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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 largest polyps in the phylum, 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 now 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!

Monterey Bay is shaped like a backwards letter 'C', with Santa Cruz on the north end and the Monterey Peninsula on the south end. The top of the 'C' is comparatively smooth, while the bottom is punctuated by the Monterey Peninsula, which juts north from the city of Monterey. The most striking geologic feature is the Monterey Submarine Canyon, but of course you can't see that from land. It is crazy to realize that the canyon starts right off the jetty at Moss Landing. It is this proximity to deep water that makes the Monterey Bay Aquarium Research Institute (MBARI) so ideally situated.

Monterey Bay, California
© Google Maps

Separated by 40.2 km (= approximately 25 statute miles) as measured harbor to harbor, Santa Cruz and Monterey represent both the same and slightly different marine habitats. On a large scale they are both part of the California Current system, strongly affected and biologically defined by seasonal upwelling in the spring and summer months. On a finer scale they differ in a few ways, primarily geologic. The rock on the Santa Cruz end of the bay is a soft sand- or mudstone, and at sites like Natural Bridges can be easily eroded; you can scratch it with your thumbnail, and falling on it might give you a bruise but probably won't beat you up more than that. The rock of the Monterey Peninsula is much less forgiving: granite with large quartz crystals. Falling on that stuff can leave you with bruises and a bad case of rock rash; I usually end up bleeding from at least one laceration when I'm in the intertidal there.

Limpet on granite on the Monterey Peninsula
16 June 2018
© Allison J. Gong
Barnacles on mudstone in Santa Cruz
17 June 2018
© Allison J. Gong

The difference in rock type between the north and south ends of Monterey Bay also manifests in the tidepools themselves. The soft mud stone of the Santa Cruz erodes into small particles, which form nice soft sandy beaches. Small particles also remain suspended in water more so than larger ones, which affects water clarity. Larger and heavier particles, on the other hand, sink out of the water, so that the water column itself tends to be less murky. Clear water has some marked advantages over murky water. For example, light transmission is directly proportional to water clarity. Thus, all other factors being equal, photosynthetic organisms such as algae have access to more light, in waters above large-grained sand than those above finer sediments.

That being said, it is not always the case that clearer water is better. Remember Phragmatopoma californica, one of the worms I wrote about recently? They build tubes out of sand grains. However, it turns out that they are particular about the sand grains they use. If you were to examine a Phragmatopoma tube under a dissecting scope you'd see that all of the sand grains are the same size. Just how they select and sort the sand grains isn't understood, but somehow they manage to choose the particles they want and cement them together underwater. Phragmatopoma is one of the most conspicuous animals at Natural Bridges on the north side of Monterey Bay, forming large mounds of hundreds of individuals, yet very few live on the Monterey Peninsula. There are likely several reasons for this, but part of the explanation is that the sand grains are too big to be used in the worms' tubes.

I live in Santa Cruz, on the north end of the bay, and most of my intertidal excursions these days are to locations in Santa Cruz and north along the coast. I haven't spent nearly as much time as I'd like to in the tidepools on the Monterey Peninsula and locations further south. It's tough getting to a site an hour away, when the low tide is at dawn. And with my post-concussion syndrome I don't yet feel comfortable driving myself that far away and back. Fortunately for me, I am currently mentoring a student working on an independent study project, and she was willing to drive down to Asilomar last weekend. So I tagged along with her.

Monterey Peninsula
© Google Maps

Asilomar State Reserve is one of California's no-take marine protected areas (MPAs), where people can look and take pictures but are not allowed to remove anything, dead or alive. It is a glorious site. The water is clear and blue, and the biota is both similar to and different from that on the north side of the bay. I want to highlight some of the organisms that I see there, that are less common here on the north side.

Black abalone (Haliotis cracherodii) at Asilomar State Beach
16 June 2018
© Allison J. Gong

Abalone (Haliotis sp.) are not unheard of here. In fact, there is a black ab (H. cracherodii) at Natural Bridges that I've been keeping an eye on since 2015, tucked into a crevice and generally not visible except on a minus tide. And further north at Pigeon Point I have seen red abalone (H. rufescens), both living and empty shells. But I've never seen as many black abs as I saw at Asilomar. Standing in a depression about as big as my kitchen table, well above the water level, I easily counted at least 20 black abs. Some of them were as big as my hand. How many can you see in the photo above?

Black abalone (Haliotis cracherodii) at Asilomar State Beach
16 June 2018
© Allison J. Gong

Abalone are large herbivorous snails. They feed on macroalgae, both reds and browns. If they venture from the safety of their nooks and crannies they can chase (at a snail's pace) down algae, but then they are vulnerable to predators such as cabezons and sea otters. Abs that live in crevices, like these, have to rely on drift algae to come to them; they don't have the luxury of choosing what to eat. It's the age-old compromise between safety and food, one of the driving forces in foraging behavior.

While we have four species of anemones in the genus Anthopleura at the Santa Cruz end of the bay, as well as other anemones such as Epiactis, we don't have any in the genus Urticina--not intertidally, at least. I have seen Urticina anemones at Carmel, and last weekend saw what I think was U. coriacea. It was in a pool, and partially obscured by sand and its own pharynx.

The anemone Urticina coriacea at Asilomar State Beach
16 June 2018
© Allison J. Gong

It's own pharynx, you ask? Yes! Anemones are cnidarians, and as such have a two-way gut. This means that food is ingested and wastes are expelled via a single opening, which for politeness' sake we call a mouth even though it also functions as an anus. Sometimes, when an anemone is expelling wastes, it also turns out the top part of its pharynx. This is a temporary condition, and the pharynx will be returned to normal soon. The anemone in the picture above appears to be in the process of spitting out something fairly large and undigestible.

Here's another example of an anemone eating a big meal, this time of mussels.

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

What do you think this thing (below) is?

Pista elongata at Asilomar State Beach
16 June 2018
© Allison J. Gong

I had at first misidentified these as something else, but have since been told that they are the tubes of another of those strange terebellid polychaete worms. This one is Pista elongata. As with many terebellids, P. elongata lives in a tube, the opening end of which is elaborated into a sort of basket. They reportedly range from British Columbia to San Diego. I think I've seen them at Carmel Point, but not at Point Piños, which I've visited more often. And I'm positive I've never seen it at Natural Bridges.

At Asilomar I saw some large clusters of P. elongata in the low intertidal. They are not clonal, to my knowledge, so these aggregations would form by gregarious settlement of competent larvae when they return to shore.

Cluster of Pista elongata at Asilomar State Beach
16 June 2018
© Allison J. Gong

One solitary ascidian that I saw at Asilomar is Clavelina huntsmani, the appropriately called lightbulb tunicate:

The "lightbulb tunicate" Clavelina huntsmani at Asilomar State Beach
16 June 2017
© Allison J. Gong

For people too young to remember what an incandescent light bulb looks like, they were made of clear or frosted glass. Inside the glass bulb were tungsten filaments, through which electricity flowed; the filaments heated up enough to emit light. In Clavelina, the two pink structures running down the length of each zooid resemble the filaments of an incandescent light bulb, but are in fact parts of the pharyngeal basket, the structure used for filter feeding.

We have neither Pista nor Clavelina in Santa Cruz--at least, I've never seen them. They remind me that although Santa Cruz and Monterey are part of the same ecosystem, they do not represent the same microhabitat. I'm pretty familiar with the intertidal floral and fauna in Santa Cruz, but I absolutely love exploring the intertidal along the Monterey Peninsula. There's something exciting about spending time a place I don't know as well as the back of my hand. I hope that as my brain continues to heal I'll eventually regain the stamina to travel so far for a low tide.

1

Today is the first day of the week of low tides dedicated to Snapshot Cal Coast, a statewide citizen science project headed in my area by the California Academy of Sciences. This week groups and individuals will be making photographing the organisms they see in the ocean or along the coast, and uploading observations to iNaturalist. Participants will include both scientists and non-scientists, making the week-long event one of the biggest citizen science projects that I regularly take part in. Next Monday I'll be taking a group of Seymour Center volunteers and staff up to Davenport to conduct a Bioblitz. The other days I'll be out on my own, or with 1 or 2 people.

This morning the low tide was very early (-1.3 feet at 05:09), so I stayed close to home and went to Natural Bridges. The tide was low but the swell was big and I wasn't able to get down to the low spots I could normally reach with this kind of tide. However, this meant that I could spend more time in the low-mid-intertidal, where there is a lot of biodiversity to document.

Today I want to write about polychaete worms. These are the segmented marine worms in the Phylum Annelida, which also includes earthworms and leeches.

Worm #1: Phragmatopoma californica

One of the most conspicuous inhabitants of this zone is the tube-dwelling polychaete worm, Phragmatopoma californica. This worm has a couple of common names: honeycomb worm, which refers to the mounds of tubes they build; and sandcastle worm, for the fact that the tubes are built of cemented sand grains. In effect, these worms are tiny masons!

Mound of Phragmatopoma californica tubes at Natural Bridges
26 May 2017
© Allison J. Gong

Each of the tubes is inhabited by a single worm. Mounds form because competent Phragmatopoma larvae, looking for a place to settle out and live permanently, are attracted to the tubes of existing adults. This phenomenon is called gregarious settlement. Once settled and metamorphosed, juvenile worms build their tubes by selecting sand grains and cementing them together around a lining of chitin-like material. How they do it, underwater, nobody knows. And these tubes are tough! The worm inside is skinny, and a humongous one would be all of 4 cm long, but it takes a lot of force to pry apart those sand grains. The openings to the tubes are 5-10 mm in diameter. Each worm can close off its tube with a circular-ish disc of stiff, fused chaetae called an operculum; this protects the worm from both predators and desiccation.

When the tide is out the worms withdraw into their tubes and clap the operculum down. They wait for the water to return. Phragmatopoma is a filter feeder; like most of the tube-dwelling polychaetes these worms use a crown of ciliated tentacles to create water currents that draw food particles to the mouth. When the tide is in the worms pull down the operculum and extend their feeding tentacles into the water. In the field, this is the most you can see of the worm's body.

Feeding tentacles of Phragmatopoma californica at Natural Bridges
13 June 2018
© Allison J. Gong

Worm #2: Serpula columbiana

Many polychaetes live in tubes, and tubes can be made of a variety of materials. Phragmatopoma californica builds tubes out of sand grains. Another worm that I saw today, Serpula columbiana, builds tubes out of CaCO3 precipitated from seawater. Like other animals that build calcareous skeletons, S. columbiana may in the future have difficulty precipitating CaCO3 in an increasingly acidic ocean. Tubes of Serpula worms are white when new and soon become fouled with algal growth, and tend to wander over the substrate. The best photo I could take this morning is a little blurry but you can see the general morphology of the tubes.

Calcareous tubes of Serpula columbiana at Natural Bridges
13 June 2018
© Allison J. Gong

These worms are incredibly shy, and react to any perceived threat by pulling into their tubes. Their tentacles have tiny eyespots that can detect changes in light, so passing a hand over them can cause them to withdraw. Fortunately I was able to sneak up on one lazy worm in a pool, and grab a shot of its 'head' region. Worms that live in tubes are poorly cephalized, with none of the structures that we generally associate with a head. Serpula columbiana's 'head' looks like this:

Anterior end of Serpula columbiana at Natural Bridges
13 June 2018
© Allison J. Gong

The tentacles of S. columbiana are morphologically complex compared to those of Phragmatopoma. Serpula's tentacles are pinnate, or feather-shaped, and in cross-section look like a V. Cilia on the side branches of the tentacle create the feeding current, and food particles are transported by other cilia down the trough of the V to the mouth.

See that long, trumpet-shaped structure? That's the worm's operculum!

Worm #3: Unidentified cirratulid

Unlike Serpula and Phragmatopoma, worms of the Family Cirratulidae don't live in tubes. Instead, they live with most of the body hidden in crevices, and extend tentacles to feed.

Feeding tentacles of an unidentified cirratulid polychaete worm at Natural Bridges
13 June 2018
© Allison J. Gong

As you can imagine, it is extremely difficult to identify a worm when all you can see of it are its tentacles; with the rest of the body hidden in a crevice, there are no visible characteristics to use to distinguish species. Cirratulids use their tentacles to feed, but in a way that is entirely unlike how Phragmatopoma and Serpula use theirs. Instead of feeding on particles suspended in the water, cirratulids are deposit feeders. They sweep their tentacles across the surface and collect organic deposits. Sticky mucus on the tentacles picks up organic matter, and cilia on the tentacles sweep the organic matter to the worm's mouth.

Don't believe me? Watch this!

It doesn't matter if the surrounding substrate is sand or rock. The cirratulid's sticky tentacles are very effective at gathering organic muck.

Worm #4: Flabesymbios commensalis

This worm remains an enigma. There doesn't seem to be much known about its biology. I have seen them twice, both times on the body of purple urchins (Strongylocentrotus purpuratus), and although the genus name has changed twice since the first time, I'm pretty sure it's the same worm. As the species epithet commensalis implies, this worm is a commensal on sea urchins. This means that it neither harms nor benefits its echinoderm host. Similar to the worm I've seen on bat stars, F. commensalis presumably cruises over the urchin's body and feeds on detritus or scraps of kelp that the urchin grabs.

When I took the photo in a tide pool this morning I didn't see the worm. It wasn't until I downloaded the pictures from the camera onto my computer that I saw it. See how well it blends in with the urchin's color?

Purple urchin (Strongylocentrotus purpuratus) at Natural Bridges
13 June 2018
© Allison J. Gong

Here's a tighter crop of that photo:

Flabesymbios commensalis on aboral surface of a purple urchin (Strongylocentrotus purpuratus) at Natural Bridges
13 June 2018
© Allison J. Gong

For many polychaete worms, another animal's body seems to be the ideal habitat. And for some reason, echinoderms are likely hosts for such commensal worms. I've written about the bat star worms, here is the urchin worm, and there's also a scale worm that I've seen crawling around on the body of a sea cucumber. What is it about echinoderms that makes them habitat for worms? Or is this type of commensalism also common, but less observed, between polychaetes and other non-echinoderm invertebrates? I don't know the answer to either of those questions, but am very intrigued.

This weekend I was supposed to take a photographer and his assistant into the field to hunt for staurozoans. I mean a real photographer, one who has worked for National Geographic. He also wrote the book One Cubic Foot. You may have heard of the guy. His name is David Liittschwager. Anyway, his assistant contacted me back in March, saying that he was working on something jellyfish-related for Nat Geo and hoped to include staurozoans in the story, and did I know anything about them? As in, maybe know where to find them? It just so happens that I do indeed know where to find staurozoans, at least sometimes, and we made a date to go hunting on a low tide. Then early in May the assistant contacted me to let me know that David's schedule had changed and he couldn't meet me today, and she hoped they'd be able to work with me in the future, and so on.

None of which means that I wouldn't go look for them anyways. I'd made the plans, the tide would still be fantastic, and so I went. And besides, these are staurozoans we're talking about! I will go out of my way to look for them as often as I can. Not only that, but I hadn't been to Franklin Point at all in 2018 and that certainly needed to be remedied.

Pigeon Point, viewed from Franklin Point trail
19 May 2018
© Allison J. Gong

The sand has definitely returned. The beach is a lot less steep than it was in the winter, and some of the rocks are completely covered again. This meant that the channels where staurozoans would likely be found are shallower and easier to search. But you still have to know where to look.

Tidal area at Franklin Point
19 May 2018
© Allison J. Gong

See that large pool? That's where the staurozoans live. They like areas where the water constantly moves back and forth, which makes them difficult to photograph in situ. And given that the big ones are about 2 cm in diameter and most of them are the same color as the algae they're attached to, they're a challenge to find in the first place. I looked for a long time and was about to give up on my search image when I found a single small staurozoan, about 10 mm in diameter, quite by accident. It was a golden-brown color, quite happily living in a surge channel. I took several very lousy pictures of it before coming up with the bright idea of moving it up the beach a bit to an area where the water wasn't moving quite as much. I sloshed up a few steps and found a likely spot, then placed my staurozoan where the water was deep enough for me to submerge the camera and take pictures.

Staurozoan (Haliclystus sp.) at Franklin Point
19 May 2018
© Allison J. Gong
Staurozoan (Haliclystus sp.) at Franklin Point
19 May 2018
© Allison J. Gong

Cute little thing, isn't it? I had my head down taking pictures of this animal, congratulating myself on having found it. When I looked around me I saw that I had inadvertently discovered a whole neighborhood of staurozoans. They were all around me! And some of them were quite large, a little over 2 cm in diameter. All of a sudden I couldn't not see them.

Staurozoan (Haliclystus sp.) at Franklin Point
19 May 2018
© Allison J. Gong

I know I've seen staurozoans in the same bottle green color as the Ulva, but this time I saw only brown ones. As you can see even the animals attached to Ulva were brown. Staurozoans seem to be solitary creatures. They are not permanently attached but do not aggregate and are not clonal. Most of the ones I found were as singles, although I did find a few loose clusters of 3-4 animals that just happened to be gathered in the same general vicinity.

Trio of staurozoans (Haliclystus sp.) at Franklin Point
19 May 2018
© Allison J. Gong

Not much is known about the biology of Haliclystus, or any of the staurozoans. I collected some one time many years ago, and brought them back to the lab for closer observation. They seemed to eat Artemia nauplii very readily, and I did get to observe some interesting behaviors, but they all died within a week or so. Given that I can find them only in certain places at Franklin Point, they must be picky about their living conditions. Obviously I can't provide what they need at the marine lab. The surging water movement, for example, is something that I can't easily replicate. I need to think about that. The mid-June low tides look extremely promising, and my collecting permit does allow me to collect staurozoans at Franklin Point. Maybe I'll be able to rig up something that better approximates their natural living conditions in the lab.

In the meantime, I just want to look at them.

Staurozoan (Haliclystus sp.) at Franklin Point
19 May 2018
© Allison J. Gong
Pair of staurozoans (Haliclystus sp) at Franklin Point
19 May 2018
© Allison J. Gong

Every once in a while some random person drops off a creature at the marine lab.  Sometimes the creature is a goldfish that had been a take-home prize at a wedding over the weekend (now weddings taking place at the Seymour Center are not allowed to include live animals in centerpieces). Once it was a spiny lobster that spent the long drive up from the Channel Islands in a cooler, and became the Exhibit Hall favorite, Fluffy. This time the objects had been collected off the beach and brought in by somebody who thought they might still be alive.

16 April 2018
© Allison J. Gong

These white objects are egg masses of the California market squid, Doryteuthis opalescens, that had been cast onto the beach at Davenport. Sometimes the masses are called fingers or candles, because they're about finger-sized. Each contains dozens of large eggs. Squids, like all cephalopods, are copulators, and after mating the female deposits a few of these fingers onto the sea floor. Many females will lay their eggs in the same spot, so the eggs in this photo represent the reproductive output of several individuals. The cephalopods as a group are semelparous, meaning that they reproduce only once at the end of their natural life; salmons are also semelparous. After mating, the squids die. Not coincidentally, the squid fishing season is open right now, the idea being that as long as the squids have reproduced before being caught in seines, little harm is done to the population. Most of the time the squids are dispersed throughout the ocean, and the only time it is feasible to catch them in large numbers is when they gather to mate.

These egg masses look vulnerable, but they're very well protected. The outer coating is tough and leathery, and the eggs must taste bad because nothing eats them. I've fed them to anemones, which will eat just about anything, and they were spat out immediately.

The eggs were brought to the Seymour Center because the person who brought them in thought they might make a good exhibit. I happened to be there that day and got permission to take a small subset of the bunch so I could keep an eye on them. And they did and still do make a good exhibit.

16 April 2018: I obtain squid eggs!

Egg mass, or 'finger, of the California market squid Doryteuthis opalescens
16 April 2018
© Allison J. Gong

At this stage it is impossible to tell whether or not the eggs are alive. The only thing to do was wait and see.

30 April 2018: After waiting two weeks with apparently no change, I decided it was time to look at the egg fingers more closely again. Lo and behold, they are indeed alive! Look at the pink spots in the individual eggs--those are eyes. And if you can see the smaller pink spots, those are chromatophores, the 'color bodies' in the squids' skin that allow them to perform their remarkable color changes.

Developing embryos of Doryteuthis opalescens
30 April 2018
© Allison J. Gong

9 May 2018: A week and a half later, the embryos definitely look more like squids! Their eyes and chromatophores have darkened to black now. The embryos are also more active, swimming around inside their egg capsules. You can see the alternating contraction and relaxation of the mantle, which irrigates the gills. Squids have two gills. More on that below.

At this point the squid fingers began to disintegrate and look ragged. They became flaccid and lightly fouled with sediment.

14 May 2018 (today): Almost a month after they arrived, my squid eggs look like they're going to hatch soon! I didn't see any chromatophore flashing, though.

In the meantime, some of the eggs on exhibit in the Seymour Center have already started hatching. The first hatchlings appeared on Friday 11 May 2018. The hatchlings of cephalopods are called paralarvae; they aren't true larvae in the sense that instead of having to metamorphose into the adult form, they are miniature versions of their parents.

Peter, the aquarium curator at the Seymour Center, allowed me to take a few of the paralarvae in his exhibit and look at them under the scope. The squidlets are about 3mm long and swim around quite vigorously. Trying to suck them up in a turkey baster was more difficult than I anticipated. But I prevailed!

Paralarva of Doryteuthis opalescens
14 May 2018
© Allison J. Gong

You can actually see more of what's going on in a video:

The cup-shaped layer of muscular tissue that surrounds the squid's innards is the mantle. When you eat a calamari steak, you are eating the mantle of a large squid.The space enclosed by the mantle is called the mantle cavity. Because the paralarvae are transparent you can see the internal organs. Each of those featherlike structures is a ctenidium, which is the term for a mollusk's gill. The ventilating motions of the mantle flush water in and out of the mantle cavity, ensuring that the gill is always surrounded by clean water.

And now we get to the hearts of the matter. At the base of each gill is a small pulsating structure called a branchial heart ('branch' = Gk: 'gill'). It performs the same function as the right atrium of our own four-chambered heart; that is, boosting the flow of blood to the gas-exchange structure. So that's two hearts. Between the pair of branchial hearts is the systemic heart, which pumps the oxygenated blood from the gills to the rest of the squid's body. This arrangement of multiple hearts, combined with a closed circulatory system, allows cephalopods to be much more active swimmers and hunters than the rest of their molluscan kin.

I expect that my fingers will hatch very soon. If and when they do, it will be a challenge getting them to eat. I've never tried it myself, and cephalopods are known to be difficult to rear in captivity. But I'm willing to give it a shot!

This week I celebrate the return of the early morning low tides! I was very much looking forward to this tide series, and even though I am in class on Tuesday, Thursday, and Friday mornings I wanted to go out on as many of the tides as possible. On Wednesday morning I went out to Natural Bridges to meet up with one of my students, Maddie, who is studying anemones for her independent research project. The tide wasn't particularly early at 07:08, but there was nobody out there. No surfers, even. The only person I saw out there was Maddie.

There are few things better than an overcast morning in the intertidal. Peaceful, calm, not windy, and uncrowded. I could feel the stress melting away as the only sounds I heard were the coming and going of the surf and the high-pitched 'cheeps' of the oystercatchers.

18 April 2018
© Allison J. Gong

Natural Bridges is probably the intertidal site that I know the best. It's close to home, so access is easy. It is a state park and a marine protected area, so collecting of any sort is not allowed and the tidepools are about as undisturbed as can be, considering that it is heavily visited. And in the early morning the intertidal is just wonderful. Visiting there and having time to slow down and really pay attention is a real treat for me.

And perhaps the homecoming I felt this morning is due to the fact that just last week I gave a talk to the docents at Natural Bridges State Park. There's something about this particular group that inspires me and rekindles my interest in this special site.

It is now springtime, and the intertidal is in the full flush of reproduction. The algae are starting to regrow and hinting of the lush coverage that we'll see in the next few months.

Ulva sp. at Natural Bridges
18 April 2018
© Allison J. Gong

There are several species in the genus Ulva, referred to as the sea lettuces. They come in a variety of morphs, but all are variations on the same theme: a thin sheet, two cell layers thick. Some Ulva species have blades that are large, while in other species the sheets are rolled into thin tubes or short tufts. Many of them look alike, making field ID problematic, so with few exceptions I simply call them all Ulva sp.

The other common green alga at Natural Bridges is one of the filamentous green, Cladophora columbiana. It has a short thallus, rising from the rock surface like a stout pincushion, which is what it feels like. It grows in little clumps among the mussels in the mid-intertidal.

The green alga Cladophora columbiana and little periwinkle snails, Littorina sp., at Natural Bridges
18 April 2018
© Allison J. Gong

Today I saw Cladophora with little periwinkle snails, an association that, in my experience, is unusual. The periwinkles are small, less than 10 mm from aperture to apex, and I tend to think of them as a high intertidal species. Cladophora can also occur in the high-mid intertidal but for some reason seeing them together with the periwinkles took me by surprise. There were many of the little snails crawling around in the mid zone, on bare rock or on other animals.

In fact, today was a good day to see lots of animal recruitment. Several areas of rock in the mid-intertidal that were recently devoid of animal life have been colonized by mussels or acorn barnacles.

Small acorn barnacles at Natural Bridges.
18 April 2018
© Allison J. Gong

Most of the individuals in this field of barnacles are Chthamalus dalli/fissus. Those are the small, light brown barnacles. The taller whitish barnacle near the center of the photo is Balanus glandula. But see all the teensy barnacles below and slightly to the left of the Balanus? Those are new recruits, 1-2 mm in diameter. If you click on the photo for a larger view, you can see that while most of the recruits are Chthamalus, there are a few Balanus in there as well. And notice that some of the recruits have landed on other barnacles. This is a smart decision for them. As I've described before, barnacles can't reproduce unless they have close neighbors of the same species. Settling on an established conspecific adult is one way to guarantee that a young barnacle will have potential mates when it grows up.

The largest barnacle in the intertidal around here is the pink barnacle, Tetraclita rubescens. It is fairly common at Natural Bridges, and quite conspicuous because of its size and pink color.

A pink barnacle, Tetraclita rubescens, encrusted with Balanus glandula and Chthamalus fissus/dalli at Natural Bridges
18 April 2018
© Allison J. Gong

And take a look at this owl limpet! She's carrying a whole world on her back.

An owl limpet (Lottia gigantea) encrusted with barnacles, at Natural Bridges
18 April 2018
© Allison J. Gong

Speaking of owl limpets, their tendency to monopolize territories in the intertidal can strongly affect the makeup of the community. It's not just the barnacles that recruit to the intertidal in the spring; mussels do the same, and often quite spectacularly. The disappearance of predatory ochre stars (Pisaster ochraceus) due to sea star wasting syndrome (SSWS) allowed mussels to expand lower into the intertidal, where they would ordinarily be eaten. The ochre stars have been reappearing in the past few years, and hand-sized P. ochraceus are now very common at Natural Bridges. We would now expect predation to cause the lower edge of the mussel bed to retreat back up a bit.

Mussels cannot recruit to Lottia farms because the limpets routinely cruise around their territories and scrape off any newly settled larvae. Lottia farms occur in what would otherwise be prime real estate for mussels, except for the fact that the larvae landing there never get a chance to become established. However, even a big owl limpet doesn't live forever, and when one dies a whole swath of now-vacant area becomes available.

Mussel bed with recent recruits at Natural Bridges
18 April 2018
© Allison J. Gong

Those two bare patches in the photo above are former Lottia farms. I looked for the owl limpets and didn't find them. And note that band of young mussels running horizontally in the middle of the photo. They are young mussels, relatively clean of encrusting mussels or algae, but aren't new recruits. I'd guess that they've been there a few months. Whatever the age of the mussels, they are taking advantage of the space that used to be occupied and defended by an owl limpet. Or maybe two owl limpets, as that space would be a very large farm for a single limpet.

After two days of class taking me out of the intertidal, I get to spend the next two mornings back out there. I have some collecting to do!

2

Who do you think makes these tracks in the sand?

15 February 2018
© Allison J. Gong

Any guesses?

Here's another photo, taken from farther away to give you a bigger picture of the scale of things.

15 February 2018
© Allison J. Gong

Believe it or not, the maker of these trails is the little black turban snail, Tegula funebralis. They are one of my favorite animals in the intertidal, for a number of reasons:

  1. I always root for the underdog and the under-appreciated, and these snails are so numerous in the intertidal that they are practically invisible. People literally do not see them. I know, because I ask.
  2. They are very useful creatures to keep as lab pets. I throw a few of them into each of my seawater tables, except for the table that contains a resident free-ranging sea star, and they do a fantastic job keeping algal growth to a tolerable minimum. They're my little marine lawnmowers!
  3. They come in very handy when I'm teaching invertebrate zoology. Students study them live to observe behavior, and the snails are not shy. They are very tolerant of being picked up and gently prodded, and soon emerge from their shells and carry on their little snail lives. Students also dissect them in lab to learn about gastropod anatomy.

So yes, these tracks in the sand are made by T. funebralis in the high intertidal. In areas where a layer of sand accumulates either at the bottom of a pool or on a flat exposed rock, it is not uncommon to see a turban snail pushing sand out of the way as it crawls along, like a miniature snow plow.

A black turban snail (Tegula funebralis) plowing through sand on a high intertidal rock at Natural Bridges
15 February 2018
© Allison J. Gong

Tegula funebralis and its congeners are called turban snails because their shells are shaped like turbans. Given their small size (a big T. funebralis would have a shell height of 2.5-3 cm), pushing sand around must be a tiresome chore. They do it because they have no choice. Most grazing gastropods, such as turban snails and limpets, can feed only when they are crawling. There may very well be a nice yummy layer of algal scum on the surface of this rock, but the snail has to push the sand out of the way before it can feed on it.

Here's another photo, taken at the snail's level.

Tegula funebralis plowing through sand at Natural Bridges
15 February 2018
© Allison J. Gong

This snail is pushing through a wall of sand as tall as itself! I don't know about you, but I sure as heck couldn't do that. Props to these little snails!

 

There are certain creatures that, for whatever reason, give me the creeps. I imagine everyone has them. Some people have arachnophobia, I have caterpillarphobia. While fear of some animals makes a certain amount of evolutionary sense--spiders and snakes, for example, can have deadly bites--my own personal phobia can be traced back to a traumatic childhood event involving an older cousin and a slew of very large tomato hornworms. Even typing the words decades later makes me want to rub my hands on my jeans.

But enough about caterpillars. This Halloween I want to share something that isn't nearly as disgusting, but can still creep me out sometimes. Commonly called skeleton shrimps, caprellid amphipods are a type of small crustacean very common in certain marine habitats. They are bizarre creatures, but a close look reveals their crustacean nature. For example, they possess the jointed appendages and compound eyes that only arthropods have.

Female caprellid amphipod (Caprella sp.)
22 October 2017
© Allison J. Gong

Around here the easiest place to find caprellids is at the harbor, where they can be extremely abundant. The last time I went to the harbor to collect hydroids for my class, the caprellids were swarming all over everything. When I brought things back to the lab I had to spend an hour or so picking the caprellids off the hydroids. I don't think they eat the 'droids, but they gallop around and keep messing up the field of view, making observation difficult. They're essentially just a PITA to deal with, and everything is easier after they've been removed.

Caprellid amphipods (Caprella sp.) at the Santa Cruz Yacht Harbor
23 June 2017
© Allison J. Gong

Caprellids are amphipods, members of a group of crustaceans called the Peracarida (I'll come back to the significance of the name in a bit). They have the requisite two pairs of antennae that crustaceans have, and seven pairs of thoracic appendages of varying morphology. Some of these thoracic legs are claws or hooked feet that like to grab onto things. A caprellid removed from whatever it's attached to and placed by itself in a bowl of seawater thrashes around spastically. Only when it finds something to grab does it calm down. Even then, they attach with their posterior appendages and wave around the front half of the body in what I call the caprellid dance: they extend up and forward, and sort of jerk front to back or side to side. It isn't pretty.

A bunch of caprellids removed from their substrate and dumped into a bowl together will use each other as something to grab. This forms the sort of writhing mass that makes my skin crawl. I was nice enough to give them a piece of bryozoan colony to hang onto, but even so they ended up glomming together.

Now, back to the thing about caprellids being peracarids. The name Peracarida means "pouch shrimp" and refers to a ventral structure called a marsupium, in which females brood their young. Males don't have a marsupium, so adult caprellids are sexually dimorphic. When carrying young, a female caprellid looks like she's pregnant. See that caprellid in the top photo? She's a brooding female. That's all fine, until her marsupium itself starts writhing. This ups the creepiness factor again. Here's that same brooding female, in live action:

Crustaceans obviously don't get pregnant the way that mammals do, but many of them spend considerable energy caring for their young. Well, females do, at least. A female caprellid doesn't just carry her babies around inside a pouch on her belly. Although she isn't nourishing them from her own body in the way of mammals (each of the youngsters in the marsupium is living off energy stores provisioned in its egg), the mother does aerate the developing young by opening and closing the flaps to the marsupium. This flushes away any metabolic wastes and keeps the juveniles surrounded by clean water. As the young caprellids get bigger, they begin to crawl around inside the pouch, and eventually leave it. They don't depart from their mother right away, though; rather they cling to her back for a while, doing the caprellid dance in place as she galumphs along herself.

Until the juveniles strike out on their own they form a small writhing mass on top of a female who can herself be part of a larger writhing mass. And the sight through the microscope of all these long skinny bodies jerking around spasmodically can indeed be very creepy. Fortunately not as creepy as caterpillars, or I wouldn't be able to teach my class or go docking with my friend Brenna. And it's a good thing caprellids are small, 'cause if they were any bigger. . . just, no.

 

1

Although the world's oceans cover approximately 70% of the Earth's surface, most humans interact with only the narrow strip that runs up onto the land. This bit of real estate experiences terrestrial conditions on a once- or twice-daily basis. None of these abiotic factors, including drying air, the heat of the sun, and UV radiation, greatly affects any but the uppermost few meters of the ocean's surface so most marine organisms don't need to worry about them. Despite the apparent paradox of where they live, intertidal organisms are also entirely marine--they cannot survive prolonged exposure to in air or freshwater. So how do they manage to live here?

Some organisms have a physiological tolerance for difficult conditions. These tidepool copepods and periwinkle snails, for example, are able to survive in the highest pools in the splash zone, where salinity can be either very high (due to evaporation) or very low (due to rain or freshwater runoff), dissolved oxygen is often depleted due to high temperature, and temperature itself can be quite warm. Sculpins and other tidepool fishes cope with low oxygen levels by gulping air and/or retreating to deep corners of their home pools.

Of course, animals that can locomote have the option of moving to a more favorable location. Other creatures, living permanently attached to their chosen site, aren't quite so lucky. Let's take barnacles as an example.

Nauplius larva of the barnacle Elminius modestus
© Wikimedia Commons

Barnacles have two planktonic larval stages: the nauplius and the cyprid. The nauplius is the first larval stage and hatches out of the egg with three pairs of appendages. It can be distinguished from the nauplius of other crustaceans by the presence of two lateral "horns" on the anterior edge of the carapace. The nauplius's job is to feed and accumulate energy reserves. It swims around in the plankton for several days or perhaps a couple of weeks, getting blown about by the currents and feeding on phytoplankton.

Cyprid larva of a barnacle

After sufficient time feeding in the plankton, a barnacle nauplius metamorphoses into the second larval stage, the cyprid. A cyprid is a bivalved creature, with the body enclosed between a pair of transparent shells. It has more appendages than the nauplius, and these are more differentiated. If the nauplius has done its  job well, then the cyprid also contains a number of oil droplets under its shell. These droplets are of crucial importance, because the cyprid itself does not feed. For as long as it remains in the plankton it survives on the calories stored in those droplets. The cyprid's job is to return to the shore and find a suitable place on which to settle. Somehow, a creature about 1 mm long, being tossed about by waves crashing onto rocks, has to find a place to live and then stick to it.

Returning to the topic of the challenges that marine organisms face when they live under terrestrial conditions, let's see how these barnacles manage. Along the northern California coast we have a handful of barnacle species living in the intertidal. In the higher mid-tidal regions at some sites, small acorn barnacles of the genera Balanus and Chthamalus may be the most abundant animals.

Mixed population of the acorn barnacles Balanus glandula and Chthamalus dalli/fissus at Davenport Landing
27 June 2017
© Allison J. Gong

However, nowhere is a particular pattern of barnacle distribution more evident than at Natural Bridges. Here, the barnacles in the high-mid intertidal are small, and concentrated in little fissures and cracks in the rock.

I think most of these small (~5 mm) barnacles are Balanus glandula:

Small acorn barnacles (Balanus glandula) at Natural Bridges
11 October 2017
© Allison J. Gong

And here's a closer look:

Small acorn barnacles (Balanus glandula) at Natural Bridges
11 October 2017
© Allison J. Gong

If all of the rock surfaces were equally suitable habitat, the barnacles would be distributed more randomly over the entire area. Instead, they are clearly segregated to the cracks in the rock. Each of these barnacles metamorphosed from a cyprid into a juvenile exactly where it is currently located. The cyprid may be able to move around to fine-tune its final location, but once the decision has been made that X marks the spot and the cyprid has glued its anterior to the rock, the commitment is real and lifelong. The barnacle will live its entire life in that spot and eventually die there. It is quite probable that cyprids landed in those empty areas on the rock, but they didn't survive to adulthood.

How did this distribution of adult barnacles come to be?

There is one very important biological reason for barnacles to live in close groups, and that is reproduction. They are obligate copulators, which I touched on in this post, and as such need to live in close proximity to potential mates. But today I'm thinking more about abiotic factors. In a habitat like the mid-mid rocky intertidal, desiccation is a real and daily threat. Even a minute crack or shallow depression will hold water a bit longer than an exposed flat surface, giving the creatures living there a tiny advantage in the struggle for survival. No doubt cyprid larvae can and do settle on those empty areas of the rock. However, they likely die from desiccation when the tide recedes, leaving only the cyprids that landed in one of the low areas to survive and metamorphose successfully. There are other factors as well, such as the presence of adult individuals, that make a location preferable for a home-hunting cyprid. In addition to facilitating copulation, hanging out in a cluster slows down the rate of water evaporation, giving another teensy edge to animals living at the upper limit of their thermal tolerance.

Lower in the intertidal, where terrestrial conditions are mitigated by more time immersed, barnacles and other organisms do indeed live on flat rock spaces. But at the high-mid tide level and above, macroscopic life exists mostly in areas that hang onto water the longest. Pools are refuges, of course, but so are the tiniest cracks that most of us overlook. Next time you venture into the intertidal, take time on your way down to stop and salute the barnacles for their tenacity.

Five days ago I collected the phoronid worms that I wrote about earlier this week, and today I'm really glad I did. I noticed when I first looked at them under the scope that several of them were brooding eggs among the tentacles of the lophophore. My attempts to photograph this phenomenon were not entirely successful, but see that clump of white stuff in the center of the lophophore? Those are eggs! Oh, and in case you're wondering what that tannish brown tube is, it's a fecal pellet. Everyone poops, even worms!

Lophophore of a phoronid worm (Phonoris ijimai)
18 Septenber 2017
© Allison J. Gong

Based on species records where I found these adult worms, I think they are Phoronis ijimai, which I originally learned as Phoronis vancouverensis. The location fits and the lophophore is the right shape. Besides, there are only two genera and fewer than 15 described species of phoronids worldwide.

Two days after I first collected the worms, I was watching them feed when I noticed some tiny approximately spherical white ciliated blobs swimming around. Closer examination under the compound scope showed them to be the phoronids' larvae--actinotrochs! Actinotrochs have been my favorite marine invertebrate larvae--and that's saying quite a lot, given my overall infatuation with such life forms--since I first encountered them in a course in comparative invertebrate embryology at the Friday Harbor Labs when I was in graduate school.

2-day-old actinotroch larva of Phoronis ijimai
22 September 2017
© Allison J. Gong

The above is a mostly top-down view on an actinotroch, which measured about 70 µm long. They swim incredibly fast, and trying to photograph them was an exercise in futility. They are small enough to swim freely in a drop of water on a depression slide, so I tried observing them in a big drop of water under a coverslip on a flat glass slide. At first they were a bit squashed, but as soon as I gave them enough water to wiggle themselves back into shape they took off swimming out of view.

Here's the same photo, with parts of the body labelled:

2-day-old actinotroch larva of Phoronis ijimai
22 September 2017
© Allison J. Gong

The hood indicates the anterior end of the larva and the telotroch is the band of cilia around the posterior end. The hood hangs down in front of the mouth and is very flexible. At this stage the larva possesses four tentacles, which are ciliated and will get longer as the larva grows. These are not the same as the tentacles of the adult worm's lophophore, which will be formed from a different structure when the larva undergoes metamorphosis.

As usual, a photograph doesn't give a very satisfactory impression of the larva's three-dimensional structure. There's a lot going on in this little body! The entire surface is ciliated, and this actinotroch's gut is full of phytoplankton cells. You can see a lot more in the video, although this larva is also a little squished.

I've been offering a cocktail of Dunaliella tertiolecta and Isochrysis galbana to the adult phoronids, and these are the green and golden cells churning around in the larva's gut. However, good eaten is not necessarily food digested, and the poops that I saw the larvae excrete looked a lot like the food cells themselves. Today I collected more larvae from the parents' bowl and offered them a few drops of Rhodomonas sp., a cryptonomad with red cells. This is the food that we fed actinotrochs in my class at Friday Harbor. We didn't have enough time then to observe their long-term success or failure, but I did note that they appeared to eat the red cells.

I don't know if phoronids reproduce year-round. It would be a simple task to run down and collect a few every month or so and see if any worms are brooding. Now that I know where they are, it would also be a good idea to keep an eye on the size of the patch. Some species of phoronid can clone themselves, although I don't know if P. ijimai is one of them. In any case, even allowing for the possibility of clonal division, an increase in the size of the adult population would be at least partially due to recruitment of new individuals. If recruitment happens throughout the year, it follows logically that sexual reproduction is likewise a year-round activity. Doesn't that sound like a nifty little project?

Besides, it's never a bad idea to spend time at the harbor!

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