Heterometrus Laoticus: the Laos Black Forest Scorpion

Just about everybody who comes to know me as a friend or acquaintance soon becomes highly aware of the fact that I am a nature lover, and that I take photographs (mostly macro) of arthropods and herpetofauna every chance I get. A few months ago, a colleague of mine brought me a gift: a live Heterometrus laoticus he had found along the rice fields near his house.

Heterometrus laoticus (Couzijn, 1981), male

Identified and described by H.W.C. Couzijn in 1981, Heterometrus laoticus — commonly known as the Laos Black Forest Scorpion — occurs in the tropical rainforests of Laos, Thailand, and Vietnam. It can grow to a size of 12-13cm, and is a communal species, meaning that it tends to live in groups, digging burrows in peaty soil or under dead branches and leaf litter. This particular individual was slightly over 13cm in length.

While most of the online information I have read (mostly care sheets for those in the pet trade) say that this species is highly aggressive, I found this individual to be rather docile: it even crawled onto my hand and was a very willing subject while I took photographs of it.

Booncham et al (2007) published a paper on this species reporting that it displays significant sexual dimorphism — a phenomenon where the males and females of a species differ in shape, size, form, colour, and various other characteristics. In Heterometrus laoticus, females were found to be broader than males, among several other distiguishing traits. For many other scorpion species, microscopic analysis needs to be done in order to tell the difference between sexes. Unforunately, I have not had the privilege of finding a female yet, so my photographs cannot show the aforementioned sexual dimorphism.

Dorsal view of mouth parts: Heterometrus laoticus (Couzijn, 1981), male

This species has been under the spotlight for the past several years, specifically due to the medical significance of its venom. Scorpion venoms are a complex combination of at least three types of toxins (Watt & Simard, 1984) — these could be proteins or peptides.

Note: amino acid molecules form simple chains called peptides. Proteins are formed when one amino acid bonds with a peptide, or also when two or more peptides form a bond together. The toxins found in venoms could be simple molecules, peptides, or proteins. 

Scientists have been studying the these venoms for years, along with those of spiders and snakes, to find medical uses for the components — specific proteins or peptides — found in the venoms.

Close-up of tail and stinger: Heterometrus laoticus (Couzijn, 1981)

In 2007, a new toxin from Heterometrus laoticus venom was isolated by Uawonggul et al, named Heteroscorpine-1, which exhibited “inhibitory activity” against harmful, disease-causing bacteria such as Klebsiella pneumoniae, Pseudomonas aeruginosa and Staphylococcus aureus. Later, in 2014, Hoang et al discovered that the venom of Heterometrus laoticus contained components that, in mice, showed anti-inflammatory properties as well as anti-nociception, which is the ability to reduce sensitivity to pain

Heterometrus laoticus (Couzijn, 1981) in defensive posture

I am quite new to the world of scorpions, and the writing of this post has been a wonderful experience for me: I found dozens of (relevant) published papers via Google Scholar, read through each one of them, and gained a whole lot of knowledge not only on this species, but on scorpions and their venom, too.

The fact that a local species of scorpion has such scientific significance amazes me. And, as always, the more I learn, the more I realize that there is so much more I do not know.

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References:

1. Booncham, U., Sitthicharoenchai, D., Pradatsundarasar, A., Prasarnpun, S., & Thirakhupt, K. (2007). Sexual Dimorphism in the Asian Giant Forest Scorpion, Heterometrus laoticus Couzijn, 1981. NU Science Journal 2007, 4(1), 42-52. Retrieved from http://www.sci.nu.ac.th/rs/upload/s/2550010001nation9.pdf
2. Couzijn, H.W.C. (1981). Revision of the genus Heterometrus Hemprich & Ehrenberg Scorpionidae, Arachnidea). Rijksmuseum of Natural History at Leiden, 184, 1-196.
3. G. (n.d.). Heterometrus laoticus Couzijn, 1981. Retrieved September 13, 2016, from http://www.gbif.org/species/6894876
4. Hoang, A. N. et al. (2014) Vietnamese Heterometrus laoticus scorpion venom: Evidence for analgesic and anti-inflammatory activity and isolation of new polypeptide toxin acting on Kv1.3 potassium channel. Toxicon 77, 40–48.
5. Uawonggul, N., Thammasirirak, S., Chaveerach, A., Arkaravichien, T., Bunyatratchata, W., Ruangjirachuporn, W., . . . Daduang, S. (2007). Purification and characterization of Heteroscorpine-1 (HS-1) toxin from Heterometrus laoticus scorpion venom. Toxicon, 49(1), 19-29. doi:10.1016/j.toxicon.2006.09.003
6. Watt, D. D. & Simard, J. M. (1984) Neurotoxic Proteins in Scorpion Venom. Journal of Toxicology: Toxin Reviews 3, 181–221.

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