Category: Marine invertebrates

Six months, and a big return

Posted on by Allison J. Gong

Next week I will be six months beyond a total replacement of my right knee. The rehab has been long and tough, and I’m nowhere near the end yet. I’ve been told by my surgeon to expect a 12- to 18-month recovery to get back to whatever my new normal will be. By that estimate I’m either 1/3 or 1/2 of the way there; given the way things are going I suspect it’s the smaller fraction, so I’m looking at another year of ongoing, slow improvement.

I’ve finally gotten strong enough that I felt ready to return to the intertidal. And yesterday being the first day of a new year, it seemed fitting to venture out into my old life again. I chose a site that didn’t involve any cliff-climbing (not quite up to that yet), but did have stairs so I could challenge the knee. Down is still hard, but up is a piece of cake now.

Two people standing among dark rocks. Person in the front is wearing a bright pink jacket and holding a green rectangular object. Person in the midground is wearing a black jacket and green knee-high boots. There is a lighthouse in the background.
My friend, Sara, and me on the rocks at Whaler’s Cove
2026-01-01
© Alex Johnson

It was great getting out to the intertidal and seeing some of my old friends again! January isn’t the best month to find happy algae, but the rockweeds were already recruiting and growing. Here’s a baby rockweed, probably Pelvetiopsis limitata (they can be hard to ID as youngsters):

Olive-green ribbon-like structure with bifurcated tips emerging from wiry dark red threads
Baby rockweed, probably Pelvetiopsis limitata, in a thicket of Endocladia muricata
2026-01-01
© Allison J. Gong

And there were some lovely stands of Fucus:

Bunches of flattened dichotomously branching algae, olive-green in color, on rocks
Thalli of the rockweed Fucus distichus
2026-01-01
©️ Allison J. Gong

Note that the tips of the Fucus branches are flattened. These are young thalli. In the summer, mature thalli will have swollen tips full of gametes. Fucus, and the rockweeds in general, have what we call an “animal-like” life cycle instead of the alternation of generations that is more typical of seaweeds. And we won’t even get into the complexity of the alternation of three generations in some of the reds! So yes, Fucus thalli come in male and female forms that produce sperm and eggs, respectively. Sounds familiar, doesn’t it?

We saw several ochre stars, none of which were ochre in color. And now that I think about it, I see many more P. ochraceus that are purple, red, or orange than are ochre.

Dark purple star-shaped animal attached to a rock
Ochre star (Pisaster ochraceus)
2026-01-01
© Allison J. Gong
Bright orange star-shaped animal stuck to a rock
Ochre star (Pisaster ochraceus)
2026-01-01
© Allison J. Gong

And lest we forget, Sea Star Wasting Syndrome (SSWS) hasn’t been banished from the world. I suspect it will always be around but won’t always be as prominent as it was 10 years ago. Yesterday we saw two disembodied arms of a purple Pisaster ochraceus. The rest of the body was nowhere to be found, and I guess this star dismembered itself a couple of days ago.

Two approximately triangular structures on a sandy background with two large rocks and a snail shell
Disembodied arms of Pisaster ochraceus in a tidepool
2026-01-01
© Allison J. Gong

On a much more pleasant topic, I noticed a pattern of different organisms lined up in rows.

Row 1: Limpet scars. These ovoid blotches are the scars made by a limpet, Discurria (formerly Lottia) insessa. The limpet lives on the stipe of feather boa kelp (Egregia menziesii), shown below. It eats the algal film that accumulates on the kelp but eventually ends up chewing through the stipe, which then breaks. They literally eat themselves out of house and home, poor guys.

Long brown strap running horizontally across the image. There are eight golden ovals along the length of the strap.
Limpet scars on stipe of Egregia menziesii
2026-01-01
© Allison J. Gong

Row 2: Anemones. Many intertidal animals (and algae, for that matter) settle preferentially in cracks and crevices. These are the places that hold water the longest at low tide, giving the organisms a slight bit of protection against desiccation. For the same reason many organisms prefer to settle on vertical rather than horizontal surfaces. I found this group of anemones in an almost-straight line in a shallow indentation in the rock.

Five roughly circular objects arranged approximately vertically against a pink background
Row of anemones (Anthopleura spp.)
2026-01-01
© Allison J. Gong

Row 3: Anemones. In geometry, two points define a line. So I can claim that these two anemones make a row! You may have to look carefully to see the second anemone.

Circular object with white protruding tentacles radiating from center. To the right, a similar object with transparent tentacles.
Moonglow anemones (Anthopleura artemisia)
2026-01-01
© Allison J. Gong

These are the same species. Anthopleura artemisia is highly variable, more so than the other species in the genus. The tentacles can be a solid opaque color, as in the animal on the left, or transparent/translucent with or without opaque patches, as in the anemone on the right. They tend to live in sandy areas and often have sand covering the oral disc. If disturbed they will retract into the sand and disappear.

Beach landscape. Large boulders covered with brown/reddish algae or green plant growth, on sandy bottom. Gray cloudy sky above greenish water.
Scenery at Whaler’s Cove
2026-01-01
© Allison J. Gong

All in all it was a fantastic re-entry into the rocky intertidal. My body remembered how to move around, my balance was not entirely shot to hell, and my knee did fine. I was able to forget about it and just use it like a normal person would. When I started physical therapy I told the therapists that one of the things I need to be able to do was work in the rocky intertidal. They were skeptical at first, because they envisioned me jumping from slippery rock to slippery rock. I had to explain that I’m very safety conscious in the field and know all the tricks of an old-timer: Keep your body low (so you have less distance to fall) and keep three of the five points of contact (two hands, two feet, and one butt) with the rock at all times.

I’m calling this a major milestone achieved, even if I still have a long way to go. Yippee!

Collateral damage

Posted on by Allison J. Gong

My home town of Santa Cruz made national news the other day, 23 December 2024, when a series of massive swells caused part of the Municipal Wharf to collapse into the ocean. People in the restaurants and other businesses had to evacuate immediately, and three people were dropped into the water of Monterey Bay (they were all rescued safely and no human lives were lost). The bathroom building fell into the water and washed up on the beach at the mouth of the San Lorenzo River. Almost immediately, memes appeared, advertising a 2-bathroom unit with both river and ocean views, renting for $6000/month. Given the exorbitant rents here, you could argue that maybe this is a pretty good deal.

That afternoon, the same swell tore through the Santa Cruz Small Craft Harbor and replicated the damage done by the Fukushima tsunami in March 2011. The damaged docks had been replaced in 2014, but this recent damage ripped them up again. Boats and docks were thrown around and crashed into each other. An unknown amount of diesel fuel and gasoline were also “liberated” into the water.

My friend Murray has a little boat, Scherzo, that lives in the upper harbor on G dock. On the day of the worst swell, Murray had gone down to see how Scherzo was faring. At that point she had taken at least some cosmetic damage to her paint but didn’t seem to be taking on any water except rain water. The harbor patrol had closed all of the docks so he couldn’t get close enough to see if there were worse injuries. At one point another boat had come down the channel and gotten wedged under Scherzo so she was floating on top of it. Somebody rescued Scherzo and tied her up at a spot just under the ramp from her usual berth. Yesterday, Christmas Day, Murray called us to say that he was down at the boat and asked if Alex (my husband) could help him get her out of the water, as more big swells were forecast. I’m not very useful when it comes to boats, but I went along to watch things from above and hold lines and such.

Before they could take Scherzo out of the water, they had to make sure she was seaworthy enough to be driven down to the boat ramp at the lower harbor.

Dock with two large boats tied up on one side and one small boat tied up on the other side. One person in the small boat. One person crouching on the dock next to the small boat
Murray and Alex give Scherzo a check-up
2024-12-25
© Allison J. Gong

Behind Murray, who is wearing the pink cap, you can see damage to the finger dock. And notice that the big boats aren’t sitting straight in their slips. Scherzo‘s usual spot is on the other side of the ramp; she got pushed under the ramp and a kind soul tied her up here.

This is the capsized boat that had gotten wedged under Scherzo. It was now stuck under the ramp, just in front of Scherzo‘s spot.

Capsized boat wedged under a pedestrian bridge
Capsized boat under ramp
2024-12-25
© Allison J. Gong

Scherzo‘s engine started right up, and the boat itself having been deemed safe to drive by Alex the Engineer, Murray took her down the harbor slowly. Alex and I met him at the boat ramp.

While we were waiting, we noticed that some of the pilings from the busted-up Wharf, which is more correctly a pier rather than a wharf, had been hauled out of the water and set in the parking lot.

Wharf pilings in the harbor parking lot
2024-12-25
© Allison J. Gong

Knowing that the biota on the pilings would be very similar to the critters I see in the rocky intertidal, I had to investigate. And it was very sad. Most of the animals had died waiting for a high tide that wouldn’t return. Some of the barnacles were still alive, albeit just barely so.

Log lying on pavement, covered with small pink blobs and large brown objects also covered with small pink blobs.
Large barnacles (Balanus nubilus) and pink corallimorpharians (Corynactis californica)
2024-12-25
© Allison J. Gong

Here’s a close-up shot of one of the big barnacles encrusted with other animals:

Beige pyramid-shaped structure with pink blobs on the lower surfaces
Large barnacle (Balanus nubilus) and pink corallimorpharians (Corynactis californica)
2024-12-25
© Allison J. Gong

There were many empty worm tubes, former homes of the beautiful Eudistylia polymorpha. I saw one dead worm that had fallen out of its tube:

De-tubed feather duster worm, Eudistylia polymorpha
2024-12-25
© Allison J. Gong

One of the rocky intertidal denizens, the pink barnacle Tetraclita rubescens, was there, too:

Pink barnacle (Tetraclita rubescens) with smaller barnacles (Balanus glandula) and mussel byssal threads
2024-12-25
© Allison J. Gong

To get a feel for how big Balanus nubilus and Tetraclita rubescens are, my left index fingernail measures exactly 10 mm across. That B. nubilus is a big sucker!

Large volcano-shaped structure with two smaller pink volcano-shaped structures on the side. Finger for size reference
Balanus nubilus and Tetraclita rubescens
2024-12-25
© Allison J. Gong

Balanus nubilus is a strictly subtidal species that I never see in the intertidal. Tetraclita rubescens occurs in both the intertidal and the subtidal; some of these subtidal specimens were larger than the ones I see in the intertidal. Most sessile marine invertebrates can feed only when they are covered by water, which means that the ones living in the intertidal don’t feed at low tide. Thus the subtidal T. rubescens can get larger than their intertidal conspecifics, simply because they can feed 24/7. We see the same pattern with mussels in the intertidal: those higher up in the mussels’ range are smaller than the ones in the lower part of the range.

Some of the barnacles were still alive. They can close up their shells and wait out a low tide. But sitting out of the water for longer than a day was more than even they could withstand.

Other old friends were there, including many sea anemones. This is the sunburst anemone, Anthopleura sola, looking the way it does when I see it in the intertidal at low tide.

Cylindrical animal hanging down from vertical surface
Sunburst anemone (Anthopleura sola)
2024-12-25
© Allison J. Gong

Other anemones had been caught in the act of dividing. These would be the cloning anemones, Anthopleura elegantissima.


2024-12-25
© Allison J. Gong

2024-12-25
© Allison J. Gong

Probably the saddest thing was a desiccated red octopus on the pavement. It had probably plopped out of a nook and tried to make its way back to water. Poor little thing.

Grayish-brown lump with suckered arms
Red octopus (Octopus rubescens)
2024-12-25
© Allison J. Gong

The organisms on these pilings were caught in their final moments of life, just as the citizens of Pompeii and Herculaneum were when Mt. Vesuvius erupted in 79 AD. Some of them had tried to escape (the octopus) and some were not quite dead yet (the barnacles), but the inevitable is well, inevitable. At some point the pilings will be removed to the landfill. The same thing happened when the harbor docks were replaced in 2014. I happened to be there with a class and we saw all of the old docks piled up in the parking lot, with all of the attached biota slowly drying up in the sun.

So while there will be reports in the coming days about how many millions of dollars it will take to rebuild the harbor (again) and the pier, let’s not forget that there were other losses that cannot be assigned a dollar value. There is also a potentially major ecological impact of new (again) harbor docks. When the old docks were removed in 2014, they had been covered with a decades-old fouling community. The new docks were pristine new habitat for recruits, and shortly after they were put in I noticed an invasive brown alga, Undaria pinnatifida, which I hadn’t seen before. Undaria is a western North Pacific edible seaweed that is known culinarily as wakame. In recent years it has become one of the most abundant macroalgae in the lower areas of the harbor. The docks that were destroyed this week had been in place for only 10 years or so, and it will be interesting to see how primary succession occurs when new docks are installed. Hmm, that sounds like something I can have my Ecology students document and monitor!

A celebration of worms

Posted on by Allison J. Gong

Yesterday, 30 June 2023, was deemed by the National Museum of Natural History to be International Polychaete Day, and the Smithsonian had an entire day of talks and activities for visitors to learn about the marine segmented worms. And you know me: I’m in favor of any event that draws attention to the animals that are not like us. So this is my own little celebration of worms I encountered over this past week.

Living with sea stars

I’ve written before about how many of the bat stars (Patiria miniata) I see at Pigeon Point carry small commensal polychaetes on their oral surface, often associated with the ambulacral groove. Several taxa of echinoderms are known to have associations with polychaetes, and I’ve seen worms crawling around on sea stars, sea urchins, and sea cucumbers. Oxydromus pugettensis is the polychaete I’ve seen on the bat stars in the field.

5-armed cream colored star-shaped animal being held in a human hand; two small brown worms on animal's surface
Commensal polychaete worms (Oxydromus pugettensis) on oral surface of bat star (Patiria miniata) at Pigeon Point
2018-06-01
© Allison J. Gong

Years ago now, I collected some bat stars to bring back to the lab. Some of them had worms, and I was interested in seeing how long the worms stuck around once the stars were in captivity. The answer was “Not very long.” I seem to remember that the stars had lost their worms within a week. And since then, despite having many bat stars come through my hands at the lab, none of them have acquired worms.

Until now. This past week I was moving stars around and cleaning tables after flushing seawater pipes. I have a large bat star and a smaller one running feral in one of the tables. I picked up the larger star and turned it over just to check on it, and saw a dark squiggly thing. It was a worm!

Hand holding a 5-pointed star shaped animal, mottled orange and brown in color
Aboral surface of bat star (Patiria miniata)
2023-06-26
© Allison J. Gong
Hand holding a 5-pointed star-shaped animal, cream in color
Oral surface of bat star (Patiria miniata)
2023-06-26
© Allison J. Gong

Can you see the dark squiggle on the oral surface?

Here’s a close-up of the worm:

Cream-colored scales surrounding groove containing flat-topped clear tubes. Small dark brown worm tucked into side of groove.
Oxydromus pugettensis in ambulacral groove of Patiria miniata
2023-06-26
© Allison J. Gong

This is the first time I have ever seen a sea star acquire a commensal worm. It’s gotta happen, because we see worms on stars in nature. But I do wonder about this relationship. The worms are highly mobile and probably leave one star and join another quite frequently, or remain free-living (i.e., not on a host star). I had brought in some algae the previous week, and it’s quite possible that the worm came along as bycatch and found its way to the bat star. I checked on the star later in the week, and did not see the worm. It hadn’t joined the smaller of the bat stars, either.

Baby worms

This past Monday I did a plankton tow off the end of the Santa Cruz Municipal Wharf. This was my first plankton tow of the year, and I wanted to see what was there. The water was very clear and the phytoplankton were lacking, but there was a decent diversity within the zooplankton. Of particular interest to this report were the baby worms.

Baby worms are present in any plankton tow collected at any time of the year, although they may be more abundant at some times compared to others. Clearly there isn’t much seasonality to reproduction in some of our local polychaetes. The most commonly seen baby worms in plankton samples are the metatrochophores of worms in the family Spionidae.

Adult spionids are benthic and live in tubes. They have two long palps that extend from the anterior end and are typically used to scrape up organic deposits from the area surrounding the tube. Like most polychaetes, spionids are broadcast spawners that cast gametes out into the water, where fertilization and development occur. Polychaetes go through a larval phase called a trochophore, defined by a ring of cilia (the prototroch) that produces the feeding current for the animal. Incidentally, many molluscs also go through a trochophore stage, but that’s a story for another time. Some polychaetes, including the spionids, have a second planktonic stage called a metatrochophore. The metatrochophore is a much larger and more elaborate version of the trochophore, with eyespots and few to many segments complete with associated bristles. They can crawl as well as swim. Some of them can be 3 mm long, which is pretty big for something that is still up in the plankton. The spionid metatrochophore also has the two long palps, which sometimes remind me of the flaps on Elmer Fudd’s hat.

These are photos of the same individual worm. It’s about 2 mm long, a little longer if all stretched out.

Tan colored, segmented object curled into a loose circle. One end is pointed and bears two ear-like flaps that extend backwards.
Metatrochophore of spionid polychaete
2023-06-26
© Allison J. Gong
Tan colored, segmented object, approximately bullet-shaped. One end is blunt, the other tapers to a rounded point. Tentacle-like structures extend along the sides of the body.
Metatrochophore of spionid polychaete
2023-06-26
© Allison J. Gong

There was another type of polychaete metatrochophore in the sample, but I don’t recognize which family this one comes from. I should, because I see it frequently enough to know it isn’t unusual. It might be a young phyllodocid metatrochophore, but that’s just a guess. Anyhow, this creature has fewer segments than the spionid metatrochophore and lacks the spionid’s long palps. It does have eyespots, segments with bristles, and (I think) two pairs of tentacles associated with the head region. This individual also contains a lot of oil droplets, visible as those small dark circles in the dorsal half of the body behind the head. Oil droplets serve as energy stores and flotation devices. Many marine invertebrate larvae stockpile calories as they feed and store them in oil. In some cases, these calories are needed to sustain a later larval stage that doesn’t feed.

Polychaete metatrochophore
2023-06-26
© Allison J. Gong

There you have it, my belated contribution to International Polychaete Day 2023. I always enjoy finding worms in our plankton. They have a lot of personality, and it’s fun to watch them zooming around. They are really fast swimmers, and I have to squash them under a coverslip—just a little—to get them to hold still long enough to take photos. Always worth the effort, though!

Exception to the rule

Posted on by Allison J. Gong

Ask any marine biology student to list some interesting factoids about barnacles, and one of them should be “Barnacles are benthic and sessile” by which they mean that barnacles live their entire lives glued to a single spot. This definitely describes what it means to be benthic. Barnacles are indeed stuck, for better or worse, to the location that their cyprid larva selected. Once the cyprid glues its head to the rock or other hard substrate, that’s it. A bad choice could mean that the barnacle starves, desiccates, or is unable to mate. A good choice means an opportunity to live long and prosper.

How is it, then, that we have things that are called pelagic barnacles? These are barnacles that live permanently attached to objects that move through the water. The objects can be living (e.g., whales or turtles) or non-living (e.g., boats). Pelagic barnacles are not just traveling versions of the species we see in the intertidal or on docks and pilings—they are different species altogether.

Yesterday morning I went to Younger Lagoon to see what had happened during the most recent storm. The lagoon had once again breached through to the ocean, and bits of Monterey Bay were sloshing into the lagoon. None of that was unexpected.

What did catch my eye were the fuzzy blotches on some of the pieces of wood that had washed up onto the beach.

Small log festooned with interesting objects
2023-03-10
© Allison J. Gong

A closer look confirmed my thought that these were pelagic barnacles in the genus Lepas. These are a type of gooseneck barnacle, similar in overall morphology to the very common intertidal Pollicpes polymerus.

Pelagic barnacles (Lepas sp.) on piece of wood
2023-03-10
© Allison J. Gong
Lepas sp. on piece of wood
2023-03-10
© Allison J. Gong

These barnacles were small, and having been emersed for at least several hours were definitely not looking their best. They didn’t smell dead just yet, but since they had zero chance of getting back into the water before the next high tide, were doomed. A few of them had their cirri—the modified thoracic appendages that barnacles sweep through the water when feeding—extended, which I’ve seen before with barnacles on their last leg. See what I did there? I did touch some of the cirri, and the barnacles did not respond at all, although they had not yet dried out to the point of crispiness.

Lepas makes a living attached to objects that float in the ocean. I usually see them on logs or smaller pieces of wood, as they are here, but do occasionally find tiny ones on the blades of giant kelp (Macrocystis pyrifera). Living attached to objects that float with the currents means the barnacles are constantly moving through the water, able to feed 24/7 without the constraints of high and low tide. Compared to the robust gooseneck and acorn barnacles of the rocky intertidal, Lepas is translucent and delicate, with plates that are only weakly calcified. Given its lifestyle, Lepas rarely has to withstand bashing surf or waves; by the time it does, its substrate is inevitably headed onto shore, where the barnacles will die anyway.

So there you have it—a barnacle that flouts the rule and manages to be both benthic and pelagic. Or perhaps I should say that it is benthic but has a pelagic lifestyle. Either way, Lepas is making the best of both worlds, isn’t it?

A different perspective

Posted on by Allison J. Gong

Yesterday I had the great fortune to visit a new intertidal site. It can be accessed only by crossing private property. The property owner is my next-door neighbor, and he said I can visit any time. As I said, lucky me! The site is a little north of Pigeon Point, and at first glance the terrain is not very different from Pigeon. But I could tell that it a site that is rarely, if ever, visited by humans. It just had that look of being mostly undisturbed. Yesterday’s marine layer was low, making for dark skies and pretty lousy light for picture-taking, so I had to try something new.

This site has a lot of lovely pools and channels to explore, and at this time of year the water is very clear, which does make for good picture-taking. Halosaccion glandiforme, one of the charismatic red algae, is more abundant here than at other sites, and in the pools it grows quite a bit taller than it does on the rocks.

Here’s what it looks like on the tops of the rocks. This is a cluster of young thalli. The tallest of these “bladders” is about 4 cm tall. Note that they are about 2/3 full of water, with a large air space at the top.

Many olive-green spherical and ovoid bladders, attached to rock.
Young Halosaccion glandiforme thalli along the San Mateo County coast
2022-08-14
© Allison J. Gong

The really cool thing is what happened when I stuck the camera in the water and took a shot. I got something like this:

Two elongate olive-green bladders, filled about 2/3 with water, submerged in a tidepool
Halosaccion glandiforme and other algae submerged in a tidepool
2022-08-14
© Allison J. Gong

I got a little carried away. But don’t things look interesting from the turban snail’s perspective?

Olive-green towers rising from a carpet of pink algae. A black snail is nestled between a trio of the towers.
Halosaccion glandiforme and a black turban snail (Tegula funebralis) in a tidepool
2022-08-14
© Allison J. Gong

I’m kind of enraptured by these towers of algae.

Olive-green towers rising from a carpet of pink algae.
Halosaccion glandiforme in a tidepool
2022-08-14
© Allison J. Gong

But the best part of these experiments was the reflections on the surface of the water. Check it out.

Olive-green towers rising from a carpet of pink algae.
Halosaccion glandiforme in a tidepool
2022-08-14
© Allison J. Gong

And this is the money shot! I just love how this turned out.

Olive-green towers rising from a carpet of pink algae in the bottom half of the image. The same tower are reflected in the top half of the image.
Halosaccion glandiforme in a tidepool
2022-08-14
© Allison J. Gong

This was a super fun morning. I’m looking forward to visiting this site again, when the light is better. When the daylight low tides return in a few months they will be in the afternoon. I anticipate some fantastic light shows in these pools and channels. I’ll be teaching most afternoons by then, but will get out as often as I can.

A most unusual sort of snail

Posted on by Allison J. Gong

One of the many delightful animals in the rocky intertidal is the vermetid snail, Thylacodes squamigerus. Unlike their more typical gastropod relations, the vermetids don’t live in a shell, per se. Instead, they live in a calcareous tube, which forms a loose coil draped over the surface of a rock. The tubes can be up to about 12 mm in diameter, and, if straightened out, about 15 cm long. In some locations, Thylacodes can be very abundant. In a recent visit to Point Pinos in Pacific Grove, I saw many of them in the low intertidal. I occasionally see them on the northern end of Monterey Bay and points farther north, but at nowhere near the abundance I see in Pacific Grove. At a larger scale, iNaturalist shows observations of T. squamigerus from northern British Columbia down to southern Mexico.

Three coiled white tubes and one spherical snail on a rock amid greenish seaweed
Trio of vermetid snails (Thylacodes squamigerus) with their more conventional cousin, the black turban snail (Tegula funebralis)
2022-06-03
© Allison J. Gong
Loosely coiled whitish tube on a rock
Thylacodes squamigerus
2022-06-03
© Allison J. Gong

Most snails are either grazers (e.g., abalones, limpets, turban snails) or predators (e.g., whelks, conchs, cone snails). Thylacodes is a bit of an outlier with regards to feeding as well as housing, for it is a suspension feeder. Being entirely sessile, it cannot go out and forage. And unlike its doppelganger, the tubeworms Serpula columbiana and S. vermicularis, Thylacodes does not create a water current to catch food on ciliated tentacles. Instead, it spins threads of sticky mucus that thrash around in the current and capture suspended detritus. When the tide is out the snail hunkers down in its tube, same as any worm. It cannot feed unless it is immersed. Where the worms live in the low intertidal on exposed rocky coasts, the water is moving constantly, and it requires relatively little energy for Thylacodes to feed the way it does. As a bonus, even the calories expended in producing the mucus are recouped, as the snail ingests the mucus strands as well as the food particles they capture.

When the tide came back, I got to watch Thylacodes in action. At Point Pinos there are some areas that form lovely tidepools, deep enough for animals to react to the return of the water and clear enough to make photography and videography possible. So standing knee-deep in a pool I stuck the camera underwater and hoped for the best. And I got lucky—you can see the mucus threads!

See here:

Thylacodes squamigerus
2022-06-03
© Allison J. Gong

and here:

Thylacodes squamigerus
2022-06-03
© Allison J. Gong

And not only that, but I captured some video footage. I use a point-and-shoot for these underwater shots, and usually don’t know what or whether I’ve shot anything good until I download images and video at home. Color me happy to have seen these clips!

Despite the unusual aspects of its biology, Thylacodes is indeed a snail. It has a conventional snail’s radula, and uses it the way, say, an owl limpet (Lottia gigantea) uses hers to scrape algae off rocks at Natural Bridges. Only instead of scraping the radula against rocks, Thylacodes uses its radula to reel in the detritus-laden mucus threads. That’s what’s going on in the second video clip above.

So there you have it, another of my favorite animals. Thylacodes is one of those animals that doesn’t look like much when you see it just sitting there. But we get to see it only during the tiny fraction of its life that it spends emersed. As with most inhabitants of the rocky intertidal, much of Thylacodes‘ life occurs out of sight for human eyes. This makes the occasional sighting of Thylacodes under water especially enlightening. And delightful!

When things are just a little too swell

Posted on by Allison J. Gong
Big waves breaking on beach, with cliffs on the right side

One of the things that I’ve been doing with my Ecology class since almost the very beginning is LiMPETS monitoring in the rocky intertidal. Usually we have a classroom training session before meeting in the field to do the actual work. This year we are teaching the class in a hybrid mode, with lecture material being delivered remotely, so we don’t have class meetings except for our field trips. The LiMPETS coordinator for the Monterey Bay region, Hannah, and I arranged to meet at our sampling site, where she would do a training session on the beach before we herded everyone out into the intertidal. It truly was a great plan! But the weather intervened and a spring storm blew through, bringing in a big swell. There was a high surf warning for our area the day of our scheduled LiMPETS work. Hannah and I conferred via email and decided that we’d still give it a shot, and at least the students would have an opportunity to learn about the LiMPETS program and practice with the datasheets and gear.

I arrived early to see how the surf was looking, and it was impressive. The waves were regularly covering our sampling location with whitewash, even as the tide was going out. When my co-instructor arrived and I showed him where the transect would lie, it was an easy decision to make to cancel the monitoring. But we would still be able to do the practice stuff, so we convened with Hannah on the bluff and she went into teacher mode.

College students standing in a circle, listening to instructor
Hannah (right) explaining the LiMPETS program
2022-04-22
© Allison J. Gong

We didn’t bother with the transect, but had groups of students work through some quadrats out on the intertidal bench, which you can just see in the background of the photo above. Hannah kept everyone out of the danger zone and we stressed the importance of having one member of each group keep an eye on the ocean at all times. We stayed mostly in the high zone, venturing down into the upper mid zone only when the tide was at its lowest. Even then, the big swells would surge up the channels and splash up onto the benches. Nobody got swept off, though, or even more than a teensy bit damp.

College students in the rocky intertidal
College students in the rocky intertidal
Students working in the high intertidal
2022-04-22
© Allison J. Gong

Most of the students left after what little work we had for them to do, and that gave me the freedom to poke around on my own and take pictures. I hadn’t had a chance to do this in a long time, and intended to make the most of a decent low tide that was almost wiped out by huge swell.

So here we go!

First up, the high-intertidal seaweeds:

Olive-green seaweed on rock, with mussels surrounding
Silvetia compressa
2022-04-22
© Allison J. Gong

And here’s a typical high intertidal community at Davenport Landing. Inhabitants include:

  • Several large clumps of rockweed (Silvetia compressa and Fucus distichus)
  • Several smaller bunches of tufty reds (Endocladia muricata)
  • Mussels (Mytilus californianus)
  • Many blotches of “tar spot alga” which is the encrusting tetrasporophyte phase of Mastocarpus papillatus
Clumps of olive-green seaweeds, dark red seaweeds, and mussels on rock
High intertidal community at Davenport Landing
2022-04-22
© Allison J. Gong

The water was pretty murky, so not great for underwater photography. Some of the shots turned out pretty well, though. The soft pale purple structures that you see in the photo below are papullae, used for gas exchange. You can see these only when the star is immersed.

Clumps of pale purple transparent tubes interspersed with white blotches
Aboral surface of the ochre star Pisaster ochraceus, showing papullae and spines
2022-04-22
© Allison J. Gong

The anemones were, as always, happy to be photographed. In this shot, the anemone was being photobombed by a turban snail.

Large green sea anemone and small purple snail in a tidepool
Green anemone (Anthopleura xanthogrammica) and black turban snail (Tegula funebralis)
2022-04-22
© Allison J. Gong

Here’s another typical intertidal assemblage:

Clump of sandy tubes with mussels, barnacles, and greenish-purple seaweed
Sandcastle worm (Phragmatopoma californica), iridescent alga (Mazzaella flaccida), gooseneck barnacles (Pollicipes polymerus), and mussels (Mytilus californianus)
2022-04-22
© Allison J. Gong
Gooseneck barnacles (Pollicipes polymerus)
2022-04-22
© Allison J. Gong

A couple of students stayed after the rest of the class had left. They were happy to see the nice fat ochre stars, and so many of them in one small area.

Ochre stars (Pisaster ochraceus)
2022-04-22
© Allison J. Gong

It’s always good to see so many big ochre stars. For this species, in the intertidal areas that I visit, sea star wasting syndrome (SSWS) no longer seems to be a problem. Fingers crossed! We’ll have to see what unfolds in the next months and years.

Glow

Posted on by Allison J. Gong

On this winter solstice, as we anticipate the return of light, I thought I’d write about a different kind of light.

Merriam-Webster defines fluorescence as “luminescence that is caused by the absorption of radiation at one wavelength followed by nearly immediate reradiation usually at a different wavelength and that ceases almost at once when the incident radiation stops”. It is a type of luminescence that occurs in both biological and non-biological objects. For example, mushrooms and scorpions are notably fluorescent, as are several minerals. Technically, to qualify as “fluorescent” an object can absorb any wavelength of radiation and re-radiate any other, although the re-radiated wavelength is usually longer than the absorbed wavelength.

We humans, with our three (and occasionally four) color photoreceptor types, can see only the tiny fraction of the electromagnetic spectrum that we call visible light. The visible light range (approximately 400-700nm) is bounded by UV on the short end and infrared on the long end. Other organisms have very different light perception capabilities. We know, for example, that insects can see in UV and pit vipers can see in infrared. And as for mantis shrimps, which have as many as 12 types of photoreceptors, we don’t yet understand how they see the world, but you can bet it’s nothing like the way we do. For practical purposes, fluorescence is most easily seen when an object absorbs UV light and re-radiates light of a longer wavelength that falls into the visible light range.

When you shine a UV light on one of these fluorescent objects, you see an apparent color change from whatever it looked like under visible light. This color change is most striking in the dark, because the fluorescent object will appear to glow. The same thing happens in daylight, but is obviously more difficult to see.

Here, let me show you. A few weeks ago I went to Natural Bridges to photograph the anemones, first under normal daylight conditions and then under UV light. I have a pretty wimpy UV flashlight, it turns out, but you can still see the fluorescence.

Here’s Anemone #1, under daylight:

Sea anemone in daylight
Sunburst anemone #1 (Anthopleura sola) at Natural Bridges
2021-12-07
© Allison J. Gong

And here’s Anemone #1 under UV light:

Sea anemone under UV light
Sunburst anemone #1 (Anthopleura sola) at Natural Bridges, under weak UV light
2021-12-07
© Allison J. Gong

Striking difference, isn’t it?

This is Anemone #2. It was getting dark by then, but this photo was also taken without flash and I did not increase exposure of the image.

Sea anemone
Sunburst anemone #2 (Anthopleura sola) at Natural Bridges
2021-12-07
© Allison J. Gong

And, under UV light:

Sea anemone under UV light
Sunburst anemone #2 (Anthopleura sola) at Natural Bridges, under weak UV light
2021-12-07
© Allison J. Gong

Here’s what’s going on. Pigment molecules in the anemones’ tissues are absorbing the UV radiation and re-radiating light in the visible range. It’s easier to see the fluorescence in Anemone #2 because it was much darker when I took that set of photos. Fluorescence still occurs during the day, but we can’t see it as well in the daylight. This is why our local bowling alley does their Atomic Bowling at night! They can dim the overhead lights, crank up the black lights, and let the tunes roll.

Incidentally, if you’ve ever wondered why so-called black lights are purple, there’s a reason for it. A true black light emits only UV light. UV light is invisible to us, hence the term “black”, as in pure darkness. UV lights that ordinary folks like us can buy are tinged purple so that we can see it. The purple isn’t UV, of course, but seeing the purple light keeps people from looking into the beam and frying their retinas from the actual UV radiation.

Sea anemones, of course, do not celebrate the solstice, but they do perceive it. They, and just about every other living thing, can sense the cyclical changes in day length as the year progresses. After tonight the days will start getting longer as we move through winter and towards spring. Personally, I cannot wait until we get the early morning low tides in the spring.

In the meantime, happy solstice, everyone!

Ready for battle

Posted on by Allison J. Gong

For some reason, many of the sunburst anemones (Anthopleura sola) in a certain area at Davenport Landing were geared up for a fight. I don’t know what was going on before I got there yesterday morning, but something got these flowers all riled up. We think of them as being placid animals, but that’s only because they operate at different time scales than we are used to. A paradox about cnidarians is that they don’t do anything quickly except fire off their stinging cells; that, however, they do with the fastest known cellular mechanism in the animal kingdom. Go figure.

Pale green sea anemone with slender feeding tentacles surrounding the oral disc. Below the ring of feeding tentacles there is a ring of thick club-shaped tentacles used for fighting.
Sunburst anemone (Anthopleura sola) with inflated acrorhagi
2021-06-27
© Allison J. Gong

What looks like an anemone wearing a tutu is actually an anemone ready to fight. The normal filiform feeding tentacles are easily recognized. But those club-shaped white tentacles below the ring of feeding tentacles are called acrorhagi. They are all about fighting. The tips are loaded with potent cnidocytes that usually aren’t used to catch food. They are used to fight off other anemones, and possibly predators.

Here’s another shot of the same animal, which shows how the feeding tentacles and acrorhagi are arranged in concentric rings:

Pale green sea anemone with slender feeding tentacles surrounding the oral disc. Below the ring of feeding tentacles there is a ring of thick club-shaped tentacles used for fighting.
Sunburst anemone (Anthopleura sola) with inflated acrorhagi
2021-06-27
© Allison J. Gong

So who would this anemone be fighting? This individual was the only one of its kind in the pool where it lives. I don’t know why its acrorhagi are inflated. I suppose they could be used to fend off a would-be predator, but I didn’t see any other animal in the pool that seemed a likely candidate.

But look at this duo:

Two pale green sea anemones with slender feeding tentacles surrounding the oral disc.The anemone on the right has inflated fighting tentacles. The animal on the left has fewer inflated fighting tentacles.
Sunburst anemones (Anthopleura sola) with inflated acrorhagi
2021-06-27
© Allison J. Gong

Now, clearly there is (or had been) something going on between these individuals. They both have their acrorhagi inflated. I’ve been looking at this photo for a while and can’t decide which is the aggressor. At first I assumed that the anemone on the right had initiated an attack on the other. But now I wonder if that is a defensive posture rather than an offensive one. That animal does seem to be more bent out of shape than the one on the left.

I’ve seen anemone fights before, and I’ve also seen anemones living side by side, tentacles touching, in apparently perfect amity. It’s very clear that they can coexist peacefully. Why, then, do they sometimes choose to fight? It’s important to point out that Anthopleura sola is an aclonal species. Unlike its congener A. elegantissima, whose primary mode of growth is cloning, each A. sola represents a unique genotype. With these anemones, whether or not two individuals fight is not determined by relatedness.

In a different pool these two anemones are sharing the carcass of a rock crab.

Sunburst anemones (Anthopleura sola)
2021-06-27
© Allison J. Gong

Maybe that third anemone at the top had also taken part in the feast, but at this point it seemed to be minding its own business. Given the demonstrated aggression of some A. sola, it would be interesting to know whether or not this trio ever fight amongst themselves. When we ‘ooh’ and ‘aah’ over them in the tidepools they look like passive flowers, and we forget that they are active predators. But we humans have access to the anemones’ home for only a few hours every month, and I have no doubt that they get up to all sorts of shenanigans when we’re not looking.

Letting gravity do the work

Posted on by Allison J. Gong

This morning I went to Natural Bridges. The tide this morning was the lowest of the season, but early enough that for the most part I had the intertidal to myself for a couple of hours. I always like those mornings best.

I did meet a docent out there, and we chatted for a few minutes. Towards the end of the excursion, when the tide had turned and I realized I had to get to the marine lab for the usual Friday feeding chores, she pointed out something that didn’t make sense to her. She described it as two anemones side-by-side, but one was really stretched out down towards the water. She wondered what could be going on, as the other anemone looked normal.

Two large sea anemones at the edge of a tidepool. The anemone on the left is stretched down to more than twice the length of the anemone on the right.
Sunburst anemone (Anthopleura sola) and giant green anemones (Anthopleura xanthogrammica)
2021-06-25
© Allison J. Gong

Looks strange, doesn’t it? What this anemone is doing, I think, is disgorging the remains of its most recent meal. If you look at the oral end, which is indeed stretched down towards the sandy bottom of the pool, you can see two things sticking out. The whitish blob is the internal part of the anemone’s pharynx. It is not at all uncommon for anemones to sort of prolapse the pharynx, especially after a big meal. Remember, anemones have a two way gut with a single opening for both food ingestion and waste expulsion. The other thing sticking out of the mouth is a clump of mussel shells thickly coated with slime.

Here’s a close-up of what’s going on at the mouth of this anemone:

Sunburst anemone (Anthopleura sola) disgorging mussels
2021-06-25
© Allison J. Gong

It’s hard to tell whether or not the mussels have been opened and digested by the anemone. It looks like at least some of the acorn barnacles attached to the mussel might still be alive, although smothered in slime. Nor can we see how many mussels are still inside the anemone’s gut. In any case, the anemone is getting rid of this part of the mussel clump. However, this isn’t a phenomenon that can really be watched, unless you can watch in time-lapse. The docent asked, “Doesn’t it use peristalsis, or something like that?” The answer is that no, anemones don’t use peristalsis. They don’t have the type of muscles that can contract in that way. The anemone still has to somehow expel wastes and undigestible matter from its gut, through that single opening that we call a mouth but functions as both mouth and anus.

Our human gut, of course, uses peristalsis to move food along from esophagus to rectum. And while for the most part we don’t like to think about how that works, we have all experienced what happens when things don’t go as planned. I doubt that anybody gets through life without vomiting, so it is probably safe to say we all know that it is a violent way to thoroughly expel food, toxins, and other noxious items from the stomach. Anemones, however, have no peristalsis and cannot vomit. How, then, does an anemone void its gut of something larger than the typical digestive waste?

This particular anemone is ideally situated to let gravity do the work. Hanging down like this and relaxing the simple sphincter muscle around the base of the tentacles will allow the mussel clump to eventually fall out. Without peristalsis to speed things along, it will probably take a while. Would it be finished by the time the tide comes back? I couldn’t stick around to watch, so I can’t say. But it was a very cool thing to see, even though it happens about as fast as paint drying.