Why I care about the horseshoe crab, and why you should, too


During my first morning tagging horseshoe crabs I was greeted warmly by two volunteers. Upon this encounter I was surprised to hear the volunteers refer to the horseshoe crabs with endearments. The horseshoe crabs were referred to as "cutie" or "little guy."

We walked as a group down then peninsula shore, counting the horseshoe crabs over a one-mile stretch. On the way back we tagged crabs as we walked. I was invited to tag a horseshoe crab myself. I picked up the crab up by the shell, instead of the telson, or tail. Picking up a horseshoe crab by its telson can cause it to break off. This would leave the horseshoe crab defenseless if it were to flip over. The telson is used to flip itself right-side up.

I looked into the bowl-shaped shell full of extremities. The naturalists pointed out the mouth and gills, surrounded by legs with claws. I was interested to learn that the function of the legs and claws are for pushing and grabbing food. Additionally the gills are able to hold in water for an extended time on land. The gills also provide easy access to the blood stream. If bacteria or a toxin enters the bloodstream, a natural endotoxin in the blood surrounds the impurity with a membrane, creating a protective barrier.

The process of tagging involves piercing the shell of the horseshoe crab, which has no nerve endings. When I tagged the crab, I was nervous to see the blue blood trickle from the spike I used to pierce the shell. However, I was ensured it is humane and painless.

The thin, plastic tag was secured and flush with the shell of the horseshoe crab. Each tag has a unique number. Project Limulus keeps track of the horseshoe crabs based on the tags. A horseshoe crab that has already been tagged when it is found is called a "recapture." During a recapture the size and location is recorded.

I participated in tagging during the morning, afternoon and evening on three separate occasions. The time of tagging is determined by the highest tides of the month, which are related to the full and new moons. This means tagging can occur at odd hours. This, however, was not a deterrent to the naturalists, who maintained focus even past midnight.

As a student of science and the environment, I was surprised to learn that a decreasing number of horseshoe crabs were identified. The conservation of a species is always important, even if they are not aesthetically appealing to most. However, I learned that many other species rely on the horseshoe crab for their existence. For example, migratory birds are dependent on the nutrition of horseshoe crab eggs. I was also surprised to learn there is a significant human use of the horseshoe crab.

The blue, copper-based blood in a horseshoe crab quickly clots in the presence of bacterial toxins. The endotoxin is called limulus amebocyte lysate, or LAL. Researchers use it to test any medical device, drug, or vaccine that comes into contact with human blood.

To obtain LAL, horseshoe crabs are harvested from their habitats. One third of their blood is taken and then they are returned to their home. Little is known about the survival rate once the horseshoe crabs are returned. If you or anyone you know has a pacemaker, is insulin dependent, or uses needles for their medication, you have been personally impacted by the LAL endotoxin found in the horseshoe crab.

Project Limulus is a tracking program where data is collected, reflecting the distribution, movement, longevity, and mortality of the horseshoe crab.

When I volunteered, the naturalists and I collected data on: water temperature, air temperature, wave height, wind speed, wind direction, start time, end time and the total number of single male horseshoe crabs, single female horseshoe crabs and groups of mating horseshoe crabs. The Watch Hill Conservancy collected additional data by tracking the horseshoe crabs according to different marked sections on the beach.

The data could be used to identify issues and barriers experienced by the horseshoe crab at Napatree Point.

The data from this research could be used to protect the horseshoe crab population from overuse. This could have a greater impact than most people would expect. It could also be used to create the optimal conditions for horseshoe crabs, in order to keep the population strong and healthy.

I was honored to participate in Project Limulus as it opened my eyes to the beauty of a species that is not typically referred to as beautiful. The structure and function of a horseshoe is unique and magnificent, with complex intricacies.

The human use and benefit we receive from the horseshoe crab is significant and lifesaving. However, as responsible researchers, we should also appreciate how we can respect the horseshoe crab and assist in its ability to thrive in our shared environment.


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