It never ceases to amaze me how excited everybody gets about the prospect of finding life elsewhere in the universe, even if that life is likely to be in a form of thin layer of slime somewhere deep in the rocks, while our own planet is bursting with forms that would be considered figments of drunk imagination, if not for the fact that they actually exist. Among them, few possess a more fantastic combination of features than vinegaroons (Thelophonida), also known as tailed whipscorpions.
I first saw a live vinegaroon in Arizona. It just happens that the southern US has the world’s largest species; one who also has a strange preference for dry habitats. Normally, vinegaroons have little tolerance for water loss, and most species are found in tropical rainforests. Vinegaroos have poor vision, and thus their picture of the world is pieced together mostly from the input of thousands of chemical, vibrational, and pressure receptors that cover their entire body. The first pair of legs acts as sensitive antennae, smelling and feeling for prey. At the opposite end of the body a long “whip” (telson) constantly scans the world around the animal like a super-sensitive aerial searching for signals from space. It can detect the faintest odors or movement of air molecules that may signify danger, and the sensors that cover its surface send a constant stream of information to the vinegaroon’s central nervous system. If a potential attacker is detected, the animal snaps into action. But rather than trying to use its formidable pedipalps, which can easily crush large prey insects, the vinegaroon engages its chemical warfare.
At the base of the “whip” a small segment known as the pygidium opens up to a gland filled with a powerful mixture of acetic, octanoid, and caprylic acids (the mix contains 83-84% acetic acid, which is also present in vinegar, hence the animal’s common name; vinegar, however, has only 5-8% of the acid.) The moment a threat is detected, the pygidium, guided with the signals from the “whip”, sends a precisely directed acid spray, smack into the face of the attacker. Being sprayed with concentrated, foul-smelling vinegar is no fun, but even worse is the aftereffect – the caprylic acid in the spray, if it lands on an arthropod’s exoskeleton, destroys the lipids that cover its surface, which not only increases its permeability to the vinegar, but also causes accelerated dehydration. To a desert spider or a ground beetle this may mean death. (Thankfully, our bodies don’t have the exoskeleton, and thus vinegaroons’s chemical weapons have little effect on us; after all, we put vinegar in our food.)
Like their close cousins, tailless whipscorpions, vinegaroons are rather peaceful creatures, with elaborate mating rituals and extensive maternal care. Although they are solitary predators, they are known to share large items of prey, and up to six individuals have been seen feeding at the same time on a particularly large millipede or beetle. Recent phylogenetic work on the relationships of vinegaroons confirms a long-held belief that their closest relatives are tiny, enigmatic shorttailed whipscorpions (Schizomida). They look like ant-sized, pale vinegaroons, but lack the long “whip”. They do, however, employ similar chemical defenses, albeit little is known about the specifics of this behavior.
Considering how incredible vinegaroons and their relatives are, it is not surprising at all that creatures in scifi movies often borrow heavily from their morphology. But if there is one thing that is certain, it is that nowhere else in the universe will you find anything like these remarkable creatures.