Tag: marine biology

Things strange and beautiful

Posted on by Allison J. Gong

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

Squidlets

Posted on by 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!

Familiarity breeds wonder

Posted on by Allison J. Gong

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!

Trailblazers

Posted on by Allison J. Gong

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!

Students begin observing succession

Posted on by Allison J. Gong

This week’s field trip for my Ecology class was the first of two visits to the Santa Cruz harbor. The students’ task was to select a site to monitor for a semester-long study of ecological succession. The floating docks at the harbor are the ideal site for this kind of study because I know from experience that the biota changes from season to season throughout the year, on a time scale that can be observed within the confines of a 16-week semester. We will return to the harbor in nine weeks and students will document how their sites have changed in that time.

California is swinging back into the severe drought situation we had before the epic 2016-2017 rainy season. Since the current rainy season began on 1 October 2017, we’ve had hardly any rain at all and very little snow in the Sierra. Fools who thought that one rainy season would get us out of drought are just that–fools. However, one nice thing about drought conditions is that visibility at the harbor is pretty good. Without any significant runoff the water is nice and clear, making it easy for the students to see what’s growing on their section of the docks.

Students examining their study plot
9 February 2018
© Allison J. Gong
Sometimes a little ballast is required!
9 February 2018
© Allison J. Gong

The assignment for this first visit to the harbor was to choose a site, identify what lives on the site, and draw a map of it. I had warned them that all the interesting biology on the docks occurs below the level of their feet, and that they would have to lie or kneel on the dock to get a good look at what’s going on down there. Some of them tried to take a photo of the entire site, but it’s impossible to get far enough away. Unless you’re actually in the water, from where it would be easy. Yeah, you could don a wetsuit and get in the water, but the harbor isn’t the most ideal place to go for a morning swim.

A little back story on the docks at the Santa Cruz harbor

Remember the magnitude 9.0 earthquake and subsequent tsunami that occurred in northern Japan several years ago? That was on 11 March 2011 at 14:46 local time. That morning in Santa Cruz we received a tsunami warning. I didn’t venture down to the harbor (I think I was working at the marine lab that day) but here’s a video shot by a woman who watched the ~0.5 meter tsunami tear through the upper harbor:

Amazing, the destructive power of such a small wave, isn’t it? Boats were wrenched from their moorings and slammed into other boats and harbor infrastructure. I forget the total dollar amount of damage that our harbor sustained, but as a result all of the docks were replaced in the next few years. I did happen to be at the harbor with a group of students on one of the days that the old docks were being removed. It was heartbreaking to see the docks, carrying decades of biological growth on them, dumped in the parking lot to dry out in the afternoon sun. I imagine they were eventually hauled out to the landfill. 

Since then, the biota on the new floating docks seems finally to be stabilizing. If I had been teaching Ecology back in 2013, we would have had pristine habitat in which to observe honest-to-goodness primary succession. As things are, however, I’m giving students the option of scraping all or part of their plot clear, to simulate primary succession. Their other option is to leave the plot as-is, and pick up the succession process somewhere in the middle and see what happens from this point forward.

So, what did they see down there? 

Well, even though the water was relatively clear, a lot of the photos looked like this:

9 February 2018
© Allison J. Gong

I can identify much of the stuff in this photo, but this isn’t the best shot to showcase the biodiversity on the docks. I decided that the camera would do a better job if I used it to photograph individual organisms instead. Here are some of my favorites.

This shot is looking straight down along the edge of one of the docks. The macroscopic life begins 2-3 cm below the waterline, and even above that the dock surface is covered with microscopic scuzzes.

White plumose anemones (Metridium senile) at the Santa Cruz harbor
9 February 2018
© Allison J. Gong
Oral view of white plumose anemones (Metridium senile) at the Santa Cruz harbor
9 February 2018
© Allison J. Gong

I had shown the students pictures of organisms they would be likely to see at the harbor. One of the critters that shows up sporadically is the introduced hydroid Ectopleura crocea. Later in the semester we will discuss species introductions and invasions in more detail. Harbors generally tend to be heavily populated by non-native species, and our local harbor is no exception. The species of Ectopleura found in harbors has hydranths that can be 8-10 cm long, and when it occurs it tends to be quite conspicuous. The congeneric species, E. marina, lives in intertidal in some areas on the open coast; I’ve seen it in a few tidepools at Davenport Landing, for example. The intertidal species is much smaller, about 2-3 cm tall and doesn’t form the dense clumps that typifies E. crocea.

The non-native hydroid, Ectopleura crocea, at the Santa Cruz harbor
9 February 2018
© Allison J. Gong
Caprellid amphipods at the Santa Cruz harbor
9 February 2018
© Allison J. Gong

The ubiquitous caprellid amphipods were crawling all over everything, as usual. Some of the students really didn’t like these guys and one of them had the same reaction to them that I do, which is a general shudder. They’re sort of cute in still photos, but when they start inchworming around they look sort of creepy. And when there’s a bunch of them writhing around in an oozy mass, they’re REALLY creepy.

One of the most conspicuous worms at the harbor is Eudistylia polymorphora, the so-called feather duster worm. They come in oranges, purples, and yellows. This one was pure white. Lovely animal!

Feather duster worm (Eudistylia polymorpha) at the Santa Cruz harbor
9 February 2018
© Allison J. Gong

Tube-dwelling polychaete worms, such as Eudistylia, don’t have much in the way of a head but they do have many light-sensitive eyespots on the tentacles. They react very quickly to many stimuli, and even a shadow passing over a worm causes it to yank its tentacles into its tube in the blink of an eye. Usually they’re not too shy, though, and will extend their tentacles soon to resume feeding.

All told we were on the docks for about 2.5 hours. Not a bad way to spend a glorious morning, is it?

9 February 2018
© Allison J. Gong

Creepy crawlies

Posted on by Allison J. Gong

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.

The tiniest advantage

Posted on by Allison J. Gong

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.

My favorite larva — the actinotroch!

Posted on by Allison J. Gong

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!

Lunacies

Posted on by Allison J. Gong

For several centuries now, Earth’s only natural satellite has been associated with odd or unusual behavior. Lunatics were people we would describe today as mentally ill, who behaved in ways that couldn’t be predicted and might be dangerous. The erratic behaviors were attributed to the vague condition of lunacy. These words are derived from the Latin luna, which means ‘moon’. The cycles of the moon have long been thought to influence human behavior as well; hence such legends as the werewolf.

We do know that the moon indeed has a very strong influence on aspects of many organisms, primarily through the tides. For example, reproduction in many marine animals is timed to coincide with a particular point in the tidal cycle. Grunion (Leuresthes tenuis, small, silver, finger-shaped fishes) run themselves up onto California beaches at night to spawn following the full and new moon high tides in the early summer months. Corals in the Great Barrier Reef spawn together in the handful of nights after the full moon in November. Animals such as these, which reproduce via broadcast spawning, are the ones most likely to benefit from synchronized spawning; after all, there is no point in spawning if you’re the only one doing it. Invertebrates don’t have watches or calendars; they keep time by sensing the natural cycles of sun and moon. The moon’s strong effect on the tides is a signal that all marine creatures can sense and use to coordinate spawning, increasing the probability of successful fertilization for all.

Last night, Wednesday 6 September 2017, the moon was full. Yesterday at the lab, I noticed that  the large Anthopleura sola anemones living in the corner of my table had spawned.

A male Anthopleura sola anemone that had spawned
6 September 2017
© Allison J. Gong

That diffuse grayish stuff in the right-hand side of the photo is a pile of sperm. I looked at a sample under the microscope, just to be sure. By this time they had been sitting at the bottom of the table for several hours and most of them were dead. But they were definitely sperm:

Whenever I see something unusual like this my first impulse is to see if it’s happening anywhere else at the lab. So I started poking around. The aquarists at the Seymour Center told me that some of their big anemones had spawned in the past couple of days; however, since they clean and vacuum the tanks every day all evidence was long gone.

Fortunately there are several A. sola anemones in other labs that aren’t cleaned as regularly as the public viewing areas. One of the animals in the lab next door to where I have my table had also spawned. . .

Female Anthopleura sola
6 September 2017
© Allison J. Gong

. . . and this one is a female! What looks like a pile of fine dust is actually a pile of eggs.

Eggs of Anthopleura sola
6 September 2017
© Allison J. Gong

And the eggs are really cool. See those spines? They are called cytospines and apparently deter predation. Other species in the genus Anthopleura (A. elegantissima and A. xanthogrammica) are known to have spiny eggs, so it appears that this is a shared feature. Now, if only I could get my hands on eggs of the fourth congeneric species–A. artemisia, the moonglow anemone–that occurs in our area, I’d know for certain, at least for California species. I examined the eggs under higher magnification, but due to their opacity I couldn’t tell if the had been fertilized. Most appeared to be solid single undivided cells; they could, however, be multicellular embryos.

All told, of the anemones that had obviously spawned, 1 was female and 4 were male. I sucked up some of the eggs and put them in a beaker of filtered seawater. I doubt that anything will happen, but I may be in for a pleasant surprise when I check on them tomorrow.

Update

Posted on by Allison J. Gong

Remember that gull we rescued last week? After my husband took it to Native Animal Rescue here in Santa Cruz it was transferred up to International Bird Rescue‘s San Francisco Bay Area center in Fairfield. I e-mailed and asked how the gull was doing and whether I’d be able to witness its release back to the ocean. Yesterday I received this response:

Hi Allison,

This is Cheryl Reynolds, the Volunteer Coordinator for Bird Rescue. Thank you so much for rescuing the juvenile Western Gull and getting him into care at Native Animal Rescue. Hooks and fishing line can cause severe injuries but fortunately this guy is doing okay at this time. He/she had surgery yesterday to repair some of the damage the line caused to his leg and is being treated with antibiotics. He’s not totally out of the woods yet but luckily gulls are pretty tough! I’m giving you his case number here at Bird Rescue #17-1887 but I will be happy to follow up with you on his progress. 
To answer your other questions.. We don’t have a timeline yet on release, it depends on how he progresses. We don’t usually send the birds back to Santa Cruz, we have so many young gulls we like to release as a group and in an appropriate location locally. 
If you would like to contribute to this birds care please go to our website at https://www.bird-rescue.org/. You can also sign up to receive our Photo of the Week and patient updates and also find us on Facebook. 
Thanks again for caring for this birds welfare. 
Kind regards,
Cheryl
We hadn’t realized that the fishing line wrapped around the bird’s leg had caused damage that would require surgery. This makes me doubly glad that we were able to rescue it from the surface of Monterey Bay before the injuries became more severe. It sounds like the prognosis is good for this juvenile western gull, and I hope it and several of its cohort can be returned to the skies and sea very soon.