Why And How Did Scorpions Evolve To Have Particularly Potent Venom?
Scorpions are among the oldest of living arachnids. Today, scorpions have evolved into small arachnids that possess highly potent venom, but scorpion-like ancestors existed 460 million years ago, long before modern arthropod species crawled the earth. This half a billion year old scorpion ancestor possessed a tail that was similar to a modern scorpion tail, but it did not transmit venom to enemies via a stinger. Not long ago, paleontologists stumbled upon a fossil containing a bizarre arthropod that appeared to be a hybrid of a scorpion and a typical spider. This fossil was determined to be 100 million years old, and it had a tail that was nearly identical to a modern scorpion tail, as it possessed a stinger that injected venom into enemies. So when did scorpions evolve the ability to produce venom, and why?
Hundreds of millions of years ago, scorpions evolved from enormous sea dwelling creatures into vulnerable land animals that needed a method of defense in order to hunt for prey and compete and defend against enemies. Luckily for scorpions, a mutation in one single gene converted an immune system protein into a lethal form of venom. Researchers believe that this very same mutation occurred in other animals that are venomous today. At the moment, more than 2,000 scorpion species have been documented by researchers, and 25 of these species possess venom that can kill a human.
Many researchers believe that scorpions originated on land, but were swept into the sea only to reemerge on land again some 400 million years ago. These early scorpions shrank considerably over time, which made it hard for them to compete with other land animals as well as catch prey. In response to this disadvantage, scorpions evolved to produce a particularly potent form of venom, allowing them to swifty kill animals much larger than them. However, scorpions were, and still are, forced to use their pincers in order to catch prey, but this has also changed over time. The oldest scorpion species possess large pincers and small tails, as early scorpions were used to hunting with their pincers, but they were still learning to hunt with their whip-like tails. As millions of years passed, scorpions came to rely more on their stinger-equipped tails for hunting and defense, as it was safer than the up close and personal pincer-method of attack. This is why the most advanced scorpion species possess large tails with small pincers. The evolutionary history of all venomous animals is similar to scorpion evolution in that venom became the most reliable and safest form of predatory attack.
Have you ever noticed a major difference between the size ratio of tails and pincers in different scorpion species?