honor of Prof. C. B. Wilson, of Westfield, Mass., well known for his work on Nemertean development, to whom I am indebted for several specimens of this and of other Nemerteans, and for valuable notes on a number of the species described in this paper."

P.S.  Last March, we found a different species of Micrura in a kelp holdfast.  Click here for pictures of Micrura verrilli.