The defense respons of scorpions to repeated attacks from a predator

Scorpions and other prey species are involved in a continuing arm race against their predators. The prey will get better in avoidance and defence and the predator tries to get better in overcoming the prey.

Mykola Rasko and co-workers have recently published a study investigating the sting use and venom expenditure during repeated attacks (simulated) in Hadurus arizonensis Ewin, 1928 (Caraboctonidae). Contrary to the projects expectations, the stinging behaviour, venom use and venom volume all decreased as the number of challenges increased. The scorpions defenses actually decreased during repeated attacks. This means that a predator of scorpions should use repeated attacks to overcome a scorpion, and this is also something that has been observed in some predators of scorpions.

Abstract:
Predatore-prey arms races ensure that a prey's defences are well matched with the predator's ability to overcome them. Scorpions have a formidable defensive capacity due to their venomous stinger. Mammalian and squamate scorpion predators overpower scorpions by making repeated attacks. We tested here how scorpions, Hadrurus arizonensis, apply their venom defensively during a simulated repeated attack, consisting of 10 consecutive challenges. Since the persistent repeated attack of a predator, even when stung in the process, seems to indicate its resolve, we expected defensive effort to increase with the number of challenges. We also expected that, owing to the life-and-death nature of a predatory attack, scorpions would be liberal in the use of their venom. We found, however, that stinging behaviour, venom use and venom volume all decreased as the number of challenges increased. Scorpions used only 7.8±9.6% (mean±SD) of their total venom volume during an attack consisting of 10 consecutive challenges. We conclude that a repeated attack seems an effective strategy for scorpion predators to reduce the defensive investment of scorpions.

Reference:
Rasko M, Coelho P, Simone Y, van der Meijden A. How to attack a scorpion: venom metering during a repeated attack. Anim Behav. 2018;145:125-9. [Subscription required for full text]

Species composition and distribution in an arid ecosystem i Algeria

Salah Eddine Sadine and co-workers recently published an article looking into the diversity and distribution of scorpions in the region of Ouargla (Eastern Algerian Sahara).

Abstract:
The present work is a study of composition and structure of scorpion fauna in the region of Ouargla (Eastern Algerian Sahara), during a period of fourteen years from 2005 to 2018, we sampled from different biotopes more than 1550 adult specimens, divided into nine 9 species of scorpions: Androctonus amoreuxi, Androctonus australis, Buthacus arenicola, Buthacus samiae, Buthiscus bicalcaratus, Buthus saharicus, Buthus tunetanus, Orthochirus innesi, and Scorpio punicus. A. australis was the most abundant species with 47.36% of the total individuals captured. Other species such as S. punicus, B. arenicola and A. amoreuxi are ranked as accidental with rates less than 20%. Among the important results in this work is reporting for the first time the presence of B. bicalcaratus in Ouargla and the new records of B. samiae and B. saharicus in this area. The Shannon’s index was H’ = 2.05 and the evenness index was 0.65, showing a very important diversity of scorpions with more than 23.5% of scorpion species reported in Algeria; however, a poor balance between the number of sampled species with dominance of the thermophilic species that are the most adapted scorpions in this arid climate.

Reference:
Sadine SE, Bissati S, Idder MA. Diversity and structure of scorpion fauna from arid ecosystem in Algerian Septentrional Sahara (2005-2018). Serket. 2018;16(2):51-9. [Open Access]

Thanks to Dr. Sadine for sending me his article!

Structure of venom molecules predicts phylogenetic relationships in scorpions

Scorpions are infamous because of their venom, which actually consist of a host of different toxins and molecules. Carlos E. Santibáñez-López and several co-workes have now published a study combining a mapping of the structure of venom molecules with the challenges and disagreements in scorpion higher-level systematics and phylogeny.

I must admit that most of the content of this article is above my head. I'm a humble animal behavior student. So I will let co-author Prashant Sharma sum up the main point of the article:

"The punchline is that we analyzed parametric analyses of the shape of venom proteins on the most comprehensive molecular phylogeny of scorpions. We found that venom shape  predicts phylogenetic relationships and provides synapomorphies for the two largest scorpion clades (Buthida and Iurida)." (Sharma personal communication 15.11.18)

As far as I understand, one important conclusion of this study is that "molecular morphology" can overcome the challenges of the traditional use of anatomical characters in scorpion higher-level systematics and phylogeny.

Abstract:
Scorpions have evolved a variety of toxins with a plethora of biological targets, but characterizing their evolution has been limited by the lack of a comprehensive phylogenetic hypothesis of scorpion relationships grounded in modern, genomescale datasets. Disagreements over scorpion higher-level systematics have also incurred challenges to previous interpretations of venom families as ancestral or derived. To redress these gaps, we assessed the phylogenomic relationships of scorpions using the most comprehensive taxonomic sampling to date. We surveyed genomic resources for the incidence of calcins (a type of calcium channel toxin), which were previously known only from 16 scorpion species. Here, we show that calcins are diverse, but phylogenetically restricted only to parvorder Iurida, one of the two basal branches of scorpions. The other branch of scorpions, Buthida, bear the related LKTx toxins (absent in Iurida), but lack calcins entirely. Analysis of sequences and molecular models demonstrates remarkable phylogenetic inertia within both calcins and LKTx genes. These results provide the first synapomorphies (shared derived traits) for the recently redefined clades Buthida and Iurida, constituting the only known case of such traits defined from the morphology of molecules.

Reference:
Santibáñez-López CE, Kriebel R, Ballesteros JA, Rush N, Witter Z, Williams J, et al. Integration of phylogenomics and molecular modeling reveals lineage-specific diversification of toxins in scorpions. PeerJ. 2018;6:e5902. [Open Access]

A news report about the article

Thanks to Carlos E. Santibanez Lopez and Prashant Sharma for sending me their article and information!

A revision of the Central Asian scorpion genus Anomalobuthus with three new species

Rolando Teruel, Frantisek Kovarik and Victor Fet have recently published a review of the little known, psammophilic ("sand loving") genus Anomalobuthus Kraepelin, 1900 (Buthidae). This genus is mainly distributed Central Asia. Here are the main conclusions from this study:

New species:

Anomalobuthus krivochatskyi Teruel, Kovarik & Fet, 2018 (Central Uzbekistan and extreme southern Kazakhstan).

Anomalobuthus lowei Teruel, Kovarik & Fet, 2018 (Southeastern Kazakhstan).

Anomalobuthus pavlovskyi Teruel, Kovarik & Fet, 2018 (South-central Kazakhstan and extreme northern Turkmenistan).

New combination:

 The genus Psammobuthus Birula, 1911 is synonymized with Anomalobuthus and its only species is transfered to the latter genus.

Anomalobuthus zarudnyi (Birula, 1911)

The article presents an updated identification key for the genus.

Abstract:
We revise the Central Asian endemic genus Anomalobuthus Kraepelin, 1900, which was considered monotypic for more than 100 years until the recent addition of a second species from Iran (Teruel et al., 2014). We redefine the generic diagnosis of Anomalobuthus and reveal that it is composed of no less than six species, three of which are described as new: A. krivochatskyi, sp. n. (central Uzbekistan and extreme southern Kazakhstan), A. lowei, sp. n. (southeastern Kazakhstan), and A. pavlovskyi, sp. n. (south-central Kazakhstan and extreme northern Turkmenistan). The monotypic genus Psammobuthus Birula, 1911 (described from the Ferghana Valley at the border of Uzbekistan and Tajikistan) is synonymized under Anomalobuthus; its single species is transferred as Anomalobuthus zarudnyi (Birula, 1911), comb. n. We also clarify the type locality of the type species A. rickmersi Kraepelin, 1900, from accurate data published by its collector Rickmer Rickmers (1913) but overlooked since its very original description: it is Baljuvon in Tajikistan. Occurrence of A. rickmersi in southern and southeastern Turkmenistan is confirmed. All available species are fully illustrated with color photos of habitus and morphologically diagnostic characters, and a key covering all six recognized species of Anomalobuthus is included.

Reference:
Teruel R, Kovarik F, Fet V. Revision of the Central Asian scorpion genus Anomalobuthus Kraepelin, 1900, with descriptions of three new species and a generic synonymy (Scorpiones: Buthidae). Euscorpius. 2018(270):1-45. [Open Access]

Thanks to Rolando Teruel for informing me about their article!

Family Buthidae

Book News: New edition of Scorpions of Southern Africa

Jonathan Leeming's great book on scorpions of southern Africa is now available in a new edition. It was originally published in 2003 and the new edition has updated information and several new topics are included. I have not seen the new edition as it is scheduled for publications in the end of November, but you can follow this link to get more information about whats new in the new edition and information on how to order.

A global review of medically important scorpions and scorpionism

Micaiah Ward and co-workers at Florida State University recently published an extensive review of medically important scorpions, epidemiology and scorpionism. The number of medical important species is raised to 104 (Buthidae: 101, Hemiscorpiidae: 2, Scorpionidae: 1). Of these, 36 species are considered dangerous (causing class II and III symptoms).

It is important to understand that a list like this can not be perfect. The species identification in many sting cases can be missing or wrong. Taxonomy is changing, and a species may turn out to be a species complex with potentially different venom potency (e.g. The Buthus occitanus complex). We should be careful not to label all species not on this list as harmless. A dangerous species may never have stung a human or the sting case was never reported. Also, many stings are dry or a reduced amount of venom is used, causing minor/mild symptoms and by this camouflaging a dangerous species. The article discuss some of these conserns.

 The article also has information about the distribution of medically important species, venom composition and the use of scorpion venom in biomedical research.

Abstract:
Scorpions are an ancient and diverse venomous lineage, with over 2200 currently recognized species. Only a small fraction of scorpion species are considered harmful to humans, but the often life-threatening symptoms caused by a single sting are significant enough to recognize scorpionism as a global health problem. The continued discovery and classification of new species has led to a steady increase in the number of both harmful and harmless scorpion species. The purpose of this review is to update the global record of medically significant scorpion species, assigning each to a recognized sting class based on reported symptoms, and provide the major toxin classes identified in their venoms. We also aim to shed light on the harmless species that, although not a threat to human health, should still be considered medically relevant for their potential in therapeutic development. Included in our review is discussion of the many contributing factors that may cause error in epidemiological estimations and in the determination of medically significant scorpion species, and we provide suggestions for future scorpion research that will aid in overcoming these errors.

Reference:
Ward MJ, Ellsworth SA, Nystrom GS. A global accounting of medically significant scorpions: Epidemiology, major toxins, and comparative resources in harmless counterparts. Toxicon. 2018;151:137-55. [Subscription required for full text]

Thanks to Matt Simon for informing me about this article!

A review of the scorpions (and other arachnid groups) from Sudan

The Republic of the Sudan is one of the largest countries in East Africa with a large diversity when it comes to habitats and climate. A few new scorpion taxa have been described from Sudan in the last years, but no recent review of the scorpion fauna has been published.

Jason Dunlop and co-workers have recently published a review of the scorpions and other arachnid groups from Sudan. 17 species from the families Buthidae (15) and Scorpionidae (2) were recorded.

Abstract:
Literature-based species lists for arachnids, excluding spiders and mites, found in the Republic of the Sudan are provided. We summarize records, references, and localities for 17 scorpions (Scorpiones), one harvestman (Opiliones), nine pseudoscorpions (Pseudoscorpiones), 21 camel spiders (Solifugae) and one whip spider (Amblypygi). There are no published records of palpigrades (Palpigradi), whip scorpions (Thelyphonida), schizomids (Schizomida) or ricinuleids (Ricinulei), although at least whip scorpions and ricinuleids would not be expected in East Africa based on their current distribution. Key literature for mites and ticks (Acari) is also mentioned. In general, the Sudanese arachnid fauna has not been documented in detail. Many more species, particularly among the harvestmen and pseudoscorpions, are to be expected, and we offer the data gathered here as a baseline for future work.

Reference:
Dunlop JA, Siyam M, Kovarik F. Smaller orders of Arachnida in Sudan: a literature review. Arachnology. 2018;17:449-57.

Thanks to Frantisek Kovarik for sending me their article!