The Iberian ribbed newt has tubercles running down each side. Through these, its sharp ribs can puncture. The ribs act as a defense mechanism, causing little harm to the newt. This mechanism could be considered as a primitive and rudimentary system of envenomation, but is completely harmless to humans. At the same time as pushing its ribs out the newt begins to secrete poison from special glands on its body. The poison coated ribs create a highly effective stinging mechanism, injecting toxins through the thin skin in predator's mouths. The newt's effective immune system and collagen coated ribs mean the pierced skin quickly regrows without infection.