Two University researchers conducted a study on six species of cactuses using various types of animal skin to examine how spine structures influence plant performance.

Postdoctoral researcher Stephanie Crofts and animal biology professor Philip Anderson both study the biomechanics of puncturing plants and animals. According to the press release, Crofts and Anderson found barbed cactus spines that can biomechanically penetrate animal flesh are difficult to dislodge afterward.

“Not only are (cactuses) a charismatic and fascinating group of organisms on their own merit, but they also present an interesting problem from the point of view of puncture mechanics,” Crofts said in an email.

Crofts and Anderson viewed the spine structures of several cactuses using a scanning electron microscope. They then compared the spines by testing the strength of their puncture on meat, such as chicken breast and pork shoulders.

Crofts said human skin would react very similarly to the pig skins because of the similarity between humans and the animal.

The researchers evaluated a branching cactus called Cylindropuntia fulgida, or jumping cholla, and found that if provoked, the plant will pierce its offender’s flesh. Of the six cactus species, Croft and Anderson also studied two opuntioid cactuses including Opuntia fragilis, or brittle prickly pear, and Opuntia polyacantha, the plains prickly pear.

“Opuntioid (cactuses) are especially interesting, since their spines are barbed and seem to help them spread clones of themselves to reproduce asexually,” Crofts said. 

Through the study, the researchers found barbed spines could puncture an animal’s flesh with more force than the spines without barbs, and it required more force to remove them as well.

“Most organisms that have puncturing tools also provide the force behind the puncture event,” Crofts said. “In contrast, cactus spines puncture passively — all of the force comes from whatever is being punctured.”

Croft said the plains prickly pear required more work to have the spines withdrawn from the chicken while the cholla spines were difficult to withdraw from pig tissue.

Barbed spines in chicken breast came out with animal tissue while barbed spines in pig flesh came out clean. Croft said she and Anderson are working on a few projects that all address different aspects of biological puncture.

“I think there’s definitely more to explore with cactus spine morphology and puncture ability, as well as looking for other similar surface structures in unrelated organisms,” she said.

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