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<p class="last">Horseshoe crabs do not only face the threat of being used for bait but instead, have a more financially driven predator in the form of the biomedical industry. If you have ever | <p class="last">Horseshoe crabs do not only face the threat of being used for bait but instead, have a more financially driven predator in the form of the biomedical industry. If you have ever | ||
Revision as of 16:03, 1 November 2017
Silver Human Practices
The Plight of the Horseshoe Crab
Horseshoe crabs aren’t just used for bait. If you have every had a flu shot, known someone with a pacemaker or joint replacement, or given your pet a rabies vaccination, a debt of gratitude is owed to the horseshoe crab. All of these devices are quality checked for safety using a test that comes from the blood of the horseshoe crab. The blood of the crab is very sensitive to endotoxins, the blood from the crab is used commercially to develop the LAL and TAL test. The Limulus amebocyte lysate (LAL)test and was commercialized in the United States in the 1970s and in Asia, there is a similar test called TAL which takes its name from an Asian species of crab, Tachypleus tridentatus. Each year, almost half a million living horse crabs are use in the development of these pharmaceuticals- for these tests 30 percent or more of the blood of the horseshoe crab is taken. It is estimated that 10-15% of 500,000 crabs harvested on the Atlantic coast do not survive the bleeding process. The market for LAL is approximately $50 million, and since no synthetic substitute has the same accuracy as LAL, crab blood must be used it is just to important not to use.
Limuli plays a vital role in the ecology of estuarine and coastal communities. Horseshoe crabs utilize autochthonous and allochthonous production from pelagic and benthic food webs(figure 2; Carmichael et al. 2004). The horseshoe crab is an integral part of many vertebrate predators diet. Benthic fish feed on horseshoe crab eggs and larvae, sharks feed on the smaller juveniles, and sea turtles feed on adults (Botton et al. 2003). Horseshoe crabs are dietary generalists, and adult crabs are ecologically essential bivalve predators in some locations. One of the most notable predator-prey relationships that were pointed out to us while we were at the Georgia Aquarium was the migratory shorebird–horseshoe crab egg interaction. Eleven species, such as the more familiar red knot(featured to the right) and the dowitcher, rely on horseshoe crab eggs for sustenance during their migration along the Atlantic Flyway (Castro and Myers 1993). Migrating birds require an estimated 539 metric tons of eggs to full the trip to the Arctic summer range(Castro and Myers 1993). To bring this into better perspective let's consider the aforementioned red knot species.The red knot species depends so heavily on the abundance of horseshoe crab eggs that with this species depletion this bird over the last 20 years has seen a population decline from over 100,000 to less than 15,000. Thus, the red knot is now a species nominated for protection under the Endangered Species Act. Horseshoe crabs are therefore a critical species. The horseshoe crab links an array of prey (bivalves and polychaete worms) and predators (fish, turtles, and birds), utilizing both autochthonous and allochthonous production from pelagic and benthic food webs(figure 2; Carmichael et al. 2004).
Commercial Fishing
The best bait to attract eel and whelk, best known as conch, is horseshoe crabs(Jay Odell, 2005). During the 1990s, the harvest of the horseshoe crab increased coastwide, with a peak of nearly six million pounds in 1997(Jay Odell, 2005). This sudden increase in harvesting leads to the Atlantic States Marine Fisheries Commission representing 15 states from Maine to Florida to develop a horseshoe crab management plan. The ASMFC plan met with vigorous opposition from commercial fishers, the program, supported by conservation groups, was implemented in 2001 (Focus, 2008). The project established state-by-state harvest quotas and establish a 1500-square mile federal horseshoe crab sanctuary in Delaware Bay (Office, 2006). Despite restrictive measures taken in recent years, populations are not showing immediate increases. Mainly, because horseshoe crabs do not breed until they reach nine or more years of age, so as of now there has been no measurably increased (Office, 2006).
Biomedical Threats
Horseshoe crabs do not only face the threat of being used for bait but instead, have a more financially driven predator in the form of the biomedical industry. If you have ever had a flu shot, known someone with a pacemaker or joint replacement, or given your pet a rabies vaccination, you owe a debt of gratitude to the horseshoe crab. All of these devices are quality checked for safety using a test that comes from the blood of the horseshoe crab. The blood of the crab is very sensitive to endotoxins, the blood from the crab is used commercially to develop the LAL and TAL test. The Limulus amebocyte lysate (LAL)test and was commercialized in the United States in the 1970s and Asia, there is a similar test called TAL which takes its name from an Asian species of crab, Tachypleus tridentatus (Jay Odell, 2005). The market for LAL is approximately $50 million (Focus, 2008). Each year, half a million living horse crabs are harvested to develop these endotoxin tests- for these kits, companies take 30 percent or more of the horseshoe crabs blood. Experts estimate that 10-15% of 500,000 crabs harvested on the Atlantic coast do not survive the bleeding process (Focus, 2008). Currently, no synthetic substitute has the same accuracy as the LAL test, so crab blood must be used, and thus the threat persists (Focus, 2008).
Interactions in Biological Systems: What are they up to?
We hosted a lecture by microbiologist Dr. Hammer. Dr. Hammer studies cell signaling in the bacterial pathogen Vibrio cholerae, and during his talk, Dr. Hammer discussed how he uses genetic engineering for his research. His lab studies microbial interactions at scales that span genes and genomes, regulatory networks, cells, populations, and communities. Harmful and beneficial bacteria are genetically encoded with regulatory networks to integrate external information that tailors gene expression to particular niches. Bacteria use chemical signals to orchestrate behaviors that facilitate both cooperation and conflict with members of the communities they inhabit. His work focuses on the waterborne pathogen Vibrio cholera, which causes the fatal diarrheal disease cholera in humans and also resides in aquatic settings in association with other animals and surfaces like crab shells and zooplankton molts composed of chitin.
CRISPER, GATTACA, and the end of the world!
Arri Eisen is a Professor of Pedagogy in biology and in the Graduate Institute for Liberal Arts; he is also the Teaching Coordinator for FIRST, a National Institutes of Health-supported postdoctoral fellowship program in research and teaching. Dr. Eisen received his undergraduate degree in 1985 in biology with honors from UNC-Chapel Hill and his PhD in Biochemistry from UW-Seattle in 1990. In addition to being on the Center faculty, Arri Eisen is a Professor of Pedagogy in Biology and in the Institute for Liberal Arts; he is also the Teaching Coordinator for FIRST, a National Institutes of Health-supported postdoctoral fellowship program in research and teaching, and a leader of the Emory Tibet Science Initiative, which has been working over the last decade with the Dalai Lama to educate Tibetan monks and nuns in science. Dr. Eisen received his undergraduate degree in 1985 in biology with honors from UNC-Chapel Hill and his PhD in Biochemistry from UW-Seattle in 1990. He has been teaching at Emory since then and joined the Center in the late 90’s where his main responsibilities now include teaching in the Center&'s Master of Arts in Bioethics and in Emory's Master of Science in Clinical Research programs. Dr. Eisen publishes in the peer-reviewed literature in science, science education, and bioethics, as well as in the popular literature. His most recent book is The Enlightened Gene: Biology, Buddhism and the Convergence that Explains the World. Dr. Eisen spoke about CRISPR technology and the future of creating human babies without certain medical conditions and specific preferred traits.
Our Synthetic Biology Club hosted a speaker series on campus during the spring semester.
Learn to Engineer Bacterial Biosensors!
The primary focus of Dr. Styczynski research is the experimental and computational study of the dynamics and regulation of metabolism, with ultimate applications in metabolic engineering, biotechnology, and biosensors/diagnostics. He spoke of the importance of micronutrient deficiencies and the importance of having an accessible and affordable way to measure deficiencies. Micronutrient deficiencies are a significant healthcare concern across the globe. Significant even in some developed nations, micronutrient deficiencies are more severe in the developing world and locally in the wake of major disasters. These conditions, though easily treated, remain a problem because they are often difficult to recognize and diagnose, requiring lab tests that are prohibitively expensive in both material and human resources for those in developing or remote areas. As obligate consumers of the same micronutrients, bacteria possess cellular machinery to control intracellular micronutrient levels and have corresponding regulatory mechanisms to respond to varying concentrations in their environment. His lab is developing a novel medical test based on bacterial sensors using designed genetic circuitry to direct existing or minimally engineered cellular machinery to trigger specific changes in color in response to defined micronutrient levels. Such a test would be cheap, requiring no complex equipment and minimal medical training to administer and interpret. This would obviate the logistical problem of laboratory access and sample transport in remote and low-resource environments, allowing on-site diagnosis of micronutrient deficiencies in the populations most at risk.
Sources
Botton ML Shuster CN Jr Keinath J . 2003. Horseshoe crabs in a food web: Who eats whom. Pages. 33-153. in Shuster CN Jr, Barlow RB, Brockmann HJ, eds. The American Horseshoe Crab . Cambridge (MA): Harvard University Press.
Carmichael RH Rutecki D Annett B Gaines E Valiela I . 2004. Position of horseshoe crabs in estuarine food webs: N and C stable isotopic study of foraging ranges and diet composition. Journal of Experimental Marine Biology and Ecology . 299: 231-253.
Castro G Myers JP . 1993. Shorebird predation on eggs of horseshoe crabs during spring stopover on Delaware Bay. The Auk . 110: 927-930.
Castro G Myers JP . 1993. Shorebird predation on eggs of horseshoe crabs during spring stopover on Delaware Bay. The Auk . 110: 927-930.
Jay Odell, Martha E. Mather, Robert M. Muth; A Biosocial Approach for Analyzing Environmental Conflicts: A Case Study of Horseshoe Crab Allocation, BioScience, Volume 55, Issue 9, 1 September 2005, Pages 735–748, https://doi.org/10.1641/0006-3568(2005)055[0735:ABAFAE]2.0.CO;2
Office, U. F. (2006). The Horseshoe Crab Limulus polyphemus A Living Fossil.
Picture Sources
Source for LAL processing facility: G. Riekerk, SCDNR Marine Resources Research Institute
Source for eel from free media commons: https://commons.wikimedia.org/wiki/File:Knobbed_whelk_shells.jpg
Source for eel from free media commons: https://commons.wikimedia.org/wiki/File:California_Moray_Eel,_San_Clemente_Island,_Channel_Islands,_California.jpg
The picture for the bleeding horse shoe crabs comes from an Atlantic article, the picture is a a still from the PBS Nature documentary Crash PBS. The image and the article can be located at this source: https://www.theatlantic.com/technology/archive/2014/02/the-blood-harvest/284078/
