Frogs to the rescue

By Ray Ford

It’s designed to benefit human health, but a new high-tech medical sensor could also be a boon to wildlife, including the horseshoe crab and an endangered shorebird, the red knot.

Developed at Princeton University, the electronic sensor scans medical devices and drugs for bacterial contamination. Until now, horseshoe crab blood has played a similar role; drug companies use its antimicrobial properties to test for even subtle traces of bacteria.

But what’s good for humans has been disastrous for crabs and the species that depend on the crabs’ eggs, including the red knot. About 15 percent of the approximately half a million horseshoe crabs caught off the U.S. east coast for their blood die after being returned to the water. An equal number are landed for use as bait.

The result: fewer crab eggs are deposited on coastal beaches, and the population of knots, which rely on the eggs to fuel their round-trip 28,000-kilometre annual migration, drops sharply. Numbers of the knot’s rufa subspecies – the same one that forages along the coasts of James and Hudson bays in Ontario – have fallen by 80 percent since the horseshoe crab fishery boomed in the 1990s.

The Princeton team circumvented the need for crab blood by borrowing a peptide (a small chain of amino acids) from the skin of the African clawed frog. Like the crab’s blood, the peptide contains natural antibacterial properties to help protect the frog in its environment. Unlike the crab’s blood, however, the peptide can be removed and synthesized in the lab without harming the frog. Attached to a scanner chip, it can alert manufacturers to the presence of contaminants such as E. coli or salmonella.

But the innovation will not produce an immediate fix. Princeton engineering professor Michael McAlpine, a member of the team developing the sensor, estimates that the technology may be five to 10 years away from commercial use. And that, in turn, underlines the importance of managing the horseshoe crab population both to ensure its survival and to maintain the food source it provides for other species, including shorebirds, fish, blue crabs and Atlantic loggerhead sea turtles.

“The horseshoe crab is a keystone species,” says Amanda Dey, principal zoologist with the New Jersey division of the U.S. Fish & Wildlife Service’s Endangered and Nongame Species Program. Even though the crab fishery is less than half the size it was at its peak during the nineties, overfishing “really hammered the population,” Dey adds. “The female side of the population has yet to recover.”

“The crabs themselves are not necessarily in danger of going extinct,” she says. “The concern is they’ll persist at a low level, but that level will be too low to support shorebirds.”

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