Sometimes when you are doing something as simple as walking on the beach there appears an unexpected opportunity to learn profound things about the world and its humblest inhabitants. My dear Uncle Al joined me on such a walk many years ago. On a sparsely populated area of the New Jersey shore we came upon dozens of small male and larger female horseshoe crabs mating in the warm May weather. The females were laying their eggs in the moist sand. My Uncle, who had been an observer of this process for years, explained that these pre-historic rituals dated to around 1/2 billion years ago adding to the paradox of this primitive arthropod known affectionately as a living fossil. He gently lifted one to show me the structure of the crab, carefully avoiding the tail, not because it could harm him, but rather because of the importance of the tail in enabling them to turn over. If the tail of the horseshoe crab is damaged, the little fella would not be able to maneuver and flip. The horseshoe crab, a misnomer, is not really a crab at all, but rather an arthropod and invertebrate with no spine. Horseshoe crabs have fascinated me ever since that first encounter.
The eggs that survive grow and molt many times until fully grown. The eggs that are eaten by shore birds are part of the ecological balance and are amazingly important to human quality and quantity of life. If fewer horseshoe crab eggs are available as a result of diminished populations, then the Red Knot birds in Delaware, New Jersey and South Carolina also end up on endangered lists. The significance of this is the effect on both declining horseshoe crabs and medical science. As it turns out the horseshoe crab provides a life saving liquid used in biotechnology that affects anyone who has ever been to the doctor or a hospital, which is just about all of us.
The liquid which at present only comes from the horseshoe crabs around the world, has to be harvested in laboratories. The horseshoe crabs are taken from the beaches and brought to labs, turned on their sides and an instrument to draw the blood is attached near their hearts. One quart of this precious liquid is valued at fifteen thousand dollars. The crabs are then returned to the sea usually within the three day period because the gills need to remain moist. It is estimated that between 15-30% are so stressed they don’t survive. Looking at both perspectives or the middle path it becomes increasingly obvious that the labs are doing everything possible to insure the survival after returning them to the sea. The researchers are also working around the clock to produce a synthetic alternative to bleeding the crabs. The value of the liquid blue blood is so important to medical science because anyone receiving a routine injection at the doctors office or injectables for insulin, knee replacements or the routine use of hospital instruments is safer from the potential of life threatening infection thanks to our little horseshoe crab friends.
The horseshoe crab swims on its back for most of the year to migrate to sand or mud. In the spring, several males fertilize the female eggs and after many years they grow and molt and emerge almost in the same area where they were born. They have survived millions of years due to their protective blood stream which prevents the ocean bacteria from killing them off like 90% of other pre-historic creatures. The horseshoe crab, unlike vertebrates have no hemoglobin. They use hemocyanin to carry oxygen and due to copper in hemocyanin their blood is blue.
The technical process includes an understanding that Amebocytes from the blood are used to make Limulus Amoebocyte Lysate (LAL) which in turn is used to detect bacterial endotoxins in medicine. They detect E.coli, for example, on the medical instruments and devices mentioned earlier. The gram stains normally used can not detect and do not recognize endotoxins leaving medical technology no choice but to use this method.
In addition the careful handling of the horseshoe crab harvesting is set by law in the states of NJ, SC and Delaware and they help fund the research of a synthetic compound. Finally, it has been suggested that feeding the little guys a diet high in copper before release might help reduce the stress and the loss of 30% of their blood supply during the process. It is certainly worthy of research by the scientific community.
So, as we walk along the shores with our children and grandchildren it might be interesting to teach our future leaders the respect, compassion and value to human life that Limulus polyphemus, the “American” Horseshoe Crab provide to all of us.