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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!

4

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.

3

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.

2

Sometimes things just work out, through no fault of my own. In terms of good minus tides occurring in daylight hours, this weekend's tides are the best we will have all season. Today (Saturday 29 May) is the third of five intertidal excursions I have planned. This morning I went up to Pistachio Beach to collect some things for the Seymour Center. I always feel a teensy bit apprehensive agreeing to collect for anybody but myself, because it is quite likely that I will get skunked and not be able to bring back what is needed. So usually I just agree to keep my eyes open for things that are on the wish list and make no promises.

The current wish list for the Seymour Center includes fishes. I've already brought them some sculpins and a clingfish, but small pricklebacks are also welcome. Pistachio is a popular place for people who fish for large pricklebacks. Apparently they (the pricklebacks) put up a good fight and make tasty eating. The usual way of fishing for them is poke-poling. I am not entirely sure how that works, but it involves a long pole and baited hooks. I think the idea is to lure a prickleback out from its hiding place at low tide, when it is sort of stranded away from open water. Adults get up to 70-80 cm long, and are as big around as my forearm.

Unlike the fishermen, I was fishing for young pricklebacks, hoping to find some that were about the length of my hand. Possessing the ideal set of characteristics for avoiding capture—a long eel-like body, small head, slimy coating, and the ability to augur really quickly into even the tiniest crack amongst the cobbles—these small fish led me on a merry chase for quite a while. However, the advantages that I have over even a wily prickleback are an enlarged cerebral cortex, opposable thumbs, and the dexterity to use both a dip net and a zip-loc baggie. When all was said and done I had two appropriately sized pricklebacks in my baggie, and two others had gotten away from me. Oh, and I did also bag another clingfish!

Having had that bit of success and not wanting to press my luck, I started poking around just for the hell of it, without any clear objective in mind. As I've said before, what we gain from a super low tide like this (-1.6 ft) is not only access to more real estate in the low intertidal, but more time to spend there before the tide returns. I took lots of photos, which I will present in chronological order. These will give you an idea of what it was like out there this morning.

Even the hike across the beach yielded something nice—this small stand of Postelsia palmaeformis, the sea palm. These poor junior kelps will be taking a beating with these spring tides rushing up and down. That's the price they pay for living out there on those exposed rocky points.

Group of 6 sea palms on the beach
06:53 Postelsia palmaeformis
2021-05-29
© Allison J. Gong

The leather star Dermasterias imbricata isn't one of the most common stars in the intertidal around here. It was one of the species that was hit pretty hard by the most recent outbreak of Sea Star Wasting Syndrome. We see one every so often, but they are nowhere as abundant as the ochre stars or bat stars.

07:10 Dermasterias imbricata
2021-05-29
© Allison J. Gong

Pistachio Beach isn't the best place for large anemones, but of course there are some. This is one of the few big Anthopleura anemones that I saw today. There are many of the small cloning anemones, A. elegantissima, in the high intertidal, as well as the moonglow anemones, A. artemisia, in the mid and low sandy areas.

07:12 Anthopleura xanthogrammica
2021-05-29
© Allison J. Gong

I was so pleased to see my favorite red alga doing really well in the low zone! It is so pretty.

Red seaweed
07:29 Erythrophyllum delesserioides
2021-05-29
© Allison J. Gong

And at the same time I accidentally discovered a pretty big rock crab, which was tucked under a rock. For its species, this one was pretty calm and didn't come at me with big claws up. It could be that this crab is a male, and is clasping a female beneath him. I didn't check.

Dorsal view of a rock crab
07:29 Romaleon antennarium
2021-05-29
© Allison J. Gong

One of the things I found while turning over rocks to look for fish is this purple urchin:

Sea urchin with purple and green coloration
08:02 Strongylocentrotus purpuratus
2021-05-29
© Allison J. Gong

And a bit later, a nice healthy group of Dictyoneurum californicum. As these thalli age, they will develop longitudinal splits at the base of the blades. Right now they are young and crispy.

Blades of a brown seaweed with a waffle-like texture
08:15 Dictyoneurum californicum
2021-05-29
© Allison J. Gong

And who can resist such an exuberantly decorated limpet? Certainly not I! Reminds me of the fancy hats that ladies used to wear for Easter. Or Beach Blanket Babylon.

Limpet heavily fouled with encrusting and upright coralline algae
08:28 Limpet, probably Lottia sp.
2021-05-29
© Allison J. Gong

Chitons, the overlooked molluscs that reach peak abundance and diversity in the intertidal, can be very common along the coast. Species composition varies from site to site, though. Here at Pistachio Beach, the two species of Tonicella are very common. I found several of them on the undersides of rocks. This one is T. lokii.

Chiton with dark wavy lines on the shell plates and alternating pink and beige patches on the girdle
08:52 Tonicella lokii
2021-05-29
© Allison J. Gong

After two hours of catching fish and looking around, I was getting cold. Time to head back up and out. That took an additional half-hour or so, because I kept getting distracted by the algae. For example, look at how beautiful this Fucus is. And note the swollen tips, which mean this thallus is getting sexy. 'Tis the season, after all.

Olive-green seaweed with wide dichotomous branches and swollen branch tips
09:15 Fucus distichus
2021-05-29
© Allison J. Gong

One of the other rockweeds, Pelvetiopsis limitata, was also very thick and abundant.

Olive-green seaweed with narrow dichotomous branches
09:19 Pelvetiopsis limitata
2021-05-29
© Allison J. Gong

The rockweeds share the high intertidal with a few species of red algae. The most common reds in this zone are the two (or however many there are) species of Mastocarpus, and Endocladia muricata.

Reddish-brown seaweed with wavy blades, covered with tiny bumps
09:21 Mastocarpus papillatus
2021-05-29
© Allison J. Gong

I always want to stop and look around in the high zone on my way down. Because when I walk past sights like this, it's hard not to stay and study more closely. Then I remember that I can take as much time as I want in the high zone on the way out. This morning I took lots of photos of these reds and rockweeds.

How many different types of seaweed can you see?

09:24 High intertidal algal assemblage
2021-05-29
© Allison J. Gong

So there you have it, my morning summarized in about a dozen photos. I hope your Saturday was as enjoyable as mine was!

1

The rocky intertidal is coming into its full summer glory right now. The early morning low tides have been spectacular in May, and they'll get better for the remaining few days of the month. This morning I went out to Franklin Point to poke around. Low tide was -1.8 feet (yippee!) at 06:13. And for once the swell was also down, so the ocean seemed very far away from the mid-tidal zone. See?

Intertidal rocks covered with algae and surfgrass
Rocky intertidal at Franklin Point
2021-05-27
© Allison J. Gong

One thing that's nice about Franklin Point is that despite its exposure, especially on the north side of the point, all those boulders provide a lot of protection from the incoming waves. It's amazing how they serve to dissipate the water's energy. Of course, that doesn't prevent the inevitable rise of water in the pools, but at least when it arrives it just floods boots instead of knocking down a distracted marine biologist.

Here's a 20-second video I shot from the same spot.

Just as in any terrestrial habitat, summer is when the photosynthetic organisms come to dominate the rocky intertidal. Even a cursory glance shows that every surface is covered with algae and/or surfgrass. So why not showcase some of these organisms when they look their best?

Fronds of feather boa kelp
Feather boa kelp (Egregia menziesii)
2021-05-27
© Allison J. Gong

In terms of biomass, Egregia is by far the most abundant alga along our intertidal coast. Individual fronds can be 5+ meters long, and several fronds arise from each holdfast. Higher up in the mid tidal zone the Egregia was forming curtains hanging down along vertical faces.

Large stand of feather boa kelp hanging down from rocks in the mid-tidal zone
Feather boa kelp (Egregia menziesii) and other intertidal algae
2021-05-27
© Allison J. Gong

But Egregia does know how to share the spotlight. Here it is posing with a couple of other low tidal denizens:

Egregia menziesii, Laminaria setchellii, and Phyllospadix torreyi
2021-05-27
© Allison J. Gong

That's Egregia on the left, of course. One of the laminarian kelps, Laminaria setchellii, is taking center stage in this shot. When it lives in the subtidal Laminaria setchellii is an understory kelp; it gets to about 1.5 meters tall and can form dense stands. In this species each holdfast gives rise to a single stipe that in turn opens into a wide blade that is deeply divided, as you can see. The surfgrass Phyllospadix torreyi is on the right. There is a lot of surfgrass in the rocky intertidal these days. It's pretty treacherous stuff, too. It's very slippery and likes to cover pools that are deeper than you'd expect. I've learned the hard way that it cannot be trusted at all.

My favorite seaweeds are always the reds. And my favorite of the reds is Erythrophyllum delesserioides, looking so lush and pretty this time of year. It is a low intertidal species, and can be locally abundant. Some years it seems to get beat up and look ratty, but this year it looks great. Here it is, surrounding a couple of Laminaria setchellii.

Leafy red seaweed and a brown kelp
Erythrophyllum delesserioides and Laminaria setchellii
2021-05-27
© Allison J. Gong

Here's a grouping of Erythrophyllum and some other reds. I can see two species of Mazzaella, and of course there are Egregia and Phyllospadix mingled together on the right. So pretty!

 in the rocky intertidal
Mixed assemblage of red algae (Mazzaella flaccida, Mazzaella splendens, and Erythrophyllum delesserioides)
2021-05-27
© Allison J. Gong

When the tide is as low as it was this morning, a marine biologist has a lot of time to explore. I had just about exhausted the batteries in both my camera and my phone and was getting uncomfortably cold when I decided to head in. On the way back I stopped to take a look at the rockweeds, which live in the high intertidal. Franklin Point isn't a hotspot for rockweed abundance or diversity, but I did see this nice thallus of Fucus.

Rockweed (Fucus distichus)
2021-05-27
© Allison J. Gong

Fucus is the seaweed with the bifurcated branch tips. The tips are starting to swell up, which means this thallus is getting ready to spawn. Of all the algae, rockweeds are unusual in that they have what phycologists call an "animal-like" life cycle. They don't have sporophytes or gametophytes. They just have bodies, or thalli. Some thalli are female and some are male. Instead of releasing multiple kinds of spores and whatnot, they release eggs and sperm. The resulting zygote develops as you would expect, only instead of forming a young animal it grows into a baby seaweed.

I do love that olive green color of the rockweeds, which belong to the phylum of brown algae (Ochrophyta). Notice that there's a bit of similarly colored sheetlike seaweed right below the Fucus. That seaweed has the same color, but is in the red algae (Phylum Rhodophyta). Once again, we are reminded that the algae cannot be reliably sorted into phyla based solely on color. Mother Nature can be very tricksy!

So there you have it, my trip report for this morning's excursion to Franklin Point. The tides are excellent for the next several days, and I will be out there for most of them. This is my favorite time of the year.

1

As we speed towards the summer solstice the days continue to get longer. The early morning low tides are much easier to get up for, as the sky is lightening by 05:30. Even so, when traveling an hour to get to the site, it's nice when the low is later than that. This past Saturday the low wasn't until 08:00. My parents were in Monterey for the weekend, so I decided it would be a good day to work the tide at the southern end of Monterey Bay, and then visit my parents. The Monterey Peninsula has some of the most spectacular tidepooling terrain in the region, and if I lived closer you can bet I'd know those sites better. Not that there is anything at all wrong with the sites on my end of the Bay and up the coast. But sometimes it's good to get out of one's comfort zone and explore the less well known.

Rocks and tidepools
Rocky intertidal at Asilomar State Beach
2021-05-15
© Allison J. Gong

So explore we did. It was cold and windy. The tide wasn't all that low and the swell was up, so we didn't get beyond the mid-tidal zone. My hip boots have deteriorated to the point that I have pinprick leaks at the seam where the boot part meets the leg part. Usually the tiny leaks don't bother me, but when the water is cold I definitely feel the trickles. What all this means is that I didn't get down into the low zone, which is fine. Biodiversity is highest in the mid zone anyway. The mediocrity of the low tide meant that I had to keep an eye out for sneaker swells, so less heads-down poking around and more scanning from above and then zooming in on individual items of interest.

One thing we noticed right away is that groups of Tegula funebralis, the black turban snail, were clumped together above the waterline of the high pools.

I'm trying to decide whether or not this is noteworthy. The pattern did catch my eye, but that might be only because it's unusual (although not particularly interesting). It was a cold and drizzly morning, so the snails didn't have to worry about desiccation. Was the clumping together benefiting the snails in any significant way? Hard to say.

The T. funebralis were also clumping together in the water! Here's a large clump of Tegula shells in a pool.

Clump of black turban snails in a tidepool
Black turban snails (Tegula funebralis) and one hermit crab (Pagurus samuelis)
2021-05-15
© Allison J. Gong

Almost all of these are snails, but can you see the one that is a hermit crab?

Poor Tegula funebralis. It is so common that it is invisible and vastly underappreciated. I find them quite charming, though. There's something about a grazing snail's slow way of life that is very soothing. Not that you might not fall asleep waiting for them to do something interesting, but it is good to slow down to the pace of nature. Anyway, Tegula is one of my favorite animals, precisely because it is so unassuming and ignored. One of delightful things about Tegula funebralis is when it plays host to Crepidula adunca. I've written about the biology of C. adunca before and don't want to rehash that here. I just wanted to show off my favorite photo of this trip to Asilomar:

Black turban snail with two attached slipper snails
Black turban snail (Tegula funebralis) wearing two slipper snails (Crepidula adunca)
2021-05-15
© Allison J. Gong

I don't know why I like this photo so much. It certainly isn't the best shot I've ever taken. There isn't any vibrant color at all. The subjects are the same color as the background. But it works for me.

When it comes to a snail's pace, you can't find anything slower than Thylacodes. That's because Thylacodes squamigerus is the snail that lives in a calcareous tube. Much like a barnacle, or the serpulid worms that have similar tubes, Thylacodes makes one decision about where to live and lives there for the rest of its life. I see Thylacodes at places like Pigeon Point up north, but they are much more abundant on the Monterey Peninsula.

Tube snail (Thylacodes squamigerus)
2021-05-15
© Allison J. Gong

And the snail winners in the Most Likely to be Overlooked have got to be the littorines. These little snails (most of which are smaller than 15 mm) live in the highest intertidal, where they get splashed by the ocean just often enough to keep their gill sufficiently moist. They are never entirely submerged, but they do tend to gather in cracks, even the tiniest of which will hold water longer than a flat rock surface.

Littorines (Littorina keenae) in the splash zone
2021-05-15
© Allison J. Gong

If you look closely at the photo above, you might see pairs of mating snails. Given where they live, high up in the intertidal where they are rarely covered by water, broadcast spawning isn't a viable option for the littorines. They have to copulate. There are, I think, eight copulating pairs in this group of ~30 snails.

Copulating pairs of Littorina keenae
2021-05-15
© Allison J. Gong

Because Littorina's habitat makes broadcast spawning an unfeasible option, the snails must lay eggs. But the splash zone isn't a very friendly place for the eggs of marine animals. The littorines lay eggs in gelatinous masses in crevices or depressions where water will remain. After a week or so of development, the egg mass dissolves as it gets splashed, and veliger larvae emerge. They recruit back to the intertidal after spending some period of time in the plankton.

When all is said and done it's difficult to make the claim that snails live exciting lives. Nonetheless, they are interesting animals. The diversity of morphology and lifestyle we see in the intertidal snails makes them eminently worthy of study and appreciation. I like to think that, as biologists once again "discover" the usefulness of natural history, students will be encouraged to fill in some of the gaps in our understanding of these and other abundant animals.

For animals that do essentially nothing when you see them where they live, chitons have a lot of charm. They are the kind of animal that, once you develop the search image for them, you start seeing everywhere. It helps that they are easily recognized as being chitons because of their eight dorsal shell plates—nothing else looks like them. Depending on species, those shell plates can be smooth or sculpted, and pigmented or not. Patterns of sculpting and pigmentation (or lack thereof) are diagnostic features used to distinguish different species. Some species are reliably consistent in appearance and look the same wherever you happen to see them. Other species show a lot of phenotypic variation, often even at a single site.

One of my favorite chitons is Mopalia muscosa, the mossy chiton. It's one of the easiest of our chitons to identify, because its girdle (the layer of tough tissue in which the shell plates are embedded) is densely covered by long, curved spines. They're called spines, but they're quite soft and flexible. Your basic Mopalia muscosa looks like this:

Mossy chiton with bare shell plates, in the rocky intertidal
Mossy chiton (Mopalia muscosa) at Pigeon Point
2016-04-24
© Allison J. Gong

Mopalia muscosa is one of the species whose appearance is quite variable. Many of them wear algae, usually reds but occasionally greens or browns, on their shell plates. Not all species of chiton do this. I've often wondered why some chiton species wear algae and others do not. This individual is probably fairly old, judging by the worn condition of the shell plates. The plates show signs of erosion, but are not decorated. There are some small pieces of coralline algae amongst the spines of the girdle, though, which I always associate with age. Smaller, and presumably younger, M. muscosa tend not to have algae on the girdle even if they are wearing some on the shell plates.

The degree of shell decoration in M. muscosa varies from none, as above, to heavy encrustation. This individual below has been colonized by only a small bit of coralline algae and perhaps some brown diatom-ish film on the edges of the shell plates:

Mossy chiton (Mopalia muscosa) at Pistachio Beach
2021-02-09
© Allison J. Gong

This next one has only a small bit of coralline alga, but sports a jaunty sprig of something quite a bit larger.

Mossy chiton (Mopalia muscosa) at Asilomar
2019-07-04
© Allison J. Gong

This season's fashionable chiton will go all out with the coralline algae, wearing both encrusting and upright branching forms. Look at this:

Mossy chiton (Mopalia muscosa) at Pigeon Point
2017-06-28
© Allison J. Gong

and this:

Mossy chiton (Mopalia muscosa) at Pigeon Point
2018-01-01
© Allison J. Gong

Sometimes the chitons wear the larger leafy red algae, in addition to or in place of the coralline algae. I always think that these individuals must be very old, by chiton standards.

Mossy chiton (Mopalia muscosa) at Pigeon Point
2020-11-14
© Allison J. Gong

And sometimes the chitons are so covered with algae that they blend in perfectly with the surrounding environment.

Mossy chiton (Mopalia muscosa) at Pistachio Beach
2021-04-06
© Allison J. Gong

These chitons can get very heavily fouled by algae. Is there any benefit to the chiton, to carry around a load of red algae? And if wearing algae is for some reason advantageous, is there a way for a chiton to attract algae to settle on their shell plates? Well, let's think about that. Chitons' main predators would be sea stars, crabs, and birds. Sea stars do not locate prey visually, so camouflage would not be very helpful in avoiding them. Birds such as oystercatchers and surfbirds certainly do pry up chitons and limpets, and blending in with the background just might help a chiton go unnoticed by an avian hunter.

Regarding the matter of how the algae end up living on chitons' bodies, I want to start with the question of how prevalent algal fouling is on Mopalia muscosa, and the extent of fouling on the chitons that are wearing algae. A little research study might be a fun way to spend my time in the intertidal. Pigeon Point is a lovely site on a foggy summer morning, and many of the most heavily decorated M. muscosa in my photo library are from there. Yes, I can foresee several visits up the coast over the next few months. Laissez les bons temps rouler!

4

On the penultimate day of 2020 I met up with my goddaughter, Katherine, and her family up at Pigeon Point to have two adventures. The first one was to find a marble that had been hidden a part of a game. We got skunked on that one, although the marble was found after we left and the hider had sent an additional clue. The second adventure was an excursion to the tidepools. I've had a lackadaisical attitude towards the afternoon low tides this winter, not feeling enthusiastic about heading out with all of the people and the wind and having to fight darkness. But the invitation to join the marble hunt, on a day with a decent low tide, meant that I could spend a good deal of quality time with Katherine.

It is not unusual for a promising low tide to be cancelled out by a big swell. It happens, especially during winter's combination of afternoon lows and occasional storms. The swell yesterday was pretty big.

Here's the view to the north, from Pigeon Point:

Looking north from Pigeon Point
View to the north from Pigeon Point
2020-12-30
©Allison J. Gong

All that whitewash breaking over the rocks is not good for tidepooling, especially with small kids in tow.

This is how things looked to the south of the point:

View to the south from Pigeon Point
2020-12-30
©Allison J. Gong

This is Whaler's Cove, a sandy beach that lies on the leeward side of the point itself. See how the water is much calmer? It's amazing how different the two sides of the point are, in terms of hydrography, wind, and biota. The south side is much easier to get to, especially for newbies or people who are less steady on their feet. Being sheltered from the brunt of the prevailing southbound current means that the biological diversity is, shall we say, a bit subdued when compared to what we see on the north side of the point.

I first took Katherine tidepooling when her sister, Lizzie, was an infant riding in her mom's backpack. Katherine was about four at the time. Her mom and I were suprised at how much she remembered. She recognized the anemones right away, even the closed up cloning anemones (Anthopleura elegantissima) on the high rocks. She remembered to avoid stepping on them—that's my girl!

She wasn't all that keen on touching the anemones, though, even after we told her it feels like touching tape.

Giant green anemone in tidepool
Giant green anemone (Anthopleura xanthogrammica)
2020-12-30
©Allison J. Gong

She did like the sea stars, too. Purple is my favorite color and I think hers, too, so the purple and orange ochre stars were a hit. It was nice to see two large healthy ones.

I had some actual collecting to do, so it was a work trip for me. Late December is not the best time to collect algae, but I wanted to bring some edible seaweeds back to the lab to feed animals. We haven't had any kelp brought in since the late summer, and urchins are very hungry. They will eat intertidal seaweeds, though, and when I go out to the tidepools I bring back what I can. It will be a couple of months until we see the algae growing towards their summer lushness, but even a few handfuls of sea lettuce will be welcome to hungry mouths.

Bright green sea lettuce growing with red algae
Sea lettuce (Ulva sp.)
2020-12-30
©Allison J. Gong

Katherine and I walked up the beach for a little way to study one of the several large-ish crab corpses on the sand. This one was a molt rather than an actual corpse.

Rock crab molt on sand
Rock crab (Romaleon antennarium) molt
2020-12-30
©Allison J. Gong

Katherine found the missing leg a little way off, and we discussed why we call these limbs legs instead of arms. "They use their claws to pinch things, like hands," she said. Not wanting to get into a discussion of serial homology and crustacean evolution with a 6-year-old, I told her that calling the claws "hands" isn't a bad idea, since they are used a lot like the way we use our hands. But, I continued, the crab walks on its other limbs like we walk with our legs, so can we call those legs? She was happy to agree with that. I can tell I will have to be careful about how I explain things to her, so that she doesn't come up with some wonky ideas about how evolution works.

In the meantime, Lizzie, the little sister, was having a grand old time. She flooded her little boots without a complaint and, after her mom emptied the water from them, squelched happily along with soggy socks. That girl may very well grow up to be a marine biologist!

Once the sun went behind the cliff it started getting cold. With one child already wet we decided to head back. On our way up the beach we saw this thing, which I pointed out to Katherine:

"What is it?" she asked. When I asked what she thought it was she cocked her head to one said and said, "It looks like a rock." Then I told her to touch it, which she didn't want to do. So I picked it up and turned it over, to show her the underside:

Gumboot chiton (Cryptochiton stelleri)
2020-12-30
©Allison J. Gong

These big gumboot chitons do look more interesting from this side, because you can at least see that they are probably some kind of animal. Katherine had seen some smaller chitons on the rocks, so she had some idea of what a chiton is, but these are so big that they don't look anything like the ones we showed her earlier. Plus, with their shell plates being covered with a tough piece of skin and invisible, there are no outward signs that this bizarre thing is indeed a chiton. Katherine was not impressed.

At this time of year, when the sun decides to go down it goes down fast. But as we were walking back across the rocks the tide was at its lowest, so there was more terrain to explore. Then it was back up the stairs to the cars, where we could get warm and dry.

Beach and lighthouse at Pigeon Point

Oh, and Katherine and her mom and sister were able to find the hidden marble! They also hid one of their own for someone else to find.

5

On the afternoon of July 31, 2020 the world of invertebrate biology and marine ecology in California lost a giant in our field. Professor Emeritus John S. Pearse died after battling cancer and the aftereffects of a stroke.

John Pearse in the intertidal at Soquel Point
2017-05-28
© Allison J. Gong

John was one of the very first people I met when I came to UC Santa Cruz. Before we moved here, my husband and I came and met with John, who was not my official faculty sponsor but agreed to show us around so we could check out different areas for a place to live. In fact, I had applied to the department to do my graduate work in John's lab, but because he was considering retirement the department wouldn't let him take on a new Ph.D. student. But when we needed some help getting acquainted with Santa Cruz, John and his wife, Vicki Buchsbaum Pearse, graciously let us stay at their house and spent a day driving us around town and showing us eateries as well as potential neighborhoods.

By happenstance we ended up living down the hill from John and Vicki. We had met their blue duck, Lily, and I used to fill spaghetti sauce jars with snails from our tiny yard and trudge up the hill to feed them to her. She gobbled them up like they were her favorite treat.

As one of the regional experts in invertebrate biology, John was on all of my graduate committees. There were always a half-dozen or so of us grad students working with invertebrates, and we all tended to hang out together. John was one of the things we shared in common. And even if he wasn't technically on one's committee, he would always be available for consultation or advice as needed.

When John retired, he didn't leave the campus. He remained a presence at the marine lab, and still did field work. He started incorporating young students in his long-term intertidal monitoring research, which morphed into the LiMPETS project. The combination of working with students while producing robust scientific data was the perfect distillation of John's legacy. He said this about LiMPETS:

This is one of the best things I could ever do to enhance science education and conservation of our spectacular coastline. Working with teachers and their students is a wonderful and fulfilling experience.

John S. Pearse, Professor Emeritus
UC Santa Cruz

The last time I saw John was in the summer of 2019, during his annual Critter Count. He started these Critter Counts back in the 1970s, monitoring biota at two intertidal sites in Santa Cruz. These sites have since been incorporated into the LiMPETS program. I'm sure it made John smile whenever he thought of generation after generation of schoolkids traipsing down to the intertidal with their quadrats and transect lines, counting organisms the way he had for so many years.

When I started teaching my Ecology class, John suggested that I take the students out to Davenport Landing to monitor at the LiMPETS site there. That is another of his long-term sites, and he was worried about losing information if it were not sampled at least once a year. My students have done LiMPETS monitoring three years now, and John accompanied us on at least two of those visits. I tried to impress upon the students that having John Pearse himself come out with us was a Big Deal, but am not sure I was able to convince them of how fortunate they were. I bet there are a lot of marine biologists in California who would dearly love to go tidepooling with John. And now no one else will.

John Pearse and Todd Newberry, the other professor who gets the blame for how I think about biology, taught an Intertidal Biology class. I came along on many of the field trips the last year they taught it. I remember getting up before dawn to drive down to Carmel, park in the posh neighborhood streets, and walk down to meet John and Todd in the intertidal. I remember slogging through the sticky mud at Elkhorn Slough, digging for Urechis and hearing John shout "It's a goddamned brachiopod!" from across the flat. I remember bringing phoronid worms back to the lab, looking at them under the scope, and watching blood flow into and out of their tentacles. I remember John taking an undergraduate, Jen, and me out to Franklin Point, and showing me my very first staurozoans. That was probably around 1996, and I'm still in love with those animals.

I'm no John Pearse or Todd Newberry, but I'm a small part of their giant legacy in this part of the world. I strive to instill in my students the joy and intellectual pleasure in studying the natural world that I inherited from John and Todd. Partly to honor them, but mostly because it suits my own inclinations, I'm on a one-woman crusade to bring natural history back into modern science and science education.

I've spent the last two mornings in the intertidal at two of the LiMPETS sites, as part of a personal tribute to John. I thought there would be no greater way to memorialize John than by spending some quality time in the intertidal, where he trained so many young minds. I was thinking of him as I took photos, and thought he would be pleased if I shared them.

Natural Bridges—4 August 2020

Shore crab (Pachygrapsus crassipes)
2020-08-04
© Allison J. Gong

And because, like me, John had a special affinity for the anemones:

Sunburst anemone (Anthopleura sola)
2020-08-04
© Allison J. Gong
Sunburst anemone (Anthopleura sola)
2020-08-04
© Allison J. Gong

And he would have loved this. What is going on here? How did this pattern come to be?

Anemones (Anthopleura elegantissima and possibly A. sola)
2020-08-04
© Allison J. Gong

And look at this, three species of Anthopleura in one tidepool! Can you identify them?

Tidepool at Natural Bridges
2020-08-04
© Allison J. Gong

Davenport Landing—5 August 2020

It was windy and drizzly this morning. I ran into a friend, Rani, and her family out on the flats; they were leaving as I arrived. I hadn't seen her since before the COVID-19 lockdown began back in March. She was also visiting the tidepools to honor John Pearse. We chatted from a distance and exchanged virtual hugs before heading our separate ways.

It felt like a John Pearse kind of morning. I recorded the video clip I needed for class, collected some algae and mussels for a video shoot tomorrow, and took a few photos.

A typical intertidal assemblage (sea stars, sea anemones, and algae) at Daveport Landing
2020-08-05
© Allison J. Gong

And even though I'm not very good at finding nudibranchs, even I couldn't miss this one. It was almost 4 cm long!

Nudibranch (Triopha maculata) at Davenport Landing
2020-08-05
© Allison J. Gong

The ultimate prize for any tidepool explorer is always an octopus. When I take newbies into the field that's what they always want to see. I have to explain that while octopuses are undoubtedly there and common, they are very difficult to find. You can't be looking for them, unless you really like being frustrated.

But John must have been with me in spirit this morning, because I found this:

Red octopus (Octopus rubescens) at Davenport Landing
2020-08-05
© Allison J. Gong

It was just a small one, with the mantle about as long as my thumb. I found it because I spotted something strange poking out from a piece of algae. It was the arm curled with the suckers facing outward. I touched it, and the arm retracted. It didn't seem to like how I tasted.

And lastly, for me this is the epitome of John Pearse's legacy: Working in the intertidal, showing students how to identify owl limpets. I hope they never forget what it was like to learn from the man who with his wife, literally wrote the book about invertebrates and founded LiMPETS.

John Pearse in the intertidal with my students
2016-04-29
© Allison J. Gong

RIP, John S. Pearse. You left behind some enormous shoes to fill and a legacy that will stretch down through generations. I count myself lucky to have spent time with you in the field and in the lab. While I will miss you sorely, it is my privilege to pass on your lessons. Thank you for all you have taught me.

Biology is a field of science with very few absolutes. For every rule that we teach, there seems to be at least one exception. I imagine this is very frustrating for students who want to know that Something = Something every single time. It certainly is easier to remember a few rules that apply to everything, than to keep track of all the cases when they don't.

Take, for example, the tube feet of sea stars. Among the generalities that we teach are: (1) sea star tube feet are used for locomotion and feeding; and (2) sea star tube feet are used to stick firmly to rocks and to pry open mussel shells. And we can show many examples of stars clinging to vertical and overhanging surfaces.

Purple sea star sticking to vertical rock surface in the intertidal
Ochre star (Pisaster ochraceus) at Franklin Point
2015-07-15
© Allison J. Gong
Purple sea star sticking to granite boulder in the intertidal
Ochre star (Pisaster ochraceus) at Mitchell's Cove
2019-06-03
© Allison J. Gong

Sometimes we can even find Pisaster doing both at the same time:

Ochre star (Pisaster ochraceus) wrapped around mussel(s) (Mytilus californianus) while clinging to an overhanging surface at Natural Bridges
2020-07-06
© Allison J. Gong

A photo like the one above is merely a snapshot of an event that lasts for hours. What's going on in there? Chances are it's a life-or-lunch battle, with the star trying to pry open the mussel just enough to slide its stomach between the shells while the bivalve is holding its shells clamped shut for dear life.

Each of these behaviors-—sticking to rocks and prying open mussels—is possible because Pisaster ochraceus has suckered tube feet. The tube foot itself has a flattened surface that squishes out a tiny dab of sticky adhesive glue. Together, the tube feet can adhere quite strongly to hard surfaces. I know from experience that it is impossible to pry an ochre star off a rock after it has had a chance to hang on, unless you're willing to damage several dozen tube feet. The tube feet will grow back, but there's no point in causing harm to the animal.

Arm tip of a sea star in a tidepool, showing suckered tube feet sticking to a rock
Tube feet at the arm tip of Pisaster ochraceus
2019-06-18
© Allison J. Gong

So that's the general story we teach in school. For most students, that's the entire story. However, it's always the exceptions, the deviations from the norm, that are the most interesting.

Not every sea star clings to rocks in the intertidal. There are several species that are equally at home on both rocks and sand. And among the rock-clingers, not all are as strong as Pisaster ochraceus. The ochre star's sucker-shaped tube feet are an example of the relationship between form and function: the tube feet's morphology provides the surface area for adhesion that allows the animal to feed and locomote over hard surfaces.

Spiny sand star (Astropecten armatus) at the Seymour Marine Discovery Center
2020-07-15
© Allison J. Gong

As you might expect, sea stars that don't cling to rocks and pry open mussels may not have sucker-shaped tube feet. The spiny sand star, Astropecten armatus, has pointed tube feet! It's hard to see exactly what the tube feet look like in the photo, but here's a video:

See how the tube feet on the underside of that arm end in points rather than suckers? If we revisit the notion of form and function, what questions come to mind when you look at the morphology of the tube feet? And given Astropecten's common name and its habitat, can you think of how it can survive and get around without the sticking power of Pisaster's tube feet?

Observation of Astropecten in its natural habitat would show that it spends a lot of time buried in the sand. It somehow has to get below the surface of the sand, where it feeds on olive snails or other animals that live buried there. How can it do that? Would the generalized sea star sucker-shaped tube feet that we teach to students be useful for burrowing? We can also think about it in a more familiar context: If you had to dig a hole in the ground, would you reach for a plunger? Clearly you wouldn't. You'd use a shovel, or a spade.

Astropecten's pointed tube feet are perfect for punching down between sand grains, enabling the star to work its way down into the sand. The sand star has hundreds of tiny spades at its disposal to use for digging. Circular structures shaped like miniature horse hooves wouldn't be very good at this job, nor would pointed tube feet be very good at sticking to rocks. This animal doesn't obey the "rules" of sea star biology, but form and function, as always, go together.

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