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If, like me, you are fortunate enough to live near the coast in Northern California, you get to visit the tidepools. And when you do, you may notice something that looks like a pile of sand in the mid tidal zone below the mussel beds. When you venture down and touch the sand, you'll find that it's hard--hard enough to walk on, if you step very carefully, but also somewhat brittle.

It might look something like this:

Mound of Phragmatopoma californica tubes at Natural Bridges
2017-05-26
© Allison J. Gong

Meet Phragmatopoma californica, the sandcastle worm. Hard to believe that these mounds, which can be the size of a small dining room table, are constructed by little worms, isn't it? Phragmatopoma is one of the many marine segmented worms grouped together as the Polychaeta. We have lots of polychaetes on our coast, ranging in size from greater-than-hand-length nereids and glycerids that can take a bite out of you and draw blood, to tiny worms small enough to swim in the layer of water between sand grains. In fact, the majority of our worm fauna on the coast consists of polychaetes.

Polychaetes make up a large and very diverse taxon, comprising some 80 or so families. Polychaete taxonomists might argue against it, but to make things simpler, we can divide them into two subclasses, the Errantia and the Sedentaria. As the name implies, the Errantia comprises the worms that are errant, or free-crawling. That said, most of them don't actually crawl around in plain sight; they tend to burrow in sediment, shell debris, or gravel, or wiggle their way through various benthic faunal communities. Some of them make temporary shelters by wrapping themselves in pieces of algae sewn shut with mucus threads. The Sedentaria, on the other hand, are pretty much all, well, sedentary. They live in more or less permanent tubes made of various materials, and generally can't live outside of them.

Phragmatopoma is very much a sedentary worm. It lives in a tube that it builds out of sand grains. Yes, this little worm is a mason!

Phragmatopoma californica tubes at Natural Bridges
2017-05-26
© Allison J. Gong

What you see in these mounds is an aggregation of hundreds of individual worms. The mounds do not form by accident or chance. Phragmatopoma has a planktonic larval stage that floats around on ocean currents for some weeks before returning to the shore. The larva is attracted to areas already colonized by members of their species, which it detects by sniffing out the chemical signal of the glue used to create the tubes (more on that below). This phenomenon is called gregarious settlement. If you consider the challenge of being a tiny creature searching the entire coastline for a place to settle and live forever, one big clue as to the suitability of a given location is the presence of conspecific adults. After all, if your parents' generation grew up there, chances are it's a good spot for you to grow up, too.

Each of those holes in the big sandy mound is the entrance to a worm's tube. Tubes might be as long as 15 cm, but the worm itself is much smaller: a whopping big one would be 4 cm long, and most are in the 2-3 cm size range. From this pair of observations I infer that the worms can and do move up and down the tube. They have to move to the open end of the tube to feed, and can withdraw towards the closed end to avoid predators, or seek protection from desiccation.

Feeding tentacles of Phragmatopoma californica at Natural Bridges
2018-06-13
© Allison J. Gong

Phragmatopoma's tube is not a haphazardly constructed object. It is the worm's home for the entirety of its post-larval life, and is constructed to shield its builder/occupant from the mechanical bashing that occurs twice daily as the tide floods and ebbs. As such, it must be strong and able to maintain its structural integrity. Let's take a closer look at an isolated tube under the dissecting scope:

Tube of Phragmatopoma californica
2019-05-16
© Allison J. Gong

The tube itself is made of debris--sand grains, bits of shell, the occasional tiny sea urchin spine--that the worm gathers from its environment. Glandular regions at the worm's anterior region secrete around the body a cylinder of sticky cement that is chemically similar to both spider silk and the byssal threads that mussels use to attach themselves to rocks in the intertidal. The inside of the tube is lined with a chitin-like material. The worm uses tentacles on its head region to collect and sort the 'stones' and glues them to the outside of the lining. There is some degree of selection involved; in the photo above you can see that all of the sand grains are more or less the same size, with none standing out as being conspicuously smaller or larger than the others. Growing worms that are actively building their tubes may be geographically restricted at least partly by the availability sand grains of the right size; if the sand is too fine or too coarse, the worm's either can't or don't live there.

Life inside a tube

Living in a tube may provide significant protection from wave bashing and predators, but does present some challenges as well. One thing that comes to mind is the matter of personal hygiene: What happens to the worm's poop? As we know, the worm lives inside the tube but it not attached to it, and can crawl up and down within it. To understand how it does, we have to review some basics of polychaete anatomy.

The word 'polychaete' comes from Greek ('many bristles') and refers to the fact that these segmented worms have chaetae, or bristles, along the left and right sides of the body. In some worms the segments, including chaetae, are pretty much the same from the anterior end of the body to the posterior end. In others, the segments and chaetae are differentiated from one body region to another. In the case of Phragmatopoma, all you can see sticking out of a tube is the head region, consisting of the slender feeding tentacles and a large disc-shaped structure called an operculum, which made of fused cephalic chaetae and serves as a door to close off the tube when the worm withdraws. Behind the head is a collar region, a series of three adjacent segments that have very stiff chaetae that can be pushed out against the lining of the tube to anchor the body in place. The rest of the body behind the collar is the trunk, which bears smaller chaetae on each segment. The entire epidermis is ciliated, which keeps water flowing around the body.

But what about the poop? As in most vermiform animals, Phragmatopoma's anus is at the posterior end of the body, which is oriented towards the closed end of the tube. How, then, does it defecate without fouling its home? The answer is both simple and ingenious. Phragmatopoma has a long rectum, which is curved to run anteriorly back towards the head. The anus, located at the terminal end of the rectum, discharges fecal pellets about halfway up the length of the body. The ciliary currents of the epidermis then flush the fecal pellets the rest of the way up the tube and out the top.

The skinny cylindrical things in the photo below are Phragmatopoma's fecal pellets!

Phragmatopoma
Tentacles of Phragmatopoma californica extending from tubes at Natural Bridges
2017-05-26
© Allison J. Gong

Gas exchange is another challenge for animals that live within tubes. Aquatic animals exchange respiratory gases with the water that surrounds them, which is easy for animals that live where the water is constantly moving over their bodies. But for tube-dwellers, gas exchange is much more difficult. Phragmatopoma has paired gills on each segment of the trunk region of the body, which greatly increase the surface area for gas exchange. Any gas exchange surface is useless unless it connects with the circulatory system, so blood vessels flow into and out of each gill. Dissolved oxygen diffuses from the water into the blood, and is then circulated throughout the body. A certain amount of gas exchange probably occurs across the surface of the tentacles, too. To make things easier, the ciliated epidermis of the body keeps that small amount of water inside the tube moving, minimizing stagnation. When the worm's head is extended out for feeding, the tube is flushed with clean water. When the worm is withdrawn into the tube at low tide, its only oxygen supply is in the water contained in the tube with it. Like most of its intertidal neighbors, Phragmatopoma hunkers down and waits for the tide to return, when it can feed and breathe more easily.

And speaking of feeding, I should mention that Phragmatopoma is a filter feeder. Those purple tentacles are ciliated and create a water current that brings small suspended particles towards the mouth located at the base of the tentacles. In the video below the operculum is the darker object to the left; it represents the dorsal side of the worm's body. The long, filiform tentacles are the feeding tentacles.

As you may imagine, living in a tube also affects the way that Phragmatopoma reproduces. The worms never leave their tubes, so copulation isn't an option for them. Despite their occurrence in large groups they are not clonal, and reproduce only sexually. Both sexes of Phragmatopoma spawn gametes into the water, where fertilization and larval development take place. Living in dense aggregations and spawning at the same time as everyone else maximizes the chance that egg and sperm of the same species will find each other. Many marine invertebrates throughout the oceans, from corals to sea urchins, spawn synchronously. After all, it does an individual no good to throw gametes out into the world if it is the only one of its type around--all of the metabolic energy that went into producing and maintaining the gametes would be entirely wasted.

Clearly, the advantages of living in a tube outweigh the costs and inconveniences. Phragmatopoma has evolved physiological, anatomical, and behavioral adaptations to deal with life in the intertidal. One of those adaptations is the tube, which solves one set of problems but creates others which also need to be solved if the animal is to survive. Evolution comes up with solutions like this all the time. Every trait has metabolic and/or fitness costs, and an organism's biology is based on this type of evolutionary compromise. Life in the intertidal is a tough game. It is probable that none of the various biological processes that keep Phragmatopoma alive work function quite as well as they could, if they were isolated systems. But inside the bodies of these little worms, everything works just well enough for them to be one of the more conspicuous inhabitants of the intertidal.

I think that's pretty damn cool.

2

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

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

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

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

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

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

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

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

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

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

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

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

2019-05-08
© Allison J. Gong

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

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

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

All semester I've been taking my Ecology students out in the field every Friday. We've visited rivers, forests, natural reserves, endemic habitats, and fish hatcheries--none of which fall into my area of expertise. This year I have several students interested in various aspects of food production, natural/holistic health practices (which sometimes conflict with actual science!), mycology, as well as some who haven't yet decided in which direction to take their academic endeavors. Until very recently I haven't been able to share with my students much of what I really know, which is marine biology. I did have them learn the organisms that live on docks at the harbor, but that was to study the process of ecological succession rather than natural history.

Yesterday, finally, I took the class into my real field, the rocky intertidal. This year it happened that the best Friday to do our annual LiMPETS monitoring was at the end of the semester. We welcomed the new regional LiMPETS coordinator, Hannah, to our classroom on Thursday for some training. Students learned about the history of the LiMPETS program, some natural history of the rocky intertidal in California, and got to practice some organism IDs with photo quadrats of actual intertidal areas.

The real fun, of course, occurs in the field where the organisms live. So we went here:

LiMPETS monitoring at Davenport Landing
2019-05-10
© Allison J. Gong
Sampling along the vertical transect
2019-05-10
© Allison J. Gong

We didn't have a very good student turnout, unfortunately, but the ones who did show up were diligent workers and we got everything finished that Hannah needed. Most of the time was spent sampling along the permanent vertical transect line. This line is sampled at 3-meter increments along a line that runs from the high intertidal into the low. The same quadrats are sampled every time, and the data collected are used to determine how specific sites change over time. The most difficult part of the monitoring is finding the eye bolts that mark where the transects begin!

Sampling along the vertical transect
2019-05-10
© Allison J. Gong

I admit, I was a little bummed at the low turnout and late arrival of my students. But the intertidal is the intertidal, and it didn't take long for me to adjust my attitude. I worked up a handful of quadrats with Hannah, then let the students do the bulk of the heavy lifting. This was their field trip, after all. So I wandered around a bit, remaining within hearing distance in case I was needed. I needed to find some stuff!

I just want to show some of the animals and algae in the intertidal yesterday. I didn't realize how much I missed this basic natural history stuff until I got to spend some time simply looking at things.

Such rich life to see! One of the students was astounded when she learned that we could visit sites like this only a few days each month. "At dinnertime today the spot where you're standing will be under several feet of water!" I told her. Mind blown.

Intertidal biota at Davenport Landing
2019-05-10
© Allison J. Gong

Looking more closely, there were, as usual, interesting zonation patterns to observe. One was the restriction of large brown algae to the vertical faces of rocky outcroppings.

The kelp Laminaria setchellii at Davenport Landing
2019-05-10
© Allison J. Gong

In the mid-intertidal, mussels (Mytilus californianus) rule the roost. They are often (but not always) accompanied by gooseneck barnacles (Pollicipes polymerus). The barnacles, for reasons discussed in this earlier post, always live in clumps and are most abundant in the lower half of the mid-intertidal mussel beds.

Gooseneck barnacles (Pollicipes polymerus) and mussels (Mytilus californianus) at Davenport Landing
2019-05-10
© Allison J. Gong

During the training session on Thursday, Hannah told the students that Pollicipes is easily identifiable because the barnacles look like dragon toes. I think I can sort of see that. They are scaly and strange enough to be dragon toes.

Gooseneck barnacles (Pollicipes polymerus) at Davenport Landing
2019-05-10
© Allison J. Gong

The algae are taking off now, and the site is starting to look very lush.

Mishmash of algae at Davenport Landing
2019-05-10
© Allison J. Gong

Even algae start as babies! These balloon-shaped things are young Halosaccion glandiforme thalli, surrounded by other red algae. The large blades belong to Mazzaella flaccida, which makes up a large portion of algal biomass in the mid-intertidal zone.

Halosaccion glandiforme and Mazzaella flaccida at Davenport Landing
2019-05-10
© Allison J. Gong

The tidepools at Davenport Landing are good places to see fish, if you have the patience to sit still for a while and watch. This woolly sculpin (Clinocottus analis) posed nicely in the perfect pool for photography--deep enough to submerge the camera, with clear, still water.

Woolly sculpin (Clinocottus analis) and purple urchins (Strongylocentrotus purpuratus) at Davenport Landing
2019-05-10
© Allison J. Gong

And I was finally able to take a good underwater shot of a turban snail carrying some slipper shells. I've already written about the story of this gastropod trio in case you need a refresher. I'm still waiting to see a taller stack of slipper shells some day.

Black turban snail (Tegula funebralis) with slipper shells (Crepidula adunca) at Davenport Landing
2019-05-10
© Allison J. Gong

It was impossible not to feel satisfied after spending some time looking at these creatures. My attitude was mercifully adjusted, and we all departed feeling that we'd done a good morning's work. Our small group of students was able to collect a full set of data for Hannah. That ended up being a very important accomplishment, as Hannah doesn't have any other groups monitoring at Davenport this spring. This means that our data will probably be the only data collected this year at this site. I'm glad the tide and weather conditions allowed us to stay out there as long as we did.

At the end of April we made another trip down to southern California to catch the tail end of the wildflower superbloom. We knew that the best part of the bloom had passed, because we had already seen lots of it a month ago, but thought that there might still be some color, especially at the higher elevations. Driving south, we chose to take a route down the eastern side of the Salinas and Central Valleys. It was a beautiful part of the drive, very much off the beaten path and blessedly peaceful and quiet.

Looking west, we could see how the marine layer had settled into the Salinas Valley, and the Santa Lucia Mountains beyond.

Salinas Valley
2019-04-27
© Allison J. Gong

We did see flowers, but the marvel of the weekend wasn't of the natural variety. We went into the Tehachapi Mountains and took a detour off the main highway to check out the Tehachapi Loop. The Loop is one of the marvels of railroad engineering (no pun intended).

On this trip I had only one lens with me, the 70-200 mm zoom. I had set myself the challenge of taking a road trip with just the one lens, knowing full well that I didn't have the proper equipment for any sort of wide-angle perspectives. It was fun learning how to work within the narrow parameters I had set for myself. However, it meant that I didn't have the ability to capture the entire diameter of the Tehachapi Loop, so I had to photograph it in pieces. Between 30 and 35 trains go through the Loop every day, and we were lucky enough to see one go down and one go up.

Here's the tail end of a train going up (clockwise) through the Loop. The two locomotives are pushing the train.

Tehachapi Loop
Train going through Tehachapi Loop
2019-04-28
© Allison J. Gong

Tehachapi Loop
Train going through Tehachapi Loop
2019-04-28
© Allison J. Gong
Tehachapi Loop
Train going through Tehachapi Loop
2019-04-28
© Allison J. Gong

Meanwhile, here's the front of the same train, being pulled by three orange locomotives:

Tehachapi Loop
Train going through Tehachapi Loop
2019-04-28
© Allison J. Gong

Loops like this one in the Tehachapi Mountains were invented to solve a problem facing railroads. Trains are a popular way to transport a lot of cargo over long distances, and are pretty efficient over flat terrain. However, mountain ranges are large obstacles, as trains can't go up or down steep grades. When railroad designers are planning rail routes, there are four options for crossing mountains:

  • Blast a tunnel through the mountains
  • Find a path that meanders through the lower elevations and doesn't get very steep
  • Switchbacks
  • Construct a loop!

I know that tunneling through mountains can be extremely expensive, perhaps prohibitively so. A long, meandering track that avoids the high passes can also be expensive to build, and would necessitate acquiring more land through eminent domain. Trains can't make sharp turns, which means that switchbacks would be impractical. That leaves the loop.

The actual spiral part of the Tehachapi Loop is is 1.17 km (=0.73 miles) long. Any train that is longer than 1200 meters (4000 feet) will cross over itself as it travels through the Loop. The elevation difference between the two tracks where they cross is 23 meters (77 feet). The Loop allows trains to gain or lose that elevation in a very short period of time (~5 minutes for the second train we watched) and relatively little track. It's a nifty invention!

Here's the video of a train going up through the Tehachapi Loop:

This whole train thing was so much fun to learn about, and to watch in action. I usually save my 'oohs' and 'aahs' for natural phenomena, but I was excited about this Loop. Maybe this is the time to discuss invention and teleology.

Innovation and invention occur in both the natural world and the human-constructed world. The main difference is that humans design and build things to solve some problem that exists--in other words, an object designed by people has a defined purpose. Think, I need something to scoop with, so I will hollow out a flat piece of wood and invent a thing that will some day be called a spoon. Whoever invented the spoon did so to carry out a specific function.

In the natural world, however, inventions don't happen because of some forecast need. Organisms have characteristics, some of which confer a slight advantage in survival and/or reproduction and are thus favored by natural selection. Incremental improvements sometimes occur, only because individuals with a minor change in some characteristic happen to leave more offspring than individuals without it. Over many generations, characteristics can change quite dramatically, but it is important to remember that the change is very slow. We must also remember that natural selection does not have foresight. Evolution doesn't operate so that organisms will be 'better' at some point in the future. Organisms evolve to survive in the conditions in which they live, not the conditions that their descendants may face some day.

In his book Climbing Mount Improbable, Richard Dawkins uses the term 'designoid' for biological organisms and their evolved phenotypes, to dissuade teleological thinking. This made-up word illustrates the notion that organisms may appear to be designed for their lifestyles and habitats, but the '-oid' suffix means 'sort of, but not really'. It is not by sheer chance that organisms appear to be suited for their environments, but neither is it by design. Natural selection does not aim towards an endpoint, or perfect goal. Populations continue to evolve at different rates, according to how quickly their environment is changing. But there is no forecasting involved.

Now that I've belabored that point to death, let's return to the Tehachapi Loop. It is both a very simple and very effective concept--that traveling in a spiral is an easy way to gain or lose altitude--but for some reason watching a train go through a loop and cross over itself was really cool. The Loop used to be open to passenger rail traffic via Amtrak, but regular passenger service over the Tehachapis ended decades ago. Every once in a while, though, Amtrak's Coast Starlight train is diverted to the Loop due to maintenance or construction along the normal route. I thought it would be fun to catch one of those trains to go through the Loop, until I realized that from the inside of the train it would just be like going through a tunnel. Passenger trains aren't long enough to cross over themselves where the Loop's rails cross, so there wouldn't be much to see. Oh well. I got to see two trains cross over themselves from the overlook, and that was super fun! Sometimes, being on the outside looking in is the perspective you want to have.

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