22 April, 2022

“When it comes to scorpions, the bigger the better”

 


The title is a quote from one of the popular Indiana Jones movies, and most of us that have been working with scorpions for many years are familiar with the rule of thumb when it comes to the potency of scorpion stings: That large scorpions have less potent venom than smaller ones or that scorpions with large pedipalps are less dangerous than scorpions with small, slender claws.

The above is also reflected in prey capture, where larger scorpions with more powerful pedipalps will more often rely on bruth force to subdue prey without using the stinger (and venom), while smaller species with more slender claws are more prone to using the stinger and venom.

Alannah Forde and co-workers have recently published an interesting study comparing LD50 potency values and morphology measures from the literature to see if the above mentioned rule of thumb when it comes to classifying dangerous scorpions is actually true.

And they did actually find that larger scorpions, with more robust chelae, are less potent than small species, with thin chelae. The evolutionary explanations for this is also discussed.

I must warn that even though it seems that Indiana Jones was correct and our commonly used rule of thumb seems to hold, there may be exceptions. Species in the infamous genus Hemiscorpius Peters, 1861 (Hemicorpiidae) are quite large and have robust pedipalps, but they can cause serious morbidity and even death in humans.

Abstract:
Scorpionism is a global health concern, with an estimation of over one million annual envenomation cases. Despite this, little is known regarding the drivers of scorpion venom potency. One widely held view is that smaller scorpions with less-developed chelae possess the most potent venoms. While this perception is often used as a guide for medical intervention, it has yet to be tested in a formal comparative framework. Here, we use a phylogenetic comparative analysis of 36 scorpion species to test whether scorpion venom potency, as measured using LD50, is related to scorpion body size and morphology. We found a positive relationship between LD50 and scorpion total length, supporting the perception that smaller scorpions possess more potent venoms. We also found that, independent of body size, scorpion species with long narrow chelae have higher venom potencies compared to species with more robust chelae. These results not only support the general perception of scorpion morphology and potency, but also the presence of an ecology trade-off with scorpions either selected for well-developed chelae or more potent venoms. Testing the patterns of venom variations in scorpions aids both our ecological understanding and our ability to address the global health burden of scorpionism.

Reference:
Forde A, Jacobsen A, Dugon MM, Healy K. Scorpion Species with Smaller Body Sizes and Narrower Chelae Have the Highest Venom Potency. Toxins. 2022;14(3):219. [Open Access]

Thanks to Jeroen for reminding me about this article!

21 April, 2022

A new species of Hottentotta from Iran

 


Ersen Yagmur and co-workers have recently published a new species of Hottentotta Birula, 1908 (Buthidae) from Iran.

Hottentotta akbarii Yagmur, Moradi, Tabatabaei & Jafari, 2022

Abstract:
A new species Hottentotta akbarii sp. nov. is described and illustrated from the Fars Province of Iran. H. akbarii sp. nov. is compared with H. navidpouri Kovařík, Yağmur & Moradi, 2018 and H. saulcyi (Simon, 1880). H. akbarii sp. nov. differs from its congeners by dense hirsuteness of the body, uniformly greenish yellow colouration, lacking black spot at the anterior portion of the carapace, fifth segment and telson and yellow chelicera. With this new species, the species number of genus Hottentotta in Iran is elevated to 10.

Reference:
Yagmur EA, Moradi M, Tabatabaei M, Jafari N. Contributions to the scorpion fauna of Iran. Part II. Hottentotta akbarii sp. nov. from the Fars Province (Scorpiones: Buthidae). Serket. 2022;18(3):252-62.

Thanks to Ersen for sending me their article!

Family Buthidae

When did scorpions develop venoms dangerous to humans and other mammals?

 


Scorpions are an old animal groups that dates back to the Siluarian period appr. 400 million years ago. In the family Buthidae we find the species that have the most potent venoms when it comes to humans and other mammals. But how and when did the evolution create the venom composition that turned out to make many scorpions effective against mammalian predators?

Carlos Santibáñez-López and a group of international cooperators have recently published an impressive study where they assembled a phylogenomic data set of 100 scorpion venom gland
transcriptomes and genomes, emphasizing the sampling of highly toxic buthid genera.

The analysis show that toxins effective against mammals developed independently several times within the family Buthidae and that the evolutionary steps for this was quite recent in evolutionary times. And the latter is not suprising, as mammal predators were not present until late in the scorpion's evolutionary time scale.

This study and its phylogenomic results will be very useful for future studies of scorpions both in taxonomy, phylogeny and toxicology.

Abstract:
Scorpions constitute a charismatic lineage of arthropods and comprise more than 2500 described species. Found throughout various tropical and temperate habitats, these predatory arachnids have a long evolutionary history, with a fossil record that began in the Silurian. While all scorpions are venomous, the asymmetrically diverse family Buthidae harbors nearly half the diversity of extant scorpions, and all but one of the 58 species that are medically significant to humans. However, the lack of a densely sampled scorpion phylogeny has hindered broader inferences of the diversification dynamics of scorpion toxins. To redress this gap, we assembled a phylogenomic data set of 100 scorpion venom gland transcriptomes and genomes, emphasizing the sampling of highly toxic buthid genera. To infer divergence times of venom gene families, we applied a phylogenomic node dating approach for the species tree in tandem with phylostratigraphic bracketing to estimate the minimum ages of mammal-specific toxins. Our analyses establish a robustly supported phylogeny of scorpions, particularly with regard to relationships between medically significant taxa. Analysis of venom gene families shows that mammal-active sodium channel toxins (NaTx) have independently evolved in five lineages within Buthidae. Temporal windows of mammal-targeting toxin origins are correlated with the basal diversification of major scorpion mammal predators such as shrews, bats, and rodents. These results suggest an evolutionary model of relatively recent diversification of buthid NaTx homologs in response to the diversification of scorpion predators.

Reference:
Santibáñez-López CE, Aharon S, Ballesteros JA, Gainett G, Baker CM, González-Santillán E, et al. Phylogenomics of Scorpions Reveal Contemporaneous Diversification of Scorpion Mammalian Predators and Mammal-Active Sodium Channel Toxins. Syst Biol. 2022. [Sunscription required for full text]

Thanks to Carlos for sending me their article and for Matt Simon for recommending it to me.

19 April, 2022

A new species of Androctonus from Western Sahara

 


Eric Ythier and Wilson Lourenco have recently described a new species of Androctonus  Ehrenberg, 1828 (Buthidae) from Western Sahara.

Androctonus agrab Ythier & Lourenco, 2022.

In addition, Androctonus bourdoni Vachon, 1948 is raised from subspecies status (Previously Androctonus mauritanicus bourdoni Vachon, 1948). 

Abstract:
A new species of Androctonus Ehrenberg, 1828 is described on the basis of one male and one female collected in the region of Adrar Sotuf, Western Sahara. This new scorpion taxon represents the 33rd known species of the genus Androctonus and the 3rd reported from Western Sahara. A geographical distribution map of the Androctonus species occurring in Morocco and Western Sahara is presented and one taxon is raised to species rank, Androctonus bourdoni Vachon, 1948 stat. n.

Reference:
Ythier E, Lourenco WR. A new species of Androctonus Ehrenberg, 1828 from Western Sahara (Scorpiones: Buthidae). Serket. 2022;18(3):239-51.

Thanks to Eric for sending me their new article!

Family Buthidae

Three new species of Isometrus from India

 


India hosts a large diversity of scorpions and many of them are still waiting to be discovered. Shauri Sulakhe and co-workers are working to discover some of these hidden scorpion gems, and in a recent article they have described two new species of Isometrus Ehrenberg, 1828 (Buthidae) from the Western Ghats, India.

Isometrus naksahatra Sulakhe, Deshpande, Gowande, Dandekar & Ketkar, 2022

Isometrus wayanadensis Sulakhe, Deshpande, Gowande, Dandekar & Ketkar, 2022

In addition, Isometrus sankeriensis Tikader & Bastawade, 1983 is restorded from synonymization as a valid species.

The article has a identification key for the Indian species of Isometrus.

Abstract:
The Western Ghats of India is considered one of the richest biodiversity hotspots in the world. Documenting scorpion diversity has always been of paramount importance due to their species richness, ecological role and endemism, which calls for conservation priority. Scorpion diversity of the Western Ghats is probably underestimated given the ancestry of the group, and more field work in the region is very likely to uncover numerous undescribed taxa. Several new Indian species have recently been discovered in the scorpion genus Isometrus Ehrenberg, 1828 (Scorpiones: Buthidae). In this communication, we resurrect I. sankeriensis Tikader & Bastawade, 1983 and describe two new species from the Western Ghats of India, I. nakshatra sp. nov. and I. wayanadensis sp. nov., using an integrative taxonomic approach. In order to replace the lost holotype of I. sankeriensis, we designate a neotype and reassess the identity of this species. This work elevates the number of species of Isometrus found in India to eight and we expect many more scorpion discoveries from India with continued research.

Reference:
Sulakhe S, Deshpande S, Gowande G, Dandekar N, Ketkar M. Arboreal gems: resurrection of Isometrus sankeriensis Tikader & Bastwade, 1983 and descriptions of two new species of Isometrus Ehrenberg, 1828 (Scorpiones: Buthidae) from the Western Ghats, India. European Journal of Taxonomy. 2022;811:1-50. [Open Access]

Thanks to Matt Simon for informing me about this article!

Family Buthidae

08 April, 2022

A new species of Buthacus from Jordan

 


Bassam Abu Afifeh and co-workers have recently described a new species of Buthacus Birula, 1908 (Buthidae) from Jordan.

Buthacus bicolor Afifeh, Al-Saraireh, Baker, Amr & Lourenço, 2022

The distribution of the genus is also discussed. 

Abstract:
The genus Buthacus Birula, 1908 (family Buthidae) has been the subject of an impressive number of studies in the past 25 years. Most of the species considered in these studies come from North Africa, in particular from countries such as Morocco, Algeria and Mauritania. Nevertheless, species were also described from the near and far Middle East. In this contribution we start the study of all the Buthacus populations present in Jordan which will be based on a precise survey of different biotopes in the country. A new species is described from the desert areas of Al- Qattafi. This preliminary study, which will be followed by others, seems to suggest the presence of microendemic populations in limited geographical zones of the desert.

Reference:
Afifeh BA, Al-Saraireh M, Baker MA, Amr Z, Lourenco WR. The genus Buthacus Birula, 1908 in Jordan: description of a new species and comments on possible micro-endemic populations (Scorpiones: Buthidae). Arthropoda Selecta. 2022;31(1):51-62. [Open Access]

Thanks to Nicolas Machiavel for sending me this article!

Family Buthidae

07 April, 2022

A new species of the humicolous scorpion genus Microananteris from French Guiana

 


Micro-scorpions like the species found in the humicolous genus Microananteris Lourenço, 2003 (Buthidae) are undercollected because of their small size and cryptic lifestyle. Wilson Lourenco and Johan Chevalier have now described a new species in this genus from French Guiana.

Microananteris abounami Lourenco & Chevalier, 2022

An identification key for the genus is proposed.

Abstract:
Subsequently to the recent descriptions of two new species of the humicolous micro-buthid genus Microananteris Lourenço, 2003, one more new species was found in French Guiana and is described here. The new description is based on three adult specimens, one female and two males collected not underground, but from the soil surface, using intensive night search with the use of UV lights. The geographic distribution of the genus Microananteris remains limited to the only territory of French Guiana.

Reference:
Lourenço W, Chevalier J. A further new species of the genus Microananteris Lourenço, 2003, from French Guiana (Scorpiones, Buthidae). Bulletin de la Société entomologique de France. 2022;127:91-9. [Subscription required for full text]

Family Buthidae