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That the three groups of spitters independently derived the same solution—increased abundance of phospholipase A2 toxins—is an example of convergent evolution, in which species that aren’t closely related but face similar survival challenges acquire similar adaptations.

However, the spitting species’ venom contained higher levels of another group of proteins known as phospholipase A2 toxins, which nonspitters produce only in small quantities, or not at all.

To probe the effects of the extra phospholipase A2 proteins, the scientists dabbed different combinations of toxins from the snakes onto isolated mouse nerves that are sensitive to pain.

The researchers determined the three-finger toxins triggered more pain when combined with phospholipase A2 toxins than alone.

In the bacterial system, the rise in cGAMP can lead to activation of a phospholipase enzyme that degrades phospholipid molecules in the bacterial cell membrane.