Holiday picnic at the beach?

  

A nice Baird's Sandpiper (Calidris bairdii) at Point Reyes this afternoon (2 September 2024).

The sandpiper was feeding along the wrack line, especially near clumps of eelgrass (Zostera marina):

 

 

Often it was possible to see prey trying to escape its grasp.  Below, look for the fly and a probable amphipod (beach hopper) in the air just to the left of the sandpiper:

 

 

 

When you least expect it

  

Okay, so this is a story about some photos that didn't quite work out.  And a follow-up when I was surprised when the same species showed up in a couple of other photos and I hadn't even realized they were there!

I was trying to photograph this small amphipod (Thorlaksonius sp., formerly Pleustes sp.) resting on algae.  They have an unusual shape — rounded at one and and pointed at the other — which makes them look like snails.  (Indeed, it's thought that this amphipod has evolved to mimic snails to avoid attention from visual predators like fish.)

I wasn't having much luck with the first one (above), but then I found another so tried again.  Still not a great photo as I was only able to photograph it from above:

 

 

I was frustrated and gave up, and didn't notice any other amphipods like this that night.  But later when I was reviewing my other photos, I noticed two more amphipods that I hadn't seen in the field.  I had been so focused on the other animals I was trying to photograph that I completely missed the amphipods.

Here's one while I was trying to photograph a Ten-tentacled Sea Anemone (Halcampa decemtentaculata):

 

 

Yes, that's an amphipod near the bottom of the photo in the center — this one was pink with white stripes.

Later I was trying to photograph a sculpin.  Can you find the amphipod in the photo below?

 

Yes, that's it, sitting on the back of the fish.  It's small, with red, white, and pink stripes, and it's resting on the wide pale stripe in the middle of the fish.

Hmmpph!  I'll have to keep my eye out for them the next time we're at this site.  And I learned a lot about the variable color patterns of this amphipod species, even if I missed them in the field.

Tattler views

  

I spent some time watching a Wandering Tattler (Tringa incana) near Salt Point today (22 May 2022).

 

 

 

The tattler seemed very interested in amphipods (small crustaceans) in shallow pools.  In the photo below, there's an amphipod at the tip of the tattler's bill (even more visible in the shadow):

 

 

 

 

One time the tattler was feeding near the edge of the water when a larger wave surged up on to the rock.  I just happened to have my camera ready and snapped a photo before it flew up higher on the shore: 

 

 

 

Watch out for sneaker waves!

Beach denizens

  

Eric and I made a quick trip out to the outer beach on Point Reyes yesterday (5 June 2021).  A few fun beach invertebrate highlights included this Red-backed Jumping Spider (Phidippus johnsoni) hanging out in a large piece of driftwood (above), a nice look at some Western Tiger Beetles (Cicindela oregona) along the upper beach near a freshwater seep :

 

 

 

Noticeably abundant amphipods, or beach hoppers, feeding on drift algae washed up along the strand line:

 

 

 

 

And a Pictured Rove Beetle (Thinopinus pictus) feeding on the aforementioned amphipods (!):

 

 

 

Expert craftsmanship

I was sitting in my office, the phone rang, and I heard Eric say, "You have to come see this."  So off I went to where Eric was looking through a microscope.  This was my first view:

 

Huh?  What is going on?  I knew these animals had been collected from an intertidal area with surfgrass, but they looked like caddisflies from streams! 

Maddy had spotted these tiny crustaceans walking around in the most beautiful, perfectly cylindrical tubes.  For scale, this tube was only ~5 mm long and ~1 mm in diameter. 

Below are two more views.  You can see the wonderful antennae, bright orange with clear tips.  I eventually figured out that these are tube-dwelling amphipods. 

 

 

The amphipods would sometimes start to emerge from the tube, revealing a little more of their elongated bodies, but they never left the tubes completely.  The amphipods could reverse direction and emerge from the opposite end of their tube, and Eric noticed that they could attach the tube to an object (like a seagrass blade) with a strand of silk.

 

I was fascinated by the expertly crafted tubes.  What were they made of?  (Could it be material from surfgrass roots?)  How did the amphipods make the tubes?  The stripes on the tubes seemed so regular that it didn't seem like they were unprocessed bits of debris stuck together, but could they have been "woven" by the amphipod?  And what happens when the amphipods need to molt to grow?  How do males and females mate?  

Here's a close-up of one of the tubes:

 

It's been a little bit of a windy road trying to identify which species of amphipod this is.  Spending some time with the Light & Smith Manual, I wondered if they could be a species of Cerapus.  However, I found a newer document online that makes it seem like there has been some taxonomic confusion in this group and they now might be considered an undescribed species of Notopoma.  I'll need to consult with some experts, and we are eager to figure out more about the identity and biology of these amphipods, so stay tuned.  

All these years looking at intertidal marine invertebrates, and I had no idea there were these amazing little tube-dwelling amphipods wandering around in surfgrass beds.  I suppose that shouldn't be surprising, but it's so awesome when you realize that there's an endless amount to discover in our own backyards!

This amphipod is brought to you thanks to Maddy's sharp eyes and to Eric's skill with the microscope camera.  I'm so thankful to have been introduced to such a cool critter!

Among the sponges

Eric recently collected some calcareous sponges (Leucilla nuttingi) in the low intertidal zone for his Invertebrate Biology course.  In the past, we had noticed some isopods living inside these tiny vase-like sponges (see post called "Sponge surprise!" from 12 January 2012).  But last week in class, two students with sharp eyes (Maddy and Michael) noticed some other interesting animals living in association with these sponges:

 

Meet the amphipod Podocerus spongicolus!  This tiny amphipod is only 3-4 mm long.  Notice its very long 2^nd antennae.  The amphipods cling tightly to the outer wall of the sponge with the pointy tips (dactyls) of their thoracic appendages.  In the photo below, you can also see the shiny calcareous skeletal elements (spicules) shining through the body wall of the sponge:

 

This amphipod can be distinguished from other Podocerus species by the fact that article 4 (A4) of the male gnathopod (feeding appendage) is extended forward (see arrow in left figure below).   The photo on the right shows this same feature in the live amphipod:

 

As its name indicates, Podocerus spongicolus is known to be associated with sponges. Otherwise, it appears that little is known about this species.  We have only been able to find a few museum records of this amphipod (from the 1930s and 1960s). 

 

It is interesting to think about its life among the sponges.  Many thanks to Maddy and Michael for spotting these amphipods, Collin for identifying them, and Eric for taking the photographs! 

Just like sand

 

I've encountered these amphipods a few times now and they're just magical!  It's amazing how much they look like sand.  

Not only because of the individual color patterns, with flecks to match the local sand grains, but also because they form dense aggregations and when nestled together they look just like a patch of sand.  

This is especially true when they're resting on a rock or a piece of seaweed — it's like "group camouflage"!  The background substrate disappears and you think you're seeing sand instead. Pretty impressive.

Here's an example (this time with a bryozoan in the background):

 

I'll be working on their identification, but for now it's fun to appreciate their remarkable color patterns.  If you have any ideas about which species this is, I'm very curious.

Beach hopper blues

 

A beautiful blue-eyed beach hopper (a type of amphipod) at the entrance to its burrow on a sandy beach in Chatham, MA, on 27 September 2018.

Surface-dipping

 

On the way back from the post office today, I noticed this young Bonaparte's Gull (Chroicocephalus philadelphia) feeding along the shoreline near Gaffney Point in Bodega Harbor.  

While walking or swimming, the gull searched and then dipped its bill below the surface to pick up small prey items.  Here's another view of it actively searching for prey:

 

There were about a dozen Red Phalaropes in the same area, also surface-dipping for small food items:

 

All of the birds were so busy feeding that I became curious about what type of prey they were after.  I walked down to the water's edge and scanned for a clue.  There were hundreds of small crustaceans swimming just below the surface!  I picked up a nearby clam shell and scooped up one of the mystery animals to see what it was:

 

I think both the Bonaparte's Gull and the Red Phalaropes were actively feeding on small amphipods.  [There are two amphipods in the photo above; perhaps a male holding a female?]

The afternoon light was nice, providing wonderful views, so here are two more pictures of the Bonaparte's Gull:

 

 

Although the amphipods were small (most were less than 1 cm long), they must have been worth the effort!

 

Sneak peek

Well, I've run out of time tonight, but since I mentioned it last night, I'll give you a "sneak peek."  (This animal was ~3-3.5 cm long.)

 

I'll explain more later, but in the meantime, you can puzzle over this amphipod with its pretty pink polka dots and its peculiar eyes!

:)

 

Like crystal

I took a short walk on Salmon Creek Beach yesterday, and was intrigued to see this animal left behind after a wave retreated:

 

It looked so delicate...like crystal...and then it moved slightly and I realized it was alive!

Do you recognize this animal?  (Hint: I have shown this species on the blog before, but it was several years ago.)

Here's a close-up:

 

And one more view after it shifted so that it was on its back:

 

This is Phronima sedenteria, a pelagic amphipod.  I found two of them yesterday — this one was without a home, while the other was still living inside a salp.

For an introduction (or a review) about this fascinating amphipod, check out the "Otherworldly" post from 8 April 2012.

P.S.  This was one of two interesting amphipods I encountered yesterday...stay tuned for #2!

   

Serena's wish

This morning Serena submitted a comment on last night's "Fire bodies" post saying that she had seen pyrosomes in the Channel Islands this summer.  At the time, she also observed a small crustacean living inside the pyrosomes.  I replied that I, too, had noticed a small crustacean inside a few of the pyrosomes washed up on Salmon Creek Beach yesterday.  Serena wrote back that she'd like to see a picture of one...so...here it is!

 

I don't know if this is the same animal that Serena saw, but it does have very large eyes, a feature that she remembered. 

At first I thought this might be an isopod because it looked fairly flattened from top-to-bottom.  However, with more attention, and some research, I'm now thinking this is probably an amphipod.  Although amphipods are often flattened side-to-side, some of the hyperiid amphipods can have a more rounded appearance. 

I didn't have a lot of time, but I also found one reference that listed a few known associates of pyrosomes which mentioned hyperiid amphipods.

For now I'll call it an amphipod, but I'd be very interested in feedback from anyone with more experience.

 

And now for some more imaginative thoughts: 

What is it like for an amphipod to live inside of a pyrosome?  When I saw one, it was positioned such that it appeared to have a view looking out at the world through the transparent tunic of the pyrosome.  It must be quite something to be drifting along inside of a long, jet-propelled cylinder.  Do they see other animals swimming by?  Can they move to different places within the pyrosome, e.g., from side to side or front to back?  What is it like for the amphipod when the pyrosome starts to bioluminesce?  Pyrosome bioluminescence can be triggered by motion.  Can the movement of an amphipod start a bioluminescent wave?

Above I mentioned that Serena remembered the amphipod's large eyes.  While observing them, I tried to come up with a name for their color.  I'll let you look, and then I'll tell you what I came up with below.

 

You're going to laugh at me, but eventually I decided on "marsala"— the 2015 Pantone Color of the Year!

What?  You hadn't heard about the color of the year yet?  Well then, you'll have to check it out here at the Pantone web site and see if you think it's a match for this amphipod's trendy eye color.

Questions

You know that question — if you were on a deserted island and could only have ten books with you, or ten songs, etc., which ones would you choose?  Well, if someone told me I could only keep a blog on one topic, ravens would have to be at the top of the list.  (What would you choose?)

On 30 September, I came upon two ravens walking along the upper beach.  They were actively (and I mean actively!) digging in the sand.  In the next two photos you can see the sand flying as they scooped it with their bills and shoved it upwards and outwards.

 

 

Every now and then the ravens would pause and look into or around the pit.

 

 

And then they would very delicately pick out something with the tip of their bills.

 

Of course, the next question is, what were they finding?  So I went up to the same zone on the beach and looked at the pits to get a feel for their size and shape and depth.

Then I started digging.  

Eventually, I encountered these:

 

I think the ravens were finding and eating beach hoppers!  The amphipods were ~1 cm long and looked similar to those I wrote about on 20 March 2012 (see better photos from that post here).

Part of natural history is watching carefully and asking questions.  I had lots of questions about this behavior.  Here are some examples, straight from my field notebook:

• Is this behavior age-dependent?  Are these juvenile birds?
• Can the ravens see the burrow entrances of the beach hoppers, or do they randomly choose a place to dig?
• Might this behavior be more common under foggy conditions, when other prey is less visible or less active?  (Does fog influence foraging?)
• Fog aside, is it based on the general availability of other prey?  (When other prey are hard to locate, they'll go for beach hoppers instead?)
• Are beach hoppers a lesser quality prey, or are they valued?
• Does it only occur during higher tides, when the wrack line is higher on the beach?
• Is it density-dependent?  (Does it only occur when beach hoppers are present at high densities?  When is it worth it to a raven to dig for beach hoppers?)
• Do ravens learn this behavior by watching other ravens, or other birds?

 
What questions do you have about this behavior?

Otherworldly

On 4 April 2012, Rebecca found an amazing pelagic amphipod washed ashore on Doran Beach.

An amphipod is a shrimp-like crustacean (think about the beach hoppers in previous posts), but this species is only found in the open ocean and is very unusual in that it lives in a transparent "barrel." Their appearance is otherworldly and a bit bizarre.

Because they modify other pelagic animals (e.g., salps and pyrosomes) into barrels, these amphipods are sometimes known as "marine coopers", or tonneliers de la mer.  And because they hold onto the barrel, deposit their young inside of it, and propel it by beating their pleopods, they are informally called "pram bug amphipods." (Although you may think of a pram as a type of boat, it's also a British term for baby carriage.)

Here's Rebecca's amphipod living inside a gelatinous barrel (probably a salp).  The amphipod is approximately 30 mm long.  The cream-colored band near the bottom is actually a cluster of juveniles (her offspring — more about them later).  Meet Phronima sedenteria!

 

Below is a dorsal view.  Although Phronima is mostly transparent, look at the interesting maroon-colored pigment spots (chromatophores).  Phronima is not attached to the barrel.  She can adjust her position within it (including somersaulting to reverse direction) and can leave through one of the openings and return.

 

And here's a side view.  Note the way she uses the front appendages to hold on to the barrel, her very elongate head, and the large claw at the end of the fifth thoracic appendage.

 

The next photos are close-ups of the claw and the tail.  (The claw is apparently not used for capturing prey, but may be utilized when defending the barrel.)

 

 

Her eyes are one of her most impressive features.  She has four of them — two lateral and two median eyes.  

Here's a close-up of her face and a diagram to help illustrate the eyes.

 

 

Figure adapted from Ball, E.E.  1977.  Fine structure of the compound eyes of the midwater amphipod Phronima in relation to behavior and habitat.  Tissue & Cell 9: 521-536.

The red spots are retinas.  The outermost or lateral eyes are small and easy to see.  The inner or median eyes are conical and very elongate, extending from the curved surface at the top down to the retina below.  The cone cells are connected to the retina by long (~5 mm) light-guides (the converging lines in the diagram).

From above, the large median eyes look somewhat like the eyes of a fly (see below).  They appear to be faceted, but you're actually seeing the individual cone cells beneath a smooth transparent surface.  There are ~400 cone cells in each eye.

These unusual eyes are apparently adapted for living inside a barrel (with a narrow field of view), seeing small objects against uniform backgrounds in low light conditions, and minimizing visibility to predators (such as albacore and other tuna).  Phronima is generally found at depths between 80-1100 meters below the surface.

One more curious fact about Phronima: they practice demarsupiation, or the deposition of progeny (juveniles) on the barrel wall (see below).  Most amphipods maintain their young in a brood pouch, or marsupium.  Phronima begins that way, but then transfers the tiny juveniles (up to 600) to the barrel wall where they continue to develop (they feed on the barrel and on food she captures and brings to them).

Phronima means "clever", and perhaps refers to their ability to fashion a barrel out of another animal and then use it for shelter and a nursery (and sometimes food).

I'm still working out the best way to photograph transparent animals.  Click on these links to see superb photographs and video footage of this remarkable amphipod.

Phronima is found throughout the world's oceans, but it's unusual to see them on shore.  Good find, Rebecca!