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:
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:
This next one has only a small bit of coralline alga, but sports a jaunty sprig of something quite a bit larger.
This season's fashionable chiton will go all out with the coralline algae, wearing both encrusting and upright branching forms. Look at this:
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.
And sometimes the chitons are so covered with algae that they blend in perfectly with the surrounding environment.
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!
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:
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:
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.
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.
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.
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:
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.
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.
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 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
And because, like me, John had a special affinity for the anemones:
And he would have loved this. What is going on here? How did this pattern come to be?
And look at this, three species of Anthopleura in one tidepool! Can you identify them?
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.
And even though I'm not very good at finding nudibranchs, even I couldn't miss this one. It was almost 4 cm long!
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:
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.
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.
Sometimes we can even find Pisaster doing both at the same time:
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.
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.
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.
I've written before about the rocky intertidal as a habitat where livable space is in short supply. Even areas of apparently bare rock prove to be, upon closer inspection, "owned" by some inhabitant or inhabitants. That cleared area in the mussel bed? Look closely, and you'll likely find an owl limpet lurking on the edge of her farm.
And of course algae are often the dominant inhabitants in the intertidal.
When bare rock isn't available, intertidal creatures need other surfaces to live on. To many small organisms, another living thing may be the ideal surface on which to make a home. For example, the beautiful red alga Microcladia coulteri is an epiphyte that grows only on other algae. Smithora naiadum is another epiphytic red alga that grows on surfgrass leaves.
We describe algae that grow on other algae (or plants) as being epiphytic (Gk: epi "on" + phyte "plant"). Using the same logic, epizooic algae are those that live on animals. In the intertidal we see both epiphytic and epizooic algae. For many of them, the epizooic lifestyle is one of opportunism--the algae may not care which animal they live on, or even whether they live on an animal or a rock. Some of the epiphytes, such as Microcladia coulteri, grow on several species of algae; I've seen it on a variety of other reds as well as on a brown or two (feather boa kelp, Egregia menziesii, immediately comes to mind). Smithora naiadum, on the other hand, seems to live almost exclusively on the surfgrass Phyllospadix torreyi.
Animals can also live as epiphytes. The bryozoan that I mentioned last time is an epiphyte on giant kelp. Bryozoans, of course, cannot move once established. Other animals, such as snails, can be quite mobile. But even so, some of them are restricted to certain host organisms.
The aptly called kelp limpet (Discurria insessa), lives only on the stipe of E. menziesii, the feather boa kelp. Its shell is the exact same color as the kelp where it spends its entire post-larval life. Larvae looking for a place to take up a benthic lifestyle settle preferentially on Egregia where adult limpets already live. It's a classic case of "If my parents grew up there it's probably a good place for me."
The limpets cruise up and down the stipe, grazing on both the epiphytic diatoms and the kelp itself. They can make deep scars in the stipe and even cause breakage. Which makes me wonder: What happens to the limpet if it ends up on the wrong end of the break? Does it die as the broken piece of kelp gets washed away? Can it release its hold and find another bit of Egregia to live on? Somehow I doubt it.
The last time I was in the intertidal I encountered another epiphytic limpet. Like the red alga Smithora naiadum, this snail one lives on the narrow leaves of surfgrass. It's a tiny thing, about 6 mm long, and totally easy to overlook, given all the other stuff going on in the tidepools. But here it is, Tectura paleacea. Its common name is the surfgrass limpet, which actually makes sense.
Tecturapalacea feeds on the microalgae that grow on the leaves of the surfgrass, and on the outer tissue layer of the plant. They can obviously grow no larger than their home, so they are narrow, about 3 mm wide. But they are kind of tall, although not as tall as D. insessa.
Cute little thing, isn't it? Tectura palacea seems to have avoided being the focus of study, as there isn't much known about it. Ricketts, Calvin, and Hedgpeth write in Between Pacific Tides:
A variety of surfgrass (Phyllospadix) grows in this habitat on the protected outer coast; on its delicate stalks occurs a limpet, ill adapted as limpets would seem to be to such an attachment site. Even in the face of considerable surf, [Tectura] palacea, . . . , clings to its blade of surfgrass. Perhaps the feat is not as difficult as might be supposed, since the flexible grass streams out in the water, offering a minimum of resistance. . . The surfgrass provides not only a home but also food for this limpet, which feeds on the microalgae coating the blades and on the epithelial layers of the host plant. Indeed, some of the plant's unique chemicals find their way into the limpet's shell, where they may possibly serve to camouflage the limpet against predators such as the seastar Leptasterias hexactis, which frequents surfgrass beds and hunts by means of chemical senses.
And that seems to sum up what is known about Tectura palacea. There has been some work on its genetic population structure, but very little about the limpet's natural history. The intertidal is full of organisms like this, which are noticed and generally known about, but not well studied. Perhaps this is where naturalists can contribute valuable information. I would be interested in knowing how closely the populations of T. palacea and Phyllospadix are linked. Does the limpet occur throughout the surfgrass's range? Does the limpet live on both species of surfgrass on our coast? In the meantime, I've now got something else to keep my eye on when I get stranded on a surfgrass bed.
I've always known staurozoans (Haliclystus 'sanjuanensis') from Franklin Point, and it goes to reason that they would be found at other sites in the general vicinity. But I've never seen them up the coast at Pigeon Point, just a short distance away. At Franklin Point the staurozoans live in sandy-bottom surge channels where the water constantly sloshes back and forth, which is the excuse I've always used for my less-than-stellar photographs of them. Pigeon Point doesn't have the surge channels or the sand, and I've never seen a staurozoan there. I'd assumed that the association between staurozoans and surge channels indicated a requirement for fast-moving water.
Turns out I was wrong. Or at least, not completely right.
A few weeks ago I was doing some identifications for iNaturalist, and came upon some sightings of H. 'sanjuanensis' at Waddell Beach. I thought it would be a good idea to check it out--to see whether or not the staurozoans were there, and to see how similar (or not) Waddell is to Franklin Point.
Photos of the sites, first Franklin Point:
And now Waddell:
They don't actually look very different, do they? But I can tell you that the channels at Franklin Point get a lot more surf action, even when the tide is at its absolute lowest, than the channels at Waddell. When we were at Waddell yesterday the channels were more like calm pools than surge channels. It sure didn't look like staurozoan habitat to me.
Which just goes to show you how much I know. It took a while, but we found lots of staurozoans at Waddell! And since the water is so much calmer there, picture-taking was a lot easier. The animals were still active in their own way, but at least they weren't being sloshed around continuously.
And a lot of them had been cooperative enough to pose on pieces of the green algae Ulva, where they contrasted beautifully.
I was even able to capture a few good video clips!
So, what have I learned? Well, I learned that I didn't know as much as I thought I did. And that's a good thing! This is how science works. Understanding of natural phenomena increases incrementally as we make small discoveries that challenge what we think we know. With organisms like these staurozoans, about which very little is known anyway, each observation could well reveal new information. The observations I made at Waddell have been incorporated into iNaturalist to join the ones that were made back in May, so little by little we are working to establish just where staurozoans live and how common they are. Maybe they aren't quite as patchy and ephemeral as I had thought!
This weekend we have some of the loveliest morning low tides of the year, and fortunately the local beaches have been opened up again for locals. The beaches in San Mateo County had been closed for two months, to keep people from gathering during the pandemic. For the first time in over a year I was able to get out to Franklin Point to check on the staurozoans. These are the elusive and camera shy animals that we don't know much about, except that they are patchy in both space and time.
Yesterday the beach at Franklin Point was quite tall, as a good meter or so of sand had accumulated. This is a normal part of the seasonal cycle of sand movement along the coast--sand piles up in the summer and gets washed away during the winter storms. The rocks that you can see only the tops of in this photo would be much more exposed in the winter.
It took a while to find the staurozoans. Every time I visit Franklin Point it takes my search image a while to kick into gear, but each time I find the staurozoans my intuition gets a teensy bit better calibrated. As usual, the staurozoans were very patchy. I'd not see any in the immediate vicinity, then I'd move a meter or so away and see them all over. Part of that is due to usual honing of the search image, but part of it is that the staurozoans really are that patchy.
They are always attached to red algae, often the most diaphanous, wispy filamentous reds out there. And they don't seem to like pools, where the water becomes still for a few moments between save surges. No, they like areas where the water sloshes back and forth constantly.
You can see why it's so difficult getting a decent photo of these animals! They're never still for more than a split-second. Staurozoans may have a delicate appearance, but they're very tough critters. Their bodies are entirely flexible, being made out of jelly, and offer zero resistance to the force of the waves. It's a very low-energy way of thriving in a very high energy environment. Who says you need a brain to be smart?
And, of course, they are predators. Being cnidarians they have cnidocytes that they use to catch prey. The cnidocytes are concentrated in the eight pompon-shaped tentacle clusters at the ends of the arms. To humans the tentacles feel sticky rather than stingy, similar to how our local anemones' tentacles feel. Still, I wouldn't want to put my tongue on one of them. The tentacles catch food, and then the arms curl inward to bring the food to the mouth, which is located in the center of the calyx.
The natural assumption to make is that animals tend feed on smaller and simpler animals. Somehow the predator is always considered to be "better" or at least more complex than the prey. I'm delighted to report that cnidarians turn that assumption upside-down. In terms of morphology, at least, cnidarians are the simplest of the true animals. Their bodies consist of two tissue layers with a layer of snot sandwiched between them. They have only the most rudimentary nervous system, and a simple network of fluid-filled canals that function as both digestive and circulatory system. That said, they have the most sophisticated and fastest-acting cell in the animal kingdom--the cnidocyte--which can inject prey with the most toxic venoms in the world.
They don't look like deadly predators, do they?
Cnidarians use cnidocytes to catch prey and defend against their own predators. The cnidocytes of Haliclystus are strong enough to catch and subdue fish. Anything that can be shoved even partway into a cnidarian's gullet will be digested, even if it isn't quite dead yet. This fish was long dead when we saw it, but its tail is still sticking out of the staurozoan's mouth.
Imagine being shoved head-first into a chamber lined with stinging cells. Death, inevitable but perhaps slow to arrive, would be a blessing. Although perhaps less horrific than being digested slowly feet-first.
Speaking of fishing, I caught one of my own yesterday. I saw it fairly high in the intertidal, above the reach of the surging waves. At first I saw only the pale blotchy tail, and even though I recognized it I didn't think it was alive.
I poked it with my toe. No reaction. Then Alex found a kelp stipe, and I poked it again. It seemed to move a little bit. I'm a lot less squeamish about live things than dead things, so I picked it up to see how alive it was.
It was a monkeyface prickleback (Cebidichthyes violaceus)!
Monkeyface pricklebacks are common enough around here that people fish for them. They (the pricklebacks) hide in crevices in the intertidal. Like other intertidal fishes, they can breathe air and are well suited to hang out where the water drains away twice daily. I put this one in a deeper pool and watched it slither away into the algae.
Staurozoans found always mean a successful day in the intertidal. Day after tomorrow I'm going to look for them at a different spot. iNaturalist says they're there, and I want to see for myself. I'm not sure exactly where to look, but I know the habitat they like. And even if I don't find them, it'll be a nice chance to explore a new site. Finger crossed!
A while back now I went out on a low tide even though the actual low was after sunset. I figured that it was low enough that I'd have plenty of time to poke around as the tide was receding. And given that there were promising clouds in the sky, I took my good camera along just in case the sunset proved to be photo-worthy. Having had enough of crowds in the intertidal at Natural Bridges the previous day, I decided to venture up to Pistachio Beach, which isn't as heavily visited.
I ended up spending only 45 minutes in the intertidal, all the while watching the sun sink lower in the sky. It was already too dark to take many photos in the tidepools, but there were some interesting things on the beach.
The majority of shells that wash up on any beach are going to be molluscs, usually either gastropods or bivalves. I've often seen living red abalone (Haliotis rufescens) hidden in nooks and crannies at this site, so it's not surprising to find their shells on the sand. Usually, though, the shells are a little beat up. This one was intact, with a lovely layer of nacre inside.
This butterfly-shaped object is one of the shell plates of Cryptochiton stelleri, also known as the gumboot chiton. Cryptochiton is the largest of all chiton species; the largest one I've ever seen is the length of my forearm from elbow to fingertip. Like all chitons, C. stelleri has a row of eight shell plates running down the dorsal side of the body. Unlike other chitons, however, in Cryptochiton the plates are covered by a layer of tissue called the girdle and not visible from the outside. If you run your finger down the back you can feel the plates under the girdle. I never thought about it before now, but it seems that the name Cryptochiton refers to the hidden chiton-ness of the animal.
Anyway, Cryptochiton lives mostly in the subtidal, although you can occasionally see them in the very low intertidal. As subtidal creatures they have neither the ability nor the need to cling tightly to rocks, as their intertidal cousins do. This means that when big swells come through at low tide, they can get dislodged and wash ashore. I know from personal experience that the tissue of Cryptochiton is really tough. Once a pal and I were trudging back after working on a low tide and came across several dead Crytochiton scattered over the beach. We decided to do an impromptu dissection and try to salvage the plates, hacking away with her pocket knife. The smell was horrendous, and after several minutes we made practically zero progress, so we gave up. I've seen gulls pecking at dead Cryptochiton, too, and they didn't seem to have any success either. However, their bodies do eventually disintegrate, or something manages to eat them, and their naked plates can often be found on beaches.
One of the coolest pattern I've ever seen in the intertidal was this:
I've never seen anything like this before. It's hard to tell from the photo, but these two rock faces converge into the crevice, sort of like the adjacent pages in an open book. This side of the rock surface faces away from the ocean and will never be subject to the main force of pounding waves. The barnacle in the middle is attached pretty much in the deepest part of the crevice, and is surrounded by mussels, which are then surrounded by limpets.
Now, all of these animals recruited to this location after spending some period of time, from a few days to a few weeks, in the plankton. The barnacle certainly can't move once it has settled and metamorphosed. Newly settled mussels have a limited ability to scoot around a bit but are generally stationary once they've extruded their byssal threads and fastened them to something hard. The limpets, on the other hand, are quite mobile. The barnacle and mussels gave up their ability to move around after they became benthic, but limpets can and do locomote quite a bit--in fact, they have to, in order to feed. So in a sense, these limpets "chose" to aggregate together long after settlement.
What are the ecological implications of this pattern?
Well, for one thing, that barnacle is a genetic dead end. I've written before about the bizarre sex lives of barnacles. This one lone barnacle, far from any others of its species, is not able to reproduce. It has nobody to copulate with. It is possible that other barnacles will recruit to the mussels (Pollicipes is often associated with Mytilus), but until then there will be no sexy times for this individual.
Another ecological consequence concerns the limpets. If these are owl limpets (Lottia gigantea), then some of them will grow up to be the big females that maintain farms on the rocks where they manage and harvest the crop of algal film that grows. These big females are territorial, and will bump or scrape off any creature found to be trespassing on their farms. Clearly, none of the limpets in the photo above are demonstrating any type of territorial behavior! So they are either some other species of Lottia, or are younger individuals of L. gigantea that haven't yet made the change from male to female.
In any case, I do think the pattern is very interesting, even though I don't understand it. Or maybe because I don't understand it. I'm always intrigued by something that I can't explain, which is a good thing because it means I don't get bored very often. If anyone reading this has an explanation for this pattern, let me know about it!
It has been a while since I've spent any time in the intertidal. There isn't really any reason for this, other than a reluctance to venture out in the afternoon wind and have to fight encroaching darkness. There's also the fact that I much prefer the morning low tides, which we'll have in the spring. However, this past weekend we had some spectacular afternoon lows, and although I was working on Friday and couldn't spare the time to venture out, I went out on Saturday and Sunday.
Saturday was a special day, because I had guests with me. A woman named Marla, who reads this blog, contacted me back in the fall. She said she wanted to do something special for her husband's birthday, and asked if I'd be willing to take them to the intertidal. It turns out that Andrew's birthday was around this past weekend, and he had family coming out from Chicago to celebrate. They picked the perfect weekend, because the low tides we had were some of the lowest of the year. So on Saturday I met up with Marla, Andrew (her husband), and Betsy (Andrew's sister) and we all traipsed out to Natural Bridges.
This was our destination for the afternoon:
Taking civilians into the intertidal can be tricky, because they often come with expectations that don't get met. Like expecting to see an octopus, for example. I explain that the octopuses are there, but are better at hiding from us than we are at finding them, but that never feels very satisfactory. This trio, however, were fun to show around. The tide was beautifully low and we had fantastic luck with the weather. It had rained in the morning, but the afternoon was clear and sunny. I congratulated Marla on remembering to pay the weather bill. And the passing stormlet didn't come with a big swell, so the ocean was pretty flat. We were able to spend some quality time in the mid-tidal zone, with occasional forays into the low intertidal.
The typical Natural Bridges fauna--owl limpets, mussels, chitons, anemones, etc.--were all present and accounted for. Of course, there isn't much algal stuff going on in mid-January.
Given the time of year (mid-January) and the time of day (late afternoon), the sun was coming in at a low angle. This was tricky for photographing, both in and out of water. However, sometimes good things happen, as in this photo below:
That's a big kelp crab (Pugettia producta) nestled among four sunburst anemones (Anthopleura sola). Kelp crabs are pretty placid creatures, for crabs, and usually take cover when approached. But this one remained in plain sight, holding so still that I thought it was dead. Even when I hovered directly over it and blocked the sun, it didn't move at all. Then it occurred to me that maybe he was having the sexy times with a lady friend. So I very carefully reached down and gave him a tap on the carapace. He flinched a little, so I knew he wasn't dead, but made no move to get away. And I caught a glimpse of a more golden leg underneath him.
Crabs live their entire lives encased in a rigid exoskeleton, and can mate only during a short window of opportunity after a female molts. Early in the breeding season, a female crab uses pheromones to attract nearby males. When a suitable male approaches, she may let him grab her in a sort of crabby hug. That's what this male kelp crab is doing to his mate. They may remain in this embrace for several days, waiting until the female molts and her new exoskeleton is soft. At that point the male will use specialized appendages to insert packets of sperm into the female's gonopores. The two will then go their separate ways.
We didn't disturb these crabs, and let them go on doing their thing. By now the sun was going down, so we headed back up and were rewarded with a glorious sunset.
The intertidal sculpins are delightful little fish with lots of personality. They're really fun to watch, if you have the patience to sit still for a while and let them do their thing. A sculpin's best defense is to not be seen, so their first instinct is to freeze where they are. Then, if a perceived threat proves to be truly frightening, they'll scoot off into hiding. They can also change the color of their skin, either to enhance camouflage or communicate with each other.
Around here we have a handful of sculpin species flitting around in our tidepools. Sculpins can be tricky to identify even if you have the fish in hand--many of the meristics (things you count, such as hard spines and soft rays in the dorsal fin, or the number of scales in the lateral line) used to distinguish species actually overlap quite a lot between species. The fishes' ability to change color means that skin coloration isn't a very reliable trait. When I was in grad school there was another student in my department who was studying the intertidal sculpins, and she told me that most of the ones we see commonly are either woolly sculpins (Clinocottus analis) or fluffy sculpins (Oligocottus snyderi). I've developed a sort of gut feeling for the gestalt of these species, but I'm not always 100% certain of my identifications.
Anyway, back to the camouflaged sculpins. The ability to change the color of the skin means that sculpins can match their backgrounds, which comes in very handy when there isn't anything to hide behind. Since the environment is rarely uniformly colored, sculpins tend to have mottled skin. Some can be banded, looking like Oreo cookies. The fish in this photo lives in a pool with a granite bottom. The rock contains large quartz crystals and is colonized by tufty bits of mostly red algae. There is enough wave surge for these fist-sized rocks to get tumbled about, which prevents larger macroalgae from colonizing them.
Other shallow pools higher up in the intertidal at Asilomar have a different type of rocky bottom. The rocks lining the bottom of these pools are whitish pebbles that are small enough to be tossed up higher onto the beach. I don't know whether or not these pebbles have the same mineral content as the larger rocks lower in the intertidal, but they do have quartz crystals. The pebbles are white. So, as you may have guessed, are the sculpins!
Other intertidal locations have different color schemes. On the reef to the south of Davenport Landing Beach, you will see a lot of coralline algae. Some pools are overwhelmingly pink because of these algae. Bossiella sp. is a common coralline alga at this location.
What color do you think the sculpins are in these pools?
Give yourself a congratulatory pat on the back if you said "pink"!
Sculpins aren't the only animals to blend in with coralline algae. Some crustaceans are remarkably adept at hiding in plain sight by merging into the background. Unlike the various decorator crabs, which tuck bits and pieces of the environment onto their exoskeletons, isopods hide by matching color.
Turning over algae and finding hidden creatures like these is always fun. For example, I saw these isopods at Pescadero this past summer. See how beautifully camouflaged they are?
Sometimes, when you're not looking for anything in particular, you end up finding something really cool. Last weekend I met up with students in the Cabrillo College Natural History Club for a tidepool excursion up at Pigeon Point. We were south of the point at Whaler's Cove, where a staircase makes for comparatively easy access to the intertidal.
It's fun taking students to the intertidal because I enjoy helping them develop search images for things they've never seen before. There really is so much to see, and most of it goes unnoticed by the casual visitor. Often we are reminded to "reach for the stars," when it is equally important to examine what's going on at the level of your feet. That's the only way you can see things like this chiton:
Mopalia muscosa is one of my favorite chitons. It is pretty common up and down the California coast. However, like most chitons it is not very conspicuous--it tends to be encrusted with algae! This individual is exuberantly covered with coralline and other red algae and has itself become a (slowly) walking bit of intertidal habitat. It is not unusual to see small snails, crustaceans, and worms living among the foliage carried around by a chiton. Other species can carry around some algae, but M. muscosa seems to be the most highly decorated chiton around here. I showed this one to some of the students, who then proceeded to find several others. A search image is a great thing to carry around!
Compared to the rocky intertidal, a sandy habitat can be a difficult place to live. Sand is inherently unstable, getting sloshed to and fro with the tides. Because of this instability there is nothing for holdfasts to grab, so there are many fewer algae for animals to eat and hide in. Most of the life at a sandy beach occurs below the surface of the sand, and is thus invisible to anyone who doesn't want to dig. There's a beach at Whaler's Cove where I've found burrowing olive snails (Olivella biplicata) plowing along just below the surface. I wanted to show them to the students, so I waded in and rooted around. I did find Olivella, but I also found a burrowing shrimp. I think it's a species of Crangon.
Now that is some damn fine camouflage! If the shrimp didn't cast its own shadow, it would be invisible. Even so, it was clearly uneasy sitting on the surface like that. I had only a few seconds to shove the camera in the water and snap a quick photo before the shrimp wriggled its way beneath the sand again.
As I've said before, observation takes practice and patience. To look at something doesn't mean you truly see it. That's why it is so important to slow down and let your attention progress at the pace of the phenomenon you're observing. If the only things that catch your eye are the ones that flit about, then I can guarantee you will never find a chiton in the intertidal. And wouldn't that be a sad thing?