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General anatomy of a scorpion. Habitus of Pandinus imperator (C. L. Koch), male from Africa (copyright by B. Duhem, reproduced with permission).
Source publication
As in previous contributions to the JVATiTD, the aim of this note is to bring some general information on a particular aspect of the scorpion biology. An attempt is made to explain the possible coevolution of telson morphology and venom glands, which took place during several hundred million years and in particular since scorpions migrated from aqu...
Contexts in source publication
Context 1
... conservative, the general morphology of scorpions seems to be extremely well adapted to both predation and defensive behaviours. The body is almost totally articulated and composed of a fixed prosoma and an opisthosoma divided into 12 segments; seven that compose the mesosoma and five the metasoma (Figure 2). The morphology of metasoma can vary greatly among species of distinct families. ...
Context 2
... Ananteris, Tityobuthus, Lychas or Isometrus), while more evolved groups Non-buthoid lineages globally correspond to larger or at least more robust scorpions. Several species possess very strong pedipalps and predation can be performed just mechanically without the use of venom (Figures 2 and 4). In other words, they can capture prey without stinging. ...
Citations
... The telson morphology is quite similar between scorpion species, with rare exceptions. It is composed of a vesicle that contains a pair of glands; this vesicle is prolonged by the aculeus, which bears two exit ducts, each corresponding to one of the glands [62]. Venom is injected through the sting by the contraction of a striated skeletal muscle present in the venom gland. ...
Sixty-seven scorpion species have been described in France and its territories, where they have been found to be heterogeneously distributed. Indeed, only one species can be found on Réunion Island, while 38 species exist in French Guiana. The number of stings is also heterogenous, with up to 90 stings per 100,000 inhabitants occurring annually. Scorpion species can frequently be determined through simple visual factors, including species of medical importance (i.e., Buthus, Centruroides and Tityus). Scorpion venom is composed of local enzymes and peptides with a cysteine-stabilized α/β motif (NaTxs, Ktxs, Calcines), which allow for venom diffusion and the prey’s incapacitation, respectively. Harmful scorpion species are limited to Centruroides pococki in the French West Indies, which can induce severe envenoming, and the Tityus obscurus and Tityus silvestris in French Guiana, which can cause fatalities in children and can induce severe envenoming, respectively. Envenomation by one of these scorpions requires hospital monitoring as long as systemic symptoms persist. Typical management includes the use of a lidocaine patch, pain killers, and local antiseptic. In the case of heart failure, the use of dobutamine can improve survival, and pregnant women must consult an obstetrician because of the elevated risk of preterm birth or stillbirth. France does not have scorpion antivenom, as scorpion stings are generally not fatal.
... Scorpions are a successful group of terrestrial arthropods, present in almost all known terrestrial habitats [18]. Although the high success of this group has been attributed to several traits, morphology plays a key role, particularly their chelae and metasoma that are linked to defense and predation [19]. Among the most characteristic structures in scorpions are the chelae and stinger (telson), which are considered the main weapons and affect several ecological functions in scorpions, including prey capture, defense, sensing and mating [20]. ...
Background:
Scorpions can use their pincers and/or stingers to subdue and immobilize their prey. A scorpion can thus choose between strategies involving force or venom, or both, depending on what is required to subdue its prey. Scorpions vary greatly in the size and strength of their pincers, and in the efficacy of their venom. Whether this variability is driven by their defensive or prey incapacitation functionis unknown. In this study, we test if scorpion species with different pincer morphologies and venom efficacies use these weapons differently during prey subjugation. To that end, we observed Opisthacanthus elatus and Chactas sp. with large pincers and Centruroides edwardsii and Tityus sp. with slender pincers.
Methods:
The scorpion pinch force was measured, and behavioral experiments were performed with hard and soft prey (Blaptica dubia and Acheta domesticus). Stinger use, sting frequency and immobilization time were measured.
Results:
We found that scorpions with large pincers such as O. elatus produce more force and use the stinger less, mostly subjugating prey by crushing them with the pincers. In C. edwardsii and Tityus sp. we found they use their slender and relatively weak pincers for holding the prey, but seem to predominantly use the stinger to subjugate them. On the other hand, Chactas sp. uses both strategies although it has a high pinch force.
Conclusions:
Our results show that scorpionspecies with massive pincers and high pinch force as O. elatus use the stinger less for prey subjugation than scorpionspecies with slenderpincers.
... The concept that larger scorpions have less potent venom compared to smaller scorpions is widely expressed in the media, and has been popularized by numerous sources, such as in the Indiana Jones movie, where the main protagonist explicitly refers to this by saying "When it comes to scorpions, the bigger the better" [12]. Apart from its use in popular fiction, the concept of relying on the size of the morphological characteristics of scorpions is used as a general medical guidance in many countries where scorpionism is an issue [13,14], as most scorpions are difficult to identify at the species level by nonexperts [14][15][16][17]. Support for this general concept can be found in the high median lethal dosage values (LD 50 ), indicating venoms of lower potency, reported for larger species of scorpions, such as Hadrurus arizonensis and Heterometrus laoticus [18][19][20][21]. ...
... While present in all scorpions, their use varies across species, following a trade-off pattern [16]. Species that primarily rely on venom, such as many species within Buthidae, often have long slender chelae [5,24], while species with more powerful chelae, such as Opistopthalmus glabrifrons, typically have comparatively less-developed stinging apparatus, with a smaller metasoma, or less potent venom, as found by Lourenço [15]. From an evolutionary perspective, such a pattern may emerge, as larger species that rely more on mechanical prey capture or that avoid predators may have fewer selection pressures on the potency of their venoms. ...
... However, while our results do not support a trade-off between telson morphology and venom potency, other features of the scorpion delivery system may be associated with this trade-off, such as the metasoma. For example, Ref. [15] associated the thickness of the metasoma with venom potency. This may highlight the relationship between how frequently venom is used by a species and the fact that species that rely on venom for predation require more well-developed metasoma. ...
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.
... At least three components can be directly associated with predation and defensive behaviors in scorpions: (1) morphology of the chelae and structure of the chelae fingers granulations; (2) morphology of the metasoma and in particular of the telson; (3) evolution of tegumentary glands in the telson toward different types of venom glands [16], the latter being one of the most studied aspects [17]. Despite venom playing a key role in prey capture, most studies have looked at the effect of venom from a defensive perspective in scorpions [18,19,20,21]. ...
Background:
Scorpions are arachnids that have a generalist diet, which use venom to subdue their prey. The study of their trophic ecology and capture behavior is still limited compared to other organisms, and aspects such as trophic specialization in this group have been little explored.
Methods:
In order to determine the relationship between feeding behavior and venom toxicity in the scorpion species Tityus fuhrmanni, 33 specimens were offered prey with different morphologies and defense mechanisms: spiders, cockroaches and crickets. In each of the experiments we recorded the following aspects: acceptance rate, immobilization time and the number of capture attempts. The median lethal dose of T. fuhrmanni venom against the three different types of prey was also evaluated.
Results:
We found that this species does not have a marked difference in acceptance for any of the evaluated prey, but the number of capture attempts of spiders is higher when compared to the other types of prey. The immobilization time is shorter in spiders compared to other prey and the LD50 was higher for cockroaches.
Conclusions:
These results indicate that T. fuhrmanni is a scorpion with a generalist diet, has a venom with a different potency among prey and is capable of discriminating between prey types and employing distinct strategies to subdue them.
... Some scorpion species belonging to three different families (Buthidae, Diplocentridae and Vaejovidae) can present a sub-aculear tubercule [117] with important taxonomic value [109] but unknown function [52]. Lourenço [118] suggested that these sub-aculear tubercles may serve as a protection against breakage for particularly long and slender aculei, although simpler reinforcing strategies, such as aculei with a thicker base, already exist within extant scorpions [52]. ...
Scorpions possess two systems of weapons: the pincers (chelae) and the stinger (telson). These are placed on anatomically and developmentally well separated parts of the body, that is, the oral appendages and at the end of the body axis. The otherwise conserved body plan of scorpions varies most in the shape and relative dimensions of these two weapon systems, both across species and in some cases between the sexes. We review the literature on the ecological function of these two weapon systems in each of three contexts of usage: (i) predation, (ii) defense and (iii) sexual contests. In the latter context, we will also discuss their usage in mating. We first provide a comparative background for each of these contexts of usage by giving examples of other weapon systems from across the animal kingdom. Then, we discuss the pertinent aspects of the anatomy of the weapon systems, particularly those aspects relevant to their functioning in their ecological roles. The literature on the functioning and ecological role of both the chelae and the telson is discussed in detail, again organized by context of usage. Particular emphasis is given on the differences in morphology or usage between species or higher taxonomic groups, or between genders, as such cases are most insightful to understand the roles of each of the two distinct weapon systems of the scorpions and their evolutionary interactions. We aimed to synthesize the literature while minimizing conjecture, but also to point out gaps in the literature and potential future research opportunities.
Millepora alcicornis (Cnidaria: Hydrozoa), known as fire coral, is a tropical species settled in marine ecosystems of the Canary Islands in the last years. This hydrocoral biosynthesizes toxins involved in chemical defense and prey capture mechanisms. Toxicological studies have shown that the venom contained in the nematocysts of Millepora species is mainly composed of thermolabile proteins that display hemolytic activity, causing skin irritation and burn-like lesions upon contact. As a continuation of a previous study, the chromatographic fractionation of the aqueous extracts of M. alcicornis has confirmed the coexistence of proteins of different nature responsible for the hemolytic effects of red blood cells (RBCs) through two different mechanisms. Aside from the already described phospholipase A2 (PLA2) activity, in this work the presence of alciporin, a pore-forming protein (PFP), has been established for the first time for M. alcicornis. The sequence analysis revealed that alciporin fit an actinoporin with high homology to stichotoxins. The hemolytic effects of alciporin were analyzed and sphingomyelin was identified as its biological target. Also, the evolution of the hemolytic damage produced at the nanoscale has been studied using atomic force microscopy (AFM).
