UPDATE: you can now upload YOUR pictures of starfish wasting disease. They are being tracked at this website (iNaturalist)
Last week I reported on an unusually large die-off of the North Pacific sunflower star, Pycnopodia helianthoides (among other starfish species) in the waters of British Columbia. The story even got picked up by National Geographic!
This sparked some good academic discussion here which I can only hope will lead to some further insight into what is happening. One useful thing which came up was the mention of something that would be a good follow up to last weeks' report: Starfish Wasting Disease!
I have spoken of ciliate protist parasites in sea stars before but this is something different.
Details of the post today about Starfish wasting disease is based on this paper in the journal, Diseases of Aquatic Organisms from an article by Amanda Bates, Brett Hilton and Christopher Harley in 2009
Other information is from an account of starfish wasting disease in the Channel Islands by Ginny Eckert and colleagues. This paper is freely available here.
I should also mention that my friend and colleague Dr. Allison Gong has documented an outbreak of wasting disease in her water table at UC Santa Cruz. I've borrowed many of her pictures below. My thanks to her for allowing me to use them!
What is Starfish Wasting Disease?
Symptoms of the disease are relatively straightforward:
- White colored lesions appear and grow rapidly
- There is a loss of body pressure (i.e., turgor)
- Body disintegration and autotomy of arms, etc.
- and finally death...
|Fig. 2 from Bates' et al. 2009
The effects DO seem very similar to what happened with the Pycnopodia die-off
|fr. Jonathan Martin
Could it be a virus? A fungus? Some strange combination thereof?
Its also unclear if it is the SAME agent at work in EVERY case. Different species? Different strains? Different diseases?
The symptoms of the disease have been documented widely: on the west coast of North America. From British Columbia down to the Gulf of California. But also in the Mediterranean and the North Atlantic coast of North America.
Nothing yet from the Southern Hemisphere.. Australia, New Zealand, etc.
What Species Does It Affect?
Wasting disease appears to be pretty widespread across MANY starfish groups.
The symptoms of the disease have been observed as early as 1972 from the east coast of North America in the "common" starfish Asterias vulgaris (now called Asterias rubens, pic on the left)
In 1982, there was a mass die-off of Heliaster kubiniji in the Gulf of California, which was so severe that it led to local extinction in several areas where it had once been abundant. (Image of Asterias by "misenus1", Image of Heliaster by manzanita-pct)
Eckert's paper speculated that warmer waters in the Southern California region accompanied the onset of wasting disease in the species they studied.
Amanda Bates & her team study studied Pisaster ochraceus in British Columbia and studied several variables and how they affected the disease.
Indeed, temperature turns out to be a very important factor in the spread of starfish wasting disease!
The graph below shows that the prevalence of the disease in starfish under experimental conditions is significantly higher under warmer conditions. This was also reflected by observations in the wild as they saw higher incidence of disease in the summer (June) than in August.
|Figure 3 from Bates et al. 2009
- Wave action? (and thus more current and temperature circulation)
- Freshwater input? resulting in higher vulnerability? (starfish don't tolerate freshwater very easily) Sewage?