Wasting Syndrome and Starfish Die-Off
By Roberta Attanasio
Up and down the U.S. and Canada Pacific coastlines, starfish are disappearing, dying by the millions of a mysterious disease that makes them “turn into goo.”
The disease — starfish wasting syndrome — initially causes white lesions that lead to death of body tissue. Eventually, the arms twist and tear off — and they do not regenerate (healthy starfish may shed their arms, but then new ones are formed in a relatively short time). At the end, the entire body of the wasting starfish disintegrates. The wasting syndrome affects about a dozen starfish species, but has been noticed mostly in sunflower starfish (Pycnopodia helianthoides) and ochre stars (Pisaster ochraceus).
Starfish die-offs have been observed along the California coast in 1983 and 1997 — however, this year, the die-off is occurring at an unprecedented rate. No cause has been identified, but speculations abound.
Claims that Fukushima radiation could be implicated in the die-off have been disproved by Chris Mah (a researcher at the Smithsonian National Museum of Natural History and one of the world’s leading experts on starfish), on the basis of three major considerations — the syndrome pre-dates Fukushima by 3 to 15 years, it occurs on both East and West coasts, and it does not seem to affect any other marine life in these regions.
Gary Wessel, a professor at Brown University, told NBC News that a combination of stressors, both pathogenic (a new bacterium or virus) and environmental (a change in ocean temperature) may be responsible for the syndrome. He also thinks that the disease is unlikely to affect humans or other larger marine life.
An accepted explanation is that an infectious microbe (a virus, bacterium, fungus or other) could impair the starfish immune system, making them susceptible to secondary bacterial infections that ultimately cause wasting.
Back in November, Pete Raimondi, a professor at the University of California, Santa Cruz, told the Los Angeles Times “Imagine a wound on your finger that you never treated. The bacteria would continue to build up and just eat away the flesh until it fell off. That’s how this disease goes.”
Global warming is an important factor in the occurrence of disease outbreaks of infectious microbes that affect marine life. Increasing temperatures favor the growth of these microbes and allow their spread across an extended geographical range. In addition, increasing temperatures induce heat stress, which adversely affects the defense/immune mechanisms. Indeed, the spread and progression of the wasting syndrome — in starfish and other species — are temperature-sensitive and increase at warmer temperatures.
The starfish is a voracious predator and a keystone species — a species that plays a critical role in maintaining the structure of an ecological community. Starfish eat snails, sea urchins, mussels and clams, and are essential to maintain kelp forests, one of the most productive ecosystems on our planet. Southern sea otters, also a keystone species in the kelp forest ecosystem, have been decimated by an ongoing epidemic of toxoplasmosis. Thus, the loss of starfish could have far-reaching consequences for the marine communities of North America.
Dropping a bottle of soda in the ocean may not seem like a big deal, but the effects of such a minor act can have big effects, like the starfish wasting syndrome. When unwanted things lands in places were they are not needed, they can cause harm. Bacteria and viruses can build in that bottle of soda and with the increasing temperatures of the ocean thanks to pollution, these microbes just grow and multiply in numbers. They start attacking starfish and cause them to disintegrate slowly and end up as “goo.” On the surface, the bottle didn’t seem like it was big deal, but white lies such as this is what allows pollution to become so abundant that it is causing adverse effects like global warming and starfish wasting syndrome. Yes, the damage might be done, so to say, but actions should be taken to reduce the level of pollution in the oceans and the temperature of the waters. Maybe such steps would reduce the number of starfish dying from this unknown illness and prevent future die off of some other species.
Although I do agree that the pollution that humans cause to marine life is detrimental, has any research shown this is the cause of wasting syndrome? It is a plausibile hypothesis no doubt, but I think there could be many other causes than pollution. Either way, the pollution we are creating is clearly having an effect on marine life. Another theory could be that these pathogens, toxins, etc that we release could be weakening the immune system, making the individual more susceptible to disease, such as wasting syndrome.
I agree that there could be many causes for this wasting syndrome however; we have to agree that pollution is a big cause and its effecting marine life in many ways. The article, Marine Pollution, is a great article because it talks about how human pollution has drastically increased in the past three centuries and hurting marine life. As humans, it is our responsibility to show care and love towards our planet and not hurt other creatures that are a big part of our ecosystem. If we can take control of reducing pollution at our level, we should take every approach to do so.
“The Ocean.” National Geographic. National Geographic Society. Web. 13 Feb. 2014.
I wonder, instead of a microbe impairing the immune system upon infection, what if it leads to an autoimmune disease? It could be possible that the immune system of the starfish starts attacking the cells of the the starfish so it does not have the opportunity to regenerate healthy cells. A microbe might have antigens that are similar enough to the host antigens that it could illicit an autoimmune response, or inflammation might introduce auto reactive lymphocytes to the site of infection before they can be properly anergized and thus cause an autoimmune reaction.
That is a great point; I did not think of autoimmunity as a cause. However, I’m wondering, can autoimmunity start targeting several starfish at the same time and at a drastic rate?
You are wondering if so many starfish start dying because of autoimmune diseases suddenly and very rapidly because autoimmunity is generally very infrequent? I agree, normally that is the case, but what if the microbe has some mechanism by which it induces autoimmunity in the host? Maybe it has antigens that are very similar to the host antigens and the immune response starts attacking the host by accident?
It is devastating that these wonderful creatures are dying off in such a horrible way. The most logical explanation for their wasting away seems to be one offered in the article, and also hinted by a couple of the comments before me, that there is an opportunistic microbe involved. Something hindered their immune system and allowed for this microbe to take over. Now, what IS that something, and why does it affect some species of starfish more than others? If we can compare the species (or a group within a species) that are unaffected to those that are, we may be able to figure out the origin of the problem. For example, maybe the ones that are affected by this illness are ones that feed at a certain location and they ate something that led to the weakening of their immune systems (whether it was due to another microbe, toxin, etc.).
That is a very interesting point. For the sake of argument we say that it was an opportunistic infection, the weakening of the immune system that allowed the opportunistic infection to occur could very well have an environmental origin. The article pointed out that starfish are predators. Maybe the species of starfish that is getting sick eats a specific species of clams that has adapted, and is excreting a toxin that the starfish is consuming along with the clam that is impairing the starfish immune system?
Mr. Haqqani made an interesting point about the possibility of the toxin being transmitted from another organism into the starfish. Even though the source may be unknown, in reference to the Sunflower sea star, they are detritivores. These family of sea stars are efficient hunters but specifically feed on dying squid. Any dying animal can increase the development of viral or bacterial infections. The sea star life span is already about 3-5 years. But it is amazing that what may pose as a nutrient source may also be detrimental to their lives and diminish that life span.
I find it interesting that the starfish are unable to regenerate their tissue. It is possible that stem cells, the cell cycle, and growth factors involved in regeneration are potential targets (direct/indirect) of the pathogen. Alternatively, it is possible that there is an uncontrolled inflammatory response contributing to the starfish wasting syndrome. As we learned in class, the site of infection is a harsh environment in the body. There is cellular debris from dying cells (lysis or apoptosis), as well as many cells of the immune system that are releasing powerful chemicals (cytokines/chemokines) at the site of infection. Though localized, the harsh conditions caused by an inflammatory response are also harmful to healthy cells near the site of infection. A balance that maximizes resolution of an infection and minimizes secondary effects to healthy tissue is necessary for the immune system to stay in check. If uncontrolled, inflammation might be harming the body of the starfish so much so that it is unable to regenerate its tissue.
This reminds me of the Chytrid disease affecting the frog population. Both diseases (the Chytrid and the starfish wasting syndrome) change the composition of the organism’s outer layer causing a detrimental effect resulting in death. There are several reasons why I think the Chytrid disease is very similar to the starfish wasting syndrome. One, the fungi can live in an amensalism relationship with the starfish. Two, fungi form spores, some are that can be easily dispersed, especially in an aquatic environments. Lastly, similarly to the Chytrid disease where some amphibians (like the American Bullfrogs) are resistant, some starfish (like the sunflower starfish) are resistant to the disease. I agree with the accepted explanation in the article, “that an infectious microbe (a virus, bacterium, fungus or other) could impair the starfish immune system, making them susceptible to secondary bacterial infections that ultimately cause wasting”. The explanation doesn’t required complicated schematic theories and it has happened to many organisms before.
It is sad to see yet another keystone species of the marine life being detrimentally affected by an unknown pathogen. It is interesting that it appears to only be on the coasts of America. I’m also interested in the fact that although the number of species it affects is rising, there are still some types of starfish unaffected. Scientists could examine each and look for differences. Could these other starfish be equipped with a certain gene that protects them from this pathogen? Star fish are often capable of regenerating arms, but in this case there is no regeneration. This leads me to wonder could it be a virus interrupting the genes therefore blocking transcription and or translation for the regeneration. It appears that no other echinoderms outside of starfish are experiencing this wasting syndrome. It could also be possible that these starfish are getting infected from what they eat (snails, barnacles, etc) and this pathogen could be just rising up the food chain, similar to toxoplasma in otters. This article,”Northwest Starfish Experiments Give Scientists Clues To Mysterious Mass Die-offs” (http://ijpr.org/post/northwest-starfish-experiments-give-scientists-clues-mysterious-mass-die-offs) also discusses these points and reminds us of the speed of transmission between these animals is fast, which gives more pressure on scientists to find a treatment.
Although devastating that another keystone species is experiencing a die-off due to microbial infections, it’s interesting that this seems to be happening more often in aquatic environments. This is most likely due to the fact that aquatic environments contain millions of microbes, many of which are capable of causing diseases. In regards to starfish wasting syndrome, I wonder if scientists have considered the possibility that the microbe responsible is not a new species, but rather an old species that has acquired pathogenic genes. There have been plenty of evidence that horizontal gene transfer occurs at high rates in oceans, and this transferring of genes may be the cause behind the starfish die-off. What if it’s a bacterial species that normally doesn’t cause disease in the starfish population, but after obtaining new genes from another species, it’s now capable of killing the starfish? It seems likely given the great mixing that occurs in oceans. Since bacteria and viruses are found throughout the water column, it’s not hard to imagine genes being easily transferred between species. However, gene transfers may not be the only reason behind the disease affecting the starfish population. It’s also possible that it’s a combination of genes and environmental changes. For example, a change in ocean temperature can increase the pathogenicity of certain genes, making it more likely to negatively impact other animals. Regardless of how starfish wasting syndrome is caused, I hope more research can go into providing a solution for the species that are infected.
So according to the article, there are two types of microbes that are involved in the starfish wasting syndrome. The one that directly causes the disease can be seen as an opportunistic microbe since it only acts on starfishes that are already infected by a previous different type of microbe. This remind me of HIV where the virus indirectly clears the way for opportunistic infections to come and kill the patients. However, in the case of starfish wasting syndrome, we are still uncertain about what type of microbes they are and how they work together in order to create this lethal disease. The first microbe might impair the starfish immune system like in the case of HIV so that the second one can come and “eat” the animal. Another hypothesis would be the first microbe produces a new metabolite due to the increase in temperature and this metabolite might be used by the second microbe to inhibit the regeneration of starfish. This disease is a real challenge for us since the knowledge we know about the microbes involved is very limited.
This is another example of how humans are negatively impacting the world we live in. While the disease seems to be somewhat naturally occurring, the impact that people have on the marine ecosystem is speeding up the spread of the disease and severity. Scientists should work on discovering what pathogen is causing the disease and see if there is anything they could do to offset the effects. As far as global warming goes, there is nothing we can really do now. We can stop polluting the ocean but that will not stop the damage that is already done. Unfortunately, more and more marine animals are dying as a result of new viruses being discovered. With the ocean temperature rising, I feel more disease will be discovered in the near future. I have recently learned about three new diseases affecting marine life since taking my Immunology of Infectious Diseases class; and I’m sure there are many more out there that have either not caught the attention of scientists or haven’t been released to the public. Two of the three diseases have affected keystone species like the article states. This is an extremely important fact to mention because if you kill off a keystone species, you completely change an ecosystem and there is a good chance that it is not going to benefit us, humans. The sad thing is that even though we may know about a disease affecting marine life, but until it directly hits home nothing will be done. Hopefully, someone will take the disease that affect our oceans seriously and do something about it before it’s too late.