At the end of August I got to play animal wrangler for a film production. Back in the late winter I had been contacted by an intern at KQED in San Francisco, who wanted to shoot some time-lapse footage of anemones dividing. We went out and collected anemones, I got them set up in tanks at the marine lab, and then COVID19 hit and everything went on shut-down. The intern finished her internship remotely and went on to her next position, and in the meantime the anemones stubbornly refused to divide.
The KQED lead videographer for the Deep Look video series, Josh Cassidy, who would had recorded the anemones dividing if they had divided and if the marine lab were not closed, asked me over the summer if we could somehow arrange to meet up to film something else. He had heard of some research that showed the emergent property of sea stars bouncing as they walk along on their many tube feet. Is there any way, he asked, that he could film some of the stars at the lab?
Well, filming at the lab was out of the question. Only essential personnel are allowed in the buildings, and there was no way I could sneak in Josh and all of his gear. We discussed options such as meeting up at a beach but I decided that I needed more control of the site to keep things safe for the animals. We ended up borrowing some friends' back yard for the day, which worked out pretty well. They have a covered pavilion, which was ideal because of course it turned out to be hot the day we filmed. I had several bags of frozen seawater to keep things cool-ish, two coolers for the movie stars themselves, a battery-operated air pump, and 30 gallons of seawater on hand.
Filming for production purposes takes a really long time. Even for a short film, we were working most of the day. Because of course most of the stars were uncooperative. They don't have anything even remotely resembling a brain, but damn if they can't bugger things up. I was feeling kind of bad that my animals were being such troublemakers; Josh, fortunately, was much more patient with them.
And here's the film! You'll see my right hand for about 1.5 seconds.
I didn't realize this at the time, but Josh also writes an article for each episode of Deep Look, for the KQED website. For this episode the article describes the research into the biomechanics of sea star bouncing. I'm quoted at the end.
So watch this short film. I hope it helps put a little bounce in your step.
Still more or less under quarantine shutdown due to COVID19, I haven't been doing much outdoor stuff over the past several months. What with the pandemic and horrid air quality due to wildfires throughout the state, spending time in places I would normally like to hang out simply hasn't been possible. We're still getting too many out-of-the-area visitors for me to feel comfortable being around people, and weekends are especially bad. But last weekend I went to Moss Landing to take pictures of birds and other wildlife—I needed visual aids for a virtual lab my students will be doing in a few weeks.
It's the time of year for birdwatchers to get excited about winter visitors. I've had golden-crowned sparrows in the canyon behind the house for almost a month now, but I hadn't been down to a beach in a while. Moss Landing is a great place for birdwatching, because you can explore the estuarine habitat of Elkhorn Slough, the sandy beach, and the harbor during a 2-mile walk. That's three distinct habitats for very little effort!
Starting at the tidal marsh, I always keep an eye out for the long-billed curlew (Numenius americanus). They have the largest beak-to-head ratio of any bird.
One of my favorite winter visitors to the marsh area is the willet (Tringa semipalmata). Unlike most shorebirds that are speckled or mottled, willets in winter plumage are a beautiful soft gray-ish brown color. Every time I see a willet I ask myself, "Willet, or won't it?"
And when they take off in flight, willets show these striking black and white wing patterns. They always take me by surprise, even though I know to expect it.
A whole flock of willets taking off at once is quite an impressive sight!
From the marsh it's a short walk over the dune and onto the beach.
I always look forward to walking this beach because of the dead things. Don't get me wrong, the living things are fun to see, but in some ways the dead critters can be more informative. For every species there is always some baseline level of mortality in the ocean, so you expect a certain number of dead things to wash up. However, an unusually high number of corpses could indicate that something is going on at sea. This trip I didn't see very many dead critters: just a few grebes that had been there for a while, nothing out of the ordinary.
Oh, and an otter pup. At least, I'm pretty certain it was an otter.
Yes, we came across a dead sea otter pup, my first ever.
The body was missing a head, but the parts that remain were a bit longer than my booted foot. Although most of the soft tissue had been scavenged, the carcass had distinct paws, meaning it wasn't any kind of pinniped (seal or sea lion). Also, pinnipeds don't have fur like this, as they rely on blubber for thermoregulation. Sea otters, on the other hand, have the densest fur of all mammals, with the oft-cited 1 million hairs/in2.
But let's be honest. I like the beach because I like photographing birds, and there is always interesting bird life at this beach. I'm not one of the crazy bird people who keep a life list and need to be the first person to spot a particular something-or-other. And, unlike the idiots I saw tramping through the pickleweed in pursuit of a Say's phoebe that day, I don't climb over fences and trespass where I'm not supposed to be. Besides, even the everyday backyard birds are fun to watch. Whoever says that familiarity breeds contempt certainly is not a naturalist!
And who doesn't love a snowy plover or two?
The snowies aren't nesting at this time of year so the upper part of the beach isn't roped off. They do still get disturbed by people wandering around, who probably don't even know the birds are there. They (the snowies, that is) are so tiny that when they hunker down behind a divot in the sand they disappear completely. If you sit or stand quietly, they will pop up and make short dashes from hillock to pile of beach wrack and back again, feeding on the insects and crustaceans they find.
In addition to the snowy plovers, another tiny "peep" bird runs around on the beaches, often in large groups. These are the sanderlings, Calidris alba. I've only ever seen them in nonbreeding plumage, as they nest in the high Arctic.
Sanderlings are the little birds that run back and forth from the waves. As a wave recedes the sanderlings frantically stab their stout beaks into the sand, grabbing up small mole crabs and other crustaceans that are right at the surface. When the next wave arrives the sanderlings run back up the beach. They have short legs and don't swim, so getting swept out to sea would be a very bad thing for them.
Sometimes even the long-legged shorebirds forage on the beach. I've seen the curlew there, as well as whimbrels and godwits. This day the godwits were stealing the show.
The godwits, with their longer legs, are able to stand their ground when the waves wash up. They can catch food that is buried more deeply into the sand. On mudflats they pick their way over the flat at low tide, digging for worms, clams, and crustaceans. They can feed on a mudflat only at low tide. But on the beach they can feed at any time, just moving with the tide as it floods and ebbs.
And my friend the long-billed curlew was there on the beach, too!
The curlews are not as eager to forage in the waves themselves as the godwits seem to be. The curlews might wander down to where their ankles are swashed by the waves, but do not seem to like getting wetter than that. But that bill can probe very deeply into the sand or mud. I've watched them feeding on mole crabs on the beach, and on worms on the mudflats.
Autumn and winter are good times to watch birds around here. There's a bit of a lull in bird activity once the swallows leave depart for the south and before the winter residents show up. For me, autumn begins when the golden-crowned sparrows arrive in the neighborhood, which this year was September 25. I'm listening to them now as I write this! Being located on the Pacific Flyway means we get lots of birds resting for a bit on their migration even if they don't winter here. I'll try to get out to Moss Landing during the winter months, to keep track of the avian comings and going.
In this strange pandemic school year with classes online and student clubs not able to meet in person, the Natural History Club has been meeting virtually twice a week. We can't go out as a group on any field trips, so the students have been sharing their nature journals online. Yesterday we played Jeopardy! I didn't win, but I didn't embarrass myself, either.
Last spring I was scheduled to give a tidepool talk as an event for the club. The talk was scheduled for mid-March, exactly the time when COVID19 arrived and threw all plans into the blender. The good news is I get to give the talk virtually next month, as the first event of the year. Please come!
California has been burning for almost a month now. Wildfires rage up and down the state, and it seems that new ones pop up every day. I haven't bothered looking up the latest stats on acreage destroyed because, frankly, it would be too depressing. All across social media today people posted photos of orange skies that made everything and everyone look kind of sick. The photo above was taken at 17:10 this afternoon, a full two hours before sunset.
There's a thick layer of smoke blanketing most of California for weeks now. Over the Labor Day weekend the smoky conditions combined with a record-breaking heat wave and made for widespread misery. Fortunately for those of us on the coast, the marine layer returned yesterday and brought cooler temperatures. The marine layer creeping in from the ocean is also acting as a buffer between the smoke and us, keeping air quality at ground level pretty nice. People even a few miles more inland from us are still suffering from dreadful air quality.
The double layer of fog and thick smoke has resulted in the twilight we've had all day. I noticed that the wildlife responded to these unusual conditions.
The cats have been sleeping more than usual, even for cats. They've been sleeping like we're near the winter solstice rather than on the sunny side of the autumn equinox. And I've also been very sleepy all day. Like the cats, it feels like mid-December to me, too.
Hummingbirds—During the heat wave they didn't visit our feeders much, I think they were trying to shelter out of the heat. Yesterday and today they were feeding frantically. They normally visit the feeders occasionally throughout the day, and in the hour before and after sunset they tank up before going into torpor for the night. The hummers and all of the other diurnal birds have gone to bed a good two hours before sunset.
Insects—The nighttime cricket serenade is going full-strength. They normally don't start up until full dark. Tonight they've started a good few hours earlier.
None of us knows how many days like this we'll have before the skies clear again. It is very unsettling, to say the least. Now imagine the same kind of thing, only more pronounced and lasting for decades or centuries, as would have occurred during periods of extreme volcanic activity in Earth's history. After today it's a little easier to understand at a gut level what I already knew at an intellectual level, that severe levels of atmospheric smoke and dust can change the biota: if the sun never gets brighter than it did today then plants would die, resulting in altered community structure.
As I finish up this post, it is now about the time that the sun should be setting, and it has been full dark for well over an hour now. Feels like bedtime!
As I write these words, a massive and powerful wildfire is raging through the Santa Cruz Mountains, approaching the city of Santa Cruz from the north and west. This morning's stats:
63,000 acres burnt/burning
1157 people fighting the fire (roughly 10% of what is needed to fight a fire of this size)
firebreaks constructed to protect the city and university
firefighters coming from out of the area and out of state
Much of the terrain burning is redwood forest. Big Basin Redwood State Park has burnt extensively. All park buildings and campgrounds have been severely damaged if not destroyed. Up the coast from me at Waddell Creek, the fire burned all the way to the ocean. Rancho del Oso, the nature center at the bottom of Big Basin at Waddell Creek, is in the middle of the forest; I don't know whether or not it still stands.
Each of these leaves tells the story of the destructive power of Nature. Most of them are from tanoak trees (Neolithocarpus densiflorus) or California bay laurel (Umbellularia californica), both of which are very common understory trees in redwood forests. For the past week, charred leaves have been tossed by updraft and carried along the wind, to be deposited miles away. Fortunately they are no longer acting as live embers when they touch down.
My camera gear is all packed up, in case we need to evacuate. I took these photos with my phone when I went to the marine lab this morning. They are completely unaltered. If they look a little too orange, well, that's how everything looks right now.
Why did I feel compelled to take these pictures? I think it's because the damage to Nature caused by Nature should be acknowledged as well as the damage to human lives, homes, and health. What I'm about to say may sound insensitive. I do not want to diminish the human tragedy of lost homes, livelihoods, and health. But I do want to shift my personal focus a little bit, because dwelling on all that has been and could be lost only renders me unable to function. If I can think about the future, perhaps even the long-term future far beyond my own life, I feel more grounded and ready to deal with the now.
What is and has been happening to the redwood forests is absolutely tragic. But the redwoods themselves are fire-adapted and resilient. The forest will recover. Already there are Facebook groups organizing to help the residents who have been displaced, begin the long and arduous process of cleaning up once the fire crews give the okay to do so, and start thinking about long-term monitoring of the forest's recovery. From a purely ecological perspective, it will be fascinating to document the process of secondary succession.
But before any of that can happen, human safety is the top priority. We are far from the end of this ordeal. While the weather has cooperated the past couple of days, with cooler temperatures and higher humidity thanks to the return of the marine layer, the forecast calls for 20-30% chance of lightning weather Sunday through Tuesday. That means more lightning strikes and more fires starting. We were visited by a firefighter yesterday afternoon, who told us that while we were not in the immediate evacuation zone we need to be ready to go. She advised us to do the usual fire prevention stuff—clear out a defensible space around the house, make sure there's no leaf litter or debris on the roof, etc. So we did. And now we stay indoors as much as possible, as the air quality outside is dismal. And we wait.
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.
Every summer, like clockwork, my big female whelk lays eggs. She is one of a pair of Kellett's whelks (Kellettia kellettii) that I inherited from a labmate many years ago now. True whelks of the family Buccinidae are predatory or scavenging snails, and can get pretty big. The female, the larger of the two I have, is almost the length of my hand; her mate is a little bit smaller.
Many marine snails (e.g., abalones, limpets, and turban snails) are broadcast spawners, spewing large numbers of gametes into the ocean and hoping for the best. These spawners have high fecundity, but very few, if any, of the thousands of eggs shed will survive to adulthood. We say that in these species, parental investment in offspring extends only as far as gamete production. Fertilization and larval development occur in the water column, and embryos and larvae are left to fend for themselves.
The whelks, on the other hand, are more involved parents. They maximize the probability of fertilization by copulating, and the female produces yolky eggs that provide energy for the developing embryos and larvae. Rather than throw her eggs to the outside world and hoping for the best, the female whelk deposits dozens of egg capsules, each of which contains a few hundred fertilized eggs.
Over a period of about three weeks I shot several time-lapse video clips of the mama whelk laying eggs. Due to the pandemic we need to work in shifts at the lab. Fortunately I have the morning shift, which means I can start as early as I want as long as I leave before 11:00 when the next person comes in. Each 2.5-hr stint at the lab yielded about 30 seconds of video, not all of which was interesting; even in time-lapse, whelks operate at a snail's pace. Still, I was surprised at how active the female could be while she was apparently doing nothing.
The freshly deposited capsules are a creamy white color, as are the embryos inside them. As the embryos and then larvae grow, they get darker. Each of the fertilized eggs develops through the first molluscan larval stage, called a trochophore larva, within its own egg membrane. The embryo, and then the trochophore, survives on energy reserves provided by the mother snail when she produced the egg. These larvae don't hatch from their egg membrane until they've reached the veliger stage.
The veliger larva gets its name from a lobed ciliated structure called a velum. Gastropods and bivalves have veliger larvae. As you might expect, the bivalve veliger has two shells, and the gastropod veliger has a coiled snail shell. These Kellettia veligers have dark opaque patches on the foot and some of the internal organs. That coloration is what you see in the photo of the egg capsule. You can see below which of the egg capsules are the oldest, right?
By the time the veligers emerge from the egg capsule, they have burned through almost all of the energy packaged in the yolk of the egg. They need to begin feeding very soon. The current generated by the beating cilia on the velum both propels the larva through the water and brings food particles to the larva's mouth. The velum can be pulled into the shell, and, as in any snail the opening to the shell can be shut by a little operculum on the veliger's foot. As is the case with most bodies, the veliger is slightly negatively buoyant, so as soon as it withdraws into the shell it begins to sink. However, once the velum pops back out the larva can swim rapidly.
Watch how the veliger swims. You can also see the heart beat!
So now the egg capsules are being emptied as the larvae emerge. I'm not keeping the veligers, so they are making their way through the drainage system back out to the ocean. As of now there are no iNaturalist observations of Kellettia kellettii in the northern half of Monterey Bay, so it appears that for whatever reason the whelks have not been able to establish viable populations here. Or it might be that the whelks are here but there aren't enough SCUBA divers in the water to see them.
These little veligers will be very lucky if any of them happen to encounter a subtidal habitat where they can take up residence as juvenile whelks. Even for animals that show a relatively high degree of parental care, the chances of any individual larva surviving to adulthood are exceedingly small. However, for the reproductive strategy of Kellettia to have evolved and persisted, there must be a payoff. In this case, the reward is an equal or greater reproductive success compared to snails that simply broadcast thousands of unprotected eggs into the water. Some gastropods such as the slipper shell Crepidula adunca, take parental care even further than Kellettia; in this species the mother broods her young under her shell until they've become tiny miniatures of herself, then she pushes them out to face the world and find a turban snail to live on. Crepidula adunca does not have a swimming larval stage at all. The fact that we see a variety of strategies—many eggs with little care, fewer eggs with more care, and brooding—indicates that there's more than one way to be successful.
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.