Scorpion
Scorpions are arachnids and have eight legs like their cousins—spiders, mites, and ticks. They can quickly grab an insect with their pincers and whip their telson, the poisonous tip of their tail forward and sting their prey. They use their poison to kill prey and to defend against predators.
Scorpions look like small lobsters and may be the first animals to move from water to land hundreds of millions of years ago. They have been around since before the age of the dinosaurs. Fossils of scorpions from Scotland hundreds of millions of years ago show that their appearance hasn’t changed over the millennia, but they are now half the size of their ancient ancestors.
Only 30 or 40 species around the world have strong enough poison to kill a person. Each species has a special type of venom that works well against a chosen prey.
Scorpions typically eat insects, but when food is scarce, they can slow their metabolism to as little as one-third the typical rate for arthropods. This technique enables some species to use little oxygen and live on only one insect per year. Such survival skills allow scorpions to live in some of the planet’s toughest environments. Researchers have even frozen scorpions overnight, only to put them in the sun the next day and watch them thaw out and walk away. However, they are burrowing animals, so in areas of permafrost or heavy grasses, where loose soil is not available, scorpions may not be able to survive.
Neuroparasitology and Tropical Neurology
Taxonomy and distribution of venomous scorpions
Scorpions are arthropods of the class Arachnidia, order Scorpiones. There are more than 1500 recognized species of scorpions, which are widely distributed all over the world with the exception of Arctic and Antarctic regions (Chippaux and Goyffon, 2008). While all scorpions are venomous to their natural prey (insects, lizards, mice), only a few species are potentially lethal to humans. Taxonomy of scorpions is continuously changing, and they are currently classified into several families, of which the most significant is the family Buthidae as it includes almost all medically important species: Androctonus spp. (fat-tailed scorpions), Centruroides spp. (bark scorpions), Leiurus spp. (death stalker), Tityus spp. (Brazilian yellow scorpion), Buthus spp., Mesobuthus spp., and Parabuthus spp. Relevant scorpions from other families include Opistopthalmus glabrifons (yellow creeping leg scorpion), Nebo hierichonticus, Hemiscorpion lepturus, as well as Hadrurus spp., Cercophonius spp., Urodacus spp., and Vaejovus spp.
Scorpions mainly inhabit desert areas, and have been adapted to live in these hot and dry regions of the world. Androctonus spp. and Leiurus spp. are found in Northern Africa and the Middle East, Buthus spp. and H. lepturus in the Mediterranean region as well as in the Middle East and East Africa, Mesobuthus spp. (Fig. 28.5) in Southern Asia and the Indian Subcontinent, Parabuthus spp. in South Africa, Centruroides spp. in North and Central America, and Tityus spp. in South America (Chippaux and Goyffon, 2008). In Australia, members of Buthidae, Bothruiridae (Cercophonius spp.) and Urodacidae (Urodacus spp.) account for most cases of scorpion stings (Isbister et al., 2003b).
Environmental Emergencies
Scorpion
Scorpions are found throughout the world. In the United States, scorpions are found mostly in the southwest. However, only one species, C. exilicauda, is particularly dangerous. At one time it was found only in Arizona, though more recently it has also been spotted in California, New Mexico, Nevada, and Texas. This species has been known by several different names, including Centruroides sculpturans. It is commonly known as the bark scorpion and is typically found on or near trees.
The venom apparatus of a scorpion is found on its tail and consists of a stinger and two venom glands. The toxicity of scorpion venom varies widely from species to species. The venom of C. exilicauda is predominantly a neurotoxin that causes or enhances repetitive firing of axons by activation of sodium channels. Despite its effects, no deaths have been reported from C. exilicauda envenomation in the United States since 1968.
Scorpions
Scorpion probes are quite unique in that the priming and product detection are accomplished through the use of a single oligonucleotide that functions both as primer and probe (Whitcombe et al., 1999). As with the TaqMan and molecular beacon probes, scorpion probes exhibit a 5′ fluorophore and a downstream non-fluorescent quencher. A stem-loop structure limits fluorescence while the 3′ end anneals to the template and supports PCR product synthesis. After a second high temperature denaturation, the stem-loop structure is disrupted, allowing the loop, which is complementary to the new strand that was synthesized by extension of the 3′ end of the scorpion, to base pair in an intramolecular manner to the PCR product which is now part of the same molecule (Fig. 19.9). The opening of the loop and physical separation of the 5′ fluorophore from the quencher results in fluorescence signal emission. This method is sometimes referred to as scorpion PCR and the resulting product might be thought of as a self-probing amplicon. Theoretically, the reaction is faster than other real-time methods because the reaction is unimolecular.
