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Researchers Stabbed Slabs of Meat With Cacti Spines to Learn About Puncture Strength

Barbed spines function much like porcupine quills, drawing on an overlapping shingled design to hook onto victims’ muscle fibers

The cholla plant’s prickly proclivities actually serve a reproductive purpose (L. Brian Stauffer)
smithsonian.com

The jumping cholla cactus’ innocuous, shrub-like appearance belies its prickly spines’ strength: As a new study published in Proceedings of the Royal Society B reveals, a single cholla spine embedded in a chunk of meat wields enough penetrative force to lift a hefty half-pound pork shoulder.

But the researchers behind this revelation didn’t just set out to test cholla’s meat-lifting skills. Instead, Ryan F. Mandelbaum reports for Gizmodo, Stephanie Crofts and Philip Anderson of the University of Illinois wanted to analyze the relationship between six cactus species’ spine structures and their puncturing capabilities, as well as the overall function of various spine shapes. (In addition to the cholla cactus, the pair evaluated samples of the golden barrel cactus, the brittle prickly pear, the rose cactus, the Argentine saguaro and the plains prickly pear.)

Crofts and Anderson found that barbed cactus spines act much like porcupine quills, easily puncturing flesh and relying on their overlapping shingled design—which Discover’s Alison Klesman says are essentially like “sharp blades”—to catch on muscle fibers and settle in for the long run. Spines featuring smoother surfaces require a bit more force to puncture prey, but are removed with far more ease.

“Most organisms that have puncturing tools also provide the force behind the puncture event,” Crofts tells the University of Illinois’ student newspaper, The Daily Illini. “In contrast, cactus spines puncture passively—all of the force comes from whatever is being punctured.”

A single cholla spine exerts enough force to lift a half-pound pork shoulder (L. Brian Stauffer)

Jennifer Leman of Science News writes that the team gauged each cactus species’ spine strength by stabbing different kinds of surfaces, including synthetic polymers to butcher meats, with the spikes. They then measured both puncture pressure and spike removal difficulty.

According to Klesman, the cholla proved most challenging to extract from pig tissue, while the plains prickly pear required more effort to remove from chicken breasts. Interestingly, cholla proved so adept at embedding itself in pork that it managed to leave some barbs behind upon extraction. The plains prickly pear, on the other hand, emerged from chicken breasts with a coating of animal tissue.

Cholla’s reputation as a “jumping” cactus derives from its habit of springing from a parent plant onto the skin or clothing of a hapless passerby, Doug Kreutz explains for The Arizona Daily Star. And, Anderson adds in a press statement, all that it takes for a cholla spine to cling to a target is “a slight brushing.”

Unlike other cactus spines, which serve functions ranging from warding off predators to providing shade and collecting water from fog, the cholla plant’s prickly proclivities actually have a reproductive purpose: hooking into a passing animal or human’s muscle fibers and hitching a ride to a new location, where the plant can begin the growing process all over again.

Perhaps the most valuable insight afforded by the report is its emphasis on porcupine quills’ and cactus spines’ shared structure.

“Researching these systems gives us the opportunity to compare evolution and biomechanics across both plants and animals,” Anderson tells Gizmodo. “You don’t often have the chance to do a direct comparison like that.”

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