27 February, 2015

A new phylogenetic study on scorpions

The phylogeny of scorpions has long been under discussion. Numerous workers have historically emphasized different morphological characters of scorpions, resulting in variable hypotheses of phylogeny, none of which has been generally accepted (e.g. there is no consensus on the family structure in scorpions). In this study, the authors have applied a phylogenomic assessment to resolve scorpion phylogeny based on molecular data. See abstract for more information.

Scorpions represent an iconic lineage of arthropods, historically renowned for their unique bauplan, ancient fossil record and venom potency. Yet, higher level relationships of scorpions, based exclusively on morphology, remain virtually untested, and no multilocus molecular phylogeny has been deployed heretofore towards assessing the basal tree topology. We applied a phylogenomic assessment to resolve scorpion phylogeny, for the first time, to our knowledge, sampling extensive molecular sequence data from all superfamilies and examining basal relationships with up to 5025 genes. Analyses of supermatrices as well as species tree approaches converged upon a robust basal topology of scorpions that is entirely at odds with traditional systematics and controverts previous understanding of scorpion evolutionary history. All analyses unanimously support a single origin of katoikogenic development, a form of parental investment wherein embryos are nurtured by direct connections to the parent’s digestive system. Based on the phylogeny obtained herein, we propose the following systematic emendations: Caraboctonidae is transferred to Chactoidea new superfamilial assignment; superfamily Bothriuroidea revalidated is resurrected and Bothriuridae transferred therein; and Chaerilida and Pseudochactida are synonymized with Buthida new parvordinal synonymies.

Sharma PP, Fernández R, Esposito LA, González-Santillán E, Monod L. Phylogenomic resolution of scorpions reveals multilevel discordance with morphological phylogenetic signal. Proceedings of the Royal Society B. 2015;282(1804):1-10. [Subscription required for full text]

Thanks to Prashant Sharma and Paulo André Margonari Goldoni for sending me this article!

06 February, 2015

A new Ananteris species from Peru

Professor Wilson Lourenco has recently published an article describing a new species of Ananteris Thorell, 1891 (Buthidae) from Peru.

Ananteris cisandinus Lourenco, 2015

New comments are proposed for the subfamily Ananterinae (sensu Pocock). The worldwide pattern of distribution of the elements associated with this subfamily, as well as aspects of their ecology, are discussed. The biogeographic patterns presented by extant and fossil elements of this subfamily confirm not only the characteristics of a group presenting a typical Gondwanian distribution, but also correspond to older Pangaean patterns. One new remarkable species is described in the genus Ananteris Thorell. This new species is also the first record of the genus for Peru.

Lourenco WR. Comments on the Ananterinae Pocock, 1900 (Scorpiones: Buthidae) and description of a new remarkable species of Ananteris from Peru. Comptes Rendus - Biologies. 2015;338:134-9. [Subscription required for full text]

Thanks to professor Lourenco for sending me his paper!

Family Buthidae

04 February, 2015

Ananteris scorpions shed tail to escape predators

Last year I reported about a paper describing autotomy in the form of tail shedding in the scorpion Ananteris mauryi Lourenco, 1982 (Buthidae). I must admit I was a little skeptical about autotomy being an adaptive anti-predator strategy in scorpions based on the costs associated with such a dramatic event (loosing stinger and venom for defense and prey capture and loosing parts of the digestive system making defecation potentially impossible). Also, tail shedding has not been reported for any other scorpion genera.

Camilio Mattoni together with several other scorpion scientists have now published a very interesting paper showing that tail shedding is actually taking place in 14 species of Ananteris. The article concludes that metasomal detachment in Ananteris meets the criteria for defensive autotomy. Detachment is provoked by external stimuli and achieved by an intrinsic mechanism and the experiments suggest that the process is mediated and controlled by the nervous system. Tail shedding has serious costs (as mentioned in the first paragraph), but individuals were alive several weeks after shedding the tail, and some individuals survived for up to eight months.

The authors tested scorpions from several other South American genera, but autotomy was not seen in any of these. An interesting questions is why this special behavior has only developed in one genus.

Video showing the complete sequence of metasomal autotomy in a male Ananteris solimariae Botero-Trujillo & Flórez, 2011 scorpion

Autotomy, the voluntary shedding or detachment of a body part at a determined cleavage plane, is a common anti-predation defense mechanism in several animal taxa, including arthropods. Among arachnids, autotomy has been observed in harvestmen, mites, and spiders, always involving the loss of legs. Autotomy of the opisthosoma (abdomen) was recently reported in a single species of the Neotropical buthid scorpion genus Ananteris Thorell, 1891, but few details were revealed. Based on observations in the field and laboratory, examination of material in museum collections, and scanning electron microscopy, we document autotomy of the metasoma (the hind part of the opisthosoma, or ‘tail’) in fourteen species of Ananteris. Autotomy is more common in males than females, and has not been observed in juveniles. When the scorpion is held by the metasoma, it is voluntarily severed at the joints between metasomal segments I and II, II and III, or III and IV, allowing the scorpion to escape. After detachment, the severed metasoma moves (twitches) automatically, much like the severed tail of a lizard or the severed leg of a spider, and reacts to contact, even attempting to sting. The severed surface heals rapidly, scar tissue forming in five days. The lost metasomal segments and telson cannot be regenerated. Autotomy of the metasoma and telson results in permanent loss of the posterior part of the scorpion’s digestive system (the anus is situated posteriorly on metasomal segment V) and the ability to inject venom by stinging. After autotomy, scorpions do not defecate and can only capture small prey items. However, males can survive and mate successfully for up to eight months in the laboratory. In spite of diminished predation ability after autotomy, survival allows males to reproduce. Autotomy in Ananteris therefore appears to be an effective, adaptive, anti-predation escape mechanism.

Mattoni CI, García-Hernández S, Botero-Trujillo R, Ochoa JA, Ojanguren-Affilastro AA, Pinto-da-Rocha R, et al. Scorpion Sheds ‘Tail’ to Escape: Consequences and Implications of Autotomy in Scorpions (Buthidae: Ananteris). PLoS One. 2015;10(1):e0116639. [Open Access]

Thanks to Matt Simon for informing me about this article!

A new species of Butheoloides from Ethiopia

Frantisek Kovarik has been able to study scorpions from Ethiopia for the last years and is now planning a series of papers concerning the different genera found in this country. In the first paper, he discuss the genus Butheoloides Hirst, 1925 (Buthidae) and a new speices is described.

Butheoloides nuer Kovarik, 2015

A new species Butheoloides nuer sp. n. is described from the Gambela State in western Ethiopia. This is the second species assigned to this genus from Ethiopia. The both Ethiopian species B. nuer sp. n. and B. polisi Lourenço, 1996 are compared and fully illustrated with color photos of habitus and localities. Information is provided on the localities and habitats of both species.

Kovarik F. Scorpions of Ethiopia (Arachnida: Scorpiones). Part I. Genus Butheoloides Hirst, 1925 (Buthidae), with description of a new species. Euscorpius. 2015 (195):1-10. [Open Access]
Family Buthidae