Scorpions Extraordinary Facts
All scorpions fluoresce under ultraviolet light. The fluorescence is caused bycalled the hyaline layer. This indicates that the an unidentified substance in a very thin layer in the cuticle of the scorpion fluorescent factor is either secreted by the scorpion shortly after molting or that the fluorescence is a by-product of the tanning process.
Scorpions have been found in many fossil records, including coal deposits from the Carboniferous Period and in marine Silurian deposits. They are thought to have existed in some form since about 425–450 million years ago. They are believed to have an oceanic origin, with gills and a claw like appendage that enabled them to hold onto rocky shores or seaweed.
Scorpion venom is used to subdue prey and to defend against threats, as well as in the mating process. The composition and action of the venom varies from species to species. The venoms are mixtures of salts, small molecules, peptides, and proteins. The peptides are specialized; some act against invertebrates and some against vertebrates, and some target both. This complex formula results in a neurotoxin which depolarizes the nervous system of the victim.
Scorpions are apparently able to regulate the delivery of the venom in scale to the size of their target. Some scorpions are known to produce a transparent prevenom in addition to the more potent opaque venom which is loaded with additional toxin. The use of the prevenom occurs at the initiation of the threat or opportunity. If the action persists, the opaque venom is released. These abilities enable the scorpion to conserve the venom for use when it is needed most, for larger predators or prey.
Medically Significant Scorpion Species
Most of the more venomous scorpions have lighter, more delicate pedipalps and larger, stronger tails. The Buthidae family contains most of the scorpions dangerous to man. They can generally be distinguished by the triangular sternal plate on their ventral side. Other species' sternal plates are more square or pentagonal.
Only one species of scorpion in North America and about 20 others worldwide have venom potent enough to be dangerous to human beings. The North American species, Centruroides exilicauda (formerly called C. sculpturatus), is found over much of Arizona and Mexico. It is also known as the Arizona Bark Scorpion. A small population occurs in extreme southeastern California, and a few records exist for southern Utah and small parts of Texas, New Mexico and Nevada. The venom of this scorpion can cause severe pain and swelling at the site of the sting, numbness, frothing at the mouth, respiratory difficulties, muscle twitching, and convulsions. The sting is more dangerous to infants, small children and the elderly. Death is rare, especially in more recent times. An antivenom was created by Arizona State University but is no longer being produced, and is not FDA approved. The FDA has recently given approval for clinical trials to evaluate a Mexican antivenom for use in the United States.
Medically significant species of scorpion occur worldwide:
- In the Mediterranean and North Africa - Buthus, Leiurus, Androdoctonus and Leiurus
- In Western and Southern Africa - Parabuthus
- Across Southern Africa to S outheast Asia - Buthotus (also known as Hottentotta)
- In Asia - Mesobuthus and the Buthotus (also known as Hottentotta)
- South America - Tityus
The pedipalps are used in scorpion courtship behavior. The male performs a kind of dance with the female, grabbing her pedipalps with his own and dragging her across the ground until he locates a preferred place to deposit his spermatophore, which is then drawn up into the female's genital pore, near the front on the underside of her abdomen. Some species' courtships include a sexual sting of the female by the male.
Scorpion gestation periods vary from several months to a year and a half, depending on the species. Each brood will consist of about 24-35 young. They are viviparious - the young develop as embryos in the female's ovariuterus. The young scorpions are born two at at time, climbing onto their mother's back to be carried there until their first molt in about two weeks, when they will be large and strong enough to take care of themselves.
Scorpions do not metamorphasize as they grow, changing only in size and sometimes to a deeper color with each molt. Typically five or six molts over two to six years are required for the scorpion to reach maturity. The molting is accomplished by a split in the outer covering through which the scorpion must crawl in order to grow.
Scorpion lifespans range from three to five years, though some species are thought to live 10-15 years. Some kinds of scorpions show more sophisticated social behaviors, like colonial burrowing, and living in familial groups that may share burrows and food.