An investigation of the defensive behaviors of the southern unstriped scorpion, Vaejovis carolinianus

 In the last decade there have been several studies looking into sting use and venom use in scorpions in relation to prey capture and defense. Venom metering in scorpions has been well documented, but few studies have focused on the other behavioral options a scorpion has in regard to prey capture or defense.

David Nelson and co-workers have now published a study on the defensive behaviors of Vaejovis carolinianus (Beauvois, 1805) (Vaejovidae) with regards to the scorpion's assessment of risk and refuge availability. The study concludes that V. carolinianus can assess risk and features of the local environment and, therefore, alter their defensive strategies accordingly.

Abstract:
Selection should favor individuals that acquire, process, and act on relevant environmental signals to avoid predation. Studies have found that scorpions control their use of venom: both when it is released and the total volume expelled. However, this research has not included how a scorpion’s awareness of environmental features influences these decisions. The current study tested 18 Vaejovis carolinianus scorpions (nine females and nine males) by placing them in circular arenas supplied with varying numbers (zero, two, or four) of square refuges and by tracking their movements overnight. The following morning, defensive behaviors were elicited by prodding scorpions on the chelae, prosoma, and metasoma once per second over 90 s. We recorded stings, venom use, chelae pinches, and flee duration. We found strong evidence that, across all behaviors measured, V. carolinianus perceived prods to the prosoma as more threatening than prods to the other locations. We found that stinging was a common behavior and became more dominant as the threat persisted. Though tenuous, we found evidence that scorpions’ defensive behaviors changed based on the number of refuges and that these dierences may be sex specific. Our findings suggest that V. carolinianus can assess risk and features of the local environment and, therefore, alter their defensive strategies accordingly.

Reference:
Nelsen DR, David EM, Harty CN, Hector JB, Corbit AG. Risk Assessment and the Effects of Refuge Availability on the Defensive Behaviors of the Southern Unstriped Scorpion (Vaejovis carolinianus). Toxins. 2020;12(9). [Open Access]

Yet another remarkable cave scorpion finding in Europe

 In Mars I blogged about the remarkable finding of the troglophile cave scorpion Sardoscorpius troglophilus Tropea & Onnis, 2020 (Belisariidae) from Sardinia (Italy). Now I can inform about a remarkable new troglobitic scorpion species from a cave system in Montenegro.

Euscorpius studentium Karaman, 2020 (Euscorpiidae)

The new species is a true troglobite missing eyes and having reduced pigmentation and is actually the first true troglobitic scorpion species in Europe. Only two specimens have been found and it is assumed that the population is very small and critical endangered due to human activities in the cave system it inhabits.

The article also has an interesting discussion about the evolution of troglobitic scorpions.

Abstract:
A troglobite, Euscorpius studentium n. sp. is described based on a single immature male specimen from Skožnica, a relatively small cave in the coastal region of Montenegro. The characteristics of the new species are compared with the characteristics of an immature male specimen of troglophile Euscorpius feti Tropea, 2013 of the same size, from another cave in Montenegro. Some identified differences indicate evolutionary changes that are the result of the process of adaptation of troglobite scorpions for life under conditions found in underground habitats: reduced eyes, depigmentation, smooth teguments with reduced granulation and tubercles, elongated sharp and thin ungues of the legs and narrowed body. The settlement of limestone caves by large troglobionts such as scorpions follows karstification processes. Lithophilic forms that evolved under these conditions possess the necessary climbing abilities that are prerequisite for settlement of hypogean habitats. Uncontrolled visits by tourists in recent years have seriously threatened the fauna of Skožnica cave, including this new and first recognized troglobite scorpion species among European fauna.

Reference:
Karaman I. A new Euscorpius species (Scorpiones: Euscorpiidae) from a Dinaric cave - the first record of troglobite scorpion in European fauna. Biologia Serbica. 2020;42. [Open Access]

Thanks to professors Ivo Karaman and Victor Fet for sending me this very interesting article!

Family Euscorpiidae

Description of the male Wernerius mumai

 

Some species are rare and found in few numbers and sometimes a species is described on the basis of just  one of the sexes. This was the case for Wernerius mumai (Sissom, 1993) (Vaejovidae). Richard Ayrey and Brandon Meyers have now found males of this species and has described this sex in a recent paper.

Abstract:
A male of Wernerius mumai (Sissom, 1993) is described for the first time, collected at the type locality (Gold Road, Black Mountains, Mohave County, Arizona). Originally placed in the genus Vaejovis, this species later was transferred by Soleglad & Fet (2008) to the genus Wernerius. It is one of the smallest vaejovid species known. The pedipalp fixed finger usually has 6 ID denticles and the movable finger has 7. The most unique characteristic of this species is the long, pointed, subaculear tubercle.

Reference:
Ayrey RF, Myers BT. Description of the male of Wernerius mumai (Sissom, 1993) from western Arizona, with data on reproduction (Scorpiones: Vaejovidae). Euscorpius. 2020(317):1-17. [Open Access]

Family Vaejovidae

How will climate changes impact the diverse scorpion fauna of Mexico?

Scorpions are infamous among many peoples and many will not focus on the conservation of this "dangerous" animal group when the global climate changes. But it is important to remember that scorpion diversity is an indicator of the health of the fauna in an area or its ecosystem and knowledge about the impact of climate changes on the scorpion fauna is important for more than scorpions alone.

Carolina Ureta and co-workers have recently published a study evaluating the vulnerability of scorpions in Mexico to climate change and if Mexican protective measures are sufficient to protect this animal group under future climate models. The short answer is that the scorpion fauna of Mexico is vulnerable under both current and under future climatic conditions.

Abstract:
Scorpions have high levels of endemism and their distributions are typically narrow, making them particularly vulnerable to changes in their environment. Unfortunately, little is known about the status ofscorpion conservation worldwide. Here, we compiled information on scorpion diversity across the world and highlighted Mexican scorpion diversity. We created and overlapped scorpions’ hotspots with the Mexican system of protected areas. We also modeled the potential distribution area of 24 wide distributed scorpion species under current and future scenarios to evaluate their vulnerability to climate change considering full and null dispersal models, and calculated the percentage of their distribution that will be protected by the natural protected areas in the future. Our results indicate that while Mexico has the greatest diversity of scorpion species compared to any other country in the world, these animals are not sufficiently protected by the system of natural protected areas under neither current nor under future climatic conditions. In terms of climate change vulnerability, we assessed the impact to these species if their migration to future more climatically suitable areas is not feasible. However, if full migration is feasible for species with broad ecological habitats, nine species might have a more widespread distribution,including three species with medical importance (Centruroides spp.).

Reference:
Ureta C, González EJ, Ramírez-Barrón M, Contreras-Félix GA, Santibáñez-López CE. Climate change will have an important impact on scorpion’s fauna in its most diverse country, Mexico. Perspectives in Ecology and Conservation. 2020;18(2):116-23. [Open Access]

Thanks to Matt Simon for informing me about this article!

 

Observations on the diet and reproduction of Centruroides gracilis from Honduras

 

Centruroides gracilis (Latreille, 1804) (Buthidae) is a widespread scorpion in Central America and Caribbean, but there is little information published on the behavior and ecology of this species. Anna Davison and co-workers have now published an obervational study on the diet and reproduction of this species on Utila Island in Honduras.

Abstract:
The brown bark scorpion Centruroides gracilis (Latreille, 1804) (Buthidae) is an abundant and widespread species, however, fairly little is known about its ecology and natural history. We include several observations from Utila Island, Honduras, that expand on the known literature regarding the diet and reproductive behavior of C. gracilis. We report several prey items for this opportunistic species, which include invertebrates such as spiders (including tarantulas), centipedes, katydids, and crickets; as well as a case of cannibalism between two adult females C. gracilis. We suggest that such cannibalism may be driven by high population densities and/or strong intraspecific competition for prey sources on the island. Additionally, we observed a courtship dance involving a female that still carried second-instar offspring, a common behavior within the Buthidae family, although, to our knowledge, not previously reported for C. gracilis.

Reference:
Davison AM, Brown TW, Arrivillaga C. Notes on the diet and reproduction of the bark scorpion Centruroides gracilis (Scorpiones: Buthidae) on Utila Island, Honduras. Euscorpius. 2020(314):1-7. [Open Access]