You are what you eat, part the third

To recap:  Way back in January I spawned some sea urchins. The resulting progeny are now almost 7.5 months old, counting from the day that they were zygotes. Once they metamorphosed and became established as post-larval urchins in June, I divided them into three feeding treatments:  the kelp Macrocystis pyrifera, the green alga Ulva sp., and a red coralline alga. Since then I’ve been counting and measuring them monthly, and today I completed the fourth data collection.

I could tell by looking at the bowls that the Macrocystis and Ulva urchins continue to grow much more quickly than the poor urchins stuck on the coralline diet. The Macrocystis urchins are, overall, bigger than the Ulva urchins, despite the qualitative observation that the Ulva urchins appear to be eating more. However, I am not monitoring the amount of food that is eaten by any of the urchins.

Test diameter of juvenile sea urchins (Strongylocentrotus purpuratus) as a function of diet. 2 September 2015. © Allison J. Gong

Test diameter of juvenile sea urchins (Strongylocentrotus purpuratus) as a function of diet.
2 September 2015.
© Allison J. Gong

In the past month I lost almost half of the coralline urchins; I’m down to six. Mortality for the other groups remains low. I think the Macrocystis and Ulva urchins have for the most part gotten big enough that, barring any unexpected disastrophe (yes, I made up that word), they shouldn’t experience much mortality.

Population sizes of juvenile sea urchins (Strongylocentrotus purpuratus) as a function of diet. 2 September 2015. © Allison J. Gong

Population sizes of juvenile sea urchins (Strongylocentrotus purpuratus) as a function of diet.
2 September 2015.
© Allison J. Gong

In terms of color, I think the differences between the Macrocystis and Ulva diets have become more pronounced in the last month. Today I tried to photograph the two groups of urchins under the same lighting conditions, with mixed success. There’s some variation within groups, of course, but overall the Macrocystis urchins have a more golden color on both the test and the spines. . .

Juvenile sea urchins (Strongylocentrotus purpuratus) eating the kelp Macrocystis pyrifera. 2 September 2015. © Allison J. Gong

Juvenile sea urchins (Strongylocentrotus purpuratus) eating the kelp Macrocystis pyrifera.
2 September 2015
© Allison J. Gong

. . . whereas the Ulva urchins have more purple coloration:

Juvenile sea urchins (Strongylocentrotus purpuratus) eating the green alga Ulva sp. 2 September 2015 © Allison J. Gong

Juvenile sea urchins (Strongylocentrotus purpuratus) eating the green alga Ulva sp.
2 September 2015
© Allison J. Gong

And, just to make sure that I hadn’t inadvertently biased the light in favor of one group at the expense of the other, I manhandled all of the urchins to one side of their respective bowls and took a picture of the two bowls side by side. Let me tell you, it was like herding cats. I’d get one group all bunched together then start working on the other, and the first ones would immediately begin wandering away from where I’d put them. This is the best shot I managed to get. Without reading the caption, you can still figure out which group is which, right?

Juvenile sea urchins (Strongylocentrotus purpuratus) feeding on Macrocystis (left) and Ulva (right). 2 September 2015 © Allison J. Gong

Juvenile sea urchins (Strongylocentrotus purpuratus) feeding on Macrocystis (left) and Ulva (right).
2 September 2015
© Allison J. Gong

We’re coming into the time of year when it might be difficult obtaining food for these urchins on a regular basis. Everybody may have to go on a diet for a few months. As long as I can get my hands on both Ulva and Macrocystis I’ll keep feeding them, and when I run out of one food the other group will have to fast also. I think they’re well enough established by now that not having unlimited food won’t do much harm.

I just had another thought. I could put the Ulva and Macrocystis urchins back on coralline rocks and see how they do over the winter. Something to think about.

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Spying on filter-feeders

Late yesterday afternoon I met my friend Brenna at the harbor to go on a slug hunt. Brenna is working on the taxonomy of a group of nudibranchs for her dissertation, and we’ve gone collecting out in the intertidal together a few times. I knew I’d need some harbor therapy after teaching a microscope class in the afternoon so when she suggested a slug hunt I didn’t have to think twice about saying “Yes!”

I arrived at the harbor before Brenna did, and spent some time lying on the docks taking pictures of the fouling community that lives there. The late summer afternoon light was perfect for picture taking, and I got some great shots.

Mussel (Mytilus sp.) at the Santa Cruz Yacht Harbor, 29 August 2015. © Allison J. Gong

Mussel (Mytilus sp.) at the Santa Cruz Yacht Harbor, 29 August 2015.
© Allison J. Gong

This is one of my favorites. It’s a view into the posterior end of a live mussel (Mytilus sp.). Mussels live inside a pair of shells and open up only the posterior end to suck in water for respiration and filter feeding. They shut the shells very quickly when disturbed, so I had to sneak up on this individual and take a picture before it knew I was there. Looking through the opening you can see a blurry pale structure running from left to right; I think this is the mussel’s gill. The elaborately fringed dark structure that looks like a pair of curtains extending towards each other is the edge of the mantle. Because most of the mussel’s body is enclosed within the shells, the mantle edge contains most of the animal’s sensory organs. Mantles are exquisitely sensitive to touch, light, and certain chemicals; scallops, another type of bivalve mollusk, often have actual eyes on the mantle edge.

In addition to spying on mussels, I also tried to catch polychaete worms off-guard. There are several different types of tube-dwelling polychaetes living at the harbor. Most of the ones I saw yesterday were serpulids living in meandering calcareous tubes. Like these:

Serpulid polychaete worm at the Santa Cruz Yacht Harbor, 29 August 2015. © Allison J. Gong

Two examples of Serpula columbiana, a tube-dwelling polychaete worm, at the Santa Cruz Yacht Harbor, 29 August 2015.
© Allison J. Gong

Polychaete worm tubes come in many different materials and morphologies. These serpulids live in calcareous tubes that snake over surfaces. Because the tubes are mineralized, they can extend upwards from a surface, too. The worm spends its entire post-larval life in the tube that it secretes, extending only its “head”, visible as a tentacular crown, for filter-feeding. Like the mussels, serpulid polychaetes are very quick to respond to anything they perceive as a threat. Even a mere shadow passing over them can cause a rapid retreat into the tube finalized by sealing off the tube with the trumpet-shaped operculum.

One of the most conspicuous animals at the harbor is an invasive encrusting bryozoan, Watersipora subtorquata. This animal is one of the first to colonize new real estate. Nothing else looks like it, so it is easy to identify.

Watersipora subtorquata, an introduced bryozoan at the Santa Cruz Yacht Harbor, 29 August 2015. © Allison J. Gong

Watersipora subtorquata, an introduced bryozoan at the Santa Cruz Yacht Harbor, 29 August 2015.
© Allison J. Gong

Watersipora grows as a crust on surfaces such as mussel shells and floating docks, but when two colonies meet they use each other as surfaces, forming these curling sheets. The faint fuzziness that you see sort of hovering above the surface of the sheets is due to the lophophores extending from the zooids. Here’s a closer shot:

Watersipora subtorquata, an introduced bryozoan at the Santa Cruz Yacht Harbor, 29 August 2015. © Allison J. Gong

Watersipora subtorquata, an introduced bryozoan at the Santa Cruz Yacht Harbor, 29 August 2015.
© Allison J. Gong

Another of the common introduced species at the harbor is the colonial sea squirt Botrylloides violaceus. This animal comes in a wide range of oranges and even purple. Here’s a colony that seems to understand the visual impact of pairing high-contrast colors:

Colony of the colonial sea squirt Botrylloides violaceus growing over mussel shells at the Santa Cruz Yacht Harbor, 29 August 2015. © Allison J. Gong

Colony of the colonial sea squirt Botrylloides violaceus growing over mussel shells at the Santa Cruz Yacht Harbor, 29 August 2015.
© Allison J. Gong

What looks like a mass of pale orange doughnuts is actually a strictly organized colony. Each of the doughnuts is a zooid, and the hole of the doughnut is the incurrent siphon through which the zooid draws water in. Each zooid has its own incurrent siphon. In this photo you can see several larger holes; these are excurrent siphons, shared by several zooids, through which waste water is expelled. It’s difficult to see in the photo, but the excurrent siphons are raised up above the level of the colony, so water that has already been filtered doesn’t get sucked in again. This is exactly the reason that human structures such as smokestacks and chimneys are tall.

Oh, and since you asked, Brenna did indeed find slugs! And she taught me some field characteristics to help me ID slugs that I find. We both got what we needed on our little jaunt to the harbor.

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Hanging on

Day 3 of wasting in Leptasterias

The saga continues. When I checked on my ailing stars yesterday I saw, as expected, that most of what I had called Leptasterias #1 (the pink star that had ripped itself into pieces the day before) had disintegrated into small piles of mush. There was no sign of life in any of the small fragments so I threw them away. The largest piece, consisting of two adjacent arms attached to what looks like most of the central disc, was still walking around so I kept it. Today I was surprised to see that it hasn’t died yet. In fact, it looks a little better, with both of the arms active and the central disc appearing to be somewhat more contracted and less sloppy.

Remnant of wasting Leptasterias star, 30 August 2015. © Allison J. Gong

Remnant of wasting Leptasterias star, 30 August 2015.
© Allison J. Gong

The two arms appear to be working together, rather than trying to walk away from each other. I think this is a good sign, although it’s too early tell how much longer this fragment of a star will survive.


The star I had designated Leptasterias #2, which had the very large lesion on Friday, had died and dissolved into a mass of amorphous tissue and skeletal ossicles when I looked at it yesterday.


On the other hand, Leptasterias #3, the larger of the two gray stars, seems to be holding its own, or at least not getting any worse. On Day 1 of the outbreak this star had a small fluffy lesion on its aboral surface. Today the wound appears to have grown a bit but its edges look a little cleaner:

Leptasterias star affected by wasting syndrome, 30 August 2015. © Allison J. Gong

Leptasterias star affected by wasting syndrome, 30 August 2015.
© Allison J. Gong

This star was particularly active this morning. I didn’t want to disturb it or give it any incentive to autotomize its arms, so I left it in its screened container to take pictures and video. It was zooming around and acting, for all intents and purposes, like a normal healthy star.

Fingers crossed that this one makes it!

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Whiskey Tango Foxtrot

Sometimes the only word that will do is a bad word. I generally try not to use a lot of bad language because on the occasions when I do swear I want my f-bombs to really mean something. Late this afternoon I was on my way out of the lab when I made a quick last trip through the wet lab just to make sure everybody would be okay for the night, when out of the corner of my eye I saw a few odd pink bits in one of my screened containers.

This container held three small six-armed stars of the genus Leptasterias. I had collected them earlier this summer with the goal of showing them to my students when we do the echinoderm diversity lab at the end of the semester. Stars in this genus are interesting because their normal arm number is six and they brood their babies instead of broadcasting gametes into the sea to meet, fertilize, and develop on their own. Plus, like all their echinoderm kin, they are pretty animals. Lastly, enamored as I am of oddballs and out-of-the-ordinary things, I am charmed by Leptasterias‘s six arms because most stars have only five.

So when I opened up the screened container and saw that one of my Leptasterias stars had torn itself into pieces, I let fly with a few f-bombs and other choice expletives. I removed the star pieces into a bowl for a better view.

Leptasterias star dismembered due to wasting syndrome, 28 August 2015. © Allison J. Gong

Leptasterias star dismembered due to wasting syndrome, 28 August 2015.
© Allison J. Gong

Seeing a star that had ripped its own arms off is every bit as horrifying when the star has six arms as when it has five. This act of self-mutilation had probably occurred today, as the star looked fine when I checked on it yesterday. All of the pieces were still alive and crawling around:

Actually, if you examined each of the pieces independently and didn’t know that it was only part of a greater whole, you’d think that they were entirely viable. I put these pieces aside in a separate bowl, although honestly I don’t know why. I’m almost certain they’ll be dead when I check on things at the lab tomorrow morning, and even if they aren’t they’ll be decomposing while still sort of alive, which is even worse. I must be a glutton for punishment.

For a while I held out a teensy glimmer of hope that the other two stars might be okay, but that didn’t last long. It took only a glance to see a big aboral lesion on the center of one of them:

Leptasterias star with large aboral lesion, 28 August 2015. © Allison J. Gong

Leptasterias star with large aboral lesion, 28 August 2015.
© Allison J. Gong

Examination under higher magnification shows just how deep and intrusive these lesions are. The body wall is entirely compromised, resulting in the exposure of internal organs to the outside environment.

Lesion on aboral surface of Leptasterias star, 28 August 2015. © Allison J. Gong

Large lesion on aboral surface of Leptasterias star, 28 August 2015.
© Allison J. Gong

It turns out that none of these Leptasterias is unaffected. The third star in my container has a small aboral lesion:

Small aboral lesion on Leptasterias, 28 August 2015. © Allison J. Gong

Small aboral lesion on Leptasterias star, 28 August 2015.
© Allison J. Gong

Whether or not this third individual will survive is up for grabs, but I wouldn’t bet on it. From my experience with wasting syndrome in Pisaster and Pycnopodia, the disorder progresses extremely rapidly once the animal starts showing signs of illness. And all of these animals appeared just fine yesterday. The small pink star is essentially dead already, it just hasn’t realized it yet. The gray star with the large lesion may very well be dead tomorrow, too. The star with the small lesion might still be alive tomorrow, and this is the only one for which I have a bit of hope for survival.

About a week ago the seawater temperature dropped to 16°C for a few days, but then started creeping back up; today it topped out at 19°C. Correlation is not causation, but I do wonder if another spike in the 19-20° range, on top of stress caused by the ongoing period of warm water, is the proverbial straw that broke the camel’s back. These poor stars have gone through hell lately, and there’s no indication that the water will cool off any time soon. I’d throw up my hands and ask, “What’s next?” but I have a sneaking suspicion that I’ll find out soon enough.

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A plug, and a caveat

Early next week (31 August – 2 September), PBS and the BBC are going to present a huge “live” media event. I say “live” because although the event will be aired in the evenings, all the preview footage I’ve seen has been shot in during daylight hours. Anyway, you can read all about it in the press release.

Big Blue Live, as it is called, is a collaboration among the Monterey Bay Aquarium, NOAA, and both media networks. I can guarantee that there will be some spectacular footage of wildlife within the Monterey Bay. You know, whales, dolphins, seals and sea lions, and perhaps the odd bird or two. This is the stuff of wildlife, the so-called charismatic megafauna, that have warm bodies and look at you with big eyes.

My concern, as a perennial fan of the overlooked and underappreciated, is that the whole media event will focus only on these large mammals (and maybe a bird and possibly even a fish), and neglect or give short shrift to the countless fascinating and ecologically crucial critters that form the lower trophic levels. In other words, the invertebrates. Not to mention the organisms that ultimately produce all of the food in the marine trophic system, the phytoplankton. I expect that there might be lip service paid to the phytoplankton, krill, and baitfish which are the reason that the whales and such come to Monterey Bay, but I will be pleasantly astonished if more than a few seconds of air time are devoted to them. Somehow it’s just not easy to make diatoms sexy to lay people, even those who say they love marine biology.

Thus, anticipating that my beloved invertebrates won’t get much mention, I’m going to post some of my favorite pictures of them here, as I photographed them in the field. And as you’re watching Big Blue Live, keep in mind that there’s more to (wild)life than charismatic megafauna.

Pisaster ochraceus in tidepool at Natural Bridges State Beach, 17 June 2014. © Allison J. Gong

Pisaster ochraceus in tidepool at Natural Bridges State Beach, 17 June 2014.
© Allison J. Gong

The vermetid snail Thylacodes squamigerus at Pistachio Beach, 18 January 2015. © Allison J. Gong

The vermetid snail Thylacodes squamigerus at Pistachio Beach, 18 January 2015.
© Allison J. Gong

Juvenile sea star at Davenport Landing, 19 January 2015. © Allison J. Gong

Juvenile sea star at Davenport Landing, 19 January 2015.
© Allison J. Gong

Octopus rubescens in a tidepool at Natural Bridges State Beach, 4 May 2015. © Allison J. Gong

Octopus rubescens in a tidepool at Natural Bridges State Beach, 4 May 2015.
© Allison J. Gong

Henricia sp. at Point Pinos, 9 May 2015. © Allison J. Gong

Henricia sp. at Point Pinos, 9 May 2015.
© Allison J. Gong

Hespererato vitellina, the appleseed erato snail, at Point Pinos, 9 May 2015. © Allison J. Gong

Appleseed erato snail (Hespererato vitellina), at Point Pinos, 9 May 2015.
© Allison J. Gong

Kelp crab (Pugettia producta) on the beach at Franklin Point, 31 July 2015. © Allison J. Gong

Kelp crab (Pugettia producta) on the beach at Franklin Point, 31 July 2015.
© Allison J. Gong

Mouth of Anthopleura sola at Natural Bridges State Beach, 6 April 2015. © Allison J. Gong

Mouth of Anthopleura sola at Natural Bridges State Beach, 6 April 2015.
© Allison J. Gong

The brittle star Ophiothrix spiculata at Franklin Point, 31 July 2015. © Allison J. Gong

The brittle star Ophiothrix spiculata at Franklin Point, 31 July 2015.
© Allison J. Gong

The anemone Anthopleura artemisia at Davenport Landing, 2 August 2015. © Allison J. Gong

The anemone Anthopleura artemisia at Davenport Landing, 2 August 2015.
© Allison J. Gong

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