Do hot temperatures cause hot tempered scorpions?

 

Scorpions are dependent on the temperatures in its environment to regulate their body temperatures (being ectothermic) and they will probably also have an effect on scorpion behavior. Scorpions use their sting and venom in prey capture and defense. 

Zia Nisani and co-workers have recently published a study looking into if and how different temperatures impact stinging behavior in Hadurus obscurus Williams, 1970 (Hadruridae). They tested how different temperatures impacted the defensive sting response and also the prey capture behavior at three different temperatures.

Scorpions with higher temperatures were faster to sting and required less provocation before stinging. In addition, "hotter" scorpions were quicker to catch prey and succeed with it. A physiological explanation for these results is probably that increased temperatures will increase muscle performance and metabolic rate. 

Abstract:
Scorpions employ their stinging mechanism both for defense and predation, and being ectothermic, temperature influences their physiology and behavior. As such, we hypothesized that temperature both affects defensive stinging and prey-capture behavior in scorpions. We tested the effects of body temperature on these behaviors in the desert hairy scorpion, Hadrurus obscurus Williams, 1970. In the first experiment, scorpions were placed in temperature-controlled chambers with either high (26-28°C) or low (21-22°C) temperatures and probed to elicit a defensive sting. We recorded the reaction time and the number of probes needed to elicit a sting. In the second experiment, we observed and recorded prey capture behavior at three different temperatures (21, 29, and 33°C). Scorpions with higher body temperatures had faster defensive reaction times and required fewer probes to elicit a sting. Furthermore, at a higher temperature, scorpions were more likely to attempt and succeed in prey capture, but temperature did not seem to affect post-capture stinging behavior. As the temperature rises, increasing muscle performance and metabolic rate in ectotherms, it may cause an increase in prey capture attempts and faster reaction times, as observed in our experiment. These results support our hypothesis that both defensive and predatory behavior in H. obscurus is affected by temperature, allowing more insight into scorpion thermal ecology.

Reference:
Nisani Z, Bennett M, Enriquez A, Iniquez M, Martinez Rios E, Stone B. Effect of temperature on the defensive and predatory behavior of the scorpion Hadrurus obscurus (Scorpiones: Hadruridae). Euscorpius. 2026;2026(433):1–9. [Open Access]

Microbiota discovered in the venom of two scorpion species

 

There is a great research interest in scorpion venom these days, especially the hunt for toxins and other elements that can be used in medical research. The scorpion venom is known to contain a cocktail of peptids, enzymes and other inorganic and organic compounds, but it has been believed that the venom has been sterile venom it comes to bacteria and other microbiota.

Barbara Murdoch and co-workers recently published an article revealing the presence of several bacteria in the venom of the scorpions Paruoctonus becki (Gertsch & Allred, 1965) (Vaejovidae) and Anuroctonus phaiodactylus (Wood, 1863) (Anuroctonidae). This is the first report of microbiota in scorpion venom.

Matt Simon, who informed me about this article, noticed several interesting facts in this article. Firstly, many of the observed bacteria are known to have evolved for extreme conditions, Secondly, one of the observed genera (Nocardioides) is known to produce antimicrobial compounds. The latter is especially interesting, as it may suggest that antibiotic properties of scorpion venom may not be caused by the scorpion itself, but by bacteria in the venom.

Abstract:
With low nutrient availability and presence of numerous antimicrobial peptides, animal venoms have been traditionally considered to be harsh sterile environments that lack bacteria. Contrary to this assumption, recent studies of animal venom and venom-producing tissues have revealed the presence of diverse microbial communities, warranting further studies of potential microbiota in other venomous animals. In this study we used 16S rRNA amplicon sequencing to elucidate whether scorpion venom contained bacteria, to characterize the bacterial communities, and determine if venom microbiomes differed across geologically complex geographic locations. Our study compares the venom microbiome of two scorpion species, sampled from sites in the Mojave and Great Basin deserts, Paruoctonus becki (family of Vaejovidae) and Anuroctonus phaiodactylus (family of Anuroctonidae), and represents the first assessment of microbial diversity ever conducted using the venom secretion itself, rather than the venom-producing organ and its surrounding tissues.

Reference:
Murdoch B, Kleinschmit AJ, Santibáñez-López CE, Graham MR. Microbiota discovered in scorpion venom. PLoS One. 2026;21(1):e0328427. [Open Access]

Thanks to Matt Simon for informing me about this papers and for his comments! 

Sting use in Centruroides sculpturatus in a defensive context

 

Several studies shows that scorpions are selective when it comes to sting and venom use i defense and prey capture. The basis for this is that venom is costly to replace and this cause the scorpions to be restrictive in using venom.

Lindsay Marston and co-workers recently published a study where they tested antipredator behaviors of Centruroides sculpturatus Ewing, 1928 (Buthidae) exposed to two different "threats" in their natural environment. 

Interestingly, the results of the different experiments contrasted with those of previous studies.The article discuss possible reasons for this.

Abstract:
Scorpion antipredator behavior incorporates risk assessment that informs decision-making and venom usage. We quantified antipredator behaviors of the clinically significant Arizona bark scorpion (Centruroides sculpturatus) in their natural environment using exposure to two stimuli: a freshly thawed laboratory mouse (Mus musculus) and a membrane-covered glass beaker. We videotaped and compared envenomation behaviors between sexes (females, gravid females, and males), across sizes, and between animal orientations (on vertical or horizontal substrates). Results failed to show consistent support for any of our four hypotheses. Females (especially gravid females) were no more likely than males to exhibit higher levels of stinging and venom expenditure. Scorpions on horizontal surfaces compared to those on vertical surfaces, and larger scorpions compared to smaller ones, were likewise no more likely to exhibit higher levels of responsiveness. Mice were more likely to be stung than the membrane-covered beaker, but with fewer and briefer stings, suggesting the scorpions did not attempt to deliver more venom into the mice. Thus, we discerned no clear patterns in risk assessment, stinging, and venom use associated with sex, substrate orientation, body size, or threat stimuli. These findings contrasted with those of several prior laboratory studies. Variation from unaccounted environmental variables may have obfuscated divergent behavioral tactics. Nevertheless, the behaviors we document here provide insights on the range of defensive behaviors exhibited by C. sculpturatus under natural environmental conditions, including the frequency of dry stings (11.8%) to the membrane-covered beakers.

Reference:
Marston LA, Fox GA, Hung KY, Delo SJ, Hayes WK. A Sting Operation: Risk Assessment and Venom Expenditure by Arizona Bark Scorpions (Centruroides sculpturatus) in a Defensive Context. Toxins. 2025;17(4):198. [Open Access]

Rediscovery of the rare species Paruroctonus williamsi from Big Bend National Park, Texas USA

 

Matthew Leister recently published an article informing about the rediscovery of the rare scorpion Paruroctonus williamsi Sissom & Francke, 1981 (Vaejovidae). Several researchers have tried to find this species again in the last 50 years, but it has stayed hidden until now. Several specimens were discovered in The Big Bend National Park in Texas, USA.

Abstract:
A recent search at Big Bend National Park has recovered specimens of Paruroctonus williamsi after a lapse of over 50 years with no records of the species, underscoring the importance of continued monitoring for rare species. This study includes photographs of living specimens, documentation of their habitat, comparisons with other species of Paruroctonus found at Big Bend National Park, and a list of scorpions observed near P. williamsi.

Reference:
Leister M. Rediscovery of a rare species of Paruroctonus (Scorpiones: Vaejovidae) from Big Bend National Park, Texas. Western North American Naturalist. 2024;84(4):524–7. [Subscription required for full text]

Thanks to Luis A. Roque for sending me this article!

Antibiotic-producing bacteria discovered in tissue from the giant sand scorpion, Smeringurus mesaensis

 

As most of you know, there is an increasing and worrying number of treatment resistant bacteria in the world. It is probably safe to say that we are now in an antibiotic resistance crisis. The venom of scorpions have for several years provided several candidates for medical treatments (e.g. Chlorotoxin from Leiurus quinquestriatus (Ehrenberg, 1828) (Buthidae)), but a recent paper suggests that scorpions can contribute with more than their venom.

In a recent article, Atkinson and co-workers present the discovery of antibiotic-producing bacteria in tissue samples from the giant sand scorpion, Smeringurus mesaensis (Stahnke, 1957) (Vaejovidae). It is important to note that this is results from laboratory studies and more research is necessary before the antibiotic effect can be confirmed for humans. But the study opens up the exciting possibility that scorpion tissues can provide a new source of antimicrobial molecules in the war against antibiotic resistance. 

Abstract:
Antibiotic resistance is a global health crisis. Our current arsenal of antibiotics—drugs meant to kill bacteria and stop their population growth—is becoming less effective at treating bacterial infections as resistant bacteria emerge, fueling the dire need to discover new antibiotics. Most antibiotics in use today have been discovered from bacteria. To increase the chances of finding potentially novel antibiotic molecules, we studied the relatively unexplored microbial environment of scorpion tissues, using the giant sand scorpion, Smeringurus mesaensis (Stahnke, 1957). Bacterial symbionts were isolated and cultured from the mesosoma and metasoma, and isolates were tested in a functional assay for production of antibiotics. Under the culture conditions utilized, most scorpion-derived bacteria were from the phyla of Firmicutes, Proteobacteria and Actinobacteria. Fifty five percent of the clonal isolates tested produced antibiotics, with most being Bacillus species. None of the bacterial conditioned media were cytotoxic to mammalian cells. This study suggests scorpion tissues may provide a rich source of antimicrobial molecules to help combat the antibiotic resistance crisis.

Reference:
Atkinson L, Shimwell C, Lucin KM, Graham MR, Murdoch B. Antibiotic-producing bacteria isolated from the giant sand scorpion, Smeringurus mesaensis (Scorpiones: Vaejovidae). The Journal of Arachnology. 2024;52(2):116-26. [Subscription required for full text]

Thanks to Matt Simon for informing me about this article!

More on the function of the pectines in scorpion navigation

 

There have been a lot of research on the morphology and the functions of the pectines, which is a unique organ found only in scorpions (Solifigae has a similar organ called malleoli or racquet (or racket) organs). Most of the research so far have focused on the "taste function" (the detection of chemical cues), but it also seems that the pectines have a "feeling function" (having mechanosensory abilities). Overall, the pectines help scorpions find food, navigate, avoid predators and find mates.

Hannah Peeples and Douglas Gaffin recently published a study investigating the role of the peg sensilla on scorpion pectines for mechanosensory responses. This is a very technical paper, but as far as I can tell the main conclusion is that pectines use mechanosensory stimuli to navigate in its activity area, to find home to its shelter and to retrieve dropped insect prey.

Abstract:
Scorpions possess midventral touch/taste organs called pectines, which may be important for learning the nuances of the substrate during navigation as well as the detection of pheromones, spermatophores, and food. The pectines possess thousands of minute structures called peg sensilla that are responsive to both chemicals and mechanical deflection of the peg shaft. While much is known about the chemical responsiveness of the pegs, very little is known about their mechanosensory properties. Here we ask if the peg mechanosensory response is “all-or-nothing” or graded depending on the intensity of stimulation. We made electrophysiological recordings of neural activity from individual peg sensilla while deflecting the peg to elicit apparent mechanosensory responses. Our records show the presence of a rapid firing (.100 Hz), quickly adapting waveform that is indicative of a mechanoreceptor and appears to be independent of previously identified chemo-responsive cells. We tested mechanosensory response dynamics in two ways. The first test focused on a shorter-duration touch versus a longer-duration touch, while the second focused on a smaller deflection versus a larger deflection. Both pairs of stimulations (short vs long touch; small vs large touch) produced repeatable and statistically distinct responses in terms of spiking frequency. These results indicate the mechanosensory responses of peg sensilla are graded, which sheds light on the textural resolvability of the pectines and informs models of the type of information that scorpions obtain while assessing surfaces in their environment.

Reference:
Peeples HM, Gaffin DD. An assessment of the mechanosensory responses of peg sensilla on scorpion pectines. The Journal of Arachnology. 2024;52(1):1-8.

Thanks to Matt Simon for informing me about this article and for providing insight about the article!

In Memoriam Richard F. Ayrey (1948 – 2024)

Previously this year we got the sad news that scorpion researcher and enthusiast Richard Ayrey had passed. The Euscorpius journal recently published a memorial article honoring Rich's life and work on scorpions.

 RIP.

Abstract:
This is a memorial issue honoring Richard F. Ayrey (1948 – 2024), a US scorpiologist. A full list of his 26 works is appended, as well as a list of scorpion taxa described by Richard (two genera and 19 species of Vaejovidae), and a map of their type localities in the USA and Mexico.

Reference:
DeBoer-Ayrey M, Myers BT, Bryson Jr RW, Webber MM, Graham MR, Lowe G, et al. In Memoriam Richard F. Ayrey (1948 – 2024). Euscorpius. 2024(384):1-11. [Open Access]