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What are scorpions?

Why study scorpions?
Life History
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Scorpions are notorious worldwide, although only about 25 species are known to be medically important.  Scorpion envenomation represents a significant cause of human morbidity and mortality in a number of countries and regions worldwide (e.g. Mexico, Brazil, North Africa, the Middle East, India).  Some 100,000 scorpion stings occur annually in Mexico and as many as 800 people (mostly young children and the elderly) die as a result (Simard & Watt 1990).  Comparable statistics probably occur in North Africa and the Middle East.

The highly venomous species are all in the family Buthidae (Balozet 1971; Bücherl 1971).  Most of these occur in the New World genera Centruroides and Tityus, and the Old World genera Androctonus, Buthus, Leiurus, Mesobuthus, and Parabuthus.  Centruroides sculpturatus (recently taken out of synonymy with C. exilicauda), from Arizona, California, and New Mexico, is the only species known to be lethal in the USA, but recent mortality rates are virtually zero for this species owing to the development of antivenins (Likes, et al. 1984).  Venoms of dangerous scorpions have their most adverse effects on young children and to adults suffering from hypertension and general debility.

Envenomation by dangerous species leads to both local and systemic symptoms (Simard & Watt 1990).  More local symptoms include burning pain, swelling, and redness.  The beginning of systemic involvement is indicated by sweating, increase in heart rate and blood pressure.  Depending on species, this may be followed by excessive salivation, wheezing, blurred vision, restlessness, anxiety, vomiting, involuntary urination and defecation, muscle twitching and convulsions, and instable temperature.  Death is usually the result of respiratory or cardiac failure.  Additional information on severe envenomation may be found in Simard & Watt (1990) and Keegan (1980).

Most scorpions are harmless; the sting of many species may be painful, causing local numbness, redness, and swelling, but is not dangerous.  The vast majority of scorpion sting cases, in fact, require no medical treatment.  Even stings of the more venomous species do not always lead to severe symptoms.  Out of 438 cases of C. sculpturatus envenomation studied in Arizona in 1980-1981 by Likes et al. (1984), 92% were treated at home; most of the 8% referred to hospital care were children under the age of five years, and there was no mortality.

Literature Cited:

Balozet, L. 1971. Scorpionism in the Old World. In: Bücherl, W. & Buckley, E.E. (Eds.) Venomous Animals and Their Venoms, Vol. 3, Venomous Invertebrates. Academic Press, New York, 349–371.

Bücherl, W. 1971. Classification, biology, and venom extraction of scorpions. In: Bücherl, W. & Buckley, E.E. (Eds.) Venomous Animals and Their Venoms, Vol. 3, Venomous Invertebrates. Academic Press, New York, 317–347.

Keegan, H. L.  1980.  Scorpions of Medical Importance.  Univ. Press of Mississippi, Jackson,  144 pp.

Likes, K. W. Banner, and M. Chavez.  1984.  Centruroides exilicauda envenomation in Arizona.  The Western Journal of Medicine, 131: 634-637.

Simard, J.M. & Watt, D.D. 1990. Venoms and toxins. In: Polis, G.A. (Ed.) The Biology of Scorpions. Stanford University Press, Stanford, CA, 414–444.


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