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Arizona Bark Scorpion - Centruroides sculpturatus
Topic Started: Mar 19 2012, 10:08 PM (6,630 Views)
Scalesofanubis
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Arizona Bark Scorpion - Centruroides sculpturatus

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Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Class: Arachnida
Order: Scorpiones
Family: Buthidae
Genus: Centruroides
Species: Centruroides sculpturatus

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The Arizona bark scorpion (Centruroides sculpturatus, included in Centruroides exilicauda), is a small light brown scorpion common to the southwest United States. The range of the scorpion is the Sonoran Desert. An adult male can reach 8 cm in length (3.14 inches), while a female is slightly smaller, with a maximum length of 7 cm (2.75 inches).

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The bark scorpion is nocturnal, prefers to ambush its prey, and usually feeds on crickets or roaches. Bark scorpions are eaten by a wide variety of animals such as birds, reptiles, and other invertebrates. Some examples include spiders, snakes, peccaries, rodents, and other scorpions. Development, pesticides and collecting scorpions for research or the pet trade also has an impact on the bark scorpion population.

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Life cycle
Arizona bark scorpions have a gestation period of several months, are born live, and are gently guided onto their mother's back. The female usually gives birth to between 25–35 young, and the young will remain with their mother until their first molt, up to 3 weeks after birth. Arizona bark scorpions may live up to 6 years. While nearly all scorpions are solitary, the Arizona bark scorpion is a rare exception: during winter, packs of 20 to 30 scorpions can congregate.

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Bark scorpions, like most other scorpions, are incredibly resilient. During US nuclear testing, scorpions, along with cockroaches and lizards, were found near ground zero with no recorded adverse effects. The bark scorpion is particularly well adapted to the desert: layers of fat on its exoskeleton make it resistant to water loss. Nevertheless, bark scorpions hide during the heat of the day, typically under rocks, wood piles, or tree bark. Bark scorpions do not burrow, and are commonly found in homes, requiring only 1/16 of an inch for entry.
Arizona bark scorpions prefer riparian areas with mesquite, cottonwood, and sycamore groves, all of which have sufficient moisture and humidity to support insects and other prey species. The popularity of irrigated lawns, and other systems which increase environmental humidity in residential areas, has led to a massive increase in the number of these animals in some areas.

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The bark scorpion is the most venomous scorpion in North America, and its venom can cause severe pain (coupled with numbness and tingling) in adult humans, typically lasting between 24 to 72 hours. Temporary dysfunction in the area stung is common; e.g. a hand or possibly arm can be immobilized or experience convulsions. It also may cause the loss of breath for a short period of time. Due to the extreme pain induced, many victims describe sensations of electrical jolts after envenomation.
Fatalities from scorpion envenomation in the USA are rare and are limited to small animals (including small pets), small children, and adults with compromised immune systems. Extreme reaction to the venom is indicated by numbness, frothing at the mouth, paralysis, and a neuromotor syndrome that may be confused with a seizure and that may make breathing difficult, particularly for small children. Two recorded fatalities have occurred in the state of Arizona since 1968; the number of victims stung each year in Arizona is estimated to be in the thousands. In Mexico, more than 100,000 people are stung annually, and during a peak period in the 1980s, the bark scorpion claimed up to 800 lives there.

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An antivenom was developed for this species at Arizona State University and produced in quantities sufficient to treat individuals within the state of Arizona up until 1999. FDA approval was not required as it was provided at no charge, and use was restricted to within the state of Arizona; it was very successful in shortening the duration of symptoms and hospitalization. Production of this antivenom ceased by 2000 and the product was unavailable by 2004. A Mexican-produced antivenom, Anascorp [Antivenin Centruroides (scorpion) F(ab′), Laboratorios Silanes, Instituto Bioclon SA de CV], is being tested and used in its place. On August 3, 2011, the FDA approved Anascorp for use in the United States.

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Basic first aid measures can be used to help remediate scorpion stings:
Clean sting site with soap and water
Apply a cool compress (cool cloth, no ice)
Take acetaminophen (paracetamol) or ibuprofen for local pain and swelling
Natural remedies include using the pulp from the prickly pear cactus on the sting site.
Since the amount of venom the scorpion injects on a sting varies, Arizona poison control centers suggest immediate medical attention only in the event of extreme pain or stings involving children.

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Bark scorpions, like most other scorpions, will glow when exposed to a blacklight. This is particularly useful in scorpion detection, since bark scorpions are active during the night, and can be easily spotted using this method. Typical UV LED flashlights are able to readily detect scorpions at a distance of approximately 6 feet. Newly molted scorpions will not glow under ultraviolet light for a few days after molting.

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Edited by Taipan, Apr 17 2014, 10:58 PM.
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How the scorpion's venomous sting evolved

By Jeremy Coles
Reporter, BBC Nature
15 January 2014 Last updated at 02:14

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Humble beginnings for a deadly sting

The sting in a scorpion's tail has been connected to common defensive proteins by scientists.

Defensins are proteins common to many plants and animals that fight off viral, bacterial and fungal pests.

Researchers investigated the relationship between these proteins and the neurotoxins present in scorpion venom.

Their results showed how just a single genetic mutation could convert such a protein into a deadly toxin.

The findings, published in the journal Molecular Biology and Evolution, are the first evidence of an evolutionary relationship between these defensins and toxins, according to scientists.

A scorpion's venom is a potent mix of genetically-encoded toxic proteins used to kill or paralyse prey and defend against predators or competitiors.

Previous evidence suggested a common ancestor between a family of neurotoxins found in this venom and defensins, insect proteins which defend against tiny pests known as microbes.

But Prof Shunyi Zhu from the Chinese Academy of Sciences, who undertook the study, explained that the similarity of the two in terms of their genetic structure was relatively low which "left a puzzle for more than 20 years" for researchers.

In order to confirm the functional link, the team of researchers from China and Belgium analysed the scorpion neurotoxin to find its "signature" - the region of the protein responsible for its structure and function.

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A 3D model of Navitoxin - the toxin engineered from defensive insect protein

They then searched for this key sequence in some of the insect defensive proteins.

It was found in green shield bugs, spined soldier bugs and three species of backswimmer.

"It is surprising that only insect defensins from venomous insects contain scorpion toxin signatures," said Prof Zhu.

"These defensins clearly represent an evolutionary intermediate and could have the potential to develop into a toxin with similar action to scorpion toxins."

To test this theory, the researchers went on to engineer the insect defensive protein to give it scorpion neurotoxin function. They were able to do so by deleting just one single loop in the protein's genetic structure.

"This is a typical example of divergent evolution," said Prof Zhu describing how the shift from microbe immunity to predator defence is a key element in the evolutionary origins of scorpions and their stings.

http://www.bbc.co.uk/nature/25683544




Experimental Conversion of a Defensin into a Neurotoxin: Implications for Origin of Toxic Function
Shunyi Zhu, Steve Peigneur, Bin Gao, Yoshitaka Umetsu, Shinya Ohki, and Jan Tytgat
Mol Biol Evol (2014)
doi: 10.1093/molbev/msu038

Abstract
Scorpion K+ channel toxins and insect defensins share a conserved three-dimensional structure and related biological activities (defense against competitors or invasive microbes by disrupting their membrane functions), which provides an ideal system to study how functional evolution occurs in a conserved structural scaffold. Using an experimental approach, we show that the deletion of a small loop of a parasitoid venom defensin possessing the “scorpion toxin signature” (STS) can remove steric hindrance of peptide-channel interactions and result in a neurotoxin selectively inhibiting K+ channels with high affinities. This insect defensin-derived toxin adopts a hallmark scorpion toxin fold with a common cysteine-stabilized α-helical and β-sheet motif, as determined by nuclear magnetic resonance (NMR) analysis. Mutations of two key residues located in STS completely diminish or significantly decrease the affinity of the toxin on the channels, demonstrating that this toxin binds to K+ channels in the same manner as scorpion toxins. Taken together, these results provide new structural and functional evidence supporting the predictability of toxin evolution. The experimental strategy is the first employed to establish an evolutionary relationship of two distantly related protein families.

http://mbe.oxfordjournals.org/content/early/2014/01/09/molbev.msu038.abstract?sid=921822c4-c8f7-49f7-872a-f207df23d376
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