The Animal That Has Saved The Most Human Lives

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The Animal That Has Saved The Most Human Lives

Horseshoe crab has saved the most human lives. Although most of people have never even heard about this animal, it is well known to medical research scientists (or some fishermen). It is all because of invaluable properties of its blood.
The blood of Limulus polyphemus does not contain hemoglobin but hemocyanin that uses copper instead of iron to carry oxygen , which also turns their blood blue. What is the most interesting about their blood is that it does not have antibodies to fight infections. Instead it produces mobile cells called amebocytes that defend against pathogens by releasing clotting granules that cover hostile bacteria membrane by using the process of coagulation.

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The extract from amebocytes called Limulus Amebocyte Lysate or LAL is used to detect bacteria in various of medical applications such as testing of new medications, vaccines or equipment. The LAL tests have been used since 1970 are highly reliable, easy to perform, and replaced older tests that used rabbits. The crabs are caught alive and some of their blood is extracted before they are put back into the ocean. Regardless, the mortality rate during this process is still quite high - different estimates say it is between 3 to 30%. Because of precious medical application, the blood of Horseshoe crab is highly valued and worth about $13,000 per litre (or $60,000 per gallon).

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Half a million of these creatures are harvested each year. Despite of many restrictions on fishing to protect them in the Eastern United States, their number have rapidly declined within last years. Mainly because of their use as a bait for eels, sea snails and conches. Also their eggs are consumed in some parts of China and Southeast Asia.
Horseshoe crabs are closely related to arachnids not crustaceans and are considered to be living fossils as they have survived on our planet for 450 million years, so they already lived 200 million years before the first dinosaurs even existed.

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References:

"Horseshoe crab", Wikipedia article.

"Hemocyanin", Wikipedia article.

"Which animal has saved the most human lives", Discover Wildlife, 2016.

"Horseshoe crabs save lives, but their numbers are dwindling", Public Radio International, 2016.

"This life-saving animal blood is bright blue and worth $60,000 a gallon", Business Insider, 2015.

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