On Beacon Hill, there’s a bill before the Senate Rules Committee that would designate the Atlantic horseshoe crab as the official marine invertebrate of the Commonwealth. What makes the Atlantic horseshoe crab special to Massachusetts? And why isn't it in the running for state crustacean?
Horseshoe crabs have a complicated history in Massachusetts. They’ve been cast as villains, with a bounty on their heads, and as heroes, saving millions of human lives.
To learn more, I turned to a horseshoe crab expert – science writer Bill Sargent, author of not one but three books about horseshoe crabs. And because a good journalist never relies on just one source, I found another horseshoe crab enthusiast. Eleven-year-old Falmouth resident Jackson Fenstermaker recently attended camp at the Waquoit Bay Summer Science School. Between them, I learned a lot about what makes this oft-misunderstood species so cool.
First of all, for the record, they’re not crabs. That explains why they're not up for the honorific 'state crustacean'.
"They are not actual crabs," Jackson explained. "They are more closely related to spiders and scorpions. What's confusing is that, unlike most arachnids, they have ten walking legs and two claws like a crab."
Jackson said, besides where they live, there’s another major difference between horseshoe crabs and their land-dwelling relatives.
"Unlike the Scorpion, which they are related to, the long tail does not sting," he said. "It is more of a rudder or helps them flip over when they’re on the back."
Science writer Bill Sargent said, even though the tail can’t sting, people should still leave it alone.
"You don't want to pick up a horseshoe crab by its tail," he said. "I mean, it's the perfect handle. It looks like it's designed to pick them up. But what happens is they're so heavy that it can dislodge that and they'll start bleeding. And then that can get infected and they can die from that."
Duly noted.
On the opposite end from the tail, Jackson said you can see two compound eyes. But, he said, that’s just the beginning as far as eyes go.
"They have some simple and compound eyes," he explained.
Depending on who you ask, horseshoe crabs have either nine or ten eyes in total. Sargent puts the number at nine.
"There was a Dr. H. Keffer Hartline, who won the Nobel Prize in 1967 for his research on the optic nerve of the horseshoe crab that runs from the compound eye to the brain," Sargent said. "Horseshoe crabs actually have nine eyes in all."
Hartline spent summers in Woods Hole, studying horseshoe crab eyes at the Marine Biological Laboratory. MBL is also where the unique, lifesaving property of horseshoe crab blood was first discovered, 70 years ago.
"Frederik Bang was working at the MBL and he noticed that one of his crabs sludged up and died," said Sargent. He added that most scientists would just start over with another crab, but not Bang.
"He realized something interesting was going on. So that led to the development of what's called limulus amebocyte lysate, where you use the blue blood of the horseshoe crab as a test for gram-negative bacteria."
That test is still used to ensure medical implants and injectable medications, like vaccines, aren’t contaminated.
"I think it's probably the most important discovery to come out of marine biology, and it saved millions and millions of lives," Sargent said. "Actually, during Covid, it probably protected over a billion people."
Now a synthetic alternative is also in use. That option doesn’t involve forcing horseshoe crabs to donate their milky blue blood, but the drug industry has yet to completely switch over, as conservationists hope they will.
Most people know that horseshoe crab blood is blue. But, at camp, Jackson learned why:
"When we were searching for horseshoe crab facts, we found out that their blood is copper-based, not iron-based."
And another fun fact?
"Well, they have been around for millions of years," Jackson said. "They lived before the dinosaurs, even."
Sargent confirmed, "They're 450 million years old and made it through the last five extinctions."
Horseshoe crabs are currently harvested in Massachusetts for biomedical bleeding as well as for use as bait in the whelk fishery. But in the mid-20th century, Massachusetts subsidized some Cape Cod and South Coast towns paying a bounty of three or four cents for every tail turned in. Horseshoe crabs were being falsely accused of depleting clam populations.
But with Bang’s discovery, the people of Massachusetts changed their views and horseshoe crabs went from villains to heroes. And they could soon be the commonwealth’s official marine invertebrate, thanks to Senator Julian Cyr, of Provincetown.
"Horseshoe crabs are remarkable creatures," Cyr said by way of explanation. The Senator, it turns out, is also a fan.
"We just felt it was fitting to introduce, perhaps playful, legislation designating the horseshoe crab as the official invertebrate of Massachusetts. And so that bill is pending in the legislature."
Cyr said the horseshoe crab is something of an unofficial mascot in his office.
"The horseshoe crab is an iconic feature of Cape Cod and Island and Massachusetts waters," said Cyr. "They've been around, gosh, a lot longer than even the Cape itself – than the existence of mammals. And I think there's something quite remarkable in their resilience and longevity."
And while the bill’s chances of passage have dwindled since the formal session ended on July 31, there’s still a chance that the Senate Rules Committee could act. Horseshoe crabs, after all, have shown they can beat the odds.
