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.
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.
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:
And, of course, there were Pycnopodia arms crawling around by themselves. They literally don’t know they’re dead.
Ralph was able to find and photograph some apparently healthy small Pycnopodia stars.
The rainbow star, Orthasterias koehleri, was also getting in on the action. These are beautiful stars in bright reds and oranges:
But Orthasterias is also twisting and autotomizing arms:
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.
5 thoughts on “Wasting disease in subtidal stars”
Hello. I have been following the news about this disintegration disease for some time and I have to ask you one thing.
Some starfish are able to regenerate their entire body from single limb, sometimes even from a fragment. My question is: isn’t it possible that what we are seeing is not a disease but actually mass reproduction phenomena?
Have anyone tried to observe these autotomized arms for longer period of time, you know to see if they are not regenerating?
You yourself said that they keep moving on their own so maybe some (not all probably) manage to regenerate into new star.
Since I’m not anywhere near the region involved nor do I have access to lab with the species required I can not test this myself obviously. There is also a possibility of sea acidification being the source of this phenomena however starfishes are relatively resistant to this problem http://www.pnas.org/content/106/23/9316
Also you could look for this factor http://www.biolbull.org/content/176/2/169.full.pdf+html in water samples it was found to cause mass loss of arms.
Some people think that radiation might be the cause however that seems very improbable to me for three reasons number one being the fact that radiation levels in seawater on western coast of US are so low that they are for all intents and purposes harmless and number two: much more radiation was released during nuclear bomb tests during last century than from Fukushima and number three if this was indeed caused by Fukushima radiation than it would be detected not only in US but also in Japan or China.
Thank you for bringing up some interesting points, George. I’ll address them based on my experiences with this particular disease outbreak.
AUTOTOMY AS A REPRODUCTIVE PROCESS: There certainly are stars that routinely autotomize their arms and grow new individuals that way. At least some members of the genus Linckia reproduce this way, and it is not uncommon to see stars regrowing missing arms and single arms growing missing bodies. The latter are often referred to as “comets” because, well, that’s what they look like.
However, I’ve been around the temperate Pisaster species for decades now, and while I have indeed seen them regenerate arms lost due to injury, I’ve never seen the cast-off arm do anything other than slowly die over a period of days. Nor have I seen any reports of autotomized Pisaster arms going on to renegerate entire stars. I think the more likely fate of autotomized Pisaster arms is to be eaten by some scavenger.
Plus, at least in my seawater table where I observed wasting disease, the lost arms very quickly turned into a pile of mush, losing their structural integrity within hours instead of days. They disintegrated so quickly that they wouldn’t have had any time to begin healing, much less regenerating. The central discs of the stars might have survived a bit longer than the severed arms, but they too were dead the next day.
AUTOTOMY AS A RESPONSE TO ACIDIFICATION: As you mentioned from the study you cited, Pisaster ochraceus was experimentally shown to have an increased growth rate when subjected to elevated water temperature and CO2 levels. But as P. ochraceus was the first species to exhibit signs of wasting disease in my table, and we had indeed experienced slightly elevated water temperatures for the previous several weeks, it doesn’t look as though higher temperature was good for these stars. In fact, it may have been a stressor that weakened the stars’ normal ability to resist disease, making them susceptible to the pathogen that causes wasting disease.
AUTOTOMY DUE TO CHEMICAL FACTORS: I remember hearing about Autotomy Promotion Factor (APF) when I was first learning about invertebrates. Pycnopodia helianthoides, the star from which APF was first characterized, does indeed lose arms quite readily. It can be very unnerving to witness. And it does seem to be the case that, at least in captivity, when one P. helianthoides starts dropping arms it doesn’t take long for others in the same tank to join in on the fun. And while I don’t have any Pycnopodia in my collection at the marine lab, two very large stars in a different building died of wasting disease shortly after my Pisasters began dying.
Pisaster, however, seems to be a more robust creature, at least in terms of holding onto its arms. A quick and by no means exhaustive search did not turn up anything about Pisaster’s response to APF. It would be interesting to know if anyone has been able to detect APF in seawater.
Lastly, thank you for your reasoned thinking about radiation.
Greetings from Trinidad, Humboldt Co., CA
Sorry to say from last year (2013) to this, it has gone from sick star fish to no starfish, in the observable intertidal zone in Trinidad Harbor and surroundings, with the exception of one lonely bat star observed in August of 2014.
I observed something I hadn’t seen previously on the Oregon or California coast, in 2012. It was a group of probably 100 starfish in a large circular shallow concave area of rock on the side of Trinidad head that is facing the harbor. They were up above the ocean at the intertidal zone. Perhaps that’s normal, but I’ve been actively observing intertidal areas since 1967 and had not seen that.
Thanks for sharing your observations, Suzanne. Would you mind if I followed up with a few questions?
1. Do you know which species of stars you saw that were sick last year and absent this year?
2. Did you happen to see any new recruits, juveniles in the 1-cm size range?
3. Did you happen to take a picture of the stars you saw in the concavity? I wonder what species they were.
Definitely your garden variety Pisaster ochraceus on both questions 1 and 3. I have seen what i thought were returns coming and going over the recent years. The population is still quite depleted and the tide pools look empty.
They are around but you have to look.
So not really on question 2.