Horseshoe Crabs

This picture was taken from the following website:
http://www-tc.pbs.org/wnet/nature/files/2008/06/590_crash_blood.jpg

This past Sunday, October 17, 2010, I watched a Nature documentary on WETA's PBS from 6-7 pm called "Crash: A Tale of Two Species." This program was interesting to me because it directly addressed my interest in biomedical advantages and using animals to our (the human) advantage. I feel like animals have a lot of unknown benefits, and they are able to survive in much harsher climates, yet for some reason, humans have not exhausted this resource. The dilemma comes when these animals are potentially harmed for our use. I struggle with this in the fact humans should not cause harm to animals, while I see no harm in using them to our benefit. After all, with as many dysfunctions as humans have, we could use all the help we can get. The problem, however, is that there is often a fine line that comes between those two areas.

This documentary described the function of the horseshoe crab in biomedical advantages such as drug testing and treating burns, while it also serves to be part of the red knot's diet through the source of its eggs. Basically, horseshoe crabs have a compound in their blood called LAL that clots to viruses and bacteria by binding to it. This substance is a natural compound in the crab that helps it fight off the many infections of the ocean environment. LAL is harvested, and is now required to test bacterial contamination by the FDA in pacemakers, IV solutions, and any other device implanted inside the human body. This spiked my interest because of how the LAL is harvested. The horseshoe crabs are harvested and bled. About one third of their blood is harvested and used to test human devices. After being "bled," the crabs are released into their natural environment, where they supposedly regain their blood volume in a week. LAL manufacturers claim that there is no long-term injury to the animals, and animals are not killed to harvest their blood, which accounts for a wealthy $15,000 for every quart harvested. The process brings concerns, however, because recent studies have found that about 10-15% of the crabs do not survive the bleeding procedure, while the LAL manufacturers claim that less than 3% of the crabs are lost to mortality. It has also been proposed that it takes a few months, as opposed to just 1 week, for the crabs to regain their original amount of blood cells. This procedure could take a bigger toll on the crabs than we realize. By potentially harming so many crabs for our benefit, it also poses a potential threat to our ecosystem. The red knot, a small bird common to the seaside, depends on the horseshoe crab for its eggs as food. An increase in bleeding of the crabs leads to less crabs, which produces less eggs for the birds to consume, which then leads to less birds being able to "bulk up" during their optimal seasons and fly south for survival. Perhaps the biggest use of horseshoe crabs is as bait in the commercial fishing industry. This is where this process sparked my interest. I didn't realize that the FDA required almost every product to be be tested because they realize how useful the substance is, and yet it poses such a large threat to these animals, and yet even a larger threat to the ecosystem that I'm not sure it's really worth it.

The other source I found on this issue is from the Fish and Wildlife Service. It talks about the many threats posed to horseshoe crabs, mainly due to humans. Most of these include basic reasons such as beach development, recreational vehicle traffic, and oil spills. Lucky for these animals though, their biomedical and ecological advantages have been noted for their great importance, and measures have been taken to protect them before their untimely demise. These measures, however, have not recently increased the crab population as much as previously estimated. Again, this spiked my interest because I'm not sure if we should still be using these crabs so much to our advantage if we are also causing them so much harm.

The documentary listed above is from a peer-reviewed source. The WETA and PBS services have qualified reporters with ample education and knowledge to have produced such a program. It directly involved science correspondents through the use of interviews. The documentary was published in 2008, although it was aired in 2010 on our local network. The documentary was only biased in the medical sense. It proved all the uses and advances these animals have in the medical world without adequately addressing the harm caused to the animals themselves. It did talk about some of the bias felt by the LAL manufacturers, but those details would have been easily glossed over unless they were being paid careful attention. As anyone trying to prove a point, no, it did not admit this bias. The citation for the documentary is as follows: "Crash: A Tale of Two Species -- The Benefits of Blue Blood -- Horseshoe Crabs." Nature. PBS. WETA, Washington, DC, 17 Oct. 2010. Television. Later on, I was able to find a synopsis of the documentary on the following website: http://www.pbs.org/wnet/nature/episodes/crash-a-tale-of-two-species/the-benefits-of-blue-blood/595/.

The website I cited from is also a credible source because it is national association. The government would only allow people with ample education and knowledge on a specific subject to report on these issues. The website was published in August of 2006, but was again, written by science correspondents. The United States Fish and Wildlife Association sponsored and published the site. This article was biased as well, seeking to prove the disastrous effects humans have on horseshoe crabs. It never admitted this bias, and depicted this information as fact. The full citation for the website is as follows: "The Horseshoe Crab -- Limulus Polyphemus -- A Living Fossil." FWS.gov. United States Fish & Wildlife Service, Aug. 2006. Web. 18 Oct. 2010. <http://www.fws.gov/northeast/pdf/horseshoe.fs.pdf>.

Down Syndrome and Mutations




This picture was taken from the following website:
https://cornellbiochem.wikispaces.com/file/view/
downsyndrome1.jpg/66756907/downsyndrome1.jpg

 
Recently in class, we have been talking about mutations. We were assigned to do a project on a specific disease, and I chose to do mine on Down syndrome. This is an abnormality caused by nondisjunction in fertilization, or the failure of homologous chromosomes to separate as they should during reproduction, resulting in an extra copy of a chromosome. This is a mutation in the sense that, normally, only two chromosomes would develop in a zygote, whereas three chromosomes develop with this syndrome. A picture of a child with Down syndrome is posted above.

One of our class textbooks, "Mutants" by Leroi, describes two noteworthy details about mutations. First, our faces seem to be the most vulnerable body part in displaying mutation's effects (Leroi). This was apparent to me because one of my sources for my project was MedLine Plus, an online journal. On this website, symptoms of Down syndrome are listed, but nearly all of them are facial disfigurements. It describes an abnormally shaped head, a flattened nose, separated brain sutures, small ears, a small mouth and upward slanting eyes (MedLine Plus). Also, it stated that Down syndrome is mainly apparent to doctors at birth because of its distinct physical abnormalities (MedLine Plus). I had noticed this during my project, but as I read from my textbook, it became more apparent to me. So my question is this: why are our faces so vulnerable to mutation? What about our faces makes mutations almost attract the area? Is there a genetic reason for this? Does the environment play a role?

The other detail Leroi suggests in his coverage of mutations is that "more than 70% of spontaneously aborted fetuses bear severe chromosomal abnormalities" (Leroi). Leroi adds, "it is now widely supported that miscarriage is an evolved device that enables mothers to screen for, and rid themselves of, genetically impaired progeny." Also while doing my project, I found that it was very common for mothers to have abortions, or miscarriages, after they got positive results from testing their babies for Down syndrome. If more than half of spontaneous abortions occur because of genetic abnormalities, such as the one that causes Down syndrome, why does it not account for fetuses with this anomaly? This suggests that spontaneous abortion must have sort of a "cut-off point," in which it can no longer occur. If not, at least some of these fetuses would have spontaneously aborted, especially more than enough to allow Down syndrome to be the "most common single cause of human birth defects" (MedLine Plus). This also peaked my interest. We have answers to the more basic questions concerning spontaneous abortion, such as how and why it happens, but we still do not have all the answers. When does it take place during the pregnancy? Does it stop after a certain point? Are there other criteria? Does the mother have to have specific qualities that allow this process to continue in her? Or is it normally built in to every female? Does it stop after the female reaches a certain age?

These questions, along with those above have yet to be answered and are useful for more research in the scientific world.

The book "Mutants" is a scientific book written in 2003 by Armand Marie Leroi as a means of finding a "direct way into the human genome and the human body" through the discovery of mutants. Leroi is an evolutionary developmental biologist, and thus, has ample experience and knowledge to write such a book. It is informative and does not take sides. Rather, it seeks to provide a new way of thinking: all humans are mutants, not merely those with severe physical disfigurements that we may more often assume. This is, therefore, a trustworthy source.

The other source I used is from an online, peer-reviewed, scientific, medical journal, and as such, does not give a specific author's name. The website is the following: http://www.nlm.nih.gov/medlineplus/ency/article/000997.htm and again, the source is informative. It does not take sides, but merely seeks to inform the public, or whoever may read this journal, of the symptoms of this disease. This website is a service of the United States National Library of Medicine, and the National Institutes of Health. Therefore, all the information posted on this site are reviewed by individuals of appropriate authority in terms of knowledge on the subject. This also, therefore, is a trustworthy source.