Does the cuticular wax layer in scorpions have a role in mate and sexual recognition in male Tityus pusillus?

 

Male and female scorpions need to be able to recognize each others and their "mood" to ensure safe and optimal mating. The mating dance in scorpions is well known and many studies have indicated that chemical substances are involved in mate and sexual recognition.

Hugo R. Barbosa-da-Silva and co-workers have recently published a study investigating the cuticular wax layer (CWL) involvement in mate and sexual recognition in the buthid Tityus pusillus Lourenço, 2013. The study found some evidence that CWL compounds were involved in sexual recognition, but there was noconfirmation that CWL compounds mediate mate recognition in this species. 

Abstract:
Hydrophobic compounds present in the cuticular wax layer (CWL) of terrestrial arthropods protect them from dehydration and are also involved in chemical communication. However, the role of CWL compounds in the behavioral ecology of scorpions has been studied less often, with most investigations focusing on their responses to mechanical stimuli. In this study, we aimed to characterize the CWL composition of Tityus pusillus (Scorpiones, Buthidae) and examine the influence of CWL solvent extracts and movement on intraspecific mate and sexual recognition by males of this species. We analyzed CWL hexane extracts of adult female and male T. pusillus by gas chromatography-mass spectrometry (GC-MS). In paired behavioral tests inside an experimental arena, we exposed adult males to i) live and intact dead conspecific females; ii) intact dead females and females without the CWL (removed with solvent washes); and iii) intact dead males with and without the CWL. Our results showed that CWL extracts of both female and male T. pusillus contained a series of linear alkanes (C21 – C34; > 54 % relative composition), as well as fatty acyls (> 9.5 %) and methyl-branched alkanes (> 9.1 %). Two unassigned C31 monomethyl-branched alkanes were exclusively identified in male CWL extracts (~ 4.7 %), while female samples contained high relative concentrations (> 22.5 %) of sterol derivatives, present only as minor constituents in male samples. Male T. pusillus performed sexually-oriented behavioral acts when paired with both live and dead conspecific females, intact or without the CWL. However, they ignored conspecific dead males. Our results show that CWL compounds have a role in intraspecific sexual recognition by male T. pusillus but only the CWL compounds does not explain mate recognition.

Reference:
Barbosa-da-Silva HR, Pontes WJT, Lira AFA, Navarro DMAF, Salomão RP, Maia ACD. The role of intraspecific mechanical and chemical signaling for mate and sexual recognition in male Tityus pusillus (Scorpiones, Buthidae). Zoology. 2025;168:126235. [Subscription required for full text]

Thanks to André for sending me their article!

Goats are not scorpions' best friend

 

                                                    Illustration: DALL-E/ChatGPT

Habitat destruction due to human impact is a threat to many animals, scorpions included. In a recent study, Thayna Rhayane Brito-Almeida and co-workers have investigated the impact of non-native, grassing goats on the scorpion fauna in Brazil.

The study showed that the goats have a negative impact on the habitat and both the species richness and abundance of scorpions in areas with grazing goats. The presence of goats also seemed to cause reduced body mass and size in the scorpions compared to areas without goats.

Abstract:
Extensive grazing carried out freely by exotic goats represents an important source of anthropogenic degradation in seasonally dry tropical forests of Brazil. The presence of these herbivores may negatively impact the local fauna through the reduction of habitat complexity. In this study, we investigate the effect of goat farming in scorpion assemblage from Brazilian seasonally dry tropical forest. Scorpions were sampled in 36 areas (18 disturbed and 18 undisturbed) distributed in three sites in the seasonally dry tropical forest of Brazil. At each location, we recorded a set of local variables such as litter depth, diameter at breast height of trees, vegetation density (trees and shrubs), and detritus (stones and fallen logs). In total, 396 scorpions were collected, distributed across six species and two families. Our results showed that scorpion diversity was negatively affected, with species richness and abundance reduced in areas influenced by goats. Furthermore, in these sites, the composition of the species was also affected, with habitat-generalist species favoring habitat-specialist species. Finally, sites with free pasture of goats presented scorpions with reduced body condition (body mass and size) than sites without goats. Furthermore, habitat degradation caused by free pasture of goats negatively affects the assemblage of scorpions in terms of their diversity and body condition the seasonally dry tropical forest of Brazil.

Reference:
Brito‐Almeida TR, Foerster SÍA, Lima JR, da Silva MA, de Moura GJB, de Araujo Lira AF. Free Pasture of Exotic Goats Reduces Diversity and Negatively Affects Body Condition in Scorpions (Arachnida: Scorpiones) Assemblage From Brazilian Seasonal Dry Tropical Forest. Ecology and evolution. 2025;15(1):e70804. [Open Access]

Thanks to André for sending me their article!

A review of the scorpion fauna of China

 

There is still a lot to learn about the large scorpion fauna of China, both when it comes to new taxa but also by evaluating old works. Victoria Tang has recently published a new review of the scorpion fauna of China. 

The article focuses especially on the genera Reddyanus Vachon, 1972 and Razianus Farzanpay, 1987 (both Buthidae). The following taxonomical changes were made:

Raised to species status from synonymization:

Reddyanus hainanensis (Lourenço, 2005) Restored from synonymy with Isometrus petrzelkai Kovarík, 2003.

Reddyanus lao (Lourenço & Leguin, 2005) Restored from synonymy with Isometrus petrzelkai Kovarík, 2003.

 Synonymization:

 Reddyanus tibetanus (Lourenco & Zhu, 2008) is synonymized with Reddyanus assamensis (Oates, 1888).

New status:

Reddyanus kanak Lourenço, 2023 is tentatively considered as a nomen dubium.

An updated catalogue of scorpiofauna of China is also provided.

Abstract:
Two genera associated with the scorpiofauna of China are reviewed, Razianus Farzanpay, 1987 and Reddyanus Vachon, 1972. Holotype female of Razianus xinjianganus Lourenço et al., 2010 is presumed to be lost, as well as all type material of other Chinese scorpions described before 2020. Comments are given on the species composition of genus Reddyanus with a new synonym: Isometrus (Reddyanus) tibetanus Lourenço & Zhu, 2008 = Reddyanus assamensis (Oates, 1888) syn. n. Reddyanus kanak Lourenço, 2023 is tentatively considered as a nomen dubium. An updated catalogue of scorpiofauna of China is provided, including their type locality and type depository, protonym, synonym(s), misidentification(s), Chinese equivalent name and distribution in China. Several Tibetan Scorpiops species will be addressed in a subsequent paper. Finally, a list of errata in the preceding taxonomic papers by the current author is also included.

Reference:
Tang V. A review of scorpiofauna of China: nomenclatural notes and updated faunistic catalogue (Arachnida: Scorpiones). Euscorpius. 2025(404):1-24. [Open Access]

Family Buthidae

Did you miss anything in 2024?

 

In the recent issue of Arachnides, Gerard Dupre presents two articles that sum up the scorpion year of 2024. One article list all scorpion papers published last year, the other article list all new taxa.

References:
Dupre G. Scorpions bibliography 2024 (without toxinology). Arachnides. 2024(119):1-20. [Open access]

Dupre G. Nouveaux taxa de scorpions pour 2024. Arachnides. 2024(119):21-7. [Open Access]

Thanks to Gerard for sharing the articles of Arachnides with us!

Arm-span competition between males in the buthid scorpion Tityus rosenbergi

 

Courtship and mating behaviors between male and female scorpions are well documented. Intrasexual interactions (between female-female or male-male scorpions) are not mentioned often in the literature. Recently, a new ritualized behavior between the same sex was described and labeled "arm-span competition”.

In a recent article, Jules Thornton Wyman and co-workers present observations of "arm-span competition" between males of Tityus rosenbergi Pocock, 1898 (Buthidae). The behavior is interpreted as a ritualized male-male contests. 

The authors suggest that the elongated pedipalps seen in males of many species might be the result of selective pressure related to ritualized arm-span competition.

Abstract:
Although courtship and mating behaviors have been described for nearly all scorpion lineages, intrasexual interactions in scorpions remain understudied. Recently, a novel ritualized behavioral unit, termed “arm-span competition,” in which individuals face off and extend their pedipalps laterally, was described from analyses of male-male contests in several scorpionid species. Here, we present the first documented observation of arm-span competition in a buthid scorpion, Tityus cf. rosenbergi Pocock, 1898. Interestingly, both T. cf. rosenbergi and most scorpionid species known to engage in arm-span competition exhibit a similar sexual dimorphism: males have markedly longer and more slender pedipalps than females. We suggest that the elongated pedipalps in males of these species might be the result of selective pressure related to ritualized armspan competition. We also highlight the potential for citizen science to contribute rare observations to scientific literature.

Reference:
Wyman JT, Wright-Ueda J, Agnew Q, Castellano I, Simone Y. First report of arm-span competition in buthid scorpions: male-male contest in Tityus cf. rosenbergi Pocock, 1898. The Journal of Arachnology. 2025;52(3):210-3. [Open Access]

Thanks to Yuri for sending me this article!

A study of the fluorescent sensilla on the scorpion aculeus (stinger)

 

It is well-known that scorpions fluorescence under UV light. This also apply for the scorpion's stinger (aculeus), but previous studies has shown a lack of fluorescence in the distal aculeus. Graeme Lowe has recently published an article where he used SEM imaging to study UV fluorescence in the acuelus of many species.

He observed numerous brightly fluorescent punctae in the non-fluorescent distal aculeus. These punctae were identified as aculear sensilla coeloconica (ASC). The ASC probably have a chemoreceptive function.

The author suggests that the ASC are playing an important role in the sensory coordination of telson function when the scorpions are trying to sting their prey and inject venom.

Abstract:
The aculeus of the scorpion telson was studied by UV fluorescence microscopy. Numerous brightly fluorescent punctae were observed on the non-fluorescent distal aculeus, including the tip region. The punctae were identified as aculear sensilla coeloconica (ASC), and were connected to fluorescent canals running through the cuticle. ASC were present in both sexes, and in adults and immatures as early as the second instar juvenile, but were absent from the first instar. The distal aculeus was found to be encased in a thick, non-fluorescent dark exocuticle (DX), covering an underlying thin, fluorescent hyaline exocuticle (HX). Fluorescent ASC were recorded from 183 species belonging to 97 genera in 19 families, encompassing all major scorpion lineages. The number of ASC in the tip region, the width of ASC canals, and the depth of the tip region, all exhibited positive correlation and allometric scaling with respect to carapace length. Higher tip densities of ASC occurred in some buthids, and in Scorpionoidea. The ASC are probably ubiquitous across the Order Scorpiones, playing an essential role in the sensory coordination of telson function during prey envenomation.

Reference:
Lowe G. Star-studded stingers: fluorescent sensilla on the scorpion aculeus (Arachnida: Scorpiones). Euscorpius. 2024;2024(402):1-39. [Open Access]

The postembryonic development of Centruroides ochraceus from Mexico

 

Happy New Year!

Wilson Lourenco and Eric Ythier have recently published some old observations of postembryonic development of Centruroides ochraceus (Pocock, 1898) (Buthidae) from Yucatan, Mexico. It is also suggested that parthenogenesis exists in this species.

Abstract:
Since general data on the biology of scorpions remain rare, we propose in this note some results on the postembryonic development of the buthid scorpion Centruroides ochraceus (Pocock, 1898), species distributed in the Yucatan peninsula, Mexico. The results were originally observed almost 40 years ago, based on some specimens collected by the senior author. A possible case of parthenogenesis is also suggested for this species.

Reference:
Lourenço WR, Ythier E. The postembryonic development of Centruroides ochraceus (Pocock, 1898) from Yucatan, Mexico (Scorpiones: Buthidae), with comments on parthenogenesis. Revista Iberica de Arachnologia. 2024(45):119-22. [Full text supplied by author]