Not all cactus spines are the same. Some are built to be more difficult to dislodge once it punctures the skin, researchers found. 

Stephanie Crofts and Philip Anderson from the University of Illinois put the spines of six species of cactus to the test to see how their structures affect their function, particularly their ability to puncture skin. They found that the microstructural traits of the cactus spine determine how well it punctures the skin and how difficult it will be to remove.

A Study Of Cactus Spines

Cactus spines have a variety of uses, including defense against predators, provide shade, and collect water. For some, the spine serves a reproductive purpose by latching onto animal or human skin to be dispersed to new locations. 

In the study published by the journal Proceedings of the Royal Society B, scientists looked at the different spines under the microscope. The spines used are from the jumping cholla, the Argentine saguaro, the golden barrel cactus, brittle prickly pear, the rose cactus, and the plains prickly pear. 

They found that there are different structures found in the spines of different species of cactus. Some, like those on jumping chollas, have barbed spines similar to porcupine quills. 

How Cactus Spine Structures Affect How They Prick Skin

To test the effectiveness of the cactus spines to puncture skin, the researchers used the flesh of dead animals. They found that spines that are barbed are just the right size to snag animal muscle fibers and, therefore, more difficult to remove. Moreover, spines with barbed structures penetrate flesh more easily. 

"In order to puncture effectively, the cholla spine has to be able to penetrate the target very easily, so that just a slight brushing is all it takes," explained Anderson. "At the same time, it has to be really hard to remove."

The study proved just how reliable the barbed structure of a spine to attach to flesh and never let go. During the experiment, removing the barbed spines also removed a coating of tissue when used to stab chicken breast. With pig flesh, however, the cactus spine came out clean, but left behind barbs inside the punctured area.