The hydroids are lovely

  

Three-lined Nudibranch (Coryphella trilineata) strolling among a forest of Orange Hydroid (Garveia annulata) polyps.  Photographed in the low intertidal zone on 14 July 2022. 

P.S.  I couldn't help hearing the Robert Frost poem when I looked at this photo, but instead of "The woods are lovely, dark and deep..." I heard hydroids instead of woods!

Bodega fireworks

 

How appropriate that we encountered a wonderful hydroid today (4 July 2019) whose tentacles look just like a fireworks display.

 

We hadn't seen the polyps of this species before, so I'll share additional details about it in a future post.

For now, we chose a few images to celebrate the holiday.  If you're curious, these hydroids are small — the individuals pictured were ~15 mm (0.6 inches) long.  We found them in the low rocky intertidal zone.

 

Below is a view showing the entire polyps, from the base attached to the rock to the rounded cluster of capitate tentacles at the top.  Meet Hydrocoryne bodegensis, which was originally described from specimens collected on one of the Bodega Harbor jetties.

 

Happy Fourth of July!

 

Peach-colored polyps

 

A nice look at the feeding polyps (gastrozooids) of a local hydroid, Hydractinia sp.  Photographed in the low intertidal zone on 19 February 2019.

 

Polyps or pancakes?

 

Which would you prefer for breakfast, polyps or pancakes?  :)

This morning (15 June 2018), Hilton's Aeolid (Phidiana hiltoni) chose polyps of the hydroid, Plumularia.

For a little more information about this nudibranch, see "A new home for Hilton's" on 29 November 2015.

 

Hometown hydromedusa

Last week, Eric's summer students were sorting through some plankton samples collected in Bodega Bay and Bodega Harbor.  Rachel spotted something different and took a closer look.  We're glad she did, because it turned out to be an interesting hydromedusa:

 

Meet Hydrocoryne bodegensis!  The scientists who first described this species (John Rees, Cadet Hand, and Claudia Mills) named it after Bodega Bay because they collected colonies from one of the Bodega Harbor jetties.  It's always fun to become familiar with local species that have "bodega" in their names!

This hydroid also has a polyp stage that grows attached to the substrate.  The tiny medusae (their bells are only ~1 mm high) develop among the clubbed tentacles of the polyp and then eventually break away to swim in the water column:

 

Modified from Rees, J.T., C. Hand, and C. Mills.  1976.  The life cycle of Hydrocoryne bodegensis, new species (Coelenterata, Hydrozoa) from California, and a comparison with Hydrocoryne miurensis from Japan.  Wasmann Journal of Biology 34: 108-118.

Although I didn't know it at the time, five years ago I photographed what might be this species, with a medusa just about to swim away:

 

Eric captured a short video of the Hydrocoryne bodegensis medusa, so I'm including a video file below.  While watching, note the following:

- 4 long tentacles, with visible (knobby) clusters of nematocysts

 

- each tentacle ends in a prominent rounded cluster of nematocysts (you can locate the end of each tentacle by looking for these rounded tips) 

 - a red ocelli (eye spot) at the base of each tentacle

- dramatic extension and contraction of the tentacles (this is likely a feeding strategy, e.g., increasing surface area to increase likelihood of prey capture)

Hydrocoryne Sanford 2017 from Jackie Sones on Vimeo.

 And one last view of this beautiful medusa with its tentacles extended:

 

P.S.  Thanks, Rachel, for spotting a seldom-seen hometown medusa!

Along for the ride -- Part 2

It's been an interesting week learning about Pelagic Red Crabs (Pleuroncodes planipes).  It's made me think about how much fun it is to watch and wonder about an animal that you've read about or seen pictures of but have never encountered before.

Pelagic Red Crabs are very rare in northern California.  According to the records we can find, this is only the second time they've made it this far north.  The last time was over 30 years ago (in 1985, following the 1982-1983 El Niño)!

 

On 24 January 2017, we collected some of the live Pelagic Red Crabs that washed up on the beach and put them into an aquarium.

Observation #1 — The crabs didn't float at the surface, but instead settled to the bottom.  They often sat in a "tip-toe" position, elevated off the bottom, raised up on their long legs.  (We learned that even though they're often called Pelagic Red Crabs, much of their life is spent on the bottom.)

Observation #2 — They're excellent swimmers and adopt a very streamlined profile when jetting through the water using "tail-flips."  After swimming to the surface, sometimes they passively drift down through the water column with their legs spread wide (some descriptions liken this to a parachute).

Observation #3 — The crabs use a variety of feeding methods, but they spend a lot of time suspension-feeding, i.e., filtering plankton from the water.  They use small mouthparts to generate a water current (drawing water towards their mouth) and then sweep noticeably setose appendages  through the water (like fine nets) to capture food particles (in photo below, see center appendages with tufts of fine bristles):

 

And then when we put one of the crabs in a bowl of seawater to take a look through the microscope, Eric noticed something else:

Observation #4 — They have "hitchhikers!"

Remember the mystery photo from last night?  (see below)

 

The claws are covered with dense setae (hair-like bristles).  These long bristles increase surface area and slow sinking rates (an adaptation for spending time near the ocean surface and in the water column).  But there was another animal there, too, growing among the setae:

 

 

This is the hydroid Obelia, possibly Obelia dichotoma.  Obelia has a life cycle that includes a sessile stage (a colony of feeding polyps that lives attached to an object) and a free-swimming medusa stage (similar to a jellyfish). 

 

Modified from The Light & Smith Manual (2007)

Eric was recording some video footage of a crab when a little medusa swam by!  The tiny medusa had just been released from one of the hydroid colonies.

So you can see for yourself, here's a collection of video clips showing some of the above.  Watch for (1) sweeping, brush-like mouthparts, (2) large compound eyes, (3) long claw with hydroids growing on it, (4) close-ups of the hydroids, (5) close-up of the setae (long, hair-like bristles), (6) swimming medusa (in the background starting at about 51 seconds).

[If you're receiving this via e-mail and can't see the video clip, click on the title of the post above to go directly to the web page.]

It's fun to think about what it would be like to be a hydroid living on a Pelagic Red Crab and all of the things you'd encounter while drifting along!

Tiny pawns

Well, this has been an interesting week for cnidarians.  Do you remember the golden planulae (larvae) of the hydroid Abietinaria from a few days ago?

 

Eric is teaching a summer class right now, and he kept a few planulae around to show his students.  But when he checked on them today, this is what he saw:

 

Tiny yellow discs attached to the bowl — the planulae had undergone metamorphosis!

Below is an even closer view.  I chose these three individuals because they're in different stages of development.  Can you guess which is youngest and which is oldest?

 

The youngest juvenile is on the far left, the oldest is in the middle (lowest), and the juvenile on the far right (highest) is at an intermediate stage.  You can tell by the number of divisions in the basal disc, and by the development (height) of the stalk growing up from the center of the disc.  

Remember that these juveniles are going to become tall, extensively branched colonies (reminiscent of a fern or a miniature tree).  These are the youngest hydroids we've ever seen.  They would be too small to see in the field, so we just got lucky that they metamorphosed in the lab.  In the next image you can see the central stalk extending upward.

 

Amazingly, when I looked around, I noticed a few juveniles that had the first developing zooids!  It did not appear that these zooids had formed tentacles yet, but two developing zooids are clearly visible attached to either side of the central stalk:

 

These little hydroids have grown very quickly.  It will be interesting to see how the branching pattern proceeds, and when the first feeding tentacles appear.

A fun side note: When I first saw the these juvenile hydroids as in the last photo, one of the first things that came to my mind was that they looked like tiny chess pieces.  And then later I read an article that described a stage similar to this as the "pawn" stage!  

P.S.  To review what an Abietinaria colony looks like when it's older, see the post from 27 June 2016.

Golden -- Part 2

Okay, remember the mystery photo from last night?

 

I received some great guesses about the identity of these small organisms — and I need to congratulate Marni for submitting a correct answer! 

These are indeed planula larvae, in this case from a hydroid called Abietinaria.

Hydroids are colonial cnidarians (related to jellyfish, sea anemones, and corals) with many connected polyps.  Colonies often have a branching structure, and because of this they are often mistaken for plants.

Most of the polyps in the colony are feeding polyps — they can extend a ring of stinging tentacles to capture small animals from the water.  Other polyps are reproductive and produce the gametes that will form the next generation.

In this case, we were fortunate to have collected a female colony.  Within small capsules (gonozooids), there are attached medusoids that produce eggs which are retained and, once fertilized, develop into planula larvae.  When they're ready to disperse, the planula larvae emerge from the gonozooids and swim to a new location to begin another colony.

Here's an expanded view of the gonozooids filled with developing planula larvae:

 

And two more views so you can really see the individual larvae:

 

 

Intriguingly, I might have also found a male colony.  I'm not sure about this, but it's possible the white, flat-topped structures in the photo below contain male medusoids that will release sperm.

 

This picture is also helpful because you can see some of the tiny feeding polyps arranged along the branches.  I've circled a few in the next image, but I'm sure you'll be able to spot others:

 

So there you have it!  Planula larvae are so tiny that you don't often get to see them, so it's fun to be able to share them with you!

P.S.  On 30 January 2014, I showed a fun sequence with a planula larva (from a different hydroid species) emerging from a capsule.  To review those pictures, click here.

How many tiny sails?

I know I just wrote about tiny By-the-wind Sailors (Velella velella) a few days ago.  I have to post about them again because I don't think I've ever seen so many of this size, and it seems worth documenting.

Here's a picture showing a variety of sizes with a ruler for scale.  The Velella on the left is the more typical size that you "expect" to encounter on a beach.

 

Below is the same picture, but it's a close-up of the left side of the ruler:

 

Now you can see the smallest of the Velella, just a couple of millimeters long.  They looked like this for almost the entire length of the beach that we walked, about 3/4 mile.

I know they were probably variable along that stretch of beach.  But if we used this picture just to come up with some sort of estimate — then there were 25 tiny Velella/10 cm or 2.5/cm, and there are 160,934 cm in a mile, so there would have been ~400,000 tiny Velella washed up on a mile-long section of Salmon Creek Beach tonight.  No wonder I kept saying, "Wow" as we walked along next to the receding waves.

 

The best-laid planulae

I have a small side project in which I'm trying (slowly) to learn and document the local hydroids.  I was photographing a common species this week — Eudendrium californicum — because it's noticeably reproductive at this time of year.

These wonderful colonial marine invertebrates are often visible in the low intertidal zone on rocky shores.  They appear plant-like at first, but remember that they're related to sea anemones (and jellyfish and corals).  Those flower-like units have tiny mouths surrounded by stinging tentacles waiting for prey to swim by too closely.

 

The bright orange clusters in the background are reproductive units.  I zoomed in on one cluster to take a picture and my eyes opened wide when I realized that a larva was hatching at that very moment!

In this species, the fertilized eggs are retained in these clusters and they develop into planula larvae that look like small, pink tear-drop shaped worms (but they're not worms!).  The planulae hatch and are free swimming for a short time before settling onto the bottom and undergoing metamorphosis into new hydroid polyps that will continue developing into larger, branched colonies like the one you see in the image above.

It didn't take very long for this planula larva to hatch, so today you (yes, you!) get to see this process in pictures.

 

For orientation, most of the developing embryos are orange.  There's one blob that's more pinkish in color near the center of the image (it's also slightly smaller).  That's the one you're going to watch through this series of pictures.  If you look carefully, you'll see that it's emerging from a clear capsule.  In the picture above, the pink larva is half outside and half inside the capsule.  Okay, here you go:

 

 

 

 

 

Fun, right?  

One more image, pulled back a little, that shows the entire hydroid polyp with a large cluster of developing embryos, and the newly hatched planula larva swimming away.  Good luck, little one!

 

 

An amazing transformation

Earlier in December I wrote about finding the first larvae of an unusual hydroid, Candelabrum fritchmanii, in California.  Well, we have continued to follow some of these larvae in the lab, and I have a few more fun photos to share.

First, here's a nice image showing a newly hatched actinula larva next to an empty egg case (the egg case is clear and partially torn).  I'm guessing the larva had emerged from this case very recently.  (If you look closely, you can see that the egg case is being held from below by a slender clasper tentacle.)

 

Next, two of my best pictures of a young Candelabrum fritchmanii larva.  These images are of the same individual, but they show how extensible the larva is — stretching outward and pulling back in.  This larva is ~1 mm long.

 

 

When the larvae are about a week old, the posterior region elongates and develops an attachment disc at the end.  Here are two different individuals, the first with the attachment disc at the bottom of the photo (a bit blurry), and the second with the disc at the top.

 

 

The next stage in the transformation is dramatic.  Once the larva attaches to the substrate (in this case the substrate is kelp), it basically collapses into a sphere.  During this process of metamorphosis, the long primary larval tentacles are resorbed, so all you see are short stubby tentacles:

 

And then it very quickly becomes a tiny polyp!  Two days after I took the picture above, here is what this polyp looked like:

 

It was amazing to see the process from hatching to a crawling actinula larva with long outstretched tentacles to an attached rounded sphere and then a tiny polyp, all within about a week and a half!

A first for California

If you've been following this blog, you may recall the spectacular hydroid called Candelabrum fritchmanii that I reported last March.

 

To our knowledge, Candelabrum fritchmanii has only been seen twice in California — once in 1950 at Pigeon Point (in San Mateo County) and then on 17 March 2013 when we found it at Salmon Creek Beach.  [The link to the original post is here if you haven't read it yet.  I also described the fascinating feeding behavior of Candelabrum here.]

The 1950 specimen wasn't reproductive.  The 2013 specimen was, but it never produced any larvae.

We've been very interested in learning more about Candelabrum, so this winter we were determined to search for more specimens.  Yesterday, on 8 December 2013, Eric discovered two more colonies in Bull Kelp (Nereocystis luetkeana) holdfasts!

And they were releasing larvae!  As far as we know, these are the very first Candelabrum fritchmanii larvae ever recorded in California.  These images were taken under a microscope.  The larva (called an actinula) was ~1 mm long.

 

Note the two types of tentacles.  Both types have capitate, or rounded tips.  The primary tentacles are very long and are found throughout the body, while the secondary tentacles are much shorter and are clustered at one end of the body (they just look like little bumps).

 

Some of the larvae were just beginning to emerge from the capsules where they developed.  You could see a few of the tentacles extending outward, while the rest of the larva was still inside.

 

 

We're very excited to have found Candelabrum again and to have a chance to study this little-known species.

P.S.  Some of you know that I often hear songs at somewhat random moments.  When I saw these larvae emerging from their capsules, I heard Diana Ross singing, "I'm Coming Out."  Some of the lyrics are a perfect match:

The time has come for me

to break out of the shell

I have to shout

that I'm coming out

I'm coming out

I want the world to know

Got to let it show

I'm coming out

I want the world to know

I got to let it show

I've got to show the world

All that I want to be

And all my abilities

There's so much more to me