Fitness differences between parthenogenetic litters of the parthenogenetic scorpion Tityus stigmurus

 

We often think that parthenogenetic reproduction produces clones that are identical in most ways. But there are non-genetical factors that may cause variations even though the organism is living in the same, stable environment. One example of this is maternal age's impact on different parthenogenetic litters.

Welton Dionisio-da-Silva and co-workers have recently pulished a study on non-Mendelian variation on parthenogenetic litters in the medical important species Tityus stigmurus (Thorell, 1876) (Buthidae). Their results indicate that T. stigmurus females allocated nutrient resources to maximize litter size rather than developmental fitness in subsequent litters. See abstract and article for more details.

I can add that knowledge of reproduction and life history of this scorpion is important as it is a medical important species that thrive in urban areas with high risk of human contact. 

Abstract:
Clonal lineages in similar environments may be influenced by non-Mendelian inheritance, such as maternal age effects and developmental instabilities. These mechanisms may affect the developmental fitness of parthenogenetic litters. In this study, the scorpion Tityus stigmurus (Thorell, 1876) was used to analyze the effects of non-Mendelian variation on parthenogenetic litters. A total of 75 juveniles from five females were reared under the same controlled conditions, while their development was observed and evaluated through differences in offspring fitness traits (litter size, prosoma size, developmental time, and mortality) between the litters. First and second litters had a similar litter size, although second litters exhibited longer developmental time in the early instar stages (second and third) than first litters. These results indicate that T. stigmurus females allocated nutrient resources to maximize litter size rather than developmental fitness in subsequent litters. Differences in developmental time found in early instars but not in late instars may have occurred as a result of stochastic developmental variations in young individuals. Such variation in duration of development has the potential to influence survival of juveniles in natural environments because individuals that grow faster may avoid large predators and consume larger prey, compared to those that do not.

Reference:
Dionisio-da-Silva W, Albuquerque CMR, Lira AFA. Fitness differences between parthenogenetic litters of the synanthropic scorpion Tityus stigmurus (Scorpiones: Buthidae). Animal Biology. 2022;72:435-46. [Subscription required for full text]

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

Has male Euscorpius scorpions "date drugs" in their venom?

 

Differences in the venom composition of scorpions have been reported for many tears, both within the same species and between species. In addition, different venom types have been related to different purposes (e.g. the findings of prevenom in some species). 

Sex-specific differences in venom composition have been demonstrated for several arthropod taxa(e.g. in spiders where males of the infamous Sydney funnel web spider has a venom lethal to humans, while the female venom is not dangerous). Less is known about this in scorpions, but many species use sexual stings during courship and it has been suggested that the male venom used for this may sedate females to make them less aggressive.

Jonas Krämer and co-workers have recently published an interesting study analyzing the venom composition of male, female and juvenile Euscorpius italicus (Herbst, 1800) (Euscorpiidae). This species uses sexual sting during courtship. Their study shows that the male venom has marked differences in venom composition from females and juveniles. The authors suggest that this may cause a reduced toxic effect on females during the sexual sting. Other suggested effects may be a reduced agggressivity in females and also physiological effects that improove the success of the mating.

More studies are necessary to understand more about this fascinating connection between venom and courtship behavior.

Abstract:
In the animal kingdom, intraspecific variation occurs, for example, between populations, different life stages, and sexes. For venomous animals, this can involve differences in their venom composition. In cases where venom is utilized in the context of mating, the differences in composition might be driven by sexual selection. In this regard, the genus Euscorpius is a promising group for further research, as some of these scorpions exhibit a distinct sexual dimorphism and are known to perform a sexual sting during mating. However, the venom composition of this genus remains largely unexplored. Here, we demonstrate that Euscorpius italicus exhibits a male-specific venom composition, and we identify a large fraction of the substances involved. The sex specificity of venom peptides was first determined by analyzing the presence/absence patterns of ion signals in MALDI-TOF mass spectra of venom samples from both sexes and juveniles. Subsequently, a proteo-transcriptomic analysis provided sequence information on the relevant venom peptides and their corresponding precursors. As a result, we show that several potential toxin precursors are down-regulated in male venom glands, possibly to reduce toxic effects caused to females during the sexual sting. We have identified the precursor of one of the most prominent male-specific venom peptides, which may be an ideal candidate for activity tests in future studies. In addition to the description of male-specific features in the venom of E. italicus, this study also includes a general survey of venom precursors in this species.

Reference:
Kramer J, Pommerening R, Predel R. Equipped for Sexual Stings? Male-Specific Venom Peptides in Euscorpius italicus. Int J Mol Sci. 2022;23(19). [Open Access]

A new species of Scorpiops from China

 

Victoria Tang has recently published a study on a population of Scorpiops kubani (Kovařík, 2004) (Scorpiopidae) in China and has revealed that these have been misidentified. A new species is described based on new materials from the Yunnan Province in China.

Scorpiops lowei Tang, 2022

Abstract:
The Yunnan population of Scorpiops kubani (Kovařík, 2004) is reassessed based on recently collected specimens from this region. A misidentification of that species is revealed, which leads to a description of a new species, Scorpiops lowei sp. n.

Reference:
Tang V. Reanalysis of the Yunnan population of Scorpiops kubani with a description of a new species, Scorpiops lowei sp. n. (Scorpiones: Scorpiopidae). Euscorpius. 2022(361):1-22. [Open Access]

Family Scorpiopidae

A new species of Buthus from France

 

Studies of the genus Buthus Leach, 1815 (Buthidae) in Europe and North Africa the last decade have revealed many micro-endemic species that previously were included in the species-complex Buthus occitanus (Amoreux, 1789) Sensu lato. Eric Ythier and Leo Laborieux have now published a new species in the genus from the mountain crest of the Sainte-Baume Massif, in the South of France.

Buthus balmensis Ythier & Laborieux, 2022

The article has an indentification key for the three French species of Buthus.

Abstract:
A new species of Buthus is described on the basis of three specimens collected on the mountain crest of the Sainte-Baume Massif, in the South of France. Buthus balmensis sp. n. is mainly characterized by a general coloration yellowish with a dark univittate pattern on tergites, chela fingers with lobe/notch combination obsolete, a size slightly larger than other species occurring in France (B. occitanus (Amoreux, 1789) and B. pyrenaeus Ythier, 2021), the male slightly smaller than female but with metasoma longer and heavier than in female, pedipalp chela manus swollen and wider than patella in both sexes, metasomal segment I as wide as long in male and longer than wide in female, and a reduced granulation on body and metasoma. The new species shows affinities with B. pyrenaeus (most similar species) and B. occitanus but can be easily distinguished from these two species by a combination of several key characters. This new scorpion taxon represents the 3rd known species of the genus Buthus reported from France and the 18th reported from Western Europe. Maps of the geographical distribution of Buthus species in France is presented and a key for their identification is provided. The presence of B. pyrenaeus in Spain is also herewith confirmed.

Reference:
Ythier E, Laborieux L. The genus Buthus Leach, 1815 (Scorpiones: Buthidae) in France with description of a new species from the Sainte-Baume Massif. Faunitaxys. 2022;10(47):1-13. [Open Access]

Family Buthidae

I play dead

 

Thanatosis, or "playing dead" is a known anti-predator behavior both in scorpions and other invertebrates. This behavior, which is also know as tonic immobility, is often associated with cryptic coloration. In a recent paper, Felipe Triana and co-workers describe and discuss this special behavior in the two buthids Tityus ocelote Francke & Stockwell, 1987 and Ananteris platnicki Lourenço, 1993 from Central America. 

The study concludes that this behavior may be more common than previously known and that it may have a basis in American buthids (but more studies are necessary to confirm the latter).

Abstract:
Thanatosis, or tonic immobility, is a behavior where animals adopt a motionless posture after a physical contact or very close proximity of a predator. This behavior has been described in a wide range of taxa, from invertebrates to vertebrates. For scorpions, tonic immobility has been reported in two buthids, Tityus pusillus and Tityus cerroazul, one hormurid, Liocheles australasiae, and one scorpiopsid, Scorpiops jendeki. Here we report other cases of this thanatosis for two buthid scorpions from lower Central America: Tityus ocelote and Ananteris platnicki. Thanatosis in these species were observed in wild, but was better documented in the laboratory. After human handling, several individuals for both species rolled over and laid on their back, adopting a distinctive rigid position, where they did not respond to external mechanical stimuli. As tonic immobility might be associated with other defense strategies, such as cryptic colorations, it is hypothesized that this behavior is used as a strategy in both species only if there is physical contact that simulated by a predator. On the other hand, the observations of thanatosis we reported here and the ones reported in other Tityus scorpions suggest that this behavior may have a phylogenetic basis in American buthids and that it could be more widespread than initially thought. However, more observations of tonic immobility in buthids would allow the evaluation of this hypothesis.

Reference:
Triana F, Bonilla F, Alfaro-Chinchilla A, Víquez C, Díaz C, Sasa M. Report of thanatosis in the Central American scorpions Tityus ocelote and Ananteris platnicki (Scorpiones: Buthidae). Euscorpius. 2022;(359):1-5. [Open Access]

A new species of Scorpiops from China

 

Victoria Tang has recently published a new article on the scorpion fauna of China and this time a new species of Scorpiops Peters, 1861 (Scorpiopidae) from Yunnan Province has been described.

Scorpiops tongtongi Tang, 2022

Updated data on several other Scorpiops species are given and based on these Scorpiops validus (Di et al., 2010) is raised to species status from synonymy with S. vachoni (Qi et al., 2005).

Abstract:
A new species of Scorpiops Peters, 1861, Scorpiops tongtongi sp. n., is described from Yingjiang, Yunnan Province, China, based on a single adult female. The morphology of the new species is fairly distinguishable from other congeners in Yunnan even with unaided eye; it is characterized by the following combination of characters in female: a pair of moderately robust pedipalp chelae without proximal lobes, small median ocular tubercle, short superciliary carinae, less granulated tergites, proportionally elongate metasoma and relatively short and bulbous vesicle. The coloration of the new species also differs from other congeners in Yunnan by being brownish in tergites and telson vesicle. The number of known species of Scorpiops from China is raised to 29 (22 endemic) and that of Yunnan is raised to 10 (9 endemic). The previously described congeners from Yunnan are also revisited, by complementing some missing data of several species, and providing new comparative data for the following species based on recently collected topotypes: S. puerensis (Di et al., 2010), S. shidian (Qi et al., 2005), S. vachoni (Qi et al., 2005), S. validus (Di et al., 2010), and S. zhangshuyuani (Ythier, 2019), as well as the Yunnan population of S. kubani (Kovařík, 2004). Finally, Scorpiops validus (Di et al., 2010) stat. rev. is restored from its synonymy with S. vachoni (Qi et al., 2005).

Reference:
Tang V. A new species of Scorpiops Peters, 1861 from Yunnan Province, China, with a preliminary review of its congeners in Yunnan (Scorpiones: Scorpiopidae). Euscorpius. 2022(360):1-44. [Open Access]

Family Scorpiopidae