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Scorpions - Order: Scorpiones
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"We may be likened to two scorpions in a bottle, each capable of killing the other, but only at the risk of its own life."
J. Robert Oppenheimer, director of the 'Manhattan Project' at the Los Alamos Laboratory. (1904-1967)
J. Robert Oppenheimer, director of the 'Manhattan Project' at the Los Alamos Laboratory. (1904-1967)
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As is the case with just about all other arachnid orders, the Order: Scorpiones too, is still in a state of flux. With regards to taxonomic arrangement considerable progress has been been made over the past 20 years or so but, there still remains some ambiguity stemming from the severity of the disagreements on the subject during the early 2000's. At present, the most informed and up-to date online resource regarding scorpion taxonomy and scorpions in general appears to be 'The Scorpion Files', a website which draws contributions from around the world and is owned and maintained by the Norwegian zoologist, Jan Ove Rein, M.Sc. For continuity purposes, information on The Northern Rivers Project, pertaining to taxonomic classification of scorpions has been derived from 'The Scorpion Files' as a neutral resource.
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The Order: Scorpiones contains 2,811* known species (as of March 2024) which are grouped into 23 * families. One family, the Buthidae, contains nearly half of all the species. Scorpions can be found on all continents except Antarctica but most diversity is found in warmer climates. They are not normally found at latitudes north of 52 degrees. In the late 19th century scorpions were introduced into Great Britain and there are now a small number of established populations there. Introductions in to New Zealand and other Pacific islands ultimately failed thanks to the newcomers having been eradicated.
Many scorpions are said to be 'xerocoles' , meaning they are specially adapted for life in some of the hottest places on Earth. Many others are found in less demanding environments. |
Scorpions are typical arachnids; they have a 'fused' head and thorax (prosoma) from which protrude the mouthparts, two pedipalps, each ending in a chela or claw, as well as four pairs of legs for walking. The carapace covering the prosoma usually has a pair of eyes at the front looking forward and a further two to five pairs of eyes located elsewhere on the carapace. The abdomen or opisthosoma, than follows and this consists of two parts: the preabdomen or mesosoma, the wider part of the abdomen, and the 'tail' or metasoma. The preabdomen is made up of seven ** segments (or somites) covered with protective plates (or tergites) on top. Underneath; segment 1 has the 'gonopore' or genital pore. Segment 2 has a sternite that doubles as a base for the 'pectines', V-shaped comb-like structures that in scorpions functions as sensory organs. Segments 3 to 7 are covered with plates (or sternites) but segments 3 to 6 also have a 'spiracle' (opening to the booklungs) on each side. The metasoma or 'tail' consists of 5 segments plus the 'telson', or stinger. Segments 1 to 4 serve no purpose but to help create a flexible abdominal extension. Segment 5 has the anal opening at the end. The five segments have keels and setae, or bristles, which may aid in species identification. The telson contains the vesicle, a membrane within which are held a pair of symmetrical venom glands, each with its own outlet duct leading to the pointy end of the stinger.
Male and female scorpions are very much alike and difficult to tell apart.
Male and female scorpions are very much alike and difficult to tell apart.
Image 1. The Swedish fossil, Palaeophoneus nuncius, found in 1884. From 'The Oldest Airbreathers.' and article in 'The Popular Science Monthly', July, 1885.
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The fossil record for scorpions goes back to the Silurian era (443-419 My ago). Fossil finds have been numerous as have been the number of locations where they were found. The first scorpion fossils found and properly described were discovered in the early 1830's in an area of Europe then known as Bohemia (roughly equiv. to modern Chech Republic). Further discoveries followed in America and various other places including England, France, Germany and other places from around the globe. The oldest fossil of a scorpion was found in Lanarkshire in southern Scotland in 1883. A fossil of similar age was discovered about a year later on the island of Gottland, Sweden. Both were remarkably good fossils in that they showed practically the entire animal in good detail. Since then, scorpion fossil finds have become fairly common to the point that they have become sought after specimens for collectors.
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Image 2. The Scottish fossil found in 1883. From 'The Oldest Airbreathers.' and article in 'The Popular Science Monthly', July, 1885.
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Infraorder: Orthosterni
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Like spiders, scorpions are unable to digest solids internally. To eat they pull small bits of their prey using their chelicerae and deposit this into a 'pre-oral cavity' where digestive fluids is secreted onto it, After a while the food has become liquid and is sucked into the gut. Any solids remaining are ejected. Prey is very much dependant on the size of the scorpion. Small scorpions tend to stick to other small invertebrates and larger scorpions manage to tackle larger prey. Even small mammals are not necessarily safe from them. Scorpions range in size from about 8 mm to a whopping 230 mm in length. All scorpions produce venom that helps them in both prey capture as well as defense.
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There appears to be solid evidence to say that some scorpions can reproduce by means of 'parthenogenesis' but most reproduce sexually and it often involves some form of mating ritual. Once mating is succesful the genital operculum is plugged and the female cannot mate with another male again. Gestation varies and in some species may take nearly a year. Scorpions give birth to 3 to 100 live young (called 'scorplings') and the mother carries them with her until after the first moult. Once moulted the juvenile scorpions resemble the adults in form but may need a few more days with the mother to allow their exoskeleton to harden and to develop their pigmentation.
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* = 2,811 is the figure as of March 2024. Many sources quote 21 or 22 families rather than 23 as mentioned here. The Family: Akravidae to date is known only from remains found in a cave in Israel and no live specimens have been found (yet). The Family: Anurotonidae was only recently split from the Family: Chactidae by Santibanez-Lopez et al in July 2023. Sources that quote 22 families usually do not include the latter.
** = The scorpion embryo has eight segments but segment number 1 disappears prior to birth leaving the newborn with segments number 2 to 8.
** = The scorpion embryo has eight segments but segment number 1 disappears prior to birth leaving the newborn with segments number 2 to 8.
Julius Robert Oppenheimer, often referred to as 'the father of the atomic bomb' was the single-most instrumental figure in the development of the atomic bomb by the United States during the early 1940's and which culminated in the world's first nuclear explosion on the 16th of July, 1945, at a test-site in New Mexico, U.S.A. Less than four weeks later, this was followed by nuclear bombs being dropped on the Japanese cities of Hiroshima and Nagasaki on the 6th and 9th of August respectively. Whereas this effectively ended WW II, it also was the catalyst for an 'Arms Race' between nations that continues to this day. His life story was depicted in the 2023 movie 'Oppenheimer', which in 2024 won seven Oscars, including 'Best Picture', Best Director' and 'Best Actor'.
References and links:
Image 1. The Swedish fossil, Palaeophoneus nuncius, found in 1884. From: 'The Oldest Airbreathers.' an article in 'The Popular Science Monthly', July, 1885.
Image 2. The Scottish fossil found in 1883. From: 'The Oldest Airbreathers.' an article in 'The Popular Science Monthly', July, 1885.
> Fet, V., Sissom, W.D., Lowe, G. and Braunwalder, M.E., (2000). ‘Catalog of the Scorpions of the World (1758-1998).’ The New York Entom. Soc.
> Lourenço, W.R., (2008). ‘Parthenogenesis in Scorpions: Some History – New Data.’ Journal of Venomous Animals and Toxins Including Tropical Diseases. 14 (1). doi:10.1590/S1678-9199200800010000
> Pocock, R.I., (1901). ‘The Scottish Silurian Scorpion.’ J. Cell. Sci. 1 March 1901; s2-44 (174): 291–311. https://doi.org/10.1242/jcs.s2-44.174.291
> Polis, G.A., (1990). ‘The Bilology of Scorpions / edited by Gary A. Polis.’ Stanford University Press, Stanford, Calif.
> Rein, J.O., ( 2017). ‘ The Scorpion Files.’ Trondheim: Norwegian University of Science and Technology. [Accessed 25-04-2024].
Available from, https://www.ntnu.no/ub/scorpion-files/
> Rein, J.O., (2023). ‘The Scorpion Files.’ In: Bánki, O., Roskov, Y., Döring, M., Ower, G., Hernández Robles, D.R., Plata Corredor, C.A., Stjernegaard Jeppesen, T., Örn, A., Vandepitte, L., Hobern, D., Schalk, P., DeWalt, R.E., Ma, K., Miller, J., Orrell, T., Aalbu, R., Abbott, J., Adlard, R., Adriaenssens, E.M. et al., ‘Catalogue of Life Checklist.’ (Apr 2023). https://doi.org/10.48580/dfs6-3f6
> Santibáñez-López, C.E., Ojanguren-Affilastro, A.A., Graham, M.R. and Prashant P. Sharma, P.P., (2023). ‘Congruence between ultraconserved element-based matrices and phylotranscriptomic datasets in the scorpion Tree of Life.’ Cladistics, 2023, Vol.39, Iss. 6, 533-547. https://doi.org/10.1111/cla.12551
https://biodiversity.org.au/afd/taxa/SCORPIONES
https://en.wikipedia.org/wiki/Gonopore
https://en.wikipedia.org/wiki/J._Robert_Oppenheimer
https://en.wikipedia.org/wiki/Parthenogenesis
https://en.wikipedia.org/wiki/Pecten_(biology)
https://en.wikipedia.org/wiki/Scorpion
https://en.wikipedia.org/wiki/Silurian
https://en.wikipedia.org/wiki/Spiracle_(arthropods)
https://en.wikipedia.org/wiki/Telson
https://en.wikipedia.org/wiki/Xerocole
https://www.mindat.org/taxon-872.html
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