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Giant Forest Scorpion - Heterometrus spp.
Topic Started: Sep 1 2012, 03:08 PM (23,254 Views)
linnaeus1758
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Giant Forest Scorpion - Heterometrus spp.

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Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Order: Scorpiones
Family: Scorpionidae
Subfamily: Scorpioninae
Genus: Heterometrus

Description
The genus Heterometrus (giant forest scorpion) is considered to be one of group of scorpion with larger sizes, hence the name giant. Many of these scorpions within the Heterometrus genus are confused because of their similarities of Emperor scorpion (genus Pandinus), which in fact is the biggest recorded scorpion species. A fully grown giant forest scorpion is 100 to 200 mm. from head to tail. Known example of a record Heterometrus swammerdami (292 mm., 56 g.), discovered in the Second World War. It also consists of a variety of colors; mostly starting with shades of mostly black or brown with either hints of blues, light browns, or greens. Some species have reflective shine on their smooth exoskeleton to emphasize the coloration.
The scorpions are heavily build with broad mesosomal tergites and a proportionally slender and thin metasoma. The telson is proportionally small and the stinger often shorter than the vesicle. The cephalothorax and mesosoma are largely devoid of carinae and granulation and the median eyes are situated in a small, lenticular depression on the cephalothorax.
Typically scorpions are loners, but like the Emperor scorpions, this scorpion is a bit of an exception. Adults can be kept in groups of three or more.

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Reproduction
Females are often bulkier and have thinner pincers than the males. These differences, however, can be subtle. The pectines on the underside of scorpions can be inspected to give the you an idea of their scorpion's sex. Place the scorpion in a clear plastic tub and hold it up to inspect the underside of the scorpion. Typically, males have longer combs on their pectines and females have shorter and often fewer combs on their pectines.
The male quickly grasps the pincers of the female and begins a shaking action known as "juddering". Then, after a short shoving match, the male deposits a spermatophore onto the substrate and positions the female over the packet of sperm. The female lowers her abdomen and picks up the spermatophore into her genital opening. The two separate and often beat a hasty retreat in opposite directions.
They reach sexual maturity at about 4 years in the wild, (though in captivity it can be closer to 1 year) and have an average life span of about 7 to 8 years.

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Distribution and habitat
It is distributed widely across tropical and subtropical southeastern Asia, including Cambodia, Laos, Thailand, Vietnam, as well as India, Sri Lanka, Nepal and China (Tibet).Species of Heterometrus live in vegetated, often forested, humid regions with subtropical to tropical climate. As most scorpions they are predominantly nocturnal and hide in burrows, below logs and in leaf litter.

Venom
As in other genera of the Scorpionidae, the symptoms from Heterometrus envenomations are rather mild and no human fatalities are known. The sting causes local pain, inflammation, oedema, swelling and redness of the skin, lasting for hours to a few days. A study has shown that plant extracts known in the traditional Thai medicine as natural scorpion venom antidotes are effective as symptomatic treatment of H. laoticus stings. The protein heteroscorpine-1 was found the major component of the venom in H. laoticus.

In captivity
Due to their impressive size, low toxicity and docile behavior, species of Heterometrus are popular pet scorpions. Unlike many other scorpions they can be kept in pairs or small groups. A group of up to three adult individuals need a vivarium c. 60 x 30 x 30 cm (for 1–3 specimens) in size with a thick layer of peat or similar plant-litter substrate at the ground. A flat hiding place (e.g. a piece of bark) must be provided for each individual. Temperature should range from 21–30°C within the vivarium and a source of water must be present. Air humidity has to be maintained at or above 80%. The scorpions will feed on living food (small insects like crickets).

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Species
Heterometrus barberi (Pocock, 1900)
Heterometrus beccaloniae (Kovařík, 2004)
Heterometrus bengalensis (C.L. Koch 1841)
Heterometrus cimrmani (Kovařík, 2004)
Heterometrus cyaneus (C.L. Koch, 1836)
Heterometrus flavimanus (Pocock, 1900)
Heterometrus fulvipes (C.L. Koch, 1837)
Heterometrus gravimanus (Pocock, 1894)
Heterometrus indus (DeGeer, 1778)
Heterometrus kanarensis (Pocock, 1900)
Heterometrus keralaensis (Tikader & Bastawade, 1983)
Heterometrus laoticus (Couzijn, 1981)
Heterometrus latimanus (Pocock, 1894)
Heterometrus liangi (Zhu & Yang, 2007)
Heterometrus liophysa (Thorell, 1888)
Heterometrus liurus (Pocock, 1897)
Heterometrus longimanus (Herbst, 1800)
Heterometrus madraspatensis (Pocock, 1900)
Heterometrus mysorensis (Kovařík, 2004)
Heterometrus nepalensis (Kovařík, 2004)
Heterometrus petersii (Thorell, 1876)
Heterometrus phipsoni (Pocock, 1893)
Heterometrus rolciki (Kovařík, 2004)
Heterometrus scaber (Thorell, 1876)
Heterometrus sejnai (Kovařík, 2004)
Heterometrus spinifer (Ehrenberg, 1828)
Heterometrus swammerdami (Simon, 1872)
Heterometrus telanganaensis (Javed, Mirza, Tampal & Lourenço, 2010)
Heterometrus thorellii (Pocock, 1897)
Heterometrus tibetanus (Lourenço, Qi & Zhu, 2005)
Heterometrus tristis (Henderson, 1919)
Heterometrus ubicki (Kovařík, 2004)
Heterometrus wroughtoni (Pocock, 1899)
Heterometrus xanthopus (Pocock, 1897)
Edited by linnaeus1758, Jun 13 2014, 03:32 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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