25 August, 2014

On the genetics of scorpion morphology

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

A new review on scorpion envenomation

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]