A clam like no other

 

 

I looked down to see this distinctive shell washed up at Point Reyes this past weekend (23 August 2025).  Note the elongate shape and the fine ridges radiating from the hinge (the hinge is at the bottom of the photo).

 

I posted briefly about this species back in 2015 (See "File this away" on 28 June 2015), but it's rare to observe Hemphill's File Clam (Limaria hemphilli) in our region, so I thought it would be worth sharing another record.  Limaria hemphilli has a more southern distribution, with most records south of Point Conception (and only a few records north of Monterey).

 

I also remembered that Sam documented a file clam in Bodega Harbor in 2024.  He was lucky to find a live individual and he captured the beautiful and intriguing tentacles.  Check it out!

 

 

 

 

Here's an even closer view of those amazing tentacles:

 

 

 

The tentacles are extensible -- they can stretch out far away from the shell.  And interestingly, there are reports of predators being distracted by tentacles that have been dropped, so at times the tentacles might be used to deter predation (somewhat similar to a lizard's tail).

 

With many thanks to Eric for the photo of the shell and to Sam Briggs for the spectacular photo of the live file clam. 

Just in time for Easter -- lots of eggs!

  

We went out to the rocky shore early this morning to start some surveys.  Right away Eric noticed that the tidepools looked unusual.  All of them appeared cloudy or milky.  We were aware recent ocean conditions might trigger spawning in some marine invertebrates, and sure enough, this was a massive spawning event of California Mussels (Mytilus californianus), probably the largest we've encountered.

In the photo above, the orange coloration is eggs released by female mussels.  Here's another example, with clusters of eggs concentrated along the edge of a pool:

 

 

In other pools, the color was white or gray, clouded by vast quantities of sperm released by male mussels:

 

 

Nearly every tidepool we observed on Bodega Head appeared to have mussels spawning, so the extent of this synchronous mass spawning event was truly remarkable.  Even the largest pools were visibly cloudy:

 

 

 

The ocean temperature went up from 11°C (52°F) to 13°C (55°F) yesterday, and there was a phytoplankton bloom nearshore — both environmental cues that are thought to trigger spawning in some invertebrates.

Amazing!  Let us know (and send photos) if you notice local marine invertebrates spawning, too!

A long way to grow!

  

Close-up of barnacles on a Californa Mussel (Mytilus californianus) shell, photographed on 29 April 2024.

There are at least two age classes of barnacles here — the larger Little Brown Barnacle (Chthamalus dalli) adults and the very tiny newly-settled recruits.  The recruits were so small they were actually hard to see in the field — just small specks scattered across the mussel shell.  They have a long way to grow!  :)

In the zones

  

This morning (24 April 2023) we were finishing some surveys at a site with lots of wave splash.  In this case that means the intertidal zonation is clearly demarcated and the zones extend very high on the rocks.  

For example, on the left, the brownish coloration is made up of seaweeds (primarily Pyropia and Pelvetiopsis), the dark blue areas are California Mussels (Mytilus californianus), and below that is a band of surfgrass (Phyllospadix scouleri) and coralline algae (some of it is bleached, likely by warm or desiccating conditions, so it's paler than usual).

In this view there was also a nice flock of Surfbirds (Calidris virgata) foraging in the zone above the mussels.

Lower limits

 

 

Whew, I'm finally getting over a heel injury...and it's just in time for spring field work!  Eric and I were doing some intertidal surveys this afternoon (1 April 2023) and Eric took this nice photo of Ochre Sea Stars (Pisaster ochraceus) —  some feeding on very large California Mussels (Mytilus californianus).

At home

  

Black Oystercatcher (Haematopus bachmani) and California Mussels (Mytilus californianus).  Photographed at sunset on 17 January 2022.

Greenery

Sola green (tentacles of the Sunburst Anemone, Anthopleura sola):

 

 

 

Sculpin green:

 

 

 

 

Siphon green (clam siphon):

 

 

 

Combination of factors

  

One morning last week when we were headed out to do field work, we noticed an odd smell in the area and later we found the source — some small patches of California Mussels (Mytilus californianus) that had died recently.

Although it's been warm inland, I didn't recall noticeably high air temperatures at the coast, so at first I was a bit puzzled.  But then I thought about how calm the ocean has been (hardly any large swell) and that this site is quite high on the rocks.  It's likely that the mussels growing here are used to getting splashed by waves, and if they didn't experience any wave action during a warm day, it could be a problem for them.

So we did a little sleuthing regarding the conditions that might have caused this mussel die-off.  Questions we wondered about included: 

 - Were there any higher air temperatures in Bodega Bay recently?  We looked back at some temperature records and noted a couple of days in early August when the air temperatures reached ~67°F (~19°C).  That was the warmest we found, so the air didn't get that hot.

- But we know that mussels and the rocks they grow on reach warmer temperatures than the air.  So how hot was the rock at the time?  Luckily, Eric had some data loggers on the rocks near mussels and so he looked back and found that rock temperatures reached ~98-100°F (~37-38°C) on those warmer afternoons.  That's warm enough to impact mussels, and if exposed long enough, it might kill them, but it would depend on other conditions at the time. So...

- What was the timing and height of the tides on those days?  Interestingly, this was during a neap tide series. Compared to tide heights during a spring tide series (around full moons and new moons)  the high tide heights during neap tides are relatively low.  For example, the morning high tide on August 1st was only 3.7 feet (higher high tides in our area are often over 6 feet).  And the low tide on August 1st was 2.7 feet at ~12 p.m.  This combination of a very low high tide in the morning followed by a low tide in the middle of the day is potentially dangerous for a marine organism living in the high intertidal zone, especially if the wave conditions are extremely calm and the air is relatively warm.  It basically means that mussels growing at that site (at about 5 feet elevation) were exposed to warm air/rock temperatures and no wave splash for the entire day — especially from late morning through late afternoon (the hottest part of the day).  On 1-3 August 2021, these mussels might have reached temperatures >86°F (>30°C) for 4.5-6 hours each day and they might not have experienced any wave splash for that entire time.  [I think it's even possible they didn't get splashed during the night-time high tide (which on August 1st was 5.6 feet at 7 p.m.)]

So questions remain about this die-off, but rather than being caused by extreme warm air temperatures alone, in this case I'm guessing it was a convergence of factors, including (1) these mussels lived very high in the intertidal zone at a very splashy site; (2) there was a low high tide in the morning (the mussels weren't submerged during high tide); (3) there was a low tide in the middle of the day (the mussels were exposed to warm air for many daylight hours); (4) there were warm air temperatures (this might not have happened if air temperatures had been cooler); and (5) this occurred during very calm sea conditions (the mussels weren't cooled down by wave splash).

This mussel die-off was restricted to a very high intertidal splash zone site.  Most of the mussels in the rest of the intertidal zone were fine.  But seeing this event was insightful for considering combinations of factors that could be lethal for mussels.

One more photo for the record:

 

 

Coastal colors

 

  

Colors on the inside of a California Mussel (Mytilus californianus) shell. 

 

Would you have guessed?  :)

Feet first?

  

Although you might have heard that sea stars use their tube feet to grab hold of mussels and to pull the two valves open slightly (enough to insert their stomach inside the shell), you don't always get to see the tube feet in action.  

Often the sea star is hunched up over the mussel, so it's hard to see what's going on.  In this case, the Ochre Sea Star (Pisaster ochraceus) is pulling on a very large mussel and it hasn't yet moved into a position where the tube feet are hard to see.

Here's an even closer view: 

 

 

Impressive!

 

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)

A clam, a sea squirt, and a snail

Well, I didn't get a chance to take any photos today, so I browsed through photos from the last month or so (from various locations) and picked a few that caught my eye.  I hope they brighten your day!

 

Juvenile Pacific Razor Clam (Siliqua patula)

 

A golden colonial tunicate (sea squirt), Pycnoclavella stanleyi 

 

Red Turban Snail (Pomaulax gibberosus) with coralline algae

P.S.  What did the clam say when the sea squirt and the snail walked into the bar?  "Sorry, I'm just about to close up for the night."  :)

Too hot -- Part 3

 

Remember the mussel mortality event that I mentioned last week?  (See posts called "Too hot" and "Too hot -- Part 2")  

Eric Simons wrote an informative article about this event for Bay Nature magazine.  You can read the article online here.

The photo above was taken on 18 June 2019 and the photo below was taken on 19 June 2019.  

In the first photo you'll notice that some mussels are empty, but others still have their adductor muscles — the white muscle that holds the two shells together.  In the photo below, the majority of mussels are empty, but in a few you can see the orange internal tissue (before it washed away or was eaten by other animals).  At low tide, healthy mussels are normally closed up tightly, so you can't see the internal tissue or the inside of the shells.

 

 

Too hot -- Part 2

For the record, I'm sharing a few more photos of the California Mussel mortality event in the intertidal zone that I mentioned last night.  We think this is the most significant mussel mortality we've seen on Bodega Head during the last 15 years (in terms of number of individuals and the amount of area impacted).

In these patches (photographed on 19 June 2019) you can see that most of the mussels in the top layer of the mussel bed have died.  The light blue color is the inside of the dead, gaping shells.  

Although it's hard to estimate percent mortality throughout the entire mussel bed, many areas across the intertidal zone look like this right now, with some shells gaping wider than others.

 

 

Too hot

Last week's record warm air temperatures (for the date) seem to have impacted some of the local rocky intertidal zone species.  Unfortunately, the high air temperatures coincided with midday low tides.  Sometimes it takes a little while for the effects to show up.  

While doing field work this morning (18 June 2019), we observed quite a bit of bleached algae in the mid-to-high zone (see below).  These seaweeds are usually darker green and brown — the whites and reds are abnormal for these species.  [In this photo, much of the white algae in the foreground is Mazzaella sp., while the reddish looking species is Dwarf Rockweed (Pelvetiopsis limitata).]

 

There has also been a significant die-off of California Mussels (Mytilus californianus).  A large percentage of the mussels were open and gaping, some were empty and some still had tissue inside.  Here's one example:

 

We're curious about how widespread this mussel die-off was.  If you see large patches of open, gaping, dead mussels in the intertidal zone and you'd be willing to share a photo, I'd be interested in hearing about your observations.

Jewelbox

 

Secret Jewelbox (Chama arcana), 26 January 2019.  The shells of this small bivalve occasionally wash up on local beaches.

Rose-painted

 

Rose-painted Semele (Semele rubropicta), photographed in Bodega Bay on 21 March 2017.  It was ~3 cm (a little over an inch) long.

Note the small circular hole — evidence that this clam was drilled by a predator.

 

Not so boring

Can you guess how this hole was made?

 

 

This beveled and circular borehole was made in a Pacific Littleneck Clam (Leukoma staminea).

 

 

And the animal responsible for the borehole?

 

Lewis's Moon Snail (Neverita lewisii).  Moon snails have an accessory boring organ (ABO) and can secrete an acidic substance that softens bivalve shells.  After securing their prey with a large muscular foot, they'll alternate applying acid (with the ABO) and rasping away the softened shell with their file-like radula until they break through.  The snails then release digestive enzymes to soften the bivalve's tissues and feed on the bivalve through the borehole.

Moon snails are remarkable predators that leave definitive evidence of their past feeding activity.

 

P.S.  If you missed them before (or just want to enjoy them again!), I posted some nice microscope pictures of a moon snail on 5 August 2013.

 

File this away

We haven't done a mystery close-up in a while.

Can you guess what this is?

 

It looks like a series of waves running towards the shore, doesn't it?

Here's another clue:

 

And this one will help a bit more:

 

It still might be hard to tell what type of animal this is.

You're seeing extreme close-ups (under the microscope) of a shell.

I'm guessing it will be difficult to identify the type of shell, so the next photo will reveal the entire shell as I found it on the beach:

 

There are a few things that stand out about this clam.  It has a very oblong shape; it has narrow ridges that look like rays running towards the edge of the shell (more prominent near the margins); and it's very thin and fragile.  (Yes, it's broken, but it's still worthy of sharing because it's a rare clam in this area!)

Meet Limaria hemphilli.  I've seen various common names for it, but I think my favorite is Hemphill's File Clam.  It was named after Henry Hemphill (from San Diego), who did a lot of the early work on molluscs in California...and its ridges give it a file-like appearance.

Limaria hemphilli is more common south of Monterey.  In fact, most books list Monterey as its northern limit.  But we've seen at least four individuals in Bodega Bay during the past ten years.  I hope to photograph one alive some day — they're quite spectacular with many long tentacles reaching far beyond the shell.  And they have interesting behaviors — they make "nests," and they swim like scallops!

P.S.  If you're curious, there's a nice picture of a live Limaria available here.

Something colorful, something new

On 15 September, Eric and I noticed some very small scallop shells washed up on Salmon Creek Beach.  Here's an example:

 

We were impressed with the diversity of shell colors and patterns:

 

Pick your favorite!

 

 

These are juvenile Rock Scallops (Crassadoma gigantea).  Not only did we discover how diverse their shells can be, but by looking at them up close, we learned something new.

 

Did you notice the row of teeth below the hinge?  (To me, it almost looks like a line of small arching waves.)  This feature is called a ctenolium.  The teeth guide the byssal threads that the scallop uses to attach to the substrate when it's young.