Why is Horseshoe Crab Blood So Expensive?

Horseshoe crab blood is one of the most valuable fluids on Earth due to it's ability to detects endotoxins released by bacteria. But what does this mean for the species? Learn what the future may hold for these primitive animals in today's episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:02):
Welcome to brain Stuff from how Stuff Works. Hey, brain Stuff,
Lauren Vogel Bomb. Here. When you look at a horseshoe crab,
you're looking at half billion years into the past. These
primitive animals were around long before the dinosaurs and survived
ice ages and asteroids almost unchanged their cozy ecological Niche

(00:22):
necessitated few body modifications, So while horseshoe crabs today are
different than their ancestors, they're not that much different. You're
also looking at a creature whose value approaches a half
billion dollars a year to the biomedical and commercial fishing industries.
The blood of horseshoe crabs is extremely important to science.
It's capable of detecting a certain type of bacteria in humans,

(00:44):
thereby saving lives. More on that in a moment, but
a bit of biology first. Horseshoe crabs resemble semi circular
armored tanks and are an appropriate army green to brown color.
Despite their name, they are more closely related to spiders
and scorpions than to crab abs. Of the four species
of horseshoe crabs around today, Limulus polyphemus is found along

(01:05):
North America's eastern coast from Maine to Mexico. The other
three species are found in Southeast Asia. Horseshoe crabs can
be found in abundance on many beaches near their spawning zones.
They commonly become overturned by the action of waves during
spawning and may not be able to write themselves, which
leads to death. But not every horseshoe crab you see
on the beach is dead. They also molt, leaving behind

(01:26):
their old exo skeleton and forming a newer, bigger one.
The horseshoe body has three sections. The large head or prosema,
houses the brain and heart, and six pairs of appendages
are attached to it. In males, the first pair are
hook like and used to clamp onto a female during mating.
In the abdomen or opus, those sma muscles control the

(01:47):
gills and tail, called the tellson. The tellson serves as
a rudder and helps crabs write themselves if they get
flipped over during spawning. Females are third bigger than males
and can weigh twice as much upwards of ten pounds
that's about four and of kilos. It takes about ten
years for horseshoe crab to grow to adult size. Spawning
peaks in May and June. At high tide during the

(02:08):
full or new moon, the female digs a hollow in
the sand beneath her and lays a cluster of several
thousand eggs, which are fertilized by the male clinging to
her back. Satellite males closely follow the couple for the
chance to pass on their jeans to some of the eggs.
The female repeats the process several times per night and
may spawn for several nights. All told, each breeding female

(02:29):
can lay up to a hundred thousand eggs a season.
Delaware Bay has the largest spotting population in the world
and as a stop oversight for shorebirds in the Atlantic Flyway,
which is the north south path to and from Arctic
breeding grounds. Up to a million birds flocked to the
site to gorge on horseshoe crab eggs, building their strength
for the journey north. But decades of overharvesting crabs as

(02:51):
bait to catch welk, eel and conk have decimated their
populations and turned the egg feast into near famine. Hundreds
of thousands of crabs are taken every year for bait.
Then there's the effect of shoreline development and habitat loss. Beaches,
intertidal flats, and deep bay waters are all necessary for
crabs survival and reproduction, but are increasingly encroached upon by

(03:12):
construction and poisoned by fertilizer runoff. We spoke via email
with John Tannacretti, a professor of earthen environmental sciences at
Malloy College and director of the Center for Environmental Research
and Coastal Oceans Monitoring. He said we monitored more than
a hundred and fifteen sites on Long Island for over
seventeen years and found that horseshoe crab habitat has declined

(03:34):
by more than eight percent. A loss of habitat means
loss of breeding animals, clearly seen in the long term
decline in horseshoe crabs in the area by about one
percent per year. Though their health is critically threatened by humans,
we benefit enormously from horseshoe crabs. Horseshoes. Copper based blue
tinged blood contains a clotting agent called lumulus ambo site

(03:55):
ly sate or l A L, which detects endotoxins released
by bacteria that can cause fever, stroke, organ damage, and
even death. L A L is used to test drugs, vaccines,
and medical devices, and it's so essential to biomedical companies
that manufacturing around the world would halt if the supply
was cut off. Understandably, L A L is one of
the most valuable fluids on Earth, at a price of

(04:17):
about fifteen thousand dollars a quart. Horseshoe blood developed this
remarkable clotting ability as a response to life in an
oceanic soup of bacteria. When microbes invadim mammal, millions of
tiny blood vessels limit their spread and white blood cells
bite them off. But not so with horseshoe crabs. Their
blood moves freely through their tissues and organs, providing a

(04:39):
wide playing field for bacterial infection. But these bacteria and
crabs have co evolved for millions of years, and so
crabs have defenses to Horseshoe crabs don't have an immune
system exactly. Their single type of blood cell and ambo site,
which is a cell that can move around, does all
the usual work of blood cells, repairing wounds, gobbling up

(05:00):
dead cells, transporting and storing digested material. But these amibo
sites also release a substance that clots like wild when
they detect a bacterial and a toxin, clots entrap the
invading bacteria, limiting further infection. Larger clots can also seal
a wound. Before L A L was discovered, BioMed companies
used rabbits to test for endotoxins because rabbit blood also

(05:22):
tends to clot in the presence of these toxins. If
after injection with the test substance and animal developed signs
of infection, which could take up to forty eight hours,
the sample was determined to be contaminated and the rabbit
would die. The discovery of L A L has saved
countless rabbits from this fatal testing, but in turn, hundreds
of thousands of crabs every year participate in an involuntary

(05:44):
blood drive to harvest horseshoe crab blood. The unspecting creatures,
larger females being preferred, are hauled out of shallow coastal
areas and brought to a lab where they're chilled for
an hour or so, and then of the crabs blood
is drained off. After leading, the animals are returned to
the ocean. The sooner they're returned, the more likely they
are to survive, which is important because though this is

(06:07):
considered a low mortality catch and release procedure, as many
as thirty percent of horseshoe crabs can die from the
bleeding process, and because of the demand for L A
L the toll on horseshoe crabs can be huge. Six
hundred thousand crabs are harvested every year for BioMed purposes,
meaning up to a hundred and eighty thousand crabs may
be lost to the procedure every year, and the long

(06:29):
term impact may be much worse. In areas where the
most crabs are harvested for blood letting, fewer females show
up to spawn. North America's own Limuleus polyphemus was placed
on the vulnerable list by the International Union for the
Conservation of Nature in and the problem is worse in Asia,
where no animals are returned to their habitat. Tan O
Creti said in Singapore, during the breeding season, ten thousand

(06:51):
adults per day are harvested blood out and then prepared
for sale as food. At this rate, they could be extinct.
At this rate, they could be extinct there in a decade.
Tennecredi boils down the next steps needed quote. Three things
have to happen immediately and consistently, one stop all collection
for bait to get FDA approval of synthetic L A L,

(07:13):
and three protect crab breeding sites. There has been progress
on synthetic L A L. Although an effective L A
L substitute has been available for fifteen years, only one
facility could produce it, and BioMed companies didn't want to
rely on a single source. But then another facility began
production and Eli Lillian Company announced it would phase out

(07:34):
natural L A L by in the next few years
and phase in synthetic L A L. Good news. Indeed.
Today's episode was written by Laura and Fick and produced
by Tyler Clang for iHeart Radio's How Stuff Works. For
more on this and lots of other continually spawning topics,
visit our home planet how stuff Works dot com and

(07:55):
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