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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.

1

Although the last thing that any of us marine invertebrate biologists want to see again is a wasted sea star, the syndrome has once again been making its presence felt at the marine lab. It has been almost two years since I documented the initial outbreak, and while nobody is convinced that it has entirely run its course, most of us, myself included, had thought that perhaps the first wave had passed. Then, back in March of this year, I saw one of my stars doing this:

Bat star (Patiria miniata) showing severe symptoms of wasting syndrome, 16 March 2015. © Allison J. Gong
Bat star (Patiria miniata) showing severe symptoms of wasting syndrome, 16 March 2015.
© Allison J. Gong

Those large white blotches on the aboral surface are open wounds, or lesions, through which some of the animal's innards are protruding. The arm towards the top of the photo has also begun dissolving, literally wasting away into the environment. The lesions eat right through the epidermis, liberating the skeletal ossicles that lie underneath it; I've circled two of them on the right side of the photo and there are two more at the bottom.

The discovery of this wasting animal was alarming and for a while I held my breath whenever I check on stars at the lab, but after several weeks of not seeing any additional sick animals I relaxed my guard and concluded the incident was a one-off. So imagine my horror to walk in this morning and see this in one of my tables:

Oral surface of a wasting bat star (Patiria miniata), 17 July 2015. © Allison J. Gong
Oral surface of a wasting bat star (Patiria miniata), 17 July 2015.
© Allison J. Gong

Sea stars generally don't just lie on their aboral surfaces, and this animal was making no attempt to right itself. See how the margin between the arms is a little wavy? That isn't normal, either, and shows that the animal's ability to regulate its internal water content has been compromised. And while bat stars routinely scavenge by extruding their stomachs through the mouth and digesting whatever it comes into contact with, they don't leave the stomach hanging outside the body when they aren't feeding.

All of which gave me a bad feeling in the pit of my own stomach, which only got worse when I turned the animal over:

Bat star (Patiria miniata) with several small aboral lesions, 17 July 2015. © Allison J. Gong
Bat star (Patiria miniata) with several small aboral lesions, 17 July 2015.
© Allison J. Gong

The animal appears deflated and has small lesions all over its aboral surface. I was feeling a little deflated myself when I saw this. With stars it can be difficult to determine just how alive (or how dead) an individual is. This one didn't fall to pieces when I picked it up, which didn't exactly surprise me because Patiria is less prone to losing its arms via autotomy than the Pisaster species (ochre, short-spined, and jewel stars) and Pycnopodia helianthoides (sunflower star), in whom one of the symptoms of wasting syndrome is a violent ripping off of one's own arms. I suppose this makes the whole episode marginally less horrific than when I saw my Pisaster stars wasting, or maybe I've become jaded.

In any case, I had to decide what to do with this sick star. It was in a table with half a dozen other bat stars, so whatever it was exposed to or was itself exuding has already been spread to the others. I couldn't leave it there to rot in place, but neither did I want to throw it away if it was still somewhat alive. I turned the animal so it was oral-side-up again and left it alone to see what would happen. If it righted itself I'd assume it was more or less alive and isolate it in a quarantine tank; if it didn't, then all hope was lost and it could be tossed. When I was ready to leave the lab several hours later, it was in the exact same position. Verdict: dead.

So, why now? I've been thinking about this, and here's what I came up with. The densovirus that has been linked to sea star wasting syndrome is always around in the environment. Like other opportunistic pathogens it doesn't usually cause a problem until a host organism becomes stressed or compromised. For the past two years we've been aware of wasting events up and down the coast, which wiped out the most vulnerable individuals. Animals with resistance, however, were able to survive. The survivors may have been weakened, though, and the mild El Niño of 2014 and the much stronger one we have now in 2015 have resulted in water temperatures much higher than normal. I haven't plotted the data yet, but in June and July the water temperature has been hovering at 15-16°C, with jumps this week up to 18.5°C over the past couple of days. These warmer temperatures can be very stressful to animals, which may be just what the densovirus needed to "announce [its] presence with authority" (that's a quote from my favorite baseball movie, Bull Durham). Outbreaks of wasting syndrome are probably caused by a combination of factors: population density of the host animal, presence of the densovirus, overall health of the host, water temperature, water chemistry, and others I haven't thought of. We are certainly not close to a complete understanding of this phenomenon.

At this point I don't have many stars left in my collection. I hope I get to keep them.

Well, fame is all relative, right?

VICE magazine's May 2015 issue is focused on environmental crises of various kinds. One of the feature articles is on sea star wasting, which I've blogged about before, beginning in September 2013. The author of the VICE article, Nathaniel Rich, came out to the marine lab and interviewed me and some other folks back in February, and a photo crew came out to do a shoot in March.

Here's the article. Overall I think Nathaniel did a good job; this is one of the better lay person articles I've read about wasting. He was able to convey the concern we biologists have about wasting, and the effects it could have on the ecology of the intertidal and subtidal marine habitats, without being too alarmist.

There is one glaring mistake in the first part of the article, which I'm positive must be a misunderstanding of something that I may have said to him. Can you find it?

Until recently I hadn't closely observed what it looks like when a leather star (Dermasterias imbricata) succumbs to wasting syndrome. When I had the outbreak of plague in my table almost 18 months ago now, my only leather star was fine one day and decomposing the next, so I didn't get to see what actually happened as it was dying.

(Un)fortunately, one of the leather stars at the marine lab started wasting a bit more than two weeks ago, and this time I was able to catch it at the beginning. This animal wasn't in my care so I didn't check on it as frequently as I would if it had been living in one of my tables, but one of the aquarists pointed it out to me when it began getting sick.

The first symptom was a lesion on the aboral surface. I say "lesion" but it's more of an open wound.

Dermasterias imbricata with aboral lesion, 2 February 2015. ©Allison J. Gong
Dermasterias imbricata with aboral lesion, 2 February 2015.
© Allison J. Gong

You can see that the animal's insides are exposed to the external environment. In the photo above the whitish milky-looking stuff is gonad (I'm pretty sure this animal was a male) and the beige ribbon bits are pyloric caeca, essentially branches of the stomach that extend into the arms. What typically happens along with the development of lesions like this is an overall deflating of the star as the water vascular system and other coelomic systems become increasingly compromised, and the tendency for the animal to start tearing off its arms.

Which results in this, a week later:

Wasting Dermasterias imbricata, autotomizing its arm, 9 February 2015. ©Allison J. Gong
Wasting Dermasterias imbricata, autotomizing its arm, 9 February 2015.
© Allison J. Gong

This poor animal had torn its arm off, and continued to live for a while. I find it fascinating that the lack of a centralized nervous system means that this animal literally didn't know it was dead. It was finally declared officially dead two days later. Compared to how quickly wasting syndrome kills the forcipulates that I've seen (Pisaster, Pycnopodia, and Orthasterias), the leather stars take a long time to die--several days from start to finish, opposed to a matter of hours as I saw with my stars. The leathers didn't seem to be hit as hard by the first wave of the disease outbreak, either. Is Dermasterias somehow able to fight off the infection a bit longer? It would be interesting to know, wouldn't it?

At last, a publication on the causative agent for sea star wasting syndrome! Several co-authors have written a paper that was published in the Proceedings of the National Academy of Sciences (PNAS), in which the culprit was identified as a densovirus.

The Smithsonian wrote up a nice article summarizing the findings here.

While it remains to be seen why the virus caused such widespread disease this time, at least now researchers have something to focus their work on.

4

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

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

So what does this all mean?

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

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

5

Since my earlier posts on Pisaster wasting disease in the lab, I've been contacted by a couple of divers who have seen afflicted stars on their dives in Monterey Bay. They have both graciously given me permission to post their photos, which clearly demonstrate that Pisaster and other stars are being stricken subtidally as well as intertidally and in the lab.

This set of photos is from Ralph Wolf, taken on 11 October 2013 off of Pacific Grove, California.

This star, a Pisaster giganteus, looks healthy.  It has no dermal lesions, the body is plump and full, and the arms are lying flat and fully attached to the rock.

An apparently healthy Pisaster giganteus
Pisaster giganteus
©2013 Ralph Wolf

This P. giganteus, on the other hand, is doing the twisty arm thing that I saw in the lab. It seems to be the precursor to the star ripping its arms off. There's an orange Patiria miniata lurking in the background, just waiting for a chance to begin feasting on a not-quite-dead-yet sick star.

Pisaster giganteus ©2013 Ralph Wolf
Pisaster giganteus
©2013 Ralph Wolf

Here are some more extreme examples of the twisty arm thing in P. giganteus that have already resulted in at least one arm being autotomized.

Pisaster giganteus
©2013 Ralph Wolf
Pisaster giganteus
©2013 Ralph Wolf

And it wasn't just a few isolated Pisaster stars that were showing early signs of the disease. Here are three of them on the same rock, all twisting their arms to some degree.

Pisaster giganteus ©2013 Ralph Wolf
Pisaster giganteus
©2013 Ralph Wolf

Pisaster stars were not the only ones that Ralph saw stricken with the disease.  The sunflower stars, Pycnopodia helianthoides, were in even worse shape. This star has contorted itself into an almost recognizable shape and lost at least a few arms, one of which is visible at the top of the photo.

Pycnopodia helianthoides ©2013 Ralph Wolf
Pycnopodia helianthoides
©2013 Ralph Wolf

And take a look at this poor star. All that remains is the central disc and a single arm. Given that Pycnopodia normally has 20-25 arms, this animal has suffered a huge loss:

OLYMPUS DIGITAL CAMERA
Pycnopodia helianthoides
©2013 Ralph Wolf

And, of course, there were Pycnopodia arms crawling around by themselves. They literally don't know they're dead.

Pycnopodia helianthoides arm ©2013 Ralph Wolf
Pycnopodia helianthoides arm
©2013 Ralph Wolf
Pycnopodia helianthoides arm ©2013 Ralph Wolf
Pycnopodia helianthoides arm
©2013 Ralph Wolf
Pycnopodia helianthoides arm ©2013 Ralph Wolf
Pycnopodia helianthoides arm
©2013 Ralph Wolf

Ralph was able to find and photograph some apparently healthy small Pycnopodia stars.

Pycnopodia helianthoides ©2013 Ralph Wolf
Patiria miniata (left) and Pycnopodia helianthoides (right)
©2013 Ralph Wolf
Pycnopodia helianthoides ©2013 Ralph Wolf
Apparently healthy Pycnopodia helianthoides
©2013 Ralph Wolf
Pycnopodia helianthoides ©2013 Ralph Wolf
Apparently healthy Pycnopodia helianthoides
©2013 Ralph Wolf

The rainbow star, Orthasterias koehleri, was also getting in on the action. These are beautiful stars in bright reds and oranges:

Orthasterias koehleri ©2013 Ralph Wolf
Orthasterias koehleri (top) and Patiria miniata (bottom). Pisaster giganteus in background in lower right corner.
©2013 Ralph Wolf

But Orthasterias is also twisting and autotomizing arms:

Orthasterias koehleri ©2013 Ralph Wolf
Orthasterias koehleri
©2013 Ralph Wolf
Orthasterias koehleri arm ©2013 Ralph Wolf
Orthasterias koehleri arm
©2013 Ralph Wolf

So, for now the disease continues to exact its toll. At least this time it appears that Patiria miniata (bat stars) and Dermasterias imbricata (leather stars) are not being sickened, although we have had outbreaks of a very similar disease in the lab that affected these species. And the fact that sick stars are being seen in the field, both intertidally and subtidally, means that the disease I documented in the lab is not strictly a captivity-related phenomenon. I think what we are witnessing is regional--the first report I read about was in British Columbia--rather than local. Only time will tell.

2

Well, it looks like the end is indeed nigh. That last Pisaster, for whom I held out unreasonable hope for so long, seems to be on its way out. Today it has lost its last two arms, leaving a central disc attached to a single arm:

Remains of Pisaster ochraceus that has lost four arms. ©2013 Allison J. Gong
Remains of Pisaster ochraceus that has lost four arms.
© 2013 Allison J. Gong

As bad as it looks, it could be a lot worse. The other stars that disintegrated to this degree were essentially amorphous piles of goo, and this one is still somewhat intact. It also hasn't gone entirely mushy, so it is somehow maintaining its internal pressure. I'm going to keep it for another day and see how it looks tomorrow.

The other two arms, on the other hand (ha!), were a mess. When I got to the table this afternoon they were both semi-attached and semi-upside down behind one of the quarantine tanks. And they were very mushy; when I picked them up they just collapsed the way sea cucumbers do before they start firming up. Gross.

Autotomized arms of Pisaster ochraceus ©2013 Allison J. Gong
Autotomized arms of Pisaster ochraceus
© 2013 Allison J. Gong

This has to be the end, if only because I don't have any more Pisaster stars to die. Unless the Patiria and Dermasterias stars that I quarantined start getting sick, the outbreak in my seawater table is over, simply because there are no more victims to be infected. From a pathogen's perspective a 100% mortality rate is a bad thing--if all hosts of a population are killed then the pathogen will die with them. However, my table is connected by water supply to other tables and labs, and I have a sneaking suspicion that the pathogen is out there in Monterey Bay (the source of our seawater), in which case there's nothing I can do about it. Actually, I can do something. I can cross my fingers and hope for the best.

 

2

Against all odds, my last Pisaster star is (literally) hanging in there. It hasn't lost any more arms in the past 24 hours, and by the standards of the past two weeks that's a rousing success.

Pisaster star that lost two arms yesterday but no more since. ©2013 Allison J. Gong
Pisaster ochraceus star that lost two arms yesterday but no more since.
© 2013 Allison J. Gong

And it hasn't lost the turgor pressure of its body, so it isn't as limp as the others were before they died. I didn't want to mess with the animal too much, but it was pretty strongly attached to the table, indicating that the water vascular system hasn't lost all of its integrity. If that inter-radial area towards the top of the photograph is one of the areas where an arm was autotomized, the wound has healed surprisingly well. I will have to see what happens tomorrow.

On the other hand, the disease has spread to the lab next door, where a Pisaster giganteus started melting away two days ago. It was discovered with a small P. ochraceus feeding on the sick star, and the two stars have been since isolated. Today the P. giganteus looked horrifying:

Pisaster giganteus star melting from wasting disease. ©2013 Allison J. Gong
Pisaster giganteus star melting from wasting disease.
© 2013 Allison J. Gong

This is a really sick animal. There's a large wound on the bottom edge where an arm had been autotomized; it looks like the wound hasn't started healing at all. One of the remaining arms has twisted so that it is upside-down with the ambulacral groove--where the tube feet are visible--is facing upwards; that arm is probably going to be cast off soon. The beige-ish fluffy bits in the top of the photo are pieces of gut and water vascular system that are protruding through wounds in the body wall. I would be very surprised if this poor animal is still alive tomorrow. So far, the one that was feeding on this creature doesn't look diseased, so perhaps it will escape the pestilence.

19

The last of my Pisaster ochraceus stars waited until today, three whole days after all of its conspecifics had died, to start ripping itself into pieces. This is the sight that greeted me when I checked on my animals this morning:

My last Pisaster and its autotomized arm ©2013 Allison J. Gong
My last Pisaster and its autotomized arm
© 2013 Allison J. Gong

I spent some time examining the severed arm because it is freakishly fascinating to watch autotomized parts continue on as though they were still attached to the main body. They literally don't know that they're dead.  I've seen almost completely eviscerated sea urchins lumber around a seawater table on about 10 tube feet for days before finally giving up the ghost. This arm remained very active for quite a while--at least an hour--before I gave up and threw it away.

While I had this severed arm in a bowl under the dissecting scope I thought I'd take a few photos of the surface. Beautifully complex animals, sea stars are, when you look at them up close.

View through dissecting microscope of aboral surface of arm of Pisaster ochraceus. ©2013 Allison J. Gong
View through dissecting microscope of aboral surface of arm of Pisaster ochraceus.
© 2013 Allison J. Gong
Oral surface of arm of Pisaster ochraceus, showing tube feet. ©2013 Allison J. Gong
Oral surface of arm of Pisaster ochraceus, showing tube feet.
© 2013 Allison J. Gong

Meanwhile, the remaining 4/5 of the star continued to walk around the table. It ended up behind one of the quarantine tanks in which I had sequestered the bat stars, where over the course of the next couple of hours it dropped another arm. Because of its location I wasn't able to get a decent photo of it, but here is a shot of the wound from the first autotomization:

Wound caused by autotomy of an arm in Pisaster ochraceus. ©2013 Allison J. Gong
Wound caused by autotomy of an arm in Pisaster ochraceus.
©2013 Allison J. Gong

And I'm not the only one at the lab dealing with this disease outbreak. The lab next door is losing a couple of stars, and the Seymour Center lost one of their Pycnopodia helianthoides (sunflower star) yesterday. And, I heard second-hand that a student in the Santa Cruz area saw some dying stars on a dive in the past few days. What happened in my seawater table over the past few weeks may be just the beginning of something really, really bad.

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