23 September, 2016

Why do some scorpions climb onto scrubs in Spain?

Foraging behavior in scorpions (as in all animals) is balance between food availability and predation risk. And in scorpions, cannibalism is a well known risk, especially when individuals of different sizes live in the same population. Distribution and behavior of foraging scorpions will therefore be shaped by resource availability and predation risk.

Francisco Sánchez-Piñero and Fernando Urbano-Tenorio have recently published a study on foraging behavior and shrub climbing in the buthid Buthus occitanus (Amoreux, 1789) in Spain. The study did not support a hypotheses explaining shrub climbing based on resource availability, but did support to the hypothesis that shrub climbing in the scorpion Buthus occitanus is related to predator (cannibal) avoidance.

The distribution and behavior of foraging animals usually imply a balance between resource availability and predation risk. In some predators such as scorpions, cannibalism constitutes an important mortality factor determining their ecology and behavior. Climbing on vegetation by scorpions has been related both to prey availability and to predation (cannibalism) risk. We tested different hypotheses proposed to explain climbing on vegetation by scorpions. We analyzed shrub climbing in Buthus cf. occitanus with regard to the following: a) better suitability of prey size for scorpions foraging on shrubs than on the ground, b) selection of shrub species with higher prey load, c) seasonal variations in prey availability on shrubs, and d) whether or not cannibalism risk on the ground increases the frequency of shrub climbing. Prey availability on shrubs was compared by estimating prey abundance in sticky traps placed in shrubs. A prey sample from shrubs was measured to compare prey size. Scorpions were sampled in six plots (50 m x 10 m) to estimate the proportion of individuals climbing on shrubs. Size difference and distance between individuals and their closest scorpion neighbor were measured to assess cannibalism risk. The results showed that mean prey size was two-fold larger on the ground. Selection of particular shrub species was not related to prey availability. Seasonal variations in the number of scorpions on shrubs were related to the number of active scorpions, but not with fluctuations in prey availability. Size differences between a scorpion and its nearest neighbor were positively related with a higher probability for a scorpion to climb onto a shrub when at a disadvantage, but distance was not significantly related. These results do not support hypotheses explaining shrub climbing based on resource availability. By contrast, our results provide evidence that shrub climbing is related to cannibalism risk.

Sanchez-Pinero F, Urbano-Tenorio F. Watch Out for Your Neighbor: Climbing onto Shrubs Is Related to Risk of Cannibalism in the Scorpion Buthus cf. occitanus. PLoS One. 2016;11(9):e0161747. [Open Access]

Thanks to Matt Simon for informing me about this paper!

14 September, 2016

Two new articles on scorpions found in Burmese amber

Even though rare, scorpions (and other arthropods) found in amber is an important tools for learning about scorpion development and evolution. Wilson Lourenco has now published two new papers with several new taxa based on scorpions found in Cretaceous amber of Myanmar.

Please note that the The Scorpion Files only lists extant taxa.

Abstract 1:
A study of three new scorpion specimens from the Cretaceous amber of Myanmar (Burma) leads to descriptions of one new genus, Burmesescorpiops gen.n., with the sole, and type, species, B. groehni sp.n., as well as of further two new species, Chaerilobuthus gigantosternum sp.n. and C. serratus sp.n., and to a confirmed validity of the subfamily Archaeoscorpiopinae Lourenço, 2015. At present, 18 scorpions and 21 fossil scorpions have been described from Burmese amber. This attests to a considerable degree of scorpion diversity in the Cretaceous Burmese amber- producing forests.

Abstract 2:
A preliminary study on fossil scorpions found in amber, from the Lower Cretaceous through the Palaeocene and up to the Miocene is proposed. Scorpions remain rare among the arthropods found trapped in amber. Only 24 specimens are known from Cretaceous amber, representing eight families and subfamilies, ten genera and 21 species; in parallel, 10 specimens have been recorded from Baltic amber representing seven genera and ten species. A few more recent fossils from Dominican and Mexican amber have also been described. The present study of a new scorpion specimen from the Cretaceous amber of Myanmar (Burmite) resulted in the description of one new species, Betaburmesebuthus bellus sp. n. – belonging to the subfamily Palaeoburmesebuthinae Lourenço, 2015. The new description brings further elements to the clarification of the status of this subfamily, which is now raised to family level. Once again, this new Burmite element attests to the considerable degree of diversity in the Burmese amber-producing forests.

Reference 1:
Lourenco W. A new genus and three new species of scorpions from Cretaceous Burmese amber (Scorpiones: Chaerilobuthidae: Palaeoeuscorpiidae). Arthropoda Selecta. 2016;25(1):67-74. [Open Access]

Reference 2:
Lourenco WR. A preliminary synopsis on amber scorpions with special reference to Burmite species: an extraordinary development of our knowledge in only 20 years. Zookeys. 2016(600):75-87. [Open Access]

Thanks to professor Victor Fet for sending me article 1!

13 September, 2016

A new species of Euscorpius from southern Turkey

Gioele Tropea and co-workers have described a new species of Euscorpius Thorell, 1876 (Euscorpiidae) from the Taurus Mountains in Antalya Province (Alanya District) in southern Turkey based on morphological and molecular evidence.

Euscorpius alanyaensis Tropea, Yagmur, Parmakelis & Kunt, 2016

The number of Euscorpius species described from Turkey is now 15.

A new scorpion species, Euscorpius alanyaensis sp. n., is described based on specimens collected from the Taurus Mountains in Antalya Province (Alanya District) in southern Turkey. It is a sibling species of the recently described E. gocmeni Tropea et al., 2014, and similarly, the new species is also characterized by a high trichobothrial count (Pv = 9–11, et = 7, em = 4, and eb = 4), a high pectinal teeth count (Dp = 9–11 in males, 8 in females), medium-small size, and light to medium brown reddish colour. In addition, for the first time a phylogenetic analysis (concatenated sequences of 16S rDNA and COI) is performed to reconstruct the relationships between E. gocmeni Tropea et al., 2014, E. koci Tropea et Yağmur, 2015, E. lycius Yağmur et al., 2013, E. avcii Tropea et al., 2012 from Turkey, and the new species herein described, E. alanyaensis sp. n.

Tropea G, Yagmur EA, Parmakelis A, Kunt KB. Another New Species of Euscorpius Thorell, 1876 from the Taurus Mountains in Antalya Province, Southern Turkey (Scorpiones: Euscorpiidae). Euscorpius. 2016(231):1-15. [Open Access]

Family Euscorpiidae

08 September, 2016

Sex differences in sting use and venom effect in Centruroides vittatus

D. W. Miller and co-workers have recently published an article demonstrating intersexual differences in sting use and venom effects in Centruroides vittatus (Say, 1821) (Buthidae). Females were more willing to sting than males, but the venom used by males was more effective (caused more pain). Interestingly, if adjusted for body size, males and females used approximately the same amount of venom when stinging. The reasons for these intersexual differences are discussed.

Studies of venom variability have advanced from describing the mechanisms of action and relative potency of medically important toxins to understanding the ecological and evolutionary causes of the variability itself. While most studies have focused on differences in venoms among taxa, populations, or age-classes, there may be intersexual effects as well. Striped bark scorpions (Centruroides vittatus) provide a good model for examining sex differences in venom composition and efficacy, as this species exhibits dramatic sexual dimorphism in both size and defensive behavior; when threatened by an enemy, larger, slower females stand and fight while smaller, fleeter males prefer to run. We here add evidence suggesting that male and female C. vittatus indeed have different defensive propensities; when threatened via an electrical stimulus, females were more likely to sting than were males. We reasoned that intersexual differences in defensive phenotypes would select for venoms with different functions in the two sexes; female venoms should be effective at predator deterrence, whereas male venoms, less utilized defensively, might be better suited to capturing prey or courting females. This rationale led to our predictions that females would inject more venom and/or possess more painful venom than males. We were wrong. While females do inject more venom than males in a defensive sting, females are also larger; when adjusted for body size, male and female C. vittatus commit equal masses of venom in a sting to a potential enemy. Additionally, house mice (Mus musculus) find an injection of male venom more irritating than an equal amount of female venom, likely because male venom contains more of the toxins that induce pain. Taken together, our results suggest that identifying the ultimate causes of venom variability will, as we move beyond adaptive storytelling, be hard-won.

Miller DW, Jones AD, Goldston JS, Rowe MP, Rowe AH. Sex Differences in Defensive Behavior and Venom of The Striped Bark Scorpion Centruroides vittatus (Scorpiones: Buthidae). Integr Comp Biol. 2016;Online first. [Subscription required for full text]

07 September, 2016

Phylogeography and population structure of two Brachistosternus species from Chile

Sara Ceccarelli and co-workers have recently published an article looking into the phylogeography and population structure of two species of Brachistosternus Pocock, 1893 (Bothriuridae) from costal deserts of Chile.

Coastal deserts are geologically dynamic areas of the Earth, affected by historical changes in sea levels and in some cases also by fault-line tectonic activity. An example of such a dynamic area is the Chilean coastal desert of the Antofagasta and Atacama regions, which harbours many endemic species, such as the bothriurid scorpion species Brachistosternus paposo and Brachistosternus roigalsinai. In this work, we carry out phylogeographic and population genetic analyses on these scorpions, using two mitochondrial (COI and cyt b) and two nuclear (Actin 5C and wingless) markers to identify species and population structuring, and link these findings to the geological history of the area. The geographical feature separating the two species is identified as the Huasco River, and distinguishing morphological features for these scorpions are presented. Population genetic and phylogeographic outcomes reflect an unstable history across this region for B. paposo and B. roigalsinai, related to sea-level changes affecting coastal habitats, including nearby islands.

Ceccarelli FS, Pizarro‐Araya J, Ojanguren‐Affilastro AA. Phylogeography and population structure of two Brachistosternus species (Scorpiones: Bothriuridae) from the Chilean coastal desert–the perils of coastal living. Biological Journal of the Linnean Society. 2016;Early View Article. [Subscription required for full text]

Thanks to Andres Ojanguren-Afillastro for sending me this article!

02 September, 2016

A new Heterometrus species from Thailand

Jana Pliskova and co-workers have recently published a new species of Heterometrus Ehrenberg, 1828 (Scorpionidae) from Thailand.

Heterometrus minotaurus Pliskova, Kovarik, Kosulic & Stahlavsky, 2016

The karyotype of the new species is presented and the known karyotypes of the genus is discussed.

A new species of the genus Heterometrus is described on the basis of a specimen recently collected in Thailand. Heterometrus minotaurus sp. nov. is morphologically closest to H. longimanus. The newly described species is well distinguished by its smaller overall size (83 mm) and shorter and less narrow metasoma with specific dorsolateral carinae on the fourth metasomal segment consisting of 9 or fewer granules. No females are known and so knowledge of sexual dimorphism in this species is currently lacking. In addition to the morphological characterization of H. minotaurus sp. nov., we present here also a description of the male holotype’s karyotype. The diploid set of H. minotaurus sp. nov. consists of 54 chromosomes with a predominance of metacentrics, which gradually decrease in size. The presence of two types of multivalent association observed in postpachytene and metaphase I is commented on. Current knowledge of karyotypes of Heterometrus species is briefly summarized and compared with our cytogenetic results. In conclusion, we discuss the possible usefulness of karyotype as another interspecific feature applicable in the taxonomy of this scorpion group.

Pliskova J, Kovarik F, Kosulic O, Stahlavsky F. Description of a new species of Heterometrus Ehrenberg, 1828 (Scorpiones: Scorpionidae) from Thailand with remarks about the utilization of cytogenetic data in taxonomy of the genus. Annales Zoologici. 2016;66(3):467-76.

Thanks to Frantisek Kovarik for sending me this article!

Family Scorpionidae