Why do some animals have venomous spines?

Venomous spines are often an adaptation to deter predators from attacking or to subdue prey. Many species of fish, such as lionfish and stingrays, have venomous spines along their fins that can inject venom when threatened. These spines serve as a defense mechanism, making the animal dangerous to predators. In other cases, venomous spines help animals like some species of sea urchins capture prey by paralyzing or killing it. The venom can also serve as a deterrent, discouraging potential predators from attacking.