Horseshoes washing ashore

  

A nectophore from Hippopodius on Salmon Creek Beach.  Although this photo is from late December 2024, we saw quite a few of these nectophores on the beach tonight (21 February 2025).

For more information about these structures, check out earlier posts:

"Hippos" on the beach from 16 April 2015

Little hippos on the sand from 21 February 2021

P.S.  My eyebrows always go up when there's an exact match between today's date and a previous date with the same topic, e.g., today's post on 21 February 2025 and the earlier post on 21 February 2021.

Happy hula-days!

  

This is a record shot -- i.e., not a great photo, but one that's important for documentation.  

We went for a short walk at Salmon Creek Beach this afternoon and recorded quite a few gelatinous species, including 5 species of siphonophores (!), a ctenophore, a pteropod, and a salp.

I'll share some more photos and information soon, but for now I just wanted to highlight this intriguing Hula Skirt Siphonophore (Physophora hydrostatica).

I wrote about this species almost 10 years ago, so for a better explanation and some additional photos and illustrations, check out the post called "A Hula Skirt!" on 7 May 2015.

On the windward side

  

While in Hawai'i, we walked some east-facing beaches to look for pelagic invertebrates washed ashore.

Above, a small Portuguese Man O' War (Physalia physalis) on Kaua'i on 4 April 2024.

Below, a Purple Sea Snail (Janthina umbilicata).  (Interestingly, the Janthina we found on Kaua'i were quite a bit smaller than the Janthina we observed in California back in March.)

 

 

 

One of the beaches where these species were found:

 

 

 

Cloudy with a chance of sailors

  

Eric and I did a quick beach survey at the end of the day today as the storm was letting up.  There were thousands of By-the-wind Sailors (Velella velella) washed up.  Some were up to ~3-4 cm long, but the vast majority were under 1 cm long and the most abundant size was only ~1-2 mm long (second photo below with millimeter ruler):

 

 

 

 

We also found one Purple Sea Snail (Janthina umbilicata), hundreds of swimming bells of the siphonophore Diphyes dispar, one pyrosome (I thought there might be more today), and pieces of driftwood with pelagic barnacles (Lepas sp.).

 

The view as rain showers were clearing:

 

 

 

Indicator?

  

I took these photos about a week ago, but wanted to share them since this is a species often associated with warmer water conditions.  

This is the nectophore (swimming bell) of Diphyes dispar, a siphonophore.  We recorded >50 individuals on Salmon Creek Beach on 1 January 2024.

The last time we observed this species was during the 2014-2016 marine heatwaves.  Recent water temperatures have been warmer than average for this time of year, hovering ~13-14°C (56-57°F), perhaps connected to this winter's El Niño.

Here's another photo with a ruler for scale:

 

 

I introduced Diphyes back in 2014, so for information about them, check out the post called "From the south" on 26 October 2014. 

Storm strandings -- Part 2

Okay, last night I mentioned there were quite a few different types of gelatinous zooplankton washed up on the beach.  Although these "gelatinous bits" can all seem similar at first, the closer you look, the easier it is to tell the different species apart.  It's often helpful to compare side-by-side photos, so here's a parade of plankton for the record:

 

 

Pyrosome (Pyrosoma atlanticum) — see "Fire bodies" from 8 December 2014

 

 

 

 

A salp, possibly Iasis zonaria — see "Wide mouth and ribbon-like muscles" from 29 March 2013

 

 

The swimming bell of a siphonophore, Chelophyes appendiculata — see "Swimming bells" from 3 April 2013

 

 

Part of a heteropod, Carinaria japonica — see "Carinaria -- Part 2" from 7 December 2014

 

 

 

The pseudoconch (false shell) of the pteropod Corolla spectabilis — see "Gelatinous thimble" from 11 August 2012

 

 

Hard to tell at first, but this is a different pteropod, Cliopsis krohni — see "Angel on the sand" from 13 March 2013

This last species can be tricky to identify.  It really does just look like a round blob on the sand.  But note the darker line running through the middle (that's the digestive tract) -- it's a hint that this is more than just a piece of a jellyfish.  These pteropods are delicate (used to being submerged in offshore waters), so they get beat up when they are tumbled in the surf zone and deposited on the sand.  But if you put them in a little bit of water, sometimes their heads (with tentacles) are revealed, as are their "wings" — the foot of a mollusc modified into swimming appendages.  Here's a short video clip so you can see the wings in action.  [If you can't see the video player in the e-mail, click here to see the video.]

Cast ashore

Spring winds pushed some gelatinous animals on shore yesterday.  Here are some examples, shown in order from the animals we encountered most frequently to those that were less common during a walk on Salmon Creek Beach on 19 March 2021:

 

 

Giant Bell Jelly (Scrippsia pacifica)

 

 

 

By-the-wind Sailor (Velella velella) — most of these were small, only ~5-6 mm long

 

 

 

 

Nectophore of the siphonophore, Hippopodius hippopus

 

 

 

 

Comb jelly, or sea gooseberry (Pleurobrachia bachei)

 

 

 

 

Moon jelly (Aurelia sp.)

 

Little horseshoes on the sand

  

Yesterday (20 February 2021) when Eric and I walked on Salmon Creek Beach, we found lots of these horseshoe-shaped gelatinous structures.  There were a variety of sizes and some variations in the details of the shape, but we think it's likely they all belong to the same species.  Here are several views with a ruler for scale:

 

 

 

 

 

 

 

 

Some of you might recall that we found something similar several years ago (in 2015 and 2016).  We think these are the nectophores of a siphonophore called Hippopodius hippopus.  This primarily southern species is not common in Bodega Bay, but yesterday we found over 50 of these nectophores on the beach in about one hour of walking. 

 

If you're not familiar with siphonophores, don't worry.  These planktonic colonial invertebrates are usually found offshore in the open ocean, so they are unfamiliar to most people.  And siphonophores are fragile, so if they wash up on the beach, they're usually found in pieces.  The entire colony looks quite different.  

 

To help you envision what the colony looks like, Eric cleaned up this older illustration of Hippopodius hippopus (see below).  The parts we found on the beach (the nectophores) are arranged adjacent to each other at the top.  The trailing sections of the colony below the nectophores include units for feeding, reproduction, and defense.

 

 

 

Modified from Haeckel, E. 1888. Report on the Siphonophorae collected by H.M.S. Challenger during the years 1873–1876. In: Report of the Scientific Results of the Voyage of H.M.S. Challenger, Zoology, 28: 1–380. https://doi.org/10.5962/bhl.title.6513

 

For more explanations and a little more information about Hippopodius hippopus, you can review the post from 16 April 2015.

 

P.S.  I'm interested in other observations of this species, so if you're out walking the beach and see one of these little "horseshoes," take a photo and send it to me! 

 

P.P.S.  I'm posting this as is, but after comparing the 2021 photos with the 2015 photos, I'm not feeling 100% certain about the identification.  I'm going to look into it further and will update this post if I find that this is a different species.

 

Local jellies

A few nights ago, I promised to show a few more examples of the gelatinous animals that might wash ashore on local beaches at this time of year.  So...here you go!

Two jellyfish:

 

Pacific Sea Nettle (Chrysaora fuscescens) — note the golden brown color (beware, sea nettles can cause painful stings)

 

Moon Jelly (Aurelia sp.) — note the pale purple color

Now, two different hydromedusae:

 

Giant Bell Jelly (Scrippsia pacifica) — note the red eye spots

 

Aglauropsis aeora — note the faint pink and blue coloration

And the swimming bell of a siphonophore:

 

Probably Praya sp. — note that in this species the "jelly" material retains its form, and overall this swimming bell has a shape somewhat like a large tooth, i.e., squared off at one end and with two pointed tips at the opposite end.

P.S.  I think I've written a little bit about all of these species before, so if you'd like to learn more about them, scroll to the bottom of the NHBH web page and use the "Search This blog" function.

"Spiky Yoda"

While walking Salmon Creek Beach on two days earlier this month (2 April and 6 April 2016), we looked down to see a few of these distinctive gelatinous bits on the sand:

 

Although they looked somewhat similar to the nectophore (swimming bell) of a siphonophore that we found last year (see post about Hippopodius on 16 April 2015), they were also quite different in that they had prominent points (especially out to the sides) and abundant little "spines," making them look very spiky.

For scale, here's a photo with Eric's finger.  This nectophore was ~15 mm across.

 

To fully appreciate the gelatinous spines, here's a view under the microscope:

 

Meet Vogtia spinosa!  This is the first time we've found this species washed up on the beach.  Usually they live offshore and at depth (often 300-500 meters below the surface).

Unfortunately, I've had trouble finding pictures or diagrams of the entire animal.  I've read that Vogtia is arranged similarly to Hippopodius, so check out the diagram on my previous post to start visualizing what Vogtia might look like.  To clarify, what we found on the beach is a single nectophore — when the animal is whole, there might be up to 16 nectophores positioned next to each other along a central stem.   

I can't resist showing one more picture.  Below is the Vogtia nectophore on Eric's thumb.  For some reason, it's shape reminded me of Yoda, so before I identified this siphonophore to species, I casually called it the "Spiky Yoda" nectophore.  What do you think?  Do you see Yoda, too?  ;)

 

A Hula Skirt!

We were walking Salmon Creek Beach on 26 April 2015, and Eric said, "What is this?"  When Eric asks that question, I know it's going to be something interesting.  I bent over to look at what he had noticed washed up in the wrack line, and I couldn't believe it.  I'd been wanting to see one, but I didn't think the chances were very good in northern California.  I had seen pictures of it online and in books.  It's a very distinctive animal, and easy to identify once you know what to look for — I was just surprised to see one!  I also warned him right away to be careful, as its sting can be very potent — it's related to a Portuguese Man O' War.

Here's what he found:

 

This is Physophora hydrostatica, sometimes called a "Hula Skirt Siphonophore."  It was in rough shape after being washed up on the beach, but most of its parts were still visible.

In the photo above, you probably noticed the pneumatophore, or float, with the dark red pigment patch.  And the wonderful tentacle-like palpons — pink and orange in color with white tips.  The palpons had become detached, but I arranged them so you could visualize their position.  Normally there are many more palpons in a full whirl — hanging like a skirt, which gives this siphonophore its informal common name.

 

Modified from A Synopsis of the Siphonophora (Totton 1965)

The pneumatophore helps with buoyancy.  The palpons are defensive (beware of powerful stings!).  The nectophores are swimming bells — they were missing on this specimen, probably dislodged in the surf.  Gonophores are reproductive structures, whereas gastrozooids are involved with feeding.  The tentacles support smaller tentilla with capsules that contain cnidobands (see below).

Here's what one of the palpons looked like on the beach:

 

And below are two pictures of the siphonophore in a small bowl of water — showing all of the various parts and a close-up of the separated palpons.

 

 

Because this is the first time we've seen this species here, I also took a few pictures under the microscope for documentation.  In the first image (below), you can see the gonophores (the grape-like clusters), and above them is the area where the palpons would have been attached.

 

The next image is a close-up of the tentilla with tightly coiled cnidobands — they contain cnidocytes that will fire nematocysts to capture prey.

 

As far as I can tell, Physophora hydrostatica is uncommon in northern California.  And it usually occurs in deep water — 700-1,000 meters — so finding it near the surface or on the beach is probably unusual.

I found one useful video of Physophora swimming.  It's very helpful to watch the swimming behavior and to see the nectophores (swimming bells) in action! 

P.S.  Many thanks to Phil Pugh for helping to evaluate Physophora hydrostatica distribution and abundance in central and northern California.

P.P.S.  Aloha to our Hawaiian friends who also enjoy beautiful cnidarians!

 

"Hippos" on the beach!

During the past month, Eric and I have been finding these very distinctive gelatinous animals on the beach.  By distinctive I mean they had a definite shape: horseshoe-shaped, rounded at one end and coming to two points at the other end.  There's a little more to it than that, but I'll let you see for yourself:

 

We've only found a few of them, but all of them were this exact shape.  The pictures I'm showing tonight are of the most recent one found on 10 April 2015.  We estimate it was about 20-22 mm across.

Below is another angle, showing the points at one end — they almost look like small "horns."  If you look very closely, you'll also see another important characteristic — four raised knobs in an arc at the rounded end (it's easier to see them in the first picture).

 

We hadn't seen this animal before, so at first we just started calling them "horseshoes."  We'd be walking along the beach, and when the sun glinted off one and we were close enough to see the shape, one of us would say, "Oh, there's another horseshoe!"  They were very different than a nondescript blob on the beach.

Well, you know me...it wasn't enough to call something so distinctive a "horseshoe" and not know what it was.  My best guess was that it was part of a siphonophore, so I started looking up possibilities.  I was struggling, so I gave in and requested help from Phil Pugh in the U.K.  Phil was very generous and responded with an identification of this siphonophore:

Hippopodius hippopus!

What a great name!  Here's an illustration of the nectophore or swimming bell of Hippopodius, along with one of my pictures to match the same orientation:

 

From A Synopsis of the Siphonophora by A.K. Totton (1965)

 

I mentioned that this is one nectophore, i.e., it's just one part of the whole colonial siphonophore.  Hippopodius has many nectophores that fit together tightly around a long central stem (see below).  The nectophores are used for swimming while the stem supports structures used for feeding and defense (e.g., stinging cells) and reproduction.

 

Modified from Jacobs, W.  1937.  Beobachtungen über das Schweben der Siphonophoren.  Z. vergl. Physiol. 24: 583-601; and Totton (1965), see above.

There are a couple of really fun facts that I can't help sharing:

- The name Hippopodius means "horseshoe"!  It's very appropriate.

- Hippopodius is a warm-water species.  It's rare to find them in northern California.

- Hippopodius is known for being bioluminescent — I think even the lone nectophores would light up in response to stimulation.  If we find another one, we'll have to look for it.

P.S.  For introductory information about siphonophores, review the posts from 23 January 2012 and 3 April 2013. 

P.P.S.  Since Hippopodius is somewhat long, we started calling it "Hippo" for short, leading to the title of this post.

Beach finds

Longer story, but we haven't been able to walk the beach lately.  But we went for a quick walk on Salmon Creek Beach after work tonight.  There were some interesting invertebrates washed up, perhaps due to the large waves during the storms this weekend?

I only took a few photos for the record.  I'll show three different animals.  Do you want to guess what they are?  I showed all three on the blog last year, so if you've been reading for a while, you might have seen them before.  If you're new to the blog, you'll be at a disadvantage, but you can still play along.  Don't worry if they're unfamiliar — these are pelagic animals not often seen onshore!

There were hundreds of Animal A:

 

Around 50 of Animal B:

 

And only a few of Animal C:

 

And the answers are:

Animal A = the swimming bell of a siphonophore, Diphyes dispar

Animal B = a small pyrosome ("fire body"), probably Pyrosoma atlanticum

Animal C = a salp, possibly Salpa fusiformis 

 

I mentioned that I posted about all of these animals in 2014.  If you'd like to review those entries (or read them for the first time), here are the links:

• From the south on 26 October 2014 (siphonophore)

• "Fire bodies" on 8 December 2014 (pyrosome)

• March Madness on 31 March 2014 (salp)

Note that some of these animals may be associated with warmer ocean water.  The water temperature is still an astounding 14.5°C (58°F) — unusually warm for this time of year.