Differences in sprinting performance between burrowing and non-burrowing scorpions

 

Scorpions are different. Some move quickly, others more slowly. Some make burrows and stay there most of the time, while others are more active on the surface and hide under suitable objects during daytime. Eran Gefen and co-workers have recently published a study where they tested the endurance of three Israeli buthids and two scorpionids. 

The study showed that buthids are fast runners, but they tire more quickly. The burrowing scorpionids are slower, but show more endurance. The authors discuss the physiology behind these differences. The faster sprinting speed in buthids are probably an adaption to escaping predators, while the endurance seen in scorpionids is probably an adaption for digging deep burrows over a longer time.

Please note that there is a correction published for this article (it is available on the article's main page). 

Abstract:
Aerobic capacity in arachnids is closely linked with considerable structural variation in their respiratory systems. However, although all scorpions are non-tracheated and possess four pairs of book lungs, they vary greatly in their locomotor activity patterns. Many nonburrowing species express short bursts of activity whereas other species dig deep burrows within hours, suggesting more aerobically fueled exercise.We hypothesized that locomotion in surface dwellers is more dependent on anaerobic ATP synthesis, and that this would be reflected in their exercise performance and functional adaptation to potential disturbance of resting-state homeostasis. We used an experimental design consisting of two surface-dwelling Buthidae species (Hottentotta judaicus and Leiurus hebraeus), a burrowing buthid (Buthus israelis) and two burrowing Scorpionidae (Scorpio fuscus and Scorpio palmatus). Maximum running speeds were higher for buthids, which were also more prone to fatigue than scorpionids. Higher respiratory exchange ratios recorded for buthids during activity and subsequent recovery indicated a higher reliance on anaerobically fueled locomotion compared with scorpionids. Our data show that quicker removal of excess CO2 resulting from anaerobic exercise and hemolymph buffering in buthids is associated with significantly higher carbonic anhydrase activity in their hemolymph, compared with that of scorpionids. Efficient CO2 emission may also contribute to the lower respiratory water losses of buthids, and thus assist in facing both biotic and abiotic challenges of surface existence, from which the scorpionid burrows provide refuge.

Reference:
Gefen E, Atiya S, David LM, Talal S. Sprinting performance is linked to surface activity in scorpions. J Exp Biol. 2026;229:jeb251978. [Open Access]

Thanks to Matt Simon for informing me about this article and for his comments about it. 

A redescription of the endemic Buthus kunti from Cyprus and information about its habitat and ecology

 

Cyprus is very special because it is the only place where you can find members of both Buthus Leach, 1815 and Aegaeobuthus Kovarik, 2019 (previously Mesobuthus Vachon, 1950) (Buthidae). For many years only A. cyprius (Gantenbein & Kropf, 2000) was known from the island, but in 2011 surprisingly a second species was described, B. kunti Yagmur, Koc & Lourenço, 2011.

Ersen Yagmur and co-workers have recently published a redescription of  Buthus kunti based on new materials. The article has updated information about the species' distribution and habita. It seems that this species has other habitat preferences than Aegaeobuthus cyprius and that the two species are not sympatric. More studies may change this assumption.

Abstract:
Buthus kunti Yağmur, Koç & Lourenço was described based on a female holotype specimen from Cyprus. This species is redescribed based on the holotype and additional specimens collected from Cyprus, with the male description and variational information presented for the first time. Detailed illustrations and UV light images of the female holotype and male specimen are provided. The first ecological observations of B. kunti are presented here. We observed that B. kunti prefers sandy soil and is a burrowing species. Additionally, we observed that B. kunti is associated with the bushes of Cistus salviifolius. According to our observations, specimens sit under the branches of these bushes or climb them. Adults were observed under the bushes, whereas subadult specimens were observed on the branches. We also report the first recorded case of cannibalism in this species, documenting two instances.

Reference:
Yağmur EA, Boğaç KK, Michael H, Hasan B, Gücel S. The morphology of Buthus kunti Yağmur, Koç & Lourenço (Scorpiones: Buthidae) and first description of male with some ecological observations. Journal of Natural History. 2025;59(25-28):1775–805. [Subscription required for full text]

Thanks to Ersen and Michael for sending me their article!

Shelter size and scent are factors that have an impact on shelter selection in females of two scorpion species

 

Shelter selection and shelters are important for the survival of most scorpions. Some scorpion dig their own burrow, others use naturally existing ones like cracks and crevices in rocks and stones, depressions under stones and burrows made by other animals.

Janina Hladik and co-workers have recently published a study investigation shelter selection (with focus on shelter size and scent) in females of Euscorpius italicus (Herbst, 1800) (Euscorpiidae) and Mesobuthus gibbosus (C.L. Koch, 1839) (Buthidae).

Females of both E. italicus and M. eupeus favor larger over smaller shelters, while they do not show clear preferences for conspecific scents. An impairment experiment showed that the scorpions could not detect size nor scent properly when either their pectines or pedipalps were impaired.

Abstract:
Shelter selection is an important task in an animal’s life. Concerning scorpions, little is known on the evaluation of potential shelters and the importance of chemosensation. To address these issues, we conducted a two-choice shelter test in rectangular open field arenas to identify properties rendering shelters attractive for female scorpions of the species E. italicus and M.  prey, aversive: rosemary oil). Contact with the shelters was video-recorded under red light for 13 h, including the whole night phase. Results revealed a preference for larger shelters, with conspecific scent having minor or no influence. Striking differences occurred with regard to prey and rosemary oil scents. Prey scent was more attractive to M. eupeus, while rosemary oil did not act as a repellent. E. italicus was not very attracted by prey scent, but was repelled by rosemary oil. These findings might reflect the different habitats, semi-arid vs. Mediterranean climates: prey and rosemary are scarce in the semi-arid climate (habitat of M. eupeus), whereas they are abundant in the Mediterranean climate (habitat of E. italicus). We carried out impairment experiments to identify the main sensory organs responsible for the above observations. These are the pectines and pedipalps which function as mechano- and chemosensors. Scorpions could not detect size nor scent properly when either their pectines or pedipalps were impaired.

Reference:
Hladik J, Bailer Y, Wolf H, Stemme T. Shelter selection in females of two scorpion species depends on shelter size and scent. J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2024. [Open Access]

Burrowing in two scorpion species from Iran

Babak Vazirianzadeh and co-workers have recently published a study of the habitat choice and burrowing behavior of the two scorpions Scorpio maurus Linnaeus, 1758 (Scorpionidae)  and Odonthubutus bidentatus (Lourenço & Pezier, 2002) (Buthidae) from Iran.

Abstract:
Background: The different features of scorpions can be successfully described by their nesting and burrowing behaviors. There is little information about burrowing activity of Iranian scorpions.
Methods: The current study was performed to compare the burrowing behavior between two burrowing Iranian scorpions, Scorpio maurus and Odonthubutus bidentatus by describing 30 nests of each species regarding collecting the scorpions.
Results: Scorpio maurus and O. bidentatus have a tendency to make nest with elliptical, round-like entrance and oval shape with arch at the top, respectively. There was not any significant difference between nest entrance properties of two scorpions. One-way ANOVA test showed that the height and diameter of two species nests were not significantly different. A Pearson correlation also showed a relative strong direct relationship between height and diameter of S. maurus nests than O. bidentatus. This correlation was not significant in the case of O. bidentatus. The results provided additional habitat information of scorpions.
Conclusion: The nests morphology characteristics of two Iranian scorpions including shape, depth, length and diameter depend are different from each other based on the following factors: species, soil texture, soil moisture and region conditions.

Reference:
Vazirianzadeh B, Jalali A, Chrom M, Mohammady A, Vatandoost H, Panahi F. A Comparative Study of Nesting Sites and Burrowing Habits of Two Iranian Burrowing Scorpions. Journal of Arthropod-Borne Diseases. 2017;11(1):78-85. [Open Access]

Similarities in scorpion burrows imply similar function

Amanda Adams and co-workers have recently published an analysis of the burrow structures of three scorpion species in the family Scorpionidae (Scorpio palmatus (Ehrenberg, 1829) from Israel and Opistophthalmus setifrons Lawrence, 1961 and O. wahlbergii Thorell, 1876 from Namibia).

The following similar architectural structures of burrows were found for all three species:

1. Just below the entrance, all species had a horizontal platform.

2. All three species had at least two bends of the vertical tunnel going down.

3. The burrows of all species ended in an enlarged terminal chamber (usually larger for female occupants).

The article concludes that the similarity of the burrow structure has a common goal of managing the scorpions physical environment (keeping temperature and humidity stable and optimal) and providing protection from predators and cannibalistic conspecifics.

This is an interesting and readable article for those of you interested in scorpion ecology and scorpions adaption to their environment.

Abstract:
Many animals reside in burrows that may serve as refuges from predators and adverse environmental conditions. Burrow design varies widely among and within taxa, and these structures are adaptive, fulfilling physiological (and other) functions. We examined the burrow architecture of three scorpion species of the family Scorpionidae: Scorpio palmatus from the Negev desert, Israel; Opistophthalmus setifrons, from the Central Highlands, Namibia; and Opistophthalmus wahlbergii from the Kalahari desert, Namibia. We hypothesized that burrow structure maintains temperature and soil moisture conditions optimal for the behavior and physiology of the scorpion. Casts of burrows, poured in situ with molten aluminum, were scanned in 3D to quantify burrow structure. Three architectural features were common to the burrows of all species: (1) a horizontal platform near the ground surface, long enough to accommodate the scorpion, located just below the entrance, 2–5 cm under the surface, which may provide a safe place where the scorpion can monitor the presence of potential prey, predators, and mates and where the scorpion warms up before foraging; (2) at least two bends that might deter incursion by predators andmay reduce convective ventilation, thereby maintaining relatively high humidity and low temperature; and (3) an enlarged terminal chamber to a depth at which temperatures are almost constant (±2–4 °C). These common features among the burrows of three different species suggest that they are important for regulating the physical environment of their inhabitants and that burrows are part of scorpions’ Bextended physiology^ (sensu Turner, Physiol Biochem Zool 74:798–822, 2000).

Reference:
Adams AM, Marais E, Turner JS, Prendini L, Pinshow B. Similar burrow architecture of three arid-zone scorpion species implies similar ecological function. The Science of Nature. 2016;103(7):1-11.[Subscription required for full text]

See also: Scorpions have similar tastes in burrow architecture

Hormuridae reinstalled after study on the evolution, biogeography and phylogeny of Indo-Pacific taxa

Indo-Pacific hormurid scorpion phylogeny from one of the two new studies on hormurid scorpions.

Lionel Monod and Lorenzo Prendini have recently published a major study on the evolution, biogeography and phylogeny of Indo-Pacific scorpions belonging to several genera previously placed in Hemiscorpiidae. This is a complicated study and I recommend to read the paper to get all details concerning the conclusions listed below.

Another paper by Monod, Harvey and Prendini on hormurid scorpions was published in the end of last year. This paper actually preceded the Monod & Prendini paper in content, and I have therefor not written about it until now, when the latter paper is published. In the first paper three new species of Hormurus are described and the evolution of burrowing behavior in the reinstalled family Hormuridae is discussed.

Main conclusions:

Family Hormuridae Laurie, 1896 is elevated to family rank after being a subfamily in Hemiscorpiidae.

The genera Hormiops Fage, 1933 and Hormurus Thorell, 1876, previously placed in synonymy with Liocheles Sundevall, 1833, are reinstated as valid genera. See Scorpion Files family page for list of species which are included in the reinstalled genera.

Genera Cheloctonus Pocock, 1892, Chiromachetes Pocock, 1899, Chiromachus Pocock, 1893, Hadogenes Kraepelin, 1894, Hormiops Fage, 1933, Hormurus Thorell, 1876, Iomachus Pocock, 1893, Liocheles Sundevall, 1833, Opisthacanthus Peters, 1861, Palaeocheloctonus Lourenco, 1996 and Tibetiomachus are included in Hormuridae.

The family Hemiscorpiidae includes now only the genus Hemiscorpius Peters, 1861.

Based on the conclusions in the current paper, I have chosen to reinstall the family Heteroscorpionidae Kraepelin, 1905 in The Scorpion Files and moved the genus Heteroscorpion Birula, 1903 from Hemiscorpiidae to Heteroscorpionidae. See familiy pages (links below) for more details.

The following new species are described from Australia:

Hormurus ischnoryctes Monod & Prendini, 2013
Hormurus macrochela Monod, 2013
Hormurus ochyroscapter Monod, 2013

Hormurus longimanus (Locket, 1995) is reinstated as the valid name for this species and the replacement name, Liocheles extensus Locket, 1997 is placed in synonymy.

Abstract 1:
Scorpions previously assigned to the genus Liocheles Sundevall, 1883, of the family Hormuridae Laurie, 1896, are widely distributed in the tropical forests of the Indo-Pacific region. Revisionary systematics of these poorly known scorpions has revealed a tremendous diversity of species. As part of an ongoing investigation, the first analysis of Indo-Pacific hormurid scorpion phylogeny based on morphological data scored for all currently recognized species of Hormiops Fage, 1933, Hormurus Thorell, 1876, and Liocheles, is presented. The taxonomy of these scorpions is reassessed and their biogeography reinterpreted in the light of the phylogeny. Phylogenetic, morphological, and distributional data support the revalidation of Hormiops and Hormurus, previously synonymized with Liocheles. The phylogeny indicates that the Australasian hormurids are more closely related to the Afrotropical and Neotropical hormurids than to the Indian hormurids, as previously proposed, refuting the “out-of-India” origin of Asian hormurids. A recent paleogeographical hypothesis, the “Eurogondwana model”, is supported instead. According to this hypothesis, hormurid scorpions colonized Laurasia from Africa via the Apulia microplate (Europa terrane) in the Cretaceous, subsequently colonized the Australo-Papuan archipelago in the early-mid Cenozoic, and then went extinct in the Northern Hemisphere during the second half of the Cenozoic. These results suggest that, contrary to the traditional paradigm, dispersal and extinction may affect spatial and temporal biotic distributions as much as vicariance, even in animals with limited vagility, such as scorpions.

Abstract 2:
Three new species from the semi-arid ecosystems of Queensland, Australia, are described in the present contribution: Hormurus ischnoryctes n. spec., Hormurus macrochela n. spec., Hormurus ochyroscapter n. spec. Additionally, the discovery of the first female specimens of Hormurus longimanus (Locket, 1995) from the Northern Territory of Australia, as well as additional diagnostic characters and locality records for this species, warranted its redescription. Hormurus longimanus (Locket, 1995) is reinstated as the valid name for this species and the replacement name, Liocheles extensus Locket, 1997 placed in synonymy. Unlike most species of Hormurus and of the closely related genera, Hormiops Fage, 1933 and Liocheles Sundevall, 1883, which inhabit humid tropical ecosystems (evergreen forests), the four Australian species treated here inhabit seasonally dry (monsoon) habitats, and two of these (H. ischnoryctes and H. ochyroscapter) are the first fossorial hormurids to be recorded in Australia, and the first fossorial species of Hormurus to be described. The four species treated here appear to be relicts of an old hygrophilous lineage that sustained a major adaptive radiation during the late Tertiary aridification of the continent. Endemism and conservation issues coneerning these phylogenetically valuable species are discussed in the context of high sensitivity to habitat disturbance and high risk of extinction of stenotopic species.

Reference 1:
Monod L, Prendini L. Evidence for Eurogondwana: The roles of dispersal, extinction and vicariance in the evolution and biogeography of Indo-Pacific Hormuridae (Scorpiones: Scorpionoidea). Cladistics. 2014;In Press. [Subscription required for full text]

Reference 2:
Monod L, Harvey MS, Prendini L. Stenotopic Hormurus Thorell, 1876 scorpions from the monsoon ecosystems of northern Australia, with a discussion on the evolution of burrowing behaviour in Hormuridae Laurie, 1896. Rev Suisse Zool. 2013 Jun;120(2):281-346.

Family Hormuridae
Family Hemiscorpiidae
Family Heteroscorpionidae

Burrows and burrowing in Scorpio maurus - and how to capture them

Burrowing in Scorpio maurus and how to capture this scorpion is presented in a recent issue of the journal Euscorius.

Mehmet Colak and Aysegül Karatas have recently published an article on burrrowing and burrows in Scorpio maurus Linnaeus, 1758 (Scorpionidae) in Turkey. The authors also present a method on how to capture burrowing scorpions.

Abstract:
Shapes of burrows built by Scorpio maurus in southern and south-eastern Turkey were investigated. S. maurus were observed to build burrows with average 20 cm depth and 30 cm length. The burrows were concentrated in agricultural fields, farms, near gardens, and in areas with 5–10% slope. 116 specimens were captured, 77.5% from underground burrows, and 22.5% from their burrows under stones. A new method was tried in order to drive Scorpio maurus, an obligate digger type of scorpions, out of their burrows. Water was poured into a burrow, and the scorpion, which came out near the entrance of the burrow, was captured by placing a shovelful of soil 10 cm behind the entrance. Habitats of Scorpio maurus were observed, and shapes of underground burrows and burrows built under stones were documented.

Reference:
Colak M, Karatas A. Shape of Burrows Built by Scorpio maurus L., 1758 (Scorpiones: Scorpionidae) from Turkey, with Description of Capture Methods. Euscorpius. 2013 (171):1-7. [Free full text]

Burrows and burrowing in Hadrurus arizonensis

Daniel Hembree and co-workers have recently published a paper describing the forms and shapes of Hadrurus arizonensis Ewing, 1928 (Caraboctonidae) burrows. The authors are geologists (and/or palaentologists), and the angle and terminology of this papers is somewhat different from what I'm used to from the traditional scorpion literature. I must admit there are quite a few terms in the paper that unknown to me (but praise Google for being a helpful friend ;)

The goal of the paper is both to learn more about scorpion burrows, but also to aid in the recognition of scorpion burrows in the fossil record and to determine if aspects of palaeoenvironment can be ascertained by variations in scorpion burrow morphology.

The paper also has a nice mini-review of scorpion burrowing behavior and several pictures of burrow castings showing the form and shape of Hadrurus burrows.

Abstract:
Bioturbation by terrestrial animals is common in arid and semi-arid continental environments. Scorpions have comprised a significant portion of the diversity of predatory arthropods in these environments from the Late Paleozoic to the Recent. Many scorpions are active burrowers and likely have a substantial, if rarely recognized, ichnofossil record. This project involved the study of the burrowing behaviors and trace morphologies of the scorpion Hadrurus arizonensis (Scorpiones: Caraboctonidae). Individual animals were placed into sediment-filled terrariums for two- to three-week periods after which burrows were cast, excavated, and described. Descriptions of the subsurface structures included architecture, dimensions, bioglyphs, complexity, and tortuosity. Additional experiments were run with differing sediment composition, density, and moisture to evaluate the animal’s behavioral response to altering environmental conditions. Specimens of H. arizonensis burrowed by scratching and kicking loose sediment from the subsurface with the first two to three pairs of walking legs. The subsurface biogenic structures produced consisted of subvertical ramps, U-shaped burrows, helical burrows, and mazeworks. In the process of excavating the burrows, the desert scorpions also produced a hummocky surface topography as well as structures in dry, sandy sediment that resembled lamination and ripple cross-lamination. Increasing clay content and sediment density increased the complexity of burrow architectures produced. Reducing these variables limited the complexity of the burrows, reduced their likelihood of preservation, and increased the abundance of biogenic cross-lamination. Data collected from these and similar experimental studies can be applied to terrestrial ichnofossil assemblages in order to better interpret the paleoecology of ancient soil ecosystems.

Reference:
Hembree DI, Johnson LM, Tenwalde RW. Neoichnology of the desert scorpion Hadrurus arizonensis: burrows to biogenic cross lamination. Palaeontologia Electronica. 2012;15(1):1-34. [ Free full text]

Thanks to Jahn Hornung for informing me about this paper!

Functional implications of pedipalp chela shapes in scorpions

Arie van der Meijden and co-workers have previously published a paper on claw size and pincer force in scorpions. A follow-up paper is now in press on the functional implications of pedipalp chela shapes in scorpions.

Abstract:
Scorpions depend on their pedipalps for prey capture, defense, mating and sensing their environment. Some species additionally use their pedipalps for burrowing or climbing. Because the pincers or chelae at the end of the pedipalps vary widely in shape, they have been used as part of a suite of characters to delimit ecomorphotypes. We here evaluate the influence of the different chela cuticular shapes on their performance under natural loading conditions. Chelae of 20 species, representing seven families and spanning most of the range of chela morphologies, were assigned to clusters based on chela shape parameters using hierarchical cluster analysis. Several clusters were identified corresponding approximately to described scorpion ecomorphotypes. Finite element models of the chela cuticulae were constructed from CT scans and loaded with estimated pinch forces based on in vivo force measurements. Chela shape clusters differed significantly in mean Von Mises stress and strain energy. Normalized FEA showed that chela shape significantly influenced Von Mises stress and strain energy in the chela cuticula, with Von Mises stress varying up to an order of magnitude and strain energy up to two orders of magnitude. More elongate, high-aspect ratio chela forms showed significantly higher mean stress compared with more robust low-aspect ratio forms. This suggests that elongate chelae are at a higher risk of failure when operating near the maximum pinch force. Phylogenetic independent contrasts (PIC) were calculated based on a partly resolved phylogram with branch lengths based on an alignment of the 12S, 16S and CO1 mitochondrial genes. PIC showed that cuticular stress and strain in the chela were correlated with several shape parameters, such as aspect ratio, movable finger length, and chela height, independently of phylogenetic history. Our results indicate that slender chela morphologies may be less suitable for high-force functions such as burrowing and defense. Further implications of these findings for the ecology and evolution of the different chela morphologies are discussed.

Reference:
van der Meijden A, Kleinteich T, Coelho P. Packing a pinch: functional implications of chela shapes in scorpions using finite element analysis. J Anat. 2012; Early View paper. [Subscription required for fulltext]

Thanks to Dr. van der Meijden for sending me this paper!