Peanuts and friends

  

Eric snapped this great photo of three peanut worms (Phascolosoma agassizii) yesterday in Monterey County.  It's one of the best photos I've seen of Phascolosoma's tentacles.  They use that beautiful ring of tentacles to reach out to find food particles on nearby surfaces.  

The tentacles are hard to photograph, though, because they're not out for very long, and then the peanut worm retracts them into the long trunk-like introvert (in the photo, the introverts have dark pigment bands). 

P.S.  I first wrote about peanut worms back in 2013.  To learn more about them, check out the post called "Introducing the introvert" from 31 January 2013. 

P.P.S.  If you're wondering, the purple rods in the photo are sea urchin spines at the bottom of the tidepool.

Festive

  

Hard to believe another year has gone by.  Here are a few festive invertebrates from our tidepooling last week to help celebrate turning the corner into 2023.  Enjoy!

Above, a beautiful tubeworm, Serpula columbiana.  

Next, an unidentified sabellid worm:

 

 

A wonderful peanut worm, Themiste pyroides:

 

 

And to wrap it up, a colorful nudibranch, Triopha catalinae:

 

 

Best wishes for the new year ahead!

Eating peanuts

  

Here's a fun story.  In Monterey County, I came across an Ida's Mitra snail (Atrimitra idae, formerly Mitra idae).  Although we see their shells occasionally in Bodega Bay, I haven't seen a live snail in the field, so I was excited to find one.

I have read that Ida's Mitra specializes on eating an unusual prey item —  peanut worms (sipunculans).  I've always been curious about how that works, since peanut worms often live deep within rock crevices.  

After photographing this individual, I looked up to see a second Ida's Mitra not too far away.  I took a quick photo and noticed something brown that I wasn't sure about.  I was under the impression that Ida's Mitra's body was primarily white, so I wasn't sure what the brown part might be.  Here's the next photo and then a second even closer image from a slightly different angle:

 

 

 

 

Ahh!  This snail was eating a peanut worm!  That brown object is the posterior end of Phascolosoma agassizii, a common peanut worm in rocky shore areas.

I waited a while to see what would happen and took a couple more photos for the record:

 

 

 

 

I didn't see the position of the peanut worm change very much.  Later I read about two possible feeding strategies in this family of snails — (1) the snail could rasp a hole in the peanut worm's skin and then extend its proboscis into the peanut worm to access the inner tissues, or (2) the snail could swallow the peanut worm whole and digest it once it reached the stomach.  I can't say for sure which was happening here, but my instinct was that the snail was swallowing this peanut worm.

Later I found a different individual under water with its siphon fully extended, apparently searching for prey (it's likely they can detect the scent of a peanut worm in the water).  The siphon is the tubular structure above the head:

 

 

And I also encountered a very pretty juvenile snail:

 

 

 

Although I'm a big fan of peanut worms (see below), it was amazing to see this feeding behavior in the field.

 

 

 

Local diversity

  

Eric noticed a beautiful scene in the low intertidal zone a few days ago.  There are six (!) different phyla (major animal groups) represented in this image, all in an area that was only ~4 cm x 4 cm (or ~1.5" x 1.5").  

Feel free to look around and see what you can find.

In the next image, I've circled or pointed to representatives of each phylum.

 

 

Green arrow = sea anemone (Epiactis handi), Phylum Cnidaria
White circle = barnacle (Chthamalus dalli), Phylum Arthropoda
Blue circles = flatworms (unidentified), Phylum Platyhelminthes
Orange arrow = peanut worm (Themiste pyroides), Phylum Sipuncula
Purple oval = tubeworm tentacles (Phragmatopoma californica), Phylum Annelida
Pink arrow = chiton (Tonicella lokii), Phylum Mollusca

A clean sweep

  

Such a cool view of a peanut worm (Phascolosoma agassizii) collecting food particles off the surface of a sponge.  The peanut worm in the foreground has its tentacles extended and is sweeping them backwards (to the right) as it retracts its trunk-like introvert.

We've seen this behavior so often now that we're wondering if it's mutualistic — e.g., does the sponge benefit from having its outer surface "cleaned" of large particles and does the peanut worm benefit from having a smooth surface from which to collect food?

Red end of the spectrum

There's a lot of red in the intertidal zone, along with pinks and oranges and golds at that end of the color spectrum.  Sometimes it's fun to scan across different species to see the color similarities.  Here's a little tour from a recent outing:

 

 Fish eggs

Aldisa sanguinea (nudibranch)

 

Peanut worm (Themiste sp.) tentacles

Clam siphons

 

 

Veiled Chiton (Placiphorella velata) in hunting position

 

Juvenile Red Sea Urchin (Mesocentrotus franciscanus)

Golden and groovy

 

This weekend we photographed some beautiful peanut worms (sipunculans).  This is Themiste pyroides, a local species that can be found in the low intertidal zone of rocky shores.  They nestle in crevices so they can be hard to see, but when their crown of tentacles is fully extended, they're pretty spectacular.

Eric photographed one individual with mostly golden-colored tentacles (above).  This individual also retracted its tentacles, revealing its introvert with dark hooks (see below; the hooks look like tiny chocolate chips).  (Peanut worms can withdraw their tentacles completely.)  We haven't been able to find any information about how these little hooks might be used in this species.  Do you have any ideas?

 

Then I photographed a different Themiste, this one with purple tips on many of its tentacles.  Here's a close-up:

 

Themiste uses this array of branched tentacles to capture food from the water.  In the next photo (below), look for the grooves in the center of the branches (especially on the right side of the image).  The tentacles are covered in cilia and mucous, and the grooves are probably involved in food gathering, but we haven't been able to locate a detailed description of the feeding behavior.

 

Tickling the tunicates

 

I was working on a backlog of photo organization tonight, so here's an image from August 2019.  The striped peanut worm (Phascolosoma agassizii) has extended its introvert and is searching for food particles with its short tentacles.  The yellowish-green animals are tunicates or sea squirts (Perophora annectens).

Up in arms?

 

Somehow I missed them when I was taking this picture in the field, but when I was reviewing photos, I noticed two peanut worms (Phascolosoma agassizii) extending their introverts up between the arms of this juvenile Ochre Sea Star (Pisaster ochraceus). 

The visible parts of the peanut worms are tubular and grayish with black stripes.  If you'd like to learn more about peanut worms, you can review the post called "Introducing the introvert" on 31 January 2013.

Branching out

 

Close-up of the beautiful tentacles of a local peanut worm (Themiste sp.).  

Here's a view of all of the tentacles:

 

I wrote about a similar peanut worm in 2014, so if you'd like to learn more about them, review the post called "Peanuts with chocolate chips" on 20 July 2014.

P.S.  Also — I have an update about the Bottlenose Dolphins photographed on 5 July 2018.  Bill wrote to say that he had identified one of them — an older female named "Sakura" that's been known to researchers since 1989!  For more information, you can read Bill's comment on that post (see link above).  Thanks, Bill!

Beauty and intrigue

A few miscellaneous images from our trip to Oregon in late May:

 

A purple encrusting bryozoan, Disporella separata

 

Peanut worm, Themiste pyroides, with coralline algae

 

The nudibranch Aeolidia loui (formerly Aeolidia papillosa) 

The beauty and intrigue of coastal marine invertebrates!

The owner of the golden branches

And the answer to last night's mystery close-up is...

 

These are the tentacles of a peanut worm (Themiste sp.)!  The body of the peanut worm is buried below the sediment.  The tentacles are extended for feeding, but they can also be withdrawn when needed (e.g., for protection).

To watch a sequence of a peanut worm pulling in its tentacles, review the post from 20 July 2014.

And in case you were wondering — a sea cucumber's tentacles can look very similar.  But note that the peanut worm's tentacles lack the shiny ossicles of a sea cucumber.  This is especially apparent in the main tentacle branches.  To compare, check the photos in the sea cucumber post from 16 April 2013.

 

Peanuts with chocolate chips

For years I've been trying to photograph this intriguing peanut worm, Themiste pyroides:

 

I've discussed peanut worms on the blog before (see post from 31 January 2013), but I haven't shown this species yet.

Remember that peanut worm tentacles are located at the tip of a long "introvert" that can be withdrawn, or rolled in on itself.  Here's a series of pictures illustrating that process (below).  Watch the tentacles disappear!

 

 

 

 

 

Themiste pyroides has wonderful golden tentacles, a purple "neck", and fascinating hooked brown spines — see close-up below.  You'll laugh, but the shape of the spines reminds us of tiny chocolate chips!

 

Because peanut worms live in crevices, you often only get to see their tentacles.  Look closely for clusters of golden tentacles extending from low intertidal zone crevices along rocky shores, and you may be rewarded with a sighting of Themiste pyroides!

P.S.  In this species, the tentacles are used for suspension feeding — gathering small food particles from the water.

Introducing the introvert

Here's an extreme close-up.  Do you have any guesses about what type of organism this is?

 

This is hard, but it's one of the animals that was in the holdfast post a few nights ago.  Here's another hint:

 

This is a sipunculan, commonly known as a peanut worm.  These pictures show the most frequently encountered species of peanut worm on Bodega Head, Phascolosoma agassizii.  Alhough often hidden, they're common in intertidal mussel beds and can also be found in rock crevices, kelp holdfasts, and among surfgrass roots.

Externally, you can see two main body parts: the trunk, which is the main portion of the body containing most of the organs; and the introvert, which is long and narrow.  The introvert is extensible — it can be much longer than the trunk when fully extended. 

Note that the skin is papillated (bumpy).  And there are rounded spots on the trunk and dark linear pigment bands on the introvert.

 

 

Once the introvert starts to extend, it happens pretty quickly (it's fast enough that it's hard to photograph under a microscope!).

 

 

 

Amazingly, the introvert can be fully retracted into the trunk.  Because this was a very small individual and somewhat transparent, you can actually see the introvert inside of the trunk in the image below.  Look for the dark pigment bands visible under the skin.

 

Although not illustrated in the pictures above, the very tip of the introvert has a tentacular crown (ring of tentacles) used in feeding and gas exchange.  The next photo shows a peanut worm using its tentacles to gather food (detritus) in a tidepool.

 

I often see peanut worms in crevices.  In his book, Invertebrates, Eugene Kozloff says, "They like tight situations into which their bodies fit almost perfectly."

Below is a view of peanut worms in a shallow, water-filled crevice (only their introverts are visible).  How many peanut worms can you find?

 

  

There are three peanut worms in the photo above — two larger individuals and one very small juvenile.  The inset below shows you where the little one is.  (When the introvert is retracted, the average length of local peanut worms is ~2-3 cm.)

 

I don't know if anyone has ever tried, but it seems like the banding patterns on the introverts could be used to identify individual peanut worms (like fluke patterns in Humpback Whales!).