This past Tuesday and Wednesday afternoon I took my marine biology students to the rocky intertidal at Natural Bridges State Beach. We completely lucked out with the weather; the storm system that brought some of the rain that we desperately need had cleared out, leaving calm, clear seas and little wind. Perfect weather for taking students out in the field, in fact.
First of all, we didn’t see any stars. Not that I was looking for them, particularly, but I was keeping an eye out for them and at this time last year I would have seen many Pisaster ochraceus hanging out in the pools and on the rocks. Here are a couple of pictures I took at Natural Bridges in years past:
The stars, when present, are prominent residents of the mid-intertidal zone, where they feed on mussels. But now, alas, there don’t seem to be any. They WILL come back, and it will be interesting to monitor their population recovery.
I enjoy taking students in the field because many of them have never been there before, and it’s always fun looking at a familiar scene with fresh eyes. When everything is new, it is very easy to be excited and enthusiastic, which these students are.
We saw, among other things:
Fish! The fish on the right was about 15 cm long. I think it’s a woolly sculpin (Clinocottus analis), but IDing sculpins in the field is pretty tricky.This fish was much smaller, only about 10 cm long. It could be a fluffy sculpin (Oligocottussnyderi), or it could be a smaller woolly.This is an encrusting sponge, Haliclona sp. I’ve seen it in shades of rosy pink, too. The large holes are oscula, the sponge’s excurrent openings. And that’s a big gooseneck barnacle (Pollicipespolymerus) hanging down from the top of the picture.An assortment of intertidal critters sharing space on a rock. How many chitons can you spot? How many barnacles? How many limpets?This is one of my favorite intertidal animals, the owl limpet (Lottiagigantea). These large limpets are farmers. They keep an area clear of settlers by grazing at high tide. You can see the marks left by this individual’s radula. The limpets also manage their farms, letting the algal film grow on one section while feeding on another.I love macro shots like this! The green tufty stuff is Cladophoracolumbiana, a filamentous green alga. Isn’t it a vibrant green color? To give you an idea of how fine the Cladophora filaments are, that snail in the background is about the size of a quarter.And last, a gratuitous anemone shot. Ahhh, Anthopleuraxanthogrammica, what a photogenic creature!
Yesterday I heard (or, more precisely, was reminded) that the quinine molecule fluoresces. Fluorescence is what happens when a molecule absorbs electromagnetic radiation–either in the visible light range or elsewhere in the spectrum–and emits light at a different wavelength. Lots of molecules fluoresce. Chlorophyll, for example, is the green molecule that captures the light photons that power the process of photosynthesis. If you shine light at a wavelength of 425 nm (violet) at a tube of chlorophyll, it will fluoresce, or emit light at 680 nm (red).
Here’s a DIY video guide to demonstrate the fluorescence of chlorophyll in the comfort of your own home:
So back to the fizzy beverages. I sing in a choir that has a long tradition of gathering after rehearsals and drinking gin-and-tonics (G&Ts). Tonic water contains quinine, which imparts fizziness and a certain bitterness to the drink. Having re-learned about the fluorescence of quinine, I thought it would be fun to watch the tonic and gin mix under a UV light. We needed a dark place for this experiment, hence the bathroom, the most convenient room that we could completely darken.
Turns out it worked amazingly well. Tonic water is entirely clear under white light, which contains all wavelengths of the visible spectrum; it looks like any other unflavored fizzy water. But under the UV light it glows with a kind of unearthly blue hue:
The quinine in tonic water fluoresces under UV light
But the real fun is in watching the tonic and gin mix in the glass. We make G&Ts this way: Put a few ice cubes in the glass, squeeze in a bit of lime, pour in two fingers’ of gin, then top off with tonic water. So we did everything but pour in the tonic water, then ventured into the bathroom with the UV light, where I recorded this:
“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.”
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.
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.
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 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.
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:
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.
Last Friday morning I was at the marine lab doing my usual feeding and cleaning stuff, and everything was fine. I was back at the lab Friday afternoon to return some animals that we had borrowed for one of the classes I’m teaching, and as soon as I got out of the car I knew something was wrong. I could smell it. Plankton bloom.
When I opened the door to one of the wet labs, it felt like walking into a wall of stench. It is a peculiar smell of excessive fecundity, which we occasionally see at the lab this time of year, due to a rapid population increase, or “bloom,” of one or a few phytoplankton species. I’m not sure if the smell is actually bad or if it just seems bad because of all the negative things I associate with it. Negative things such as: Sludge accumulating and decomposing on any horizontal surface in a table, including the surfaces of animals; said animals being fouled and dying because their respiratory surfaces are gunked up; seeing water straight from the tap coming in brown.
But whenever we get a nasty bloom like this, I am always curious about which critter it actually is. Back in the summer of 2010 there was a phytoplankton bloom in Santa Cruz that was at least partially caused by a dinoflagellate in the genus Alexandrium, some of which are known to produce toxins that work their way up the food chain and cause paralytic shellfish poisoning in people.
I took a sample from some build-up from this current bloom and looked at cells under the microscope (fun!). I was able to identify a couple of dinoflagellates right off the bat.
This is Ceratium. I saw a lot of cells that look like these:
Various species of Ceratium are present in plankton tows most of the year and as far as I know are pretty innocuous.
I also saw lots of these cells, too. This is Prorocentrum, a dinoflagellate that is pretty easy to recognize because of the little spine at one end of the cell. I don’t think these guys are toxic, either.
Lastly, there were a lot of these cells. I wasn’t able to get a very good look at them and don’t know for sure who they are, but they may be a species of Cochlodinium polykrikoides. I saw single cells and chains of two cells. C. polykrikoides is not nearly as harmless as the other two algae I saw. It has been responsible for fish kills in Asia.
On my way out of the marine lab yesterday I stopped by the overlook to see what the surf looked like. I could see that the water was discolored with a brownish tinge. Look at the water as it recedes from the rocky bench. It would normally be white, but here it is kind of a dirty gray-brown color.
The good news is that today, Monday, the bloom seems to have abated quite a bit. I cleaned all of my tables and tanks on Saturday (extremely gross) and Sunday (not nearly as gross) and this morning there wasn’t very much sludge at all. And the smell was nothing like it had been on Friday afternoon. So maybe we’re getting a reprieve and won’t have to deal with weeks and weeks of this stuff. That would be nice. My poor animals need a break from environmental conditions that are trying to kill them.
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:
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.
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.
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.
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:
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.
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:
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.
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:
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.
As of today, I am cautiously optimistic that the Pisasterwasting disease I’ve been dealing with for the past couple of weeks has run its course. There has been quite a cost, however, as a mortality rate of 90% leaves me with one lonely star remaining.
This lone survivor reminds me of Brother John Clyn, a Franciscan monk and chronicler in Ireland who recorded the deaths of his fellow brothers during the Black Death in the 14th century and may have been the only inhabitant of his monastery not to die of the plague. It remains to be seen whether or not my star eventually succumbs and starts wasting away. But given how quickly all the other Pisasters were affected and killed, I think it’s a good sign that this individual isn’t sick already.
In the meantime, the quarantined Patiria miniata (bat stars) and Dermasterias imbricata (leather star) remain apparently unaffected. Keep your fingers crossed!
And I don’t mean plague as in “too many stars to know what to do with,” but as in “disastrous sickness that you don’t want to catch.” Some of the stars in my seawater table have been succumbing to some awful disease lately. A week ago today I noticed that many stars had been busy cannibalizing one of their compadres. Sometimes this just happens, and it doesn’t necessarily indicate that things are about to go south. But when I looked more closely I noticed that the victim, instead of just being eaten, had autotomized its arms. Autotomy occurs in most sea stars and other invertebrates, and in fact is used as a method of clonal replication in some stars and many cnidarians. The species of star that is being affected by this plague (Pisaster ochraceus, the common ochre star) isn’t one that readily autotomizes except in response to some external stress, such as a predator pulling on an arm.
So something was going on in this table. On Monday (Labor Day) I popped in for a quick check and although nobody had lost any arms I couldn’t be absolutely sure that everything was okay. Some of the Pisasters were a little squishy and had arms that were a little twisted. On Tuesday morning there was no autotomy but in the afternoon a star had lost an arm, greatly disturbing the student lab assistant who discovered it. On Wednesday the table looked like an asteroid battlefield:
Many of the other Pisasters were also showing signs of sickness: curly arms (visible in the yellow star in the lower right corner of the photo above. Another ominous sign is that some of the apparently sickly stars were kind of squishy, indicating that the water vascular systems were somehow compromised.
Severed arms littered the table. The autotomized arms retain mobility for quite a while after being cast off–they literally don’t know that they’re dead.
After removing the corpses and cleaning the table as best I could I was able to take a closer look at the survivors. I noticed that most of the remaining Pisaster stars had twisty or crossed arms, and some showed pretty severe stretching in the interambulacral area (“armpit” between adjacent rays), which I think is the first stage of autotomy.
Unfortunately, this disease also affects other species. My Orthasterias koehleri (rainbow star) decided to join the fun. When I arrived Wednesday morning it was intact. It dropped an arm. I went away for about 40 minutes to take care of tasks in a different building, and when I returned it had lost two more arms:
Alas, my one and only Orthasterias succumbed later in the day and was dead on Thursday. Interestingly, the disease does not seem to affect either Patiria miniata (bat stars) or Dermasterias imbricata (leather stars). In fact, the Patiria have been eating pretty well over the past week, scavenging on the carcasses of the plague victims. I don’t know if eating the diseased tissue will cause problems later on.
On Friday I lost two more Pisasters and isolated the Patiria and Dermasterias into tanks. A colleague of mine calls this the Molokai treatment, and I probably should have done it sooner, but I figured that at this point all the stars in the table were exposed to whatever pathogen is causing this disease so at that point why bother? However, I will need to sequester the healthy stars in order to disinfect the table once the disease has run its course, so into tanks they went.
After checking on the stars Saturday morning I am cautiously optimistic that the plague may have run its course. One more Pisaster, that was looking sickly the day before, had died, but my last two appeared healthy. Their arms were not curly, I didn’t see any interambulacral stretching, and they felt nice and hard when I poked at them. All of these are good signs, but I will continue to keep close watch on them. If they make it to Monday we just might be out of the woods.
As of today, one week after I noticed the first severe symptoms, I have lost 80% of my Pisaster collection. To put that in to context, this mortality rate is every bit as bad as some villages that were virtually wiped out by the medieval Black Death.
