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This morning as I was doing my rounds at the marine lab I noticed a pile of eggs next to one of the bat stars (Patiria miniata) in a large table. Somebody, or more likely, multiple somebodies, had spawned overnight. I have absolutely zero time to deal with another ongoing project right now, but I have even less self-control when it comes to culturing invertebrate larvae. So I sucked up as many of the eggs as I could, along with a fair amount of scuzz from the bottom of the table, and took a look.

Assortment of bat star (Patiria miniata) embryos
Embryos of the bat star Patiria miniata, about 1 day old
2020-06-19
© Allison J. Gong

As I've come to expect with stars, the early embryonic stages are developing asynchronously. There were unfertilized eggs (obviously not going to develop at all), zygotes that hadn't divided yet, and other stages.

The coolest thing, though, will take some explaining. Animals begin life as a zygote, or fertilized egg. The zygote undergoes a number of what are called cleavage divisions, in which the cell divides but the embryo doesn't grow. A logical necessity of these two facts is that the cells get smaller and smaller as cleavage continues.

Now let's go back to the earliest cleavage divisions. One cell divides into two, each of those divides into two, and so on. The cell number starts with 1 and goes to 2, then 4, then 8, then 16, and so on. The process is more or less the same for all animals, but in only a few can these divisions be easily seen. Many echinoderms have nice distinct cleavage divisions and transparent-ish embryos, which is why the old-school embryologists in the early 1900s studied them.

Echinoderms are the major phylum in a group of animals called the deuterostomes. Incidentally, chordates (ahem--us) are also deuterostomes. The word "deuterostome" refers to the fact that during development in these animals the anus forms before the mouth does. That's right, folks, you had an anus before you had a mouth.

Another feature that is generally associated with the deuterostomes occurs in early cleavage. Picture this: A cell divides into two cells. Then each of those divides, resulting in four cells. Geometry dictates that the four cells form a plane. That makes sense, right? When the four cells divide again to make the 8-cell embryo, a second plane of cells is formed on top of the first. The second tier can either sit directly on top of the cells of the first tier (radial cleavage) or be twisted 45º so that the cells sit in the grooves between cells in the first tier (spiral cleavage).

Take a look at this embryo. Do you think it has undergone spiral cleavage or radial cleavage?

8-cell embryo of Patiria miniata
8-cell embryo of Patiria miniata
2020-06-19
© Allison J. Gong

This is a textbook example of radial cleavage. In all the sea urchin embryos I've watched over the years, I've never seen radial cleavage as clear and unambiguous as this. It was one of those moments when you actually get to see something that you've known (and taught) about forever.

So yes, echinoderms and other deuterostomes generally undergo radial cleavage. And I will hopefully have larvae to look after again! They will probably hatch over the weekend. On top of everything else that's going on now, additional mouths to feed are the last thing I need. But fate dropped them into my lap and who am I to argue with fate?

Every year, in June, my big whelk lays eggs. I have a mated pair of Kellettia kellettii living in a big tub at the marine lab. I inherited them from a lab mate many years ago now, and they've been nice pets. They've lived together forever, and make babies reliably. As June rolls around I start looking for eggs. This year I want to document the entire process, from egg-laying to larval development. Fortunately, I had the foresight to photograph the parents in May, as I didn't want to disturb the female once she began laying.

The female is significantly larger than the male. I know the big one is the female because that's the one that lays the eggs. I've never managed to catch the whelks copulating, but given the female's track record they either copulate regularly or she is able to store sperm for a long period of time.

In any case, she started laying eggs today. I went in to check on them and there she was!

Female whelk laying eggs
Female whelk (Kellettia kellettii) laying eggs
2020-06-12
© Allison J. Gong

I know from previous years that it can take over a week for the female to lay her entire clutch of eggs. Each of those pumpkin seed-shaped objects is an egg capsule, containing a few dozen embryos. The newly lain capsules are white, as you see above, and will gradually get darker as the embryos develop into larvae. The mother will lay the eggs and then depart. When the larvae are ready to leave the capsule, a small hole will wear through in the top of the capsule and the larvae will swim out. More on that later, hopefully.

I took some time-lapse video of the female, and was able to record her moving over the egg capsules and then leaving. I'd also put some food in the tub, and I think she got distracted.

I think it's really cool to see how well the snail can swivel around on her foot. Snails are attached to their shell at only a single point called the columella, the central axis around which the shell coils. Some snails can extend quite far outside the shell, and they can all pull inside for safety. The dark disc on the back of the foot is the operculum that closes up the shell when the snail withdraws into it.

Tomorrow when I check on things at the lab I'll see if she has resumed laying.

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!

Today was the first time I've gone out on a low tide since before the whole COVID19 shelter-in-place mandates began. Looking back at my records, which I hadn't done until today because it was much too depressing, I saw that my last time out was 22 February, when the low tides were in the afternoon. At the time I made what seemed to be the not-too-bad decision to stay away from the remaining afternoon lows and wait until the spring shift to morning lows, which I like much more. And then then COVID hit and we all had to stay home and beaches were closed. So yeah, it has been much too long and I really needed this morning's short visit to the intertidal.

Pair of black oystercatchers (Haematopous bachmani) at Mitchell's Cove
My companions for a short while this morning, a pair of black oystercatchers (Haematopus bachmani) at Mitchell's Cove
2020-05-08
© Allison J. Gong

Beaches in Santa Cruz County are closed between the hours of 11:00 and 17:00, except that we are allowed to cross the beach to get to the water. This means that surfers, kayakers, SUP-ers, and marine biologists can get out and do their thing. Of course, my particular thing took place hours before the beach restrictions began, so I was in the clear anyway. I didn't venture too far from home, as I wasn't quite certain how easy it would be to get down to the beach.

Spring is the prime recruitment season for life in the intertidal. The algae are coming back from their winter dormancy, and areas that had been scraped clean by sand scour or winter storms are being recolonized. Many of the invertebrates have or will soon be spawning. And larvae that have spent weeks or even months in the plankton are returning to the shore to metamorphose and begin life as an adult. Just as it is on land, spring is the time for life in the sea to go forth and multiply.

For several decades now, marine ecologists have been studying barnacles and barnacle recruitment. Barnacles are a nice system for studying, for example, recruitment patterns and mortality. The cyprid larva, the larval stage whose job it is to find a permanent home in the intertidal, readily settles and metamorphoses on a variety of man-made surfaces; this makes it easy to put out plates or tiles and monitor who lands there. The fact that barnacles, once metamorphosed, remain attached to the same place for their entire lives means an ecologist can measure mortality (or survivorship, which is the inverse) by counting the barnacles every so often.

These are young barnacles (Chthamalus sp.), about 4-5 mm in diameter. I don't know how old they are, but would guess that they recruited in the past couple of months. These individuals all found a nice place to set up, because as I've written before, barnacles need to be in close proximity to conspecifics in order to mate.

Young acorn barnacles (Chthamalus dalli/fissus) on a rock at Mitchell's Cove
Small barnacles (Chthamalus sp.) on a rock at Mitchell's Cove
2020-05-08
© Allison J. Gong

This is a mixed group of Chthamalus sp. and Balanus glandula. Balanus is taller and has straighter sides and a more volcano-like appearance. Larvae of both genera recruit to the same places on rocks in the intertidal, and it is not uncommon to see assemblages like this.

Mixed assemblage of Balanus and Chthamalus barnacles at Mitchell's Cove
Barnacles Balanus glandula and Chthamalus sp. at Mitchell's Cove
2020-05-08
© Allison J. Gong

Both species of barnacles are preyed upon by birds, sea stars, and snails. Predatory snails use their radula to drill a hole through the barnacle's plates and then suck out the body. Some of the barnacles in the photo below are dead--see the empty holes? Those are barnacles that were eaten by snails such as these.

Small barnacles and predatory snails at Mitchell's Cove
2020-05-08
© Allison J. Gong

What was unusual about this morning was the number of snails of the genus Acanthinucella. I don't know that I've ever seen this many of them before.

Large group of Acanthinucella snails at Mitchell's Cove
2020-05-08
© Allison J. Gong

Lots of Acanthinucella means that lots of barnacles are being eaten. And empty (i.e., dead) barnacle tests are more easily dislodged from the rock than live ones are. A lot of dead barnacles could result in bare patches. And guess what? That's what I saw this morning!

Bare patches in barnacle population
Bare patches in barnacle population at Mitchell's Cove
2020-05-08
© Allison J. Gong

And those aren't just empty spaces where nobody settled. Notice the clean edges. These empty spaces formed because barnacles were there, but died recently and fell off. The abundance of Acanthinucella may have indirectly caused these patches to form--by eating barnacles and weakening the physical structure of the population. Bare space is real estate that can be colonized by new residents. See?

Newly settled barnacles
2020-05-08
© Allison J. Gong

These brand new recruits are about 1 mm in diameter. No doubt more will arrive in the coming months, and this patch will fill up with barnacles again. Vacant space is a limited resource in the rocky intertidal, and the demise of one generation provides opportunity for new recruits. And if the barnacles themselves don't occupy all of the space, then other animals and algae will. That's one of the things I love about the intertidal--it is a very dynamic habitat, and every visit brings something new to light. No wonder I missed it so much!

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!

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.

Shell plate of Cryptochiton stelleri
2020-01-12
© Allison J. Gong

One of the coolest pattern I've ever seen in the intertidal was this:

Leaf barnacle (Pollicipes polymerus), mussels (Mytilus californianus), and limpets (Lottia sp.)
2020-01-12
© Allison J. Gong

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!

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.

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