It turns out that the terrifying stonefish isn't content with already having two big defense mechanisms. It has been keeping a third defense mechanism a dangerously guarded secret. Stonefish have a switchblade-like protrusion that comes out of its heads, which it can use to defend itself when in danger.
This only makes stonefish all the more dangerous to encounter.
Switchblade On The Head
Researchers from the University of Kansas found that stonefish have a bony, switchblade-like protrusion called a lachrymal saber. They were able to detect it on a bone under the stonefish's eyes. The results were published in the journal Copeia.
Stonefish can be found in the Indo-Pacific coastal waters. Scientists are still trying to determine how this change happened in the stonefish's evolution and how they may have missed a largely defensive strategy.
Study author William Leo Smith says that scientists may have missed this discovery because of the small group of people that have studied stonefish in the past. In the study, scientists were able to reclassify five or six families of stonefish. Smith says that this is the first step because they may now be able to create an evolutionary map of the stonefish's genes to see how this feature formed.
For the study, scientists completed a genetic analysis of stonefish, which revealed that those who possess the lachrymal saber are more closely related. This finding could change the way stonefish, flatheads, scorpionfish, and sea robins are classified.
The researchers used specimens of stonefish that were part of the pet-fish trade, and some were observed from fieldwork done in Taiwan.
Speaking to CNN, Smith said that this could also be part of a courtship behavior that could help the stonefish gain a mate. He says that there is evidence that can push the researchers toward this fact. Smith adds that they may use the lachrymal sabers to ward off members of their own species in battles to fight, and they also compared them to ram horns.
Another interesting fact about the lachrymal saber is that it glows fluorescent green. Stonefish are known for being adept at camouflaging themselves for protection and while they hunt. Smith added that he doesn't think the color is used to ward off predators.
To use the lachrymal saber, stonefish have a large number of muscles and ligaments that are attached to the bone.