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3

In the parlance of invertebrate zoologists, competence is the state of development when a larva has all of the structures and energy reserves it needs to undergo metamorphosis into the juvenile form. In the case of my sea urchins, this means that they have four complete pairs of arms, each with its own skeletal rod, and a fully formed juvenile rudiment, which contains the first five tube feet of the water vascular system. A continuous ciliated band runs up and down all eight arms and provides the water current used both for swimming and feeding. The larva will have been eating well and its gut will be full of food. It will have lost the transparency it had when it was younger and will appear to be more solid-looking in the central area.

The first batch of larvae that I began culturing this season are now 42 days old. Some of these are competent, or very nearly so. Last week I isolated about a dozen of these big guys into a small dish, making it easier for me to observe them closely every day. Today they looked decidedly opaque and dumpy, and although some of them were still swimming others were heavy and tended to rest on the bottom of the dish.

Here's a photo that I took yesterday:

41-day-old pluteus larva of Strongylocentrotus purpuratus, 2 March 2015. ©Allison J. Gong
41-day-old pluteus larva of Strongylocentrotus purpuratus, 2 March 2015.
©Allison J. Gong

General orientation: This is a ventral view. The animal swims with its arms forward, which defines the anterior portion. Thus the bottom of the cup-shaped body is the posterior. This larva measures ~900 microns along the anterior-posterior axis. Plutei have bilateral symmetry that goes all to hell during metamorphosis, from which the urchin crawls away with typical echinoderm pentaradial symmetry. This wholescale change in body organization is one of the truly amazing things about metamorphosis in these animals. It boggles my mind every time I think about it.

You can see that this pluteus has eight arms. The oblong reddish structure in the middle is the stomach, which has taken on the color of the food the animal has been eating. The strange mixed-up looking structure adjacent to the stomach on the animal's left side is the juvenile rudiment. Focusing up and down through the rudiment shows that it contains five tube feet. After metamorphosis, the juvenile urchin will use those first five tube feet to walk around as a benthic creature, having spent all of its life up to this point as a member of the plankton.

Today I captured about 20 seconds of a larva feeding. This individual is a day older than the one in the photo above and has more of that opacity that I associate with competence.

This is a dorsal view; if you imagine that you're looking at the animal's back, you see that the rudiment is indeed on its left side. The larva's ciliated band is moving a lot of water, and the little specks that you can see flying around are food cells. There wasn't enough water in this drop for the pluteus to do any actual swimming, but at this point it's pretty heavy and would tend to sink to the bottom.

Some time in the next several days these guys are going to start metamorphosing. I will be examining them every day; keep your fingers crossed that I catch them in the act!

 

 

1

Thirty-one days ago, on 20 January 2015, I spawned purple sea urchins (Strongylocentrotus purpuratus) and generated six jars of larvae. I've been examining the larvae twice a week ever since. At first they were doing great, developing on schedule with no appreciable abnormalities or warning flags. Then, at about Day 24, the cultures began crashing for no apparent reason. At first I expected to see lots of malformed, shriveled, or underdeveloped larvae, but the thing that I don't understand is that for the most part they look great. They're eating, pooping, growing, and (apparently) doing everything that they should be doing.

Case in point:

31-day-old pluteus larva of Strongylocentrotus purpuratus, 20 February 2015. © Allison J. Gong
31-day-old pluteus larva of Strongylocentrotus purpuratus, 20 February 2015.
© Allison J. Gong

This larva is PERFECT. It has all four pairs of arms now, and they are growing symmetrically. The stomach (the inverted-pear-shaped structure in the middle of the cup-shaped region) is pigmented with the red food it has been eating, and there are no skeletal rods protruding beyond the tips of the arms. This individual doesn't give me any clues as to why the culture it came from took a nosedive this past week. The other larvae that I sampled from this jar today also look good. There aren't many left in the jars from this spawning, but if they all look as promising as this one then I still have hope that some will be able to metamorphose successfully.

So what gives? I suspect that Day 24 has something to do with it. I'm working on a hypothesis and need to let it percolate inside my brain a bit more. When it's ready I want to test it, although that will have to wait until next year, as we've reached the end of this year's spawning season.

Yesterday I drove up the coast to Pigeon Point to do a little poking around. I had originally planned to search for little stars, survivors that had made it through the most recent outbreak of wasting syndrome. But I got distracted by other things and gave up on the stars, for now. I need to do some thinking about the best way to find tiny animals in a very complex 3-dimensional habitat.

I did spend quite a bit of time turning over rocks in tidepools. The most common critters I found were the usual suspects--porcelain crabs, limpets, snails, the odd sculpin or two, and chitons. One rock yielded a gold mine: five chitons of a species I didn't recognize (which doesn't mean I haven't seen it before, just that I didn't immediately know its name) that demonstrated a most interesting behavior.

Stenoplax heathiana, on underside of rock, 31 January 2015. Photo credit:  Allison J. Gong
Stenoplax heathiana, on underside of rock, 31 January 2015.
© Allison J. Gong

I turned the rock over and watched as the chitons ran away from the exposed surface onto the other side. Yes, RAN. I've never seen a chiton do anything this fast. Chitons, for the most part, lead apparently inactive lives. When we do get to see them in their natural setting, at low tide, they are usually scrunched down hard on the rock waiting for the water to come back. Obviously they are much more active when covered with water, but we don't get to see them then. In the lab, where they can be immersed all the time unless they crawl up the walls, they do wander around a bit; however, to see a chiton do much of anything requires time-lapse photography.

Don't believe that a chiton can run? Well, get a load of this:

This is in real-time, not sped up. Watch the chiton push a limpet and the snail out of the way. Okay, I'll grant that a limpet and a snail are not the strongest obstacles one could face when trying to flee from the light. But you can't deny that this chiton seems to be feeling a sense of urgency.

This species, Stenoplax heathiana, spends its days buried in sand on the underside of rocks. It comes out to feed at night, not on algal scums as most chitons do, but on bits of algae that drift by and get caught between rocks. Apparently the chiton can be found exposed in the very early morning. I'm going to have to try finding some this spring when we get our morning low tides back.  Anybody want to come with me?

 

1

On another glorious afternoon low tide the other day, with the help of a former student I collected six purple urchins, Strongylocentrotus purpuratus. Given that we're in about the middle of this species' spawning season, I reasoned that collecting six gave me a decent chance of ending up with at least one male and one female that hadn't spawned yet.

Yesterday, after the urchins had been in the lab for somewhat less than a whole day, I shot them up and waited. Three females began spawning almost immediately (yes!) and one male started a few minutes later. When all was said and done I ended up with four females and two males. It turns out that the largest individual, with a test diameter of almost 10 cm, was a male but didn't spawn very much at all. I infer from this that he had already spawned in the field before I collected him.

Female (left) and male (right) spawning purple sea urchins (Strongylocentrotus purpuratus). 20 January 2015. Photo credit:  Allison J. Gong
Female (left) and male (right) spawning purple sea urchins (Strongylocentrotus purpuratus), 20 January 2015.
© Allison J. Gong

At the current ambient sea water temperature of 14°C, hatching begins around 24 hours post-fertilization. Early this afternoon I checked on the beakers and they had indeed begun hatching. Sea urchins hatch at the blastula stage of development, when they are essentially a ciliated hollow ball of cells. The cilia allow the larvae to swim, but at this size they are at the mercy of even the weakest current. Thus, for the most part they act as particles, getting carried wherever the current takes them.

1-day-old embryos of S. purpuratus. The empty space inside each embryo is called the blastocoel. 20 January 2015. Photo credit:  Allison J. Gong
1-day-old embryos of S. purpuratus. The empty space inside each embryo is called the blastocoel. 20 January 2015.
© Allison J. Gong

As the embryos hatch, they swim up to the top of the beaker, then move down towards the bottom. I call this "streaming." At this point in our artificial culturing system the embryos are living in still water without any current, so this behavior is due primarily to their ability to swim. There is probably some interesting physics involved, but I'm not enough of a physicist to figure out what's going on at that level. But whatever it is, it's a really cool behavior to watch:

Rather mesmerizing, isn't it? Each of those tiny orange dots is an individual embryo. Once the embryos hit the water column I pour them off into larger jars and begin stirring them. Right now they're small enough to swim on their own, but once they start feeding and growing they get heavier and would sink to the bottom without some current to keep them suspended. The contraption we use to stir jars of larvae is a manifold of paddles connected to a motor that moves the paddles back and forth, creating the right amount of current to keep the larvae from settling on the bottom without getting beat up by the turbulence.

Here's the paddle table in action. It's a noisy SOB.

For now the embryos just hang out in the jars and get stirred. Their first gut, the archenteron, will be visible tomorrow and the larvae will be able to eat on Friday. Stay tuned!

The temperate rocky intertidal is about as colorful a natural place as I’ve seen. Much of the color comes from algae, and in the spring and early summer the eye can be overwhelmed by the emerald greenness of the overall landscape due to Phyllospadix (surf grass, a true flowering plant) and Ulva (sea lettuce, an alga). However, close observation of any tidepool reveals that the animals themselves, as well as smaller algal species, are at least as colorful as the more conspicuous surf grass and sea lettuce.

Take the color pink, for example. Not one of my personal favorites, but it is very striking and sort of in-your-face in the tidepools. Maybe that’s because it contrasts so strongly with the green of the surf grass. In any case, coralline algae contribute most of the pink on a larger scale. These algae grow both as encrusting sheets and as upright branching forms. They have calcium carbonate in their cell walls, giving them a crunchy texture that is unlike that of other algae. They grow both on large stationary rocks and smaller, easily tumbled and turned over rocks.

A typical coralline “wall” looks like this:

Coralline rock with critters, 18 January 2015.  Photo credit:  Allison J. Gong
Coralline rock with critters, 18 January 2015.
© Allison J. Gong

Mind you, this “wall” is a bit larger than my outspread hand. The irregular pink blotches are the coralline algae. Near the center of the photo is a chiton of the genus Tonicella; its pink color comes from its diet, which is the same coralline alga on which it lives. The most conspicuous non-pink items on this particular bit of rock are the amorphous colonial sea squirt (shiny beige snot-like stuff) and the white barnacles on the right.

What really caught my eye today were the sea slugs Okenia rosacea, known commonly as the Hopkins’ Rose nudibranch. Now, it is very easy to love the nudibranchs because they are undeniably beautiful. The fact of the matter is that they are predators, and some of them eat my beloved hydroids, but that’s a matter for another post. Today I saw dozens of these bright pink blotches dotting the intertidal, both in and out of the water:

Okenia rosacea, the Hopkins' Rose nudibranch, emersed. 18 January 2015. Photo credit:  Allison J. Gong
Okenia rosacea, the Hopkins' Rose nudibranch, emersed. 18 January 2015.
© Allison J. Gong
Okenia rosacea, immersed. 18 January 2015. Photo credit:  Allison J. Gong
Okenia rosacea, immersed. 18 January 2015.
© Allison J. Gong

Only when the animal is immersed can you see that it is a slug and not a pink anemone such as Epiactis prolifera, which I’ve seen in the exact shade of pink. But anemones don’t crawl around quite like this:

Whenever I see O. rosacea I automatically look for its prey, the pink bryozoan Eurystomella bilabiata. Lo and behold, I found it! The bryozoan itself is also pretty.

The bryozoan Eurystomella bilabiata, preferred prey of the nudibranch Okenia rosacea. 18 January 2015.  Photo credit:  Allison J. Gong
The bryozoan Eurystomella bilabiata, preferred prey of the nudibranch Okenia rosacea. 18 January 2015.
© Allison J. Gong

Can you distinguish between the coralline algae and the pink bryozoan in the photo? Is it shape or color that gives it away? If you had to explain the difference in appearance between these two pink organisms to a blind person, how would you do it?

Every winter northern elephant seals (Mirounga angustirostris) return to their breeding rookeries in central and northern California. These animals spend the majority of their time foraging at sea, but as with all pinnipeds they must return to land to birth their pups. The breeding site in central California is Piedras Blancas, a few miles north of San Simeon. In the northern part of the state the elephant seals breed at Ano Nuevo, about 20 miles north of Santa Cruz. While elephant seals do occasionally haul out along other beaches, the best places to see them are at the rookeries during the breeding season.

The adult males typically show up first, in late November and early December. They arrive early to set up and defend territories. Adult females arrive mid-December and are herded into harems by the alpha males, who meanwhile continue to fight over territory and dominance. Since the seals' food is found at sea, all adults and subadults fast while at the rookery. They loll about in the sun, flip sand over themselves, and doze.

Elephant seals at Piedras Blancas, 3 January 2015. Photo credit:  Allison J. Gong
Elephant seals at Piedras Blancas, 3 January 2015. © Allison J. Gong

For female elephant seals, the first order of business is to give birth to their pups. The pregnant females arrive carrying a pup that was conceived during the previous year's haul-out. A given female will give birth about a week after her arrival, and pupping season lasts until around mid-January. Pups are born with very dark fur and loose, wrinkly skin, until they fill out and take on the e-seal look of fat sausages. On my visit I saw pups that still had their umbilical cords attached, as well as pups that had been nursing for a while and gotten fat.

Despite the apparent laziness of the seals themselves, a rookery can be a noisy place. Pups and mothers squawk to each other, and males bellow a sort of low-pitched rumble as part of their dominance displays. Listen to the various e-seal vocalizations in this video:

In the right side of this video clip a female e-seal is being forcibly mounted by a male. I say "forcibly" because she does seem to be protesting and trying to get away. Of course, this is all just sexual selection in action--it is in the female's best interest, in terms of the quality of next year's pup, to be mated by the strongest male on the beach. Thus if she makes it difficult for him to copulate with her and he still manages to succeed, she can be reasonably certain that the father of her pup is healthy and vigorous.

However, notice that large male on the left. He doesn't like seeing "his" female being approached by another male. We kept waiting to see if a full-blown altercation would develop, but when all is said and done the animals are pretty lazy and won't waste energy on fights that aren't absolutely necessary. That big male on the left made a couple of feints towards the interloper but it didn't seem that his heart was in it.

All in all it was a fairly peaceful late afternoon at the rookery. We watched a spectacular sunset and then left the e-seals to their own devices on the beach.

Sunset at Piedras Blancas, 3 January 2015.  Photo credit:  Allison J. Gong
Sunset at Piedras Blancas, 3 January 2015. © Allison J. Gong

 

2

Yesterday I collected three very small Pycnopodia helianthoides stars. When I brought them back to the marine lab I decided to photograph them because with stars this small I could easily distinguish between the original five arms and the new ones:

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These guys began their post-larval life with the typical five arms you'd expect from an asteroid. At this stage they are pretty conspicuous because they are the largest arms. The other arms arise in the inter-radial regions between arms. For years now I've been wanting to watch juvenile Pycnopodia stars growing their extra arms, and it looks like I finally have my chance. I noted that these stars are all about the same size, but don't have the same number of arms. It would be interesting to see if the rate of arm appearance and growth is related to how much food the stars have. Hmmm, that sounds like a study I should do.

And then one of the stars started running. And I mean running. Watch:

You might wonder how in the heck they can run so fast, and it's a valid question. We can actually examine the animal's scientific name to get an answer. "Pycnopodia" means "dense foot" and "helianthoides" means "sunflower-like." So these guys have a lot of tube feet, and they use them to run and feed. Imagine how fast we could run if we had more than two feet and could co-ordinate them this well:

So, when these guys (gals?) grow up, they'll be at least half a meter in diameter with 20-24 arms. With all those tube feet, they'll be Speedy Gonzales! In fact, they will be the terror of the intertidal--big, fast, and voracious. Anything that can't get out of their way will be eaten.

We air-breathing land mammals should be grateful that echinoderms never managed to get out of the sea. Can you imagine this monster chasing you down a dark alley, or climbing through your bedroom window?

On 11 March 2011 a magnitude 9.0 earthquake occurred off the coast of Japan. About 14 hours later, at 11:15 a.m. local time a tsunami came through the Santa Cruz Small Craft Harbor. It sank dozens of boats and significantly damaged several of the docks. People were ordered to evacuate the area before the expected arrival of the tsunami, but of course there were those who chose to stay behind and shoot videos like this one (the real action starts at about 1:00):

 

As a result of the damage to the infrastructure of the marina itself, many of the docks have been replaced since 2011, including those that are closest to the mouth of the harbor. For several years now I have been taking marine biology students to the docks to examine the organisms growing on the undersides of the docks, and this year the biological community is finally getting interesting again. These particular organisms are described as "fouling" because they are the ones that colonize the bottoms of boats and have to be scraped off periodically. They are characterized by fast growth rates and short generation times; many of them are also colonial. The first arrivals settle onto the surface of the docks, and later arrivals can take up residence either on the docks or on their predecessors. A healthy fouling community has a rich diversity of marine invertebrates, algae, and the occasional fish. This semester's trip to the harbor occurred a few weeks ago, and as usual the students were amazed at the amount and diversity of life on the docks. I remembered to bring the waterproof camera and snapped some shots.

This is what you see when you lie on the dock and hang your head over the edge:

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It's a mosaic of color and texture, really quite beautiful. You can see that mussels are the largest organisms in this community, and in turn are substrate for a variety of other animals.

Peering a bit closer to take notice of individual animals, you start to see things like this:

A perennial favorite because of its beautiful coloring. It eats my hydroids, though, so I don't like it.
Hermissenda opalescens, a perennial favorite because of its beautiful coloring. It eats my hydroids, though, so I don't like it.

 

One of the colonial hydroids, Plumularia sp. that grow at the harbor.
One of the colonial hydroids, Plumularia sp. that grow at the harbor. This species always grows in this pinnate form. Absolutely gorgeous under the microscope.
These small white anemones (Metridium senile) are about 3 cm tall.
These small white anemones (Metridium senile) are about 3 cm tall.
Feather duster worm, Eudistylia vancouveri, easily one of the most conspicuous animals on the docks.
Feather duster worm, Eudistylia vancouveri, easily one of the most conspicuous animals on the docks.
Colonial sea squirts, Botryllus sp. and Botrylloides sp.
Colonial sea squirts, Botryllus sp. and Botrylloides sp.

Colonial sea squirts, those orange-ish blobs in the last picture, are extremely common in marinas. In this photo, each distinct colored blob is an individual colony, and each colony consists of several genetically identical zooids connected by a protective covering called a tunic. Each teardrop-shaped zooid has its own incurrent siphon (the visible hole) through which it sucks in water, and the zooids in a group within a colony share a single excurrent siphon through which waste water is discharged. In Botryllus, the zooids are arranged into flower-like configurations called systems. In Botrylloides the systems are much less distinctive and wind around over the substrate. I've outlined a nice colony of Botryllus in the photo below, so you can see the easily recognized systems.

A colony of Botryllus, with zooids arranged in flower-shaped systems.
A colony of Botryllus, with zooids arranged in flower-shaped systems.

Such a wonderful world of animals and algae, right under our feet. Even people who spend a lot of time around boats don't pay attention to the stuff on the docks. To me it is a secret garden that is easily overlooked but greatly appreciated when you take a moment to get your face down where your feet are.

This past Tuesday and Wednesday afternoon I took my marine biology students to the rocky intertidal at Natural Bridges State Beach. We completely lucked out with the weather; the storm system that brought some of the rain that we desperately need had cleared out, leaving calm, clear seas and little wind. Perfect weather for taking students out in the field, in fact.

First of all, we didn't see any stars. Not that I was looking for them, particularly, but I was keeping an eye out for them and at this time last year I would have seen many Pisaster ochraceus hanging out in the pools and on the rocks. Here are a couple of pictures I took at Natural Bridges in years past:

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The stars, when present, are prominent residents of the mid-intertidal zone, where they feed on mussels. But now, alas, there don't seem to be any. They WILL come back, and it will be interesting to monitor their population recovery.

I enjoy taking students in the field because many of them have never been there before, and it's always fun looking at a familiar scene with fresh eyes. When everything is new, it is very easy to be excited and enthusiastic, which these students are.

We saw, among other things:

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Fish! The fish on the right was about 15 cm long. I think it's a woolly sculpin (Clinocottus analis), but IDing sculpins in the field is pretty tricky.
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This fish was much smaller, only about 10 cm long. It could be a fluffy sculpin (Oligocottus snyderi), or it could be a smaller woolly.
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This is an encrusting sponge, Haliclona sp. I've seen it in shades of rosy pink, too. The large holes are oscula, the sponge's excurrent openings. And that's a big gooseneck barnacle (Pollicipes polymerus) hanging down from the top of the picture.
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An assortment of intertidal critters sharing space on a rock. How many chitons can you spot?  How many barnacles?  How many limpets?
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This is one of my favorite intertidal animals, the owl limpet (Lottia gigantea). These large limpets are farmers. They keep an area clear of settlers by grazing at high tide. You can see the marks left by this individual's radula. The limpets also manage their farms, letting the algal film grow on one section while feeding on another.
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I love macro shots like this! The green tufty stuff is Cladophora columbiana, a filamentous green alga. Isn't it a vibrant green color? To give you an idea of how fine the Cladophora filaments are, that snail in the background is about the size of a quarter.
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And last, a gratuitous anemone shot. Ahhh, Anthopleura xanthogrammica, what a photogenic creature!

4

"Perhaps" being the operative word here. I was up at Davenport Landing the other day to do some collecting, and saw some healthy stars. Alas, no pictures, as I'm not coordinated enough to do photography and collecting on the same trip. But here's what I saw:

  • 5 healthy Pisaster ochraceus stars. This was the first species to start melting in my seawater table back in September, and they've suffered a lot subtidally as well. These five were all at least as big as my outstretched hand, so were several years (decades?) old. They were nice and stiff, unlike the flabby ones that died, and firmly attached to the rocks, indicating that the water vascular system was functioning normally. Yippee!
  • 6 healthy Dermasterias imbricata stars. I haven't personally observed this species being affected by wasting syndrome, and the stars I saw the other day all looked good. This species as a whole does not have the sticking power of P. ochraceus, but the ones I picked up had the right texture and consistency to make me think they were in good shape.
  • 1 tiny Pycnopodia helianthoides, about the size of my thumbnail. It had 10 arms of various lengths and was very active. I really wished I had my camera when this little guy floated into view on a piece of algae.

So what does this all mean?

Probably not much, in and of itself. This is a single observation at one site on one day. But finding live,  healthy stars is a lot more encouraging than seeing only dead or dying stars. The fact that I saw a very small P. helianthoides makes me wonder. Usually at Davenport Landing I see a few hand-sized or larger Pycnopodia stars. . . I saw none the other day, so does that mean they've all died? And how old is this little 1-cm star? Did it recruit before or after the wasting event?

I also noticed something else, which may or may not be related to the recent star deaths: Turban snails (Chlorostoma funebralis and C. brunnea) seemed to be more abundant than usual. Also, the C. funebralis, which are typically roughly spherical and the diameter of about a quarter, were larger and had the more slightly conical shape of C. brunnea. Just a coincidence? Hard to say, without quantifiable data, but I'm guessing "Yes."

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