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It has taken me months to gather all the photos and videos I needed for this post. I could blame it on the stress of teaching online for the first time, the COVID-19 pandemic itself, or residual malaise from the dumpster fire that was 2020. But really, it's the animal's fault.

In this case the animal is the orange cup coral, Balanophyllia elegans. I've written about this beast before, and lately I've been paying more attention to the corals that we have in the lab. In many ways it is the typical anthozoan—its life cycle consists of only a polyp stage (i.e., no medusa), it is benthic, and its body is vaguely anemone-like. Like the reef-building corals of the tropics, Balanophyllia is a scleractinian coral. This means that it secretes a calcareous base, or exoskeleton, upon which sits the living tissue of the polyp. But unlike the reef-building corals of the tropics, Balanophyllia is solitary, which means that it does not clone or form colonies. Nor does it contain photosynthetic zooxanthellae in its cells, as the reef-builders do. This means that Balanophyllia is a strict carnivore: unable to rely on photosynthetic symbionts to do the hard work of fixing carbon, Balanophyllia has to catch its own prey.

Balanophyllia has separate sexes and reproduces sexually. Males release sperm that are ingested by the female, and she then broods larvae for several months. What is strange about this is that, when you consider the anatomy of Balanophyllia (or any cnidarian polyp, for that matter) the question that comes to mind is, "Where are the larvae brooded?" So let's take a look at the basic cnidarian body plan.

Adult cup coral (Balanophyllia elegans)
© Allison J. Gong

The professor who taught my undergraduate course in invertebrate zoology described a cnidarian's body as a baggie inside a baggie, with a layer of jelly between the two baggies. The inner and outer baggies represent the tissue layers that developmental biologists refer to as endoderm and ectoderm, respectively. The jelly between the two tissue layers is called mesoglea. For the sake of this discussion, it's the endoderm that interests us. In a cnidarian, the endoderm is also called gastrodermis, because it is, literally, the skin of the digestive system. The cnidarian gut is a cavity that opens to the outside via a single opening. We could call that opening either a mouth or an anus, since both food and wastes pass through it, but for politeness' sake we call it a mouth. The gut itself does double duty as both the digestive system and the circulatory system, so its formal name is gastrovascular cavity (GVC).

It's easy to imagine the GVC as being essentially a tubular vase, but it's more complex than that. The GVC extends into each of the tentacles, so the tentacles are actually hollow. The main cavity of the GVC, in the stalk of the polyp, is partitioned by thin layers of endoderm. The partitions are called septa, and serve to increase the surface area of the endoderm for digestion. Think of a large office building, divided into small cubicles by movable partial walls—there's much more total wall space for hanging things such as calendars than there would be in the big room with only four walls. In anthozoans, gonad tissue is associated with the septa.

Now back to how Balanophyllia broods its larvae. As we've seen before, Balanophyllia's planula larva is an orange-reddish wormlike blob about 2 mm long, which is ciliated all over. It doesn't feed, but survives on energy reserves supplied by the mother in the egg; it may also be able to take up dissolved organic material directly from the seawater. After brooding larvae for some period of time in their GVC, Balanophyllia females release larvae. Or rather, the larvae ooze out of their mother's mouth and crawl around to settle and metamorphose nearby.

The planulation season, when larvae show up amongst the corals we keep in the lab, begins in the fall and runs through winter into the spring. Sometimes the larvae metamorphose right away—one day there are no larvae and the next day there are baby corals. Other larvae squirm around for days or weeks, not getting any smaller but not metamorphosing, either. This past season (Fall 2020-Spring 2021) we saw both extremes: planulae that settled and metamorphosed right away, and others that I collected weeks ago and are still worming around.

Orange cup coral (Balanophyllia elegans) with a planula larva
2020-12-12
© Allison J. Gong

I peered into a bunch of corals, hoping to see what the larvae are doing inside the GVC, with no luck. Then I decided to try some time-lapse video under the dissecting scope, and had a bit of success with that. In the video below you'll see about two hours of action compressed into about 1 minute. Watch for a small red ball squirming around inside the GVC. And remember that the GVC extends into the tentacles, so the larva can wiggle its way in there, too.

All of which makes me wonder if the pathway from mother's GVC to the scary world outside travels in only one direction, or if the larvae can retreat back into the safety of the mom's digestive system. How strange is it, that the safer location might be inside the mother's gut!

Eventually, whether it be a matter of hours or weeks, the planula larva settles (i.e., sticks to a surface and stops crawling) and metamorphoses (i.e., makes the anatomical and physiological changes into the juvenile body). There doesn't seem to be a clear connection between surface characteristics and whether or not larvae will settle there. You might think that they'd choose to settle nearby or maybe actually on the parent, but that's not always the case. At some point, however, the larva will have to either settle and metamorphose, or die. When they metamorphose into juveniles, they reveal other aspects of their nature as scleractinian corals.

From what I've seen, the larva begins the settlement process by sticking to a chosen spot and becoming a more circular (i.e., less elongated) blob. On the other hand, I've seen perfectly round red blobs that look for all the world as though they might be pushing out tentacles, change their minds and go vermiform again. But once they stick permanently and begin to metamorphose by forming the polyp's body, they have to continue.

Newly settled orange cup coral (Balanophyllia elegans)
2021-01-29
© Allison J. Gong

The juvenile in the photo above has not yet pushed out any tentacles, but it does show signs of its scleractinian ancestry. The Scleractinia (stony corals) and Actiniaria (sea anemones) are both members of a group called the Hexacorallia. The Hexacorallia and Octocorallia are in turn grouped together as members of the class Anthozoa. As you might infer from the name 'Hexacorallia', animals in this group of a body symmetry based on the number six. And you can see in the photo above that the juvenile coral's body is divided into 12 wedges. When the juvenile begins growing tentacles and a more polyp-like body, the hexamerous symmetry becomes even more evident:

Young orange cup coral (Balanophyllia elegans)
2021-02-22
© Allison J. Gong

The young coral begins by forming six primary tentacles, which establishes the visible hexamerous symmetry. Then it grows the six shorter secondary tentacles. The bumps on the tentacles are cnidocyte batteries, clusters of stinging cells, indicating that the animal can already capture and kill prey. Good thing, too, because if it hasn't already then it soon will deplete the energy stores its mother partitioned into its egg.

By this stage in its development the coral will remain where it is for the rest of its life. As it grows it will deposit CaCO3 and grow taller, but the living tissue will always be restricted to a layer sitting on top of the calcareous base. Once the base grows more than a few millimeters tall, there is no living tissue in contact with the surface. Thus there is no mechanism for the animal to move to another location, or even to re-attach itself if it gets broken off its surface. There are many animals that are likewise unable to move once their larvae have attached and metamorphosed. The decision of where to put down roots becomes quite stark for them, as a bad one can result in a very short life indeed. The selective pressures that enforce a good decision are quite clear, and are important factors in the distribution patterns we observe in the intertidal.

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.

2

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.

California coastline from Waddell to Pigeon Point

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:

Rocky intertidal at Franklin Point
Rocky intertidal at Franklin Point
2020-06-06
© Allison J. Gong

And now Waddell:

Rocky intertidal at Waddell
Rocky intertidal at Waddell
2020-06-09
© Allison J. Gong

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.

Staurozoan attached to red algae at Waddell
Staurozoan (Haliclystus 'sanjuanensis') at Waddell
2020-06-09
© Allison J. Gong

And a lot of them had been cooperative enough to pose on pieces of the green algae Ulva, where they contrasted beautifully.

Staurozoan attached to green alga at Waddell
Staurozoan (Haliclystus 'sanjuanensis') at Waddell
2020-06-09
© Allison J. Gong
Staurozoan attached to green alga at Waddell
Staurozoan (Haliclystus 'sanjuanensis') at Waddell
2020-06-09
© Allison J. Gong

I was even able to capture a few good video clips!

Staurozoans at Waddell
2020-06-09
© Allison J. Gong

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!

2

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.

Beach and rocks at Franklin Point
2020-06-06
© Allison J. Gong

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.

Staurozoan (Haliclystus 'sanjuanensis)
Staurozoan (Haliclystus 'sanjuanensis') at Franklin Point
2020-06-06
© Allison J. Gong

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?

Trio of staurozoans (Haliclystus 'sanjuanensis')
Trio of staurozoans
2020-06-06
© Allison J. Gong

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?

Staurozoan (Haliclystus 'sanjuanensis')
Staurozoan (Haliclystus 'sanjuanensis') at Franklin Point
2020-06-06
© Allison J. Gong

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.

Monkeyface prickleback in a tidepool
Hmm, dead or alive?
2020-06-06
© Allison J. Gong

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 prickleback (Cebidichthyes violaceus)
Monkeyface prickleback (Cebidichthyes violaceus) at Franklin Point
2020-06-06
© Allison J. Gong

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!

4

I'm willing to bet that when you think about coral, what comes to mind is something like this:

Great Barrier Reef
A Blue Starfish (Linckia laevigata) resting on hard Acropora coral. Lighthouse, Ribbon Reefs, Great Barrier Reef
© 2004 Richard Ling

The reef-building corals of the tropics are indeed spectacular structures, incredibly rich in biodiversity and worthy of a visit if you ever get the chance. These coral colonies come in many shapes, as you can see in the photo above. Each colony consists of hundreds or thousands of tiny polyps, all connected by a shared gastrovascular cavity, or gut. The living polyps secrete a skeleton of CaCO3, which grows slowly over decades or even millennia as successive generations of polyps live their lives and then die. It's this slow accumulation of CaCO3 that makes up the physical structure of the reef.

Reef-building corals are members of the Scleractinia, the so-called stony corals. The stoniness refers to the calcareous skeleton that they all have. But not all corals live in the tropics. We actually have two species of stony corals in Northern California. The brown cup coral, Paracyathus stearnsi, lives subtidally, and I think I've seen maybe a handful in all my intertidal explorations. The orange cup coral, Balanophyllia elegans, extends up into the low intertidal, and can be very common at certain sites I visit regularly. When I see them at low tide they are emersed and look like orange blobs. But if you touch one with your finger, you can feel the hardness of the calcareous base.

Orange cup corals growing among coralline algae
Orange cup coral (Balanophyllia elegans) at Asilomar
2015-10-26
© Allison J. Gong

Stony corals they may be, but Paracyathus and Balanophyllia are both solitary; that is, they aren't colonial. Each polyp developed from its own larva and lives its own life independent from all other corals. Its bright orange color makes Balanophyllia pretty conspicuous, even though most of them are less than 10 mm in diameter. They do occur in patches, which makes one wonder. If they're solitary rather than clonal or colonial, how do these patches arise?

To answer this question we need to venture into the lab and examine the biology of Balanophyllia more closely. Fortunately, they grow in the lab quite happily. Years ago my friend Cris collected a bunch of Balanophyllia and glued them to small tiles so they could be moved around and managed in the lab. Cris has since moved on to other things, but the corals remain in the lab to be studied. They are beautiful animals, and can't really be appreciated in the intertidal because at low tide they're all closed up. But look at how pretty they are when they're relaxed and open:

Group of adult cup corals, Balanophyllia elegans
Cluster of orange cup corals (Balanophyllia elegans)
2020-05-01
© Allison J. Gong

Like all cnidarian polyps, these corals have long tentacles loaded with stinging cells, or cnidocytes. See the little bumps on the otherwise translucent tentacles? Those are nematocyst batteries, clusters of stinging cells.

Orange cup coral, Balanophyllia elegans
Orange cup coral (Balanophyllia elegans)
2020-05-01
© Allison J. Gong

Let's get back to the biology of this beast and how it is that they seem to live in groups. Balanophyllia is a solitary coral with separate sexes--each polyp is either male or female. They are also brooders. Males release sperm, which are ingested by a nearby female. The female broods fertilized eggs in her gastrovascular cavity. After a long period, perhaps several months, a large reddish planula larva oozes out of the mother's mouth and crawls around for a while, generally settling and metamorphosing near its parent.

Planula larva of Balanophyllia elegans
Planula larva of Balanophyllia elegans
29 April 2020
© Allison J. Gong

This planula is a very squishy elongate blob, and can measure anywhere from 1-4 mm in length. It is an opaque red color, has a ciliated epidermis, and lacks a mouth or digestive system. Instead of feeding, it survives on energy reserves that its mother partitioned in the egg. You might surmise that not being able to eat would necessitate a quick metamorphosis into a form that has a mouth, but you'd be wrong. While some of them do indeed settle and metamorphose very close to their parent, others crawl around for several weeks, showing no inclination to put down roots and take on life as a sessile polyp. Perhaps they can take up enough dissolved organic matter from the seawater to sustain them through a long period of fasting.

At some point, though, the larva settles and metamorphoses into a little polyp. In the lab at least, Balanophyllia larvae settle on a variety of surfaces--glass, various plastics, even the fiberglass of the seawater tables.

Juvenile cup coral and three planula larvae of Balanophyllia elegans
Recently metamorphosed coral and three planula larvae of Balanophyllia elegans
2020-04-29
© Allison J. Gong

The little coral measures about 2 mm in diameter and has 12 tentacles. It feeds very happily on brine shrimp nauplii and should grow quickly. Those three larvae, though, may hang around forever. I got tired of waiting for them to do something and released them into the seawater system. It might or might not have been an accident.

So there we have it. Our local cold-water coral, which doesn't form reefs or live in colonies. Balanophyllia may seem atypical for corals, but what it really demonstrates is the diversity within the Scleractinia. It reminds us that generalities do indeed have some value, and that for the discerning mind it is the exceptions to the generalities that are most interesting.

3

Of course, sea anemones don't have faces. They do have mouths, though, and since a mouth is usually part of a face, you can sort of imagine what I'm getting at. The sunburst anemone, Anthopleura sola, is one of my favorite intertidal animals to photograph. Of the four species of Anthopleura that we have on our coast, A. sola is the most variable, which is why it keeps catching my eye.

This afternoon I met the members of the Cabrillo College Natural History Club for the low tide at Natural Bridges. Here are some of the A. sola anemones we saw.

Sunburst anemone (Anthopleura sola) at Natural Bridges
2020-02-22
© Allison J. Gong
Sunburst anemone (Anthopleura sola) at Natural Bridges
2020-02-22
© Allison J. Gong
Sunburst anemone (Anthopleura sola) at Natural Bridges
2020-02-22
© Allison J. Gong
Sunburst anemone (Anthopleura sola) at Natural Bridges
2020-02-22
© Allison J. Gong
Sunburst anemone (Anthopleura sola) at Natural Bridges
2020-02-22
© Allison J. Gong

Such an amazingly photogenic animal, isn't it?

This past Fall semester the NHC went tidepooling at Pigeon Point. Today we were at Natural Bridges, and later in the spring we are going to Asilomar. I didn't intend it, but this school year the club is getting a look at three very different intertidal sites.

I love it when things work out that way!

4

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:

Intertidal "island" at Natural Bridges
2020-01-11
© Allison J. Gong

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.

Andrew, Marla, and Betsy standing on intertidal mussel bed at Natural Bridges State Beach
Andrew, Marla, and Betsy at Natural Bridges
2020-01-11
© Allison J. Gong

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:

Tidepool at Natural Bridges
2020-01-11
© Allison J. Gong

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.

Pair of courting kelp crabs (Pugettia producta)
2020-01-11
© Allison J. Gong

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.

Always a great way to end the day!

2

When we stop to marvel at the wonders of the natural world, we usually forget about all the life that is going on that we don't get to see. But there is a lot happening in places we forget to look. For example, any soil is an entire ecosystem, containing a variety of small and tiny animals, bacteria, and fungi. In fact, if a fungus didn't send up a fruiting body (a.k.a. mushroom) every once in a while, most observers wouldn't realize it was there at all. We humans tend to behave as though something unseen is something that doesn't exist, and I admit to the very same thinking with regards to my own kitchen: anything stored way up in cupboards I can't reach, may as well not be there at all.

But there are places where we can witness the life occurring below our feet, and floating docks in marinas and harbors are some of the best. Of course, the trick is to "get your face down where your feet are", a piece of advice about how to observe life in tidepools that applies just as well to investigating the dock biota. Once you get used to the idea of lying on the docks, which can be more or less disgusting depending on time of year and number of birds hanging around, a whole new world literally blossoms before your eyes.

Some of the flower-looking things are indeed anthozoans ('flower animal') such as this plumose anemone:

Plumose anemone (Metridium senile) at the Santa Cruz harbor
09 October 2019
© Allison J. Gong

and this sunburst anemone:

Sunburst anemone (Anthopleura sola) at the Santa Cruz harbor
09 October 2019
© Allison J. Gong

Other animals look like dahlias would look if they were made of feathers. Maybe that doesn't make sense. But see what I mean?

This is Eudistylia polymorpha, the so-called feather duster worm. These worms live in tough, membranous tubes attached to something hard. They extend their pinnate tentacles for feeding and are exquisitely sensitive to both light and mechanical stimuli. There are tiny ocelli (simple, light-sensing eyes) on the tentacles, and even casting a shadow over the worm causes it to pull in its tentacles very quickly. This behavior resembles an old-fashioned feather duster, hence the common name. These were pretty big individuals, with tentacular crowns measuring about 5 cm in diamter. Orange seems to be the most common color at the Santa Cruz harbor.

One of the students pointed down at something that he said looked like calamari rings just below the surface. Ooh, that sounds intriguing!

And he was right! Don't they look like calamari rings? But they aren't. These are the egg ribbons of a nudibranch. They appeared to have been deposited fairly recently, so I went off on a hunt for the likely parents. And a short distance away I caught the nudibranchs engaging in the behavior that results in these egg masses. Ahem. I don't know if the term 'orgy' applies when there are three individuals involved, but that's what we saw.

Mating aggregation of Polycera atra
09 October 2019
© Allison J. Gong

To give you some idea of how these animals are oriented, that flower-like apparatus is the branchial (gill) plume, which is located about 2/3 of the way down the animal's dorsum. The anterior end bears a pair of sensory organs called rhinophores; they look kind of like rabbit ears. You can see them best in the animal on the left.

When you see more than one nudibranch in such immediate proximity it's pretty safe to assume that they were mating or will soon be mating. Nudibranchs, like all opisthobranch molluscs, are simultaneous hermaphrodites, meaning that each can mate as both a male and a female. The benefit of such an arrangement is that any conspecific individual encountered is a potential mate. The animals pair up and copulate. I'm not sure if the copulations are reciprocal (i.e., the individuals exchange sperm) or not (i.e., one slug acts as male and transfers sperm to the other, which acts as female). In either case, the slugs separate after mating and lay egg masses on pretty much whatever surface is convenient. Each nudibranch species lays eggs of a particular morphology in a particular pattern. Some, such as P. atra, lay eggs in ribbons; others produce egg masses that look like strings of miniature sausages.

Nudibranch (Polycera atra) at the Santa Cruz harbor
09 October 2019
© Allison J. Gong

This is the first time I've seen big Polycera like these. The slugs were about 4 cm long. They eat a bryozoan called Bugula, and there is a lot of Bugula growing at the harbor these days. Maybe that's why there were so many Polycera yesterday. Nudibranchs are the rock stars of the invertebrate world--they are flamboyantly and exuberantly colored, have lots of sex, and die young. They can be very abundant, but tend to be patchy. Quite often an egg mass is the only sign that nudibranchs have been present.

The next time you happen to be at a marina poke your head over the edge and take a look at the stuff living on the dock. Even if you don't know what things are, you should see different textures and colors. With any luck, you'll be pleasantly surprised at the variety of life you find under your feet.

2

In my experience, the most difficult organisms to photograph in the wild are staurozoans. Even birds in flight are easier. The problem with staurozoans is where they live. I never see them in calm, still pools, where taking pictures would be easy. Instead, they seem to like surge channels where the water constantly sloshes back and forth, and even in the few seconds between a wave coming in and receding they never really stop moving. Their bodies are extremely soft and squishy, so the slightest current causes them to flutter and make blurry photos. When they are emersed their bodies don't really look like anything except a soggy booger, so they aren't recognizable as staurozoans unless they are underwater. And when underwater they don't hold still, and so on and so forth.

Still, finding them is always a treat, even if I can't capture photographic proof. They really are extremely gorgeous creatures.

Staurozoan (Haliclystus 'sanjuanensis') at Franklin Point
2019-05-08
© Allison J. Gong

They are also enigmatic creatures. Much of staurozoan biology, including their evolutionary relationships, remains poorly understood. Until recently the staurozoans were considered a subgroup of the Scyphozoa, the taxon that includes the large medusae such as moon jellies (Aurelia spp.) and sea nettles (Chrysaora spp.). However, using data from more extensive morphological and molecular studies, most taxonomists now agree that the Staurozoa should be elevated to a level equivalent to the Scyphozoa. In other words, the staurozoan lineage probably evolved alongside, but separate from, the scyphozoan lineage.

Whatever their evolutionary history and relationships, what we know about staurozoans is very limited. They are considered to be stalked jellies (hence their previously assumed close affinity to the scyphozoans) that do not have a separate polyp stage. Their bodies consist of an adhesive peduncle, or stalk, that attaches to algae or surfgrasses, and a calyx or goblet-shaped portion surrounded by eight tapering arms. Each of the eight arms is topped with a puffball of stinging tentaches which are uses to catch food and presumably to defend the animal against predators. The mouth is located in the center of the calyx, usually lifted up on a short stalk called a manubrium. The animal feeds by capturing prey on the tentacles and flexing the arm so the food is brought to the mouth. Staurozoans are not permanently attached and can sort of 'walk' with a somersault-like motion, flipping end-over-end.

Staurozoan (Haliclystus 'sanjuanensis') at Franklin Point
2019-05-08
© Allison J. Gong
Haliclystus 'sanjuanensis' at Franklin Point
2019-05-08
© Allison J. Gong

Haliclystus 'sanjuanensis' at Franklin Point grows to a length and diameter of ~3 cm, although most of the ones that I see are smaller than that. The most common color is this reddish brown, but I've also seen them in a gorgeous bottle green that makes them much easier to see against the background of their habitat. I usually see them attached to pieces of red algae, but I'm not sure they actually prefer red algae to either green or brown algae. I don't think I've ever seen one attached to a rock.

Last week I had one of those moments in the intertidal when I felt something stuck on my finger and I couldn't get rid of it. That happens frequently, with small bits of algae getting caught on everything; usually I just flick my hand and they go flying off. But this thing wouldn't leave. I finally stuck my hand in the water to rinse it off, and saw that I had been glommed onto by a small staurozoan!

Staurozoan (Haliclystus 'sanjuanensis') on my finger at Franklin Point
2019-05-08
© Allison J. Gong

See how the animal stuck to me with its tentacles, while its peduncle is still attached to a piece of Ulva?

As I mentioned, not much is known about these strange animals. They possess the stinging cells to prove their inclusion within the Cnidaria, but are aberrant medusae which stick to algae instead of swimming around in the water column. Their life cycle is more or less cnidarian-like, but their planula is non-ciliated. Their ecological relationships haven't really been studied at all.

Which is why this photograph is so informative. It's not a great picture, by any means, but it shows a glimpse of how staurozoans interact with other species.

2019-05-08
© Allison J. Gong

This is a picture of two animals, a staurozoan (H. 'sanjuanensis') and a nudibranch (Hermissenda opalescens). Both of these animals are predators. Hermissenda is well known for its affinity for general cnidarian prey, from which it steals the stinging cells to defend its own body (a behavior known as kleptocnidae). But the staurozoan should be quite capable of defending itself. So, who is doing the eating, and who is being eaten?

Given the dastardly nature of Hermissenda, I'd bet on it as the eater. Those damned nudibranchs have to spoil everything! The staurozoan will probably sustain damage, perhaps losing a tuft of tentacles, but should be able to regrow the lost parts. And the sting of the staurozoan may keep the nudibranch from eating as much as it would like. That's the thing. We just don't know.

I'll definitely be keeping an eye out for the staurozoans at Franklin Point the rest of this tide season. I may even bring a few back to the lab for closer inspection; my collecting permit allows me to do so. I could then photograph them under controlled conditions and hopefully get some better pictures. I find these animals very intriguing, being both so clearly cnidarian-like and simultaneously so inscrutable. I always did like a good mystery story!

When low tides occur at or before dawn, a marine biologist working the intertidal is hungry for lunch at the time that most people are getting up for breakfast. And there's nothing like spending a few morning hours in the intertidal to work up an appetite. At least that's how it is for me. Afternoon low tides don't seem to have the same effect on me, for reasons I can't explain. A hearty breakfast after a good low tide is a fantastic way to start the day.

Sea anemones are members of the Anthozoa (Gk: 'antho' = 'flower' and 'zoa' = 'animal'). These 'flower animals' are the largest cnidarian polyps and are found throughout the world's oceans. They are benthic and sedentary but technically not sessile, as they can and do walk around, and some can even detach entirely and swim away from predators. The anthozoans lack the sexual medusa stage of the typical cnidarian life cycle, so the polyps eventually grow up and have sex. In addition to the sea anemones, the Anthozoa also includes the corals, sea pens, and gorgonians.

With their radial symmetry and rings of petal-like tentacles, the sea anemones do indeed resemble flowers. You've seen many of my anemone photos already. Here's one more to drive home the message.

Anthopleura artemisia at Pistachio Beach
27 January 2017
© Allison J. Gong

Sea anemones are cnidarians, and cnidarians are carnivores. Most of the time  anemones in the genus Anthopleura feed on tiny critters that blunder into their stinging tentacles, although the occasional specimen will luck into a much more substantial meal. I've watched hermit crabs crawl right across the tentacles of a large anemone (Anthopleura xanthogrammica), and while the anemones did react by retracting the tentacles, the crabs easily escaped their grasp.

Of course, not all potential prey items are so fortunate. Sometimes even big crabs get captured and eaten, like this poor kelp crab (Pugettia producta):

Kelp crab (Pugettia producta) being eaten by an anemone (Anthopleura sp.) at Davenport Landing
8 March 2017
© Allison J. Gong

There's no way to know exactly how this situation came to be. Was the crab already injured or weakened when the anemone grabbed it? Or was the anemone able to attack and subdue a healthy crab? I've always assumed that the exoskeleton of a crab this size would be too thick for the rather wimpy nematocysts of an Anthopleura anemone to penetrate, but maybe I'm wrong. A newly molted crab would be vulnerable, of course; however, they tend to stay hidden until the new exoskeleton has hardened, and the crab in the above photo doesn't appear to have molted recently.

Even big, aggressive crabs can fall prey to the flower animals in the tidepools. I'd really like to have been there to watch how this anemone captured a rock crab!

Giant green anemone (Anthopleura xanthogrammica) eating a rock crab, possibly (Romaleon antennarium) at Natural Bridges
17 June 2018
© Allison J. Gong

And crabs aren't the only large animals to be eaten by sea anemones. Surprisingly, mussels often either fall or get washed into anemones, which can close around them. Once a mussel has been engulfed by an anemone, the two play a waiting game. Here's what I imagine goes on inside the mussel: The bivalve clamps its shells shut, hoping to be spit back out eventually; meanwhile, the anemone begins trying to digest the mussel from the outside; sooner or later the mussel will have to open its shells in order to breathe, and at that point the anemone's digestive juices seep inside and do their work on the mussel's soft tissues. When the digestive process is finished, the anemone spits out the perfectly cleaned mussel shells.

Giant green anemone (Anthopleura xanthogrammica) digesting a clump of mussels (Mytilus californianus) at Natural Bridges
17 June 2018
© Allison J. Gong

In the photo above, the anemone is working on a clump of several mussels. I can't see that any of these mussels have been compromised, but the pale orange stringy stuff looks like mussel innards and slime. It could be that several mussels are still engulfed within the anemone. There is always a chance that an anemone will give up on a mussel that remains tenaciously closed, and spit it out covered with slime but otherwise unharmed. I assume that hungry anemones are less likely to give up their meals than ones that have recently fed.

So how, exactly, does an anemone eat a mussel, or a crab? The answer lies within the anemone's body. Technically, the gut of an animal is outside its body, right? Don't believe me? Let's think it through. An animal with a one-way gut can be modeled as a tube within a tube, and by that reasoning the surface of a gut is contiguous with the outer surface of the body. Our gut is elaborated by pouches and sacs of various sizes and functions, but is essentially a long, convoluted tube with a mouth on one end and an anus on the other. Sea anemones, as all cnidarians, have a two-way gut called a coelenteron or gastrovascular cavity (GVC), with a single opening serving as both mouth and anus. Anemones, being the largest cnidarian polyps, have the most anatomically complex gut systems in the phylum.

Imagine a straight-sided vase with a drawstring top. The volume of the vase that you'd fill with water and flowers represents the volume of the anemone's gut. Anemones can close off the opening to their digestive system by tightening sphincter muscles that surround the mouth; these muscles are analogous to the drawstring closure of our hypothetical vase. Now imagine that the inner wall of the vase is elaborated into sheets of curtain-like tissue that extend towards the center of the cavity. These sheets of tissue are called mesenteries. They are loaded with various types of cnidocytes that immobilize prey and begin the process of digestion. The mesenteries greatly increase the surface area of tissue that can be used for digestion. The mesenteries are also flexible and can wrap around ingested prey to speed things up.

This anemone (below) that was eating both a mussel and a piece of kelp:

Sunburst anemone (Anthopleura sola) having brunch at Davenport Landing
4 May 2018
© Allison J. Gong

Those frilly ruffles are the mesenteries. You can see how greatly they'd increase the surface area of the gut for digestion. They are also very soft, almost flimsy. Here's a close-up shot:

Gastric mesenteries of the sea anemone Anthopleura sola at Davenport Landing
4 May 2018
© Allison J. Gong

Maybe I'm especially suggestible, but seeing these animals working on their own meals makes me hungry, too. After crawling around the tidepools for a few hours I'm always ready for a second breakfast or brunch of my own.

Bon appétit!

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