Using chemical cues to avoid intraguild predators and to find potential mates

 

It is well known that scorpions can detect and use chemical cues thanks to chemosensitive hairs on the pectins and on part of the pedipalps. Chemical cues can be used to discover and seek out conspecifics for mating, but also to avoid conspecifics or other scorpions that want to eat you (cannibalism is well documented in scorpions, often larger individuals preying on smaller and larger females may also kill and eat potential suitors).

Welton Dionisio-da-Silva and co-workers published earlier this summer a study of the use of chemical cues in the two Brazilian scorpions Bothriurus rochai Mello-Leitão, 1932 (Bothriuridae) and Jaguajir rochae (Borelli, 1910) (Buthidae). They tested the behavioral response to chemical cues from a heterospecific scorpion, and the response of male individuals (B. rochai and J. rochae) to chemical cues from conspecific females.

The study showed that smaller individuals avoided sites with the "smell" of larges individuals, whiles larger predators preferred the sites with the "smell" of smaller scorpions. In addition, males of both species trailed the chemical cues of females. 

According to the authors, this is the first evidence of a scorpion species detecting and hunting a heterospecific scorpion through chemical cues.

Abstract:
Chemical perception is essential among arthropods for mate recognition, prey search, and predator avoidance, especially for solitary predators which are often aggressive. Such mechanisms may be intensified in environments like the Caatinga, a seasonally dry tropical forest in Brazil, characterized by low habitat complexity and high seasonal variation. Thus, we investigated chemical perception between two scorpion species from this environment, involved in intraguild competition. Experiments assessed their response to chemical cues from prey, predators, and potential mates. We use Y-mazes to test the time spent by the scorpions between Y-arms with or without a given substrate-borne chemical cue (site preference) and the number of active individuals during trials (presence of activity). Scorpions’ activity was not influenced by chemical stimuli, although they clearly exhibit site preferences. The smaller predators avoided sites with the larger species’ chemical cues, while the larger predators preferred sites with the smaller species’ cues. Additionally, both species trailed female chemical cues. These findings suggest a dual-oriented arms race where prey and predator modulate their behaviour to avoid and hunt heterospecifics, respectively. This study provides the first evidence of a scorpion using chemical cues to detect a heterospecific scorpion and highlights the importance of this trait in arachnids.

References:
Dionisio-da-Silva W, Araujo Rocha-da-Silva KL, Veloso HMG, DaSilva MB. Hide and seek: chemical cues drive site preference among potential mates and intraguild competitors. Biological Journal of the Linnean Society. 2024:blae058. [Subscription required for full text]

Thanks to Welton Dionisio-da-Silva for sending me their article!

 

Phylogenetic analysis reveal cryptic subspecies of Euscorpius borovaglavaensis in Croatia

 

The genus Euscorpius Thorell, 1876 (Euscorpiidae) from Europa has become notorious for its hidden, cryptic species. A few decades ago this genus consisted of less than 10 species, today the number of taxa is closed to 100.

Martina Podvar and co-workers have publised a phylogenetic and phylogeographic  study of the populations of Euscorpius borovaglavaensis Tropea, 2015 in Croatia. Two distinct lineages were discovered and the population distributed in the northwestern part of the range was given subspecies status.

Euscorpius borovaglavaensis flavus Vignoli, 2024

Abstract:
The European scorpion Euscorpius borovaglavaensis Tropea, 2015 is a morphologically cryptic species that is distinguishable only with difficulty from E. tergestinus (C. L. Koch, 1837). It is distributed in the middle part of the Dinaric Alps chain and along part of the Eastern Adriatic coast, specifically, in Croatia (Middle Dalmatia, Lika karst upland), as well as in the southern part of Bosnia and Herzegovina. The new findings reported here have enhanced our knowledge of its geographic distribution in Croatia. Detailed morphological analyses highlighted the importance of carination in the ventral metasomal segments as morphological traits. Phylogenetic analyses, based on the mitochondrial cytochrome c oxidase subunit I (COI) gene, have revealed the existence of two distinct lineages. One of them, distributed in the northwestern part of the range, is described here as E. b. flavus n. ssp., while the nominal subspecies occurs in the southeastern part. A time-calibrated phylogenetic analysis has established their divergence around 0.9 million years ago, coinciding with the Mid-Pleistocene Transition (MPT) period. In contrast to the nominal subspecies, E. b. flavus n. ssp. exhibits significant phylogeographic structuring, indicating recent isolation events in multiple glacial microrefugia after the initial divergence, followed by a final Holocene dispersal in the northwestern direction deep between the mountain chains.

Reference:
Podnar M, Vignoli V, Tvrtković N. Phylogeographic structuring within recently diverged scorpion species, Euscorpius borovaglavaensis Tropea, 2015 (Scorpiones: Euscorpiidae) in Croatia, with the description of a new subspecies. Natura Croatica: Periodicum Musei Historiae Naturalis Croatici. 2024;33(1):29-52. [Open Access]

Thanks to Valerio and Gerard who both sent me this article!

Family Euscorpiidae

A new paper investigating the phylogeography and evolutionary history of the burrowing scorpion genus Scorpio

 

The genus Scorpio Linnaeus, 1758 (Scorpionidae) was for most of the last century known to have only one species, Scorpio maurus Linnaeus, 1758, which has an impressing distribution ranging from most of North Africa to the eastern parts of the Middle East. 

In the last decades it became clear that Scorpio maurus was a species complex with many hidden species, and today the genus consists of 24 species. However, the taxonomical and phylogentic situation of the genus is challenging, especially because of the lack of reliable morphological characters to distinguish the species and subspecies. Also, several new species have been described without genetic analysis confirming the species status. 

Manel Khammassi and co-workers have recently published a study with the aim of the present study to analyze the phylogenetic relationships and the evolutionary events that promoted diversification within the genus Scorpio. The study revealed twenty distinct lineages forming two geographically separate clades, a Maghrebian clade and a Middle Eastern clade. Most named species were found within the lineages, but additional lineages found are indicating potential new, unnamed species.

Abstract:
The burrowing scorpions of the genus Scorpio Linnaeus, 1758 were considered to be a single polymorphic species, Scorpio maurus Linnaeus, 1758, distributed from West Africa across the Sahel and the Saharan highlands through the Maghreb and the Middle East, to Iran. After various revisions, the complex was treated as including 18 species and seven subspecies. Five additional new Scorpio species were recently described. However, doubts remain regarding the validity of these taxa due to the lack of reliable characters and the lack of genetic data for many species. The aim of the present study was to analyze the phylogenetic relationships and the evolutionary events that promoted diversification within the genus. Phylogenetic analyses were performed using 633 base pairs of the mitochondrial COI gene from 51 individuals collected in Tunisia, Morocco, and Egypt, combined with 74 previously published sequence data. Phylogenetic analyses revealed twenty distinct lineages forming two geographically separate clades, a Maghrebian clade and a Middle Eastern clade. Although most named species formed distinct lineages, various additional lineages were identified, highlighting potential unnamed species. Divergence time estimates indicate that the division within the genus Scorpio began during the Mid-Miocene, a period characterized by tectonic events coupled with climatic oscillations. Further differentiation occurred during the Miocene-Pliocene transition when climatic fluctuations resumed and the Mediterranean became increasingly arid. Speciation within the genus Scorpio may have been driven by the expansion of the savannas and Sahara Desert, the associated reduction of a once widespread rainforest into numerous micro-refugia in the mountains of the Mediterranean region, and by adaptation to these new habitats

Reference:
Khammassi M, Nouira S, Badry A, Sadine SE, Harris DJ. Phylogeography and evolutionary history of the burrowing scorpion genus Scorpio Linnaeus, 1758 (Scorpiones: Scorpionidae) in the Mediterranean Basin. Organisms Diversity & Evolution. 2024:1-18. [Subscritpion required for full text]

Family Scorpionidae

A study on the relative efficacy of three antivenoms against medically significant Centruroides species from Mexico

 

Mexico is a hot spot for medical important scorpions and at least 21 species from the Centruroides Marx, 1890 (Buthidae) genus cause a large number of serious envenomations every year. Good treatment options is important and using antivenom is one of the most important tool.

Sam Campbell and co-workers have recently published a study looking into the ability of three  antivenoms to neutralize the activity of the venoms of several Centruroides species. One important result from this study is that the truly “broad” neutralization capacity of the antivenoms can be questioned as there were variations in the neutralization of several medical important Centruroides species (even though the venom of these were included in the antivenoms).

The author also stress the importance of proper laboratory studies and methods for studying the effects of antivenom candidates.

Abstract:
In this study, we report the innovative application of whole-cell patch-clamp electrophysiology in assessing broad-spectrum neutralisation by three different antivenoms, of venoms from the medically significant scorpion genus Centruroides. Envenomations by as many as 21 species from the Centruroides genus result in up to 300,000 envenomations per year in Mexico, which poses significant and potentially life-threatening pathophysiology. We first evaluated the in vitro manifestation of envenomation against two human voltage-gated sodium (hNaV) channel subtypes: hNaV1.4 and hNaV1.5, which are primarily expressed in skeletal muscles and cardiomyocytes, respectively. The neutralisation of venom activity was then characterised for three different antivenoms using a direct competition model against the more potent target, hNaV1.4. While broad-spectrum neutralisation was identified, variation in neutralisation arose for Centruroides elegans, C. limpidus, C. noxius and C. suffusus venoms, despite the presence of a number of these venoms within the immunising mixture. This raises questions regarding the truly “broad” neutralisation capacity of the antivenoms. This study not only extends previous validation of the in vitro investigation of antivenom efficacy utilising the whole-cell patch-clamp technique but also underscores the potential of this animal-free model in exploring cross-reactivity, experimental scalability, and most importantly, informing clinical management practices regarding the administration of antivenom in Mexico.

Reference:
Campbell SID, Chow CY, Neri-Castro E, Alagón A, Gómez A, Soria R, et al. Taking the sting out of scorpions: Electrophysiological investigation of the relative efficacy of three antivenoms against medically significant Centruroides species. Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology. 2024;283:109977. [Open Access]

Thanks to Jeroen Kooijman for informing me about this article!

New information about medical important Tityus species in Brazilian Amazonas

 

It is well known that several species of Tityus C. L. Koch, 1836 (Buthidae) causes death and serious morbidity in Brazil. Most infamous among these are probably Tityus serrulatus Lutz & Mello, 1922, but also other species cause serious sting incidents in humans in Brazil and the Amazon region, though reports are often sporadic. More studies are necessary to learn more about the effects of other Tityus species in the region.

Jonas Martins and co-workers published previously this summer a study on the systemic effects caused by the venom of the Amazonian scorpions Tityus dinizi Lourenço, 1997 and T. strandi Werner, 1939 using a murine model. The results indicates that both species may have a medical importance for humans, T. strandi being the most potent of the two. 

This information is important both for preventive measures and for therapeutic choices when dealing with scorpion stings caused by Amazonian scorpions.

Abstract:
The Brazilian Amazon is home to a rich fauna of scorpion species of medical importance, some of them still poorly characterized regarding their biological actions and range of clinical symptoms after envenoming. The Amazonian scorpion species Tityus strandi and Tityus dinizi constitute some of the scorpions in this group, with few studies in the literature regarding their systemic repercussions. In the present study, we characterized the clinical, inflammatory, and histopathological manifestations of T. strandi and T. dinizi envenoming in a murine model using Balb/c mice. The results show a robust clinical response based on clinical score, hyperglycemia, leukocytosis, increased cytokines, and histopathological changes in the kidneys and lungs. Tityus strandi envenomed mice presented more prominent clinical manifestations when compared to Tityus dinizi, pointing to the relevance of this species in the medical scenario, with both species inducing hyperglycemia, leukocytosis, increased cytokine production in the peritoneal lavage, increased inflammatory infiltrate in the lungs, and acute tubular necrosis after T. strandi envenoming. The results presented in this research can help to understand the systemic manifestations of scorpion accidents in humans caused by the target species of the study and point out therapeutic strategies in cases of scorpionism in remote regions of the Amazon.

Reference:
Martins JG, Reis MB, Zuanazzi BA, Bordon KdCF, Zoccal KF, de Lima Procópio RE, et al. Clinical outcomes in a murine model after envenoming by the Amazonian scorpions Tityus strandi and Tityus dinizi. Toxicon. 2024;246:107797. [Subscription required for full text]

Thanks to Jonas Martins for sending me their article!

 

A new cave-dwelling species of Chaerilus from Myanmar

 

Eric Ythier and Wilson Lourenco recently published a study describing a new cave-dwelling species in the genus Chaerilus Simon, 1877 (Chaerilidae) from Myanmar (Burma). Even though the new species was found in caves, it is not a true troglobite, but rather a trogloxene. 

Here are the taxonomical decision in this paper:

Chaerilus adrianoi Lourenco & Ythier, 2024 (new species)

Chaerilus birmanicus Thorell, 1899 (restored from synonymy with Chaerilus variegatus Simon, 1877)

Chaerilus anneae Lourenço, 2012 (restored from synonymy with Chaerilus julietteae Lourenço, 2011)

Chaerilus kampuchea Lourenço, 2012 (species status confirmed. Previous status "Nomen dubium"

Abstract:
A new species belonging to the genus Chaerilus Simon, 1877 is described from Myanmar: Chaerilus adrianoi sp. n., which was collected in a cave located in the East of the country. The new species is compared with some other Chaerilus species also described from Southeast Asia and in particular from Myanmar. The comparative study of the new species with other congenerics suggests, as in previous cases, that different species do not show very marked morphological differences, but rather correspond to micro-endemic populations. The new species is the second Chaerilus collected from Myanmar, together with Chaerilus birmanicus Thorell, 1899, restored from its synonymy with Chaerilus variegatus Simon, 1877. Chaerilus anneae Lourenço, 2012 is also restored from its synonymy with Chaerilus julietteae Lourenço, 2011 and the validity of Chaerilus kampuchea Lourenço, 2012 is confirmed.

Reference:
Lourenço WR, Ythier E. A new cave species of Chaerilus Simon, 1877 from Myanmar (Scorpiones: Chaerilidae). Revista Iberica de Arachnologia. 2024(44):51-6. [Full text provided by authors]

Thanks to Eric for sending me their article!

Family Chaerilidae

A new species of Buthus from southern Spain

 

Antonio L. González-Moliné and Luis F. de Armas recently published an article describing a new, psammophilous spcies in the genus Buthus Leach, 1815 (Buthidae) from the province of Huelva in southern Spain.

Buthus gonzalezdelavegai Gonzalez-Moline & de Armas, 2024

Abstract:
Since the description of Buthus ibericus Lourenço & Vachon 2004, a total of 17 congeneric species have been identified in the Iberian Peninsula; nine of which are from the Andalucía region. As result of a recently published revision of specimens from the southwestern area of this peninsula, only two species were recognized for Huelva Province: Buthus baeticus Teruel & Turiel, 2020 and B. delafuentei Teruel & Turiel, 2020. A new Buthus population discovered in the onubense coast (southeast of Huelva) represent an undescribed psammophilous species, closely related to B. delafuentei but having well defined diagnostic characters that facilitates its easy identification. Also, new localities are recorded for Buthus delafuentei and B. baeticus Teruel & Turiel, 2020; as well as one specimen of the new species having an anomalous pectine and other specimen of B. delafuentei with teratological carapacial carinae.

Reference:
Gonzalez-Moline AL, de Armas LF. Una especie nueva del genero Buthus (Scorpiones: Buthidae) de la Provincia de Huelva, España. Revista Iberica de Arachnologia. 2024(44):75-84. [No full text available]

Thanks to Leo Lindvall for sending this article!

Family Buthidae

A new species of Vaejovis from Mexico

 

Gerardo A. Contreras Félix and José L. Navarrete Heredia have recently published a description of a new spcies of Vaejovis C.L. Koch, 1836 (Vaejovidae) from Michoacan in Mexico.

Vaejovis castanoae Contreras-Felix & Navarrete Heredia, 2024

Abstract:
A new species of Vaejovis is described for Michoacan, Mexico belonging to the nigrescens/nitidulus group, the less diverse group of species from the genus. This species has a preference for synanthropic environments and inhabits rock walls within the city limits. Additionally, the pictures of the hemispermatophore are presented and characters are named according to new terminology. This species is named honoring Dr. Gabriela Castaño Meneses for her great contributions to arthropods research in Mexico and the world.

Reference:
Félix GAC, Heredia JLN. Hidden in the cracks, a new species of Scorpion from Michoacan, Mexico (Scorpiones: Vaejovidae). Dugesiana. 2024;31(2):159-73. [Open Access]

Thanks to Gerard Dupre for sending me this article!

Family Vaejovidae