25 August, 2014
Scorpions have an unique morphology that separate them from other arthropods, especially the specialized grouping of multiple segments dedicated exclusively to prey capture and defence: the flexible metasoma (tail). Prashant Sharma and co-workers have now published an article on the genetics behind the morphology of the scorpion tail.
I embarrassingly have to admit that this article is way over my head, but I hope that readers with more knowledge into genetics will understand more than I do on this topic.
The evolutionary success of the largest animal phylum, Arthropoda, has been attributed to tagmatization, the coordinated evolution of adjacent metameres to form morphologically and functionally distinct segmental regions called tagmata. Specification of regional identity is regulated by the Hox genes, of which 10 are inferred to be present in the ancestor of arthropods. With six different posterior segmental identities divided into two tagmata, the bauplan of scorpions is the most heteronomous within Chelicerata. Expression domains of the anterior eight Hox genes are conserved in previously surveyed chelicerates, but it is unknown howHox genes regionalize the three tagmata of scorpions. Here, we show that the scorpion Centruroides sculpturatus has two paralogues of all Hox genes except Hox3, suggesting cluster and/or whole genome duplication in this arachnid order. Embryonic anterior expression domain boundaries of each of the last four pairs of Hox genes (two paralogues each of Antp, Ubx, abd-A and Abd-B) are unique and distinguish segmental groups, such as pectines, book lungs and the characteristic tail, while maintaining spatial collinearity. These distinct expression domains suggest neofunctionalization of Hox gene paralogues subsequent to duplication. Our data reconcile previous understanding of Hox gene function across arthropods with the extreme heteronomy of scorpions.
Sharma PP, Schwager EE, Extavour CG, Wheeler WC. Hox gene duplications correlate with posterior heteronomy in scorpions. Proc Biol Sci. 2014 Oct 7;281(1792). [Subscription required for full text]
Thanks to Dr. Prashant Sharma for sending me their article!
07 August, 2014
|Pathophysiological and clinical effects of systemic scorpion envenomation. Isbister & Bawaskar/New England Journal of Medicine, 2014 (C).|
With more than one million cases of scorpion envenomation each year worldwide with substantial morbidity and even death in children, scorpions pose a health challenge in many countries. Geoffrey Isbister and Himmatrao Bawaskar have recently published a updated review on the effects of scorpion envenomation and the current treatment knowledge in the top medical journal New England Journal of Medicine.
This article is essential for health personnel dealing with scorpion envenomation patients, scorpion researchers and others interested in scorpions as it sums up symptoms, pathophysiology, clinical manifestations and treatment for scorpion envenomations.
Scorpion stings and envenomation are of clinical importance worldwide, and although most stings cause only local effects, severe envenomation that causes either excessive autonomic activity and cardiovascular toxic effects or neuromuscular toxic effects results in illness and, in the case of children, in death. The specific treatment is the administration of antivenom combined with symptomatic and supportive treatment, including prazosin and dobutamine in patients with cardiovascular toxic effects and benzodiazepines when there is neuromuscular involvement.
Isbister GK, Bawaskar HS. Scorpion Envenomation. N Engl J Med. 2014;371(5):457-63. [Subscription required for full text]
31 July, 2014
Ismail Lotfy Mohamad and co-workers have recently published a retrospective study of the outcome of scorpion sting incidents in children referred to Assiut University Children Hospital
from January to December 2012.
Of the 111 cases evaluated, more than half of the stung children had a severe clinical presentation and 19 children died mainly of pulmonary edema and cardiogenic shock.
The results of this study are quite dramatic and show that scorpions are a public health problem in parts of Egypt, especially for children. The study doesn't mention scorpions species involved, but Egypt harbors several dangerous species of Androctonus and the infamous Leiurus quinquestriatus.
Scorpion envenomation is a health problem in children in tropical and subtropical regions. The aim of this study was to evaluate demographic and clinical characteristics as well as outcomes in referred children to Assiut University Children Hospital during the year 2012 with a history of scorpion sting. The medical files of these patients were reviewed retrospectively for demographic data, time and site of biting, and clinical manifestations. Laboratory investigations of the patients were reviewed for complete blood count (CBC), liver function tests, creatinine phosphokinase (CPK), lactate dehydrogenase (LDH), arterial blood gases, and serum electrolytes. Results showed 111 children with a history of scorpion sting; 69 males and 42 females with a median age of 5 years. Out of the studied patients, 53.2 % were classified as class III of clinical severity with recorded pulmonary edema in 33.3 %, cardiogenic shock in 46.8 %, and severe neurological manifestations in 22.8 %. Twelve patients (10.8 %) were classified as class II with mild systemic manifestations, and 36 % of the patients were classified as class I with only local reaction. Outcomes of these patients were discharge without sequelae in 55.8 %, discharge with sequelae in 26.1 %, and death in 18.1 %. Conclusion: more than half of stung children had a severe clinical presentation and about one fifth died. Aggressive treatment regimens are recommended for such patients to improve the outcome.
Mohamad IL, Elsayh KI, Mohammad HA, Saad K, Zahran AM, Abdallah AM, et al. Clinical characteristics and outcome of children stung by scorpion. Eur J Pediatr. 2014 June;173(6):815-8. [Subscription required for full text]
30 July, 2014
Richard Ayrey is continuing his studies of the scorpion fauna of Arizona and has now described a new species of Vaejovis C. L. Koch, 1876 (Vaejovidae) from Arizona, USA.
Vaejovis grayae Ayrey, 2014
A new scorpion species, Vaejovis grayae sp. nov. is described and placed in the “vorhiesi” group of the genus Vaejovis. This small brown species is found near Yarnell, Arizona, USA. It appears most similar to V. trinityae Ayrey and V. crumpi Ayrey et Soleglad. It can be distinguished from the other members of the “vorhiesi” group by a unique combination of non-overlapping morphological characters and multilocus DNA data (Bryson et al., 2013). The pedipalp fixed finger has 6 ID denticles and the movable finger has 7, like most other northern Arizona “vorhiesi” group species. Another characteristic of this species is its unique Arizona chaparral habitat.
Ayrey RF. A new species of Vaejovis from chaparral habitat near Yarnell, Arizona (Scorpiones: Vaejovidae). Euscorpius. 2014 (188):1-13. [Free full text]
29 July, 2014
Wilson Lourenco has recently described a new species of Broteochactas Pocock, 1893 (Chactidae) from the Amazon Region in Brazil.
Broteochactas silves Lourenco, 2014
Scorpions belonging to the genus Broteochactas Pocock, 1893 are studied and a new species is described, Broteochactas silves sp. n., based on nine male specimens collected in the region of Silves in the State of Amazonas, Brazil. The new species is characterized by a small size, reddish-brown coloration, body and appendages with punctations and metasomal segment V and telson with conspicuous spinoid granulations.
Lourenco WR. The genus Broteochactas Pocock, 1893 in Brazilian Amazonia, with a description of a new species from the State of Amazonas (Scorpiones: Chactidae). Entomologische Mitteilungen aus dem Zoologischen Museum Hamburg. 2014;17(192):153-9.
Thanks to professor Lourenco for sending me his article!
28 July, 2014
The large scorpions from West Africa in the genus Pandinus Thorell, 1841 (Scorpionidae) are well known among both experts and amateurs, and in particular the "celebrity" species Pandinus imperator (C. L. Koch, 1841). Surprisingly, very little research have been done on the different Pandinus populations of western Africa.
Wilson Lourenco has recently published an article on the genus Pandinus in western Africa which resulted in one new species and one restored species from synonymy.
Pandinus camerounensis Lourenco, 2014 - New species from Cameroon.
Pandinus roeseli (Simon, 1872) - Restored from synonymy with P. imperator. Guinea.
Among the ‘giant species’ of scorpions which belong to the genus Pandinus Thorell, 1876, three are protected by the Washington Convention. These are Pandinus imperator (Koch, 1841), Pandinus dictator (Pocock, 1888) and Pandinus gambiensis Pocock, 1899. In theory, these species can be easily recognised by scorpion experts and even non-experts. However, at least one, P. imperator, remains dubious and unclearly characterized. Herein, the argument pleading for the status of P. imperator is discussed. It is hypothesized that across the known distribution of P. imperator at least three or four distinct populations may be recognized. Pandinus roeseli (Simon, 1872) is restablished as a valid species and a new species, Pandinus camerounensis sp. n. is described from the North of Cameroon.
Lourenco WR. Further considerations on the identity and distribution of Pandinus imperator (C. L. Koch, 1841) and description of a new species from Cameroon (Scorpiones: Scorpionidae). Entomologische Mitteilungen aus dem Zoologischen Museum Hamburg. 2014;17(192):139-51.
Thanks to professor Lourenco for sending me his article!
27 June, 2014
|Two-tailed female Centruroides nitidus with scorplings on her back.|
Body malformations and anomalies in scorpions are reported from time to time. One of the most famous cases was Pepe - The two-tailed scorpion (a Centruroides excilicauda with two tails). In a recent article, Michael Seiter and Rolando Teruel report of two more cases of metasomal duplication (two-tailed scorpions). Interestingly, the female Centruroides nitidus (Thorell, 1876) with two tails grew up, mated and got offspring.
Herein we report two further cases of metasoma duplication in buthid scorpions: a second instar juvenile Tityus obscurus (Gervais, 1843) and an adult female Centruroides nitidus Thorell, 1876. Both individuals were born in captivity; the former died after its first ecdysis, but the latter reached adulthood and reproduced normally. This represents the first published record of the occurrence of such an anomaly in either species.
Seiter M, Teruel R. Two new cases of metasomal duplication in scorpions, with notes on their reproductive biology (Scorpiones: Buthidae). Revista Iberica de Arachnologia. 2014 (24):127-9.
Thanks to Rolando for sending me his article!