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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?

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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:

OLYMPUS DIGITAL CAMERA OLYMPUS DIGITAL CAMERA Pycnopodia juvenile

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:

OLYMPUS DIGITAL CAMERA

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.

It has been almost a month since my big female whelk started laying her eggs, and the embryos seem to be developing nicely. The first time I witnessed this phenomenon I saw the egg capsules begin to turn black, and worried that the eggs inside were dead and decomposing. But the cool thing about Kelletia development is that the larvae themselves become darkly pigmented as they develop, which we see as an overall dingy grayness of the egg capsules:

Kellettia eggs

 

Nosy as ever, I pulled one of the egg capsules off the side of the bin and took it back to my desk for closer examination under my dissecting scope. At the "top" of the capsule (the end that is attached to the bin), the material was quite thin, and I could some vague dark lumps inside. They were slowly moving around, so I knew they were alive.

Individual larvae resemble bubbles with dark stuff inside.
Individual larvae resemble bubbles with dark stuff inside.

 

Viability! This makes me happy and encourages me to "liberate" a few larvae to look at under higher magnification. I squeezed out a few veligers and put them under a coverslip with just enough water to keep their shells from cracking but not enough to let them swim away. Here's a tip for observing small aquatic critters under a microscope:  If you make their universe (i.e., the drop of water you are observing) small, they will be less able to swim away from you. Flattening the drop of water with a judiciously placed coverslip will also help immobilize the creature, as well as taking best advantage of the microscope's optics.

Early veliger of Kelletia kellettiiNot too much to look at while stationary, is it? You can see a coiled shell (this is a snail after all) and some blobby structures inside it. At this stage the larva isn't feeding and relies on yolk reserves provided by the mother when she deposited the eggs. Some of the opaque stuff inside the shell is yolk and other bits are various parts of the digestive system. At about 11:00 just underneath the shell there is an elongated transparent area: the larva's heart; you can see it beating in the video below. The light mohawk-looking structure facing to the right is the larva's velum, a lobed ciliated structure that the animal will use to swim after it hatches. The last structure of note is the wedge-shaped thing that points to about 5:00; this is the larva's foot, on the back of which sits the operculum that is used to close up the shell.

After a bit of trial and error I was able to catch some decent video footage through the microscope of a trapped larva:

Kellettia larva under compound scope

The larva rhythmically extends and retracts its velum. Because of the coverslip the larva can't go anywhere, but if unencumbered it would be able to use that velum to zip around really fast. It is very difficult to keep up with swimming veligers under a microscope!

My guess is that the larvae will begin hatching on their own in the next couple of weeks. They will be washed out of their tub and down the drain of the seawater table, to take their chances in the big ol' Pacific Ocean.

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This week my female Kellet's whelk (Kelletia kelletii) started laying eggs. She's been doing this every summer for the past several years. She lives with one other whelk, presumably the father of her brood, as the eggs are both fertilized and viable even though I've never seen the snails copulating.

That's right, copulating. Whelks are predatory marine snails, some of which get quite large. My big female's shell is a heavily calcified 12 cm or so; she's a beefy mother! Her mate is smaller, but other than the size difference I wouldn't be able to tell them apart. Anyway, whelks copulate, with the male using a penis to transfer sperm into the female's body. Not very different from the way we humans do things, actually.

So at some point in the recent past my whelks copulated, and this week the female began depositing egg cases on the walls of their shared tub. I first noticed them on Monday, but she may have started over the weekend.

Female whelk (right) laying eggs. ©Allison J. Gong
Female whelk (right) laying eggs.
© 2013 Allison J. Gong

Those pumpkin seed-shaped objects are the egg capsules. Each is actually about the size and shape of a pumpkin seed and has a tough outer covering that contains 20-50 developing embryos. After the entire clutch is lain, which usually takes this particular female a week or so, the mom will leave the eggs to develop on their own.

I'll keep an eye on these eggs for the next week or so, and might be able to get some photos of the embryos and larvae as they begin developing. Keep your fingers crossed!

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Over the Memorial Day weekend I took my students out on the early morning low tides at Natural Bridges State Beach.  While they were ooh-ing and ahh-ing and filling out their assignment worksheet, I was playing around with my new camera, taking pictures in the water.  Because I am not a photographer and sea anemones just sit there, they quickly became my favorite subjects.  Not to mention the fact that they are simply  beautiful and photogenic creatures.

At Natural Bridges we have four species of anemones in the genus Anthopleura:

  • A. xanthogrammica - giant green anemone
  • A. sola - sunburst anemone
  • A. elegantissima - aggregating anemone
  • A. artemisia - moonglow anemone

Of these species, the first two are notable for their large size.  At Natural Bridges they can get to be the size of a dinner plate.  They live side-by-side in tidepools, and since there are many deep-ish pools at Natural Bridges they are among the most conspicuous animals in the intertidal along the northern California coast.

Anthopleura sola (left) and A. xanthogrammica (right) in a shallow pool at Franklin Point.
Anthopleura sola (left) and A. xanthogrammica (right) in a shallow pool at Franklin Point.

It's easy to identify these animals when they're sitting right next to each other.  The difficulty comes when you see only one in a pool by itself with nothing to compare it to.  In a nutshell, here are some things you can use as clues to determine which species you have in front of you.

Let's start with Anthopleura xanthogrammica, the giant green anemone.  This animal's oral surface and tentacles are a solid color, varying from bright green to golden brown.  There are no conspicuous stripes on the central disc and the tentacles are relatively short and stubby, without any white patches.

Anthopleura xanthogrammica, photographed at Natural Bridges State Beach
Anthopleura xanthogrammica, photographed at Natural Bridges State Beach

Anthopleura sola, on the other hand, usually has distinctive radiating lines on the oral disc.  Hence the common name of Sunburst Anemone.  Its tentacles are generally longer and more slender than those of A. xanthogrammica, and often have sharp-edged white patches.  Sometimes the tips of the tentacles are tinged a pale purple.  Anthopleura sola are usually brownish-green in color, and I haven't seen any that are as bright green as the A. xanthogrammica anemones.

Anthopleura sola, photographed at Natural Bridges State Beach
Anthopleura sola, photographed at Natural Bridges State Beach

That's all well and good, but sometimes you come across an individual that doesn't completely follow the rules.  Or rather, it looks like it could belong to both species. Such as this fellow (fella?):

Hmmm...sola or xanthogrammica?
Hmmm. . . sola or xanthogrammica?

The animals obviously don't read the descriptions.  This one has xanthogrammica shape and overall color, but those lines on the disc read as sola-ish.  I would call this one a xanthogrammica.  What do you think?

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I was making my usual feeding and checking rounds at the marine lab last Wednesday, when I saw this:

Pugettia producta, molting.  Time 10:09:12

This crab is a kelp crab, Pugettia producta. It is one of the common crab species on the California coast; you can find them in the low intertidal clinging to algae. Many of them are this golden-brown color, coincidentally(?) the same color of the kelp Macrocystis pyrifera. Juveniles are often reddish or dark brown in color, again matching or blending in with the algae where you see them. This particular crab has always been this color, at least since it has been in my care.

Crustaceans, as all arthropods, periodically molt their entire exoskeleton in one fell swoop. The exoskeleton splits along the transverse seam between the carapace and the abdomen, then the crab sort of slithers out backward. The entire exterior of the body, including legs, antennae, and mouthparts, is left behind as a larger version of the crab scuttles away to hide out for a few days until its new shell hardens.

I've kept lots of crabs and seen lots of molts show up in their tanks, but have never caught one in the act before. From when I started watching, in the photo above, to the final wiggle out of the old exoskeleton took no longer than 5 minutes.  Here's the sequence of photos documenting the molt:

Pugettia producta molting. Time 10:09:41
Pugettia producta molting. Time 10:12:18
Pugettia producta, molting. Time 10:13:57

Pretty nifty, eh?

 

As I suspected, the little Dendronotus veligers didn't last very long.  On Wednesday the very last survivors had kicked the proverbial bucket.  All that was left in the jar was some debris and scum from leftover food.  They lasted nine days post-hatching, which is about the norm for me when I've tried to raise nudibranch larvae.  Something just happens (or doesn't happen) around Day 10 and they all crash after a week or so of apparently vigorous life.  Someday I may figure out what's going on.  In the meantime, RIP, little guys.

On the more fun side of marine biology, there's a new exhibit at the Seymour Center that is extremely cool.  Someone brought in a buoy that had been out in the ocean for a long time.  It's a perfect example of a fouling community.

People who have boats or just spend time in marinas know about fouling communities.  They're all the stuff that gets scraped off the bottoms of boats.  It's also the same stuff that grows on pilings and the underside of floating docks.  In this case the term "fouling" refers to early recruiting animals and algae that grow quickly to monopolize space.  Many of the fouling species seen in harbors are invasive non-natives.

A few years ago I hung a box of slides off one of the docks at the Santa Cruz Yacht Harbor and left them there for several months to see what would grow.  Here's what recruited and grew on a single slide measuring about 5x7.5 cm:

Fouling community of invertebrates and algae on a glass slide.
© Allison J. Gong

As you can see, it's a very colorful world down there!  The brightest red curly stuff is an introduced species of bryozoan called Watersipora.  It is a fast grower and can overtake the other stuff and form large clumps.  It grows as an encrusting sheet over surfaces, but when two sheets make contact they grow up each other and form those curly upright bits.  To model how this works, hold your hands in front of you, palms down, with the fingers facing each other.  Push your hands together until your fingertips meet, then continue to move them towards each other.  What happens is that your hands flex and your finger tips get moved upwards until your palms come together in a praying position.  If your hands were encrusting sheets of bryozoan colonies, that's how you'd get those curly pieces.

Anyway, the buoy on display at the Seymour Center has a lot of large barnacles.  The barnacles have been actively feeding and molting since they arrived last week.  They are definitely the most animated critters growing on the buoy, as shown here:

 

Barnacles are crustaceans that lie on their backs entirely encased in hard shells glued to other surfaces.  They feed by extending their thoracic appendages and sweeping them through the water to capture detritus and plankton.  It's a strange way to make a living, but it does work.

 

 

 

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What better way to start a new blog than to talk about sex?

This morning at the Seymour Center I noticed a blob of what looked like nudibranch eggs on the wall of one of the tanks. Looking around for the likely culprit I saw three big nudibranchs on the tank. Ooh, cool!

One of two slugs of this species in this tank.

This is Dendronotus iris, a large nudibranch, or sea slug. This bad boy/girl had a foot (the flat white bit that you see reflected in the aquarium glass) that was about 15 cm long. The brownish branched structures on the slug's back are its cerata, which function as gills. These animals do not have the ctenidium, or gill, that is typical of marine snails. Other nudibranchs carry their gills in a single plume that surrounds the anus.

This species is distinguished from D. iris by its coloration and some details of its anatomy.

There is one other big slug in this tank. It has a paler body color and cerata that are banded with orange and tipped with white.

Nudibranchs are among the rock stars of marine invertebrates--they are flamboyantly colored, have short adult lives with lots of sex, and leave beautiful corpses when they die. After a planktonic larval life of a few weeks, adult nudibranchs spend their time eating, copulating, and laying eggs. Each slug is a simultaneous hermaphrodite, capable of functioning as both male and female, and mating involves an exchange of sperm. In some other species of nudibranch the act of love can be followed by an act of cannibalism.

Nudibranchs lay egg masses in ribbons or strings that are characteristic of the species. It turns out that Dendronotus egg masses look like Top Ramen noodles:

Egg mass of Dendronotus.

Each of those individual little white blobs is an egg capsule that contains 10-30 developing embryos. These eggs were deposited yesterday (3 June) and the embryos have been developing but are not yet at any distinct stage. With water temperature at about 13C, I think they'll develop pretty quickly.

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