The horseshoe crab, which can be commonly found along the East Coast of the United States, is of ancient ancestors that have seemingly experienced arrested evolutionary development since before the Age of Dinosaurs. This surprisingly useful and important organism is considered a “living fossil”. The conservation of their archaic, a morphology over 150 million years old, can be seen in the physical and on the molecular level. Due to a normalcy, or lack of in genetic variation, the primitive forms of horseshoe crabs are very similar to the modern ones we see today.
These ancient relics survived the extinction of the dinosaurs, thankfully, because they have proved exceptionally useful in the biomedical industry. Horseshoe crabs spawn and congregate in the shallow intertidal flats and other accessible coastal areas, which make them an undeniable target of human population expansion and are easily gathered for commercial use. The blood of horseshoe crabs contains Limulus amebocyte lysate or LAL, which is blue! LAL is used for prevention of bacterial contaminants in injectable medications and devices. If you have ever received a shot you have directly benefited from horseshoe crabs. The crabs are collected and transported to a laboratory for the bleeding process and then released to the wild. The majority of the horseshoe crabs survive this processes but the death rate is increased by 10-15% in come cases.
Furthermore, horseshoe crab’s cells are made predominantly of chitin, which is similar to the protein keratin that strengthens our nails, skin, and hair. Chitin is commonly used for burn victims due to its remarkable healing properties as it has been shown to greatly reduce healing time. Additionally, researchers have discovered critical insights about the functioning of the human eye by studying the 10 eyes of the horseshoe crab!
These living renditions of the ancient past must be protected. Horseshoe crab abundances are threatened by their slow sexual maturation, which takes approximately 10 years. This coupled with their use as bait, habitat infringement, and easily exploitable breeding grounds, is a recipe for abuse. Hopefully their medical uses, which hold both economic worth and human health benefits, will be enough justification to preserve these antique creatures.
-by Samantha Flounders
Avise, J.C., Nelson, W.S., and Sugita, H. 1994. A speciational history of “living fossils”: molecular evolutionary patterns in horseshoe crabs. Evolution. 48(6): 1986-2001.
Ropes, John. 2011. Longevity of the horseshoe crab, Limulus polyphemus (L). Transactions of the American Fisheries Society. 90: 79-80.
Rudloe, Anne. 1983. The effect of heavy bleeding on mortality of the horseshoe crab, Limulus polyphemus, in the natural environment. Journal of invertebrate Pathology. 42(20) 167-176.
Sekander, R.K., Yang, S.Y. Lewontin, R.C. and Johnson, W.E. 1970. Genetic variation in the horseshoe crab (Limulus polyphemus), a phylogenetic “relic”. Society for the Study of Evolution. 24(2): 402-41.