A thorough investigation of the anatomy and morphology of the pedipalps the Australian black rock scorpion, Urodacus manicatus

 

The pedipalps in scorpions are important for prey capture, defense and reproduction. Russel Bicknell and co-workers recently published a thorough investigation of the anatomy and morphology of the pedipalps the Australian black rock scorpion, Urodacus manicatus (Thorell, 1876) (Scorpionidae) and related these to the behavioral use of them.

Abstract:
Pedipalps – chelate ‘pincers’ as the second pair of prosomal appendages – are a striking feature of scorpions and are employed in varied biological functions. Despite the distinctive morphology and ecological importance of these appendages, their anatomy remains underexplored. To rectify this, we examined the pedipalps of the Australian black rock scorpion, Urodacus manicatus, using a multifaceted approach consisting of microcomputed tomography, scanning electron microscopy, energy dispersive X-ray spectroscopy, and live pinch force measurements. In doing so, we document the following aspects of the pedipalps: (1) the musculature in three dimensions; (2) the cuticular microstructure, focusing on the chelae (tibial and tarsal podomeres); (3) the elemental construction of the chelae teeth; and (4) the chelae pinch force. We recognise 25 muscle groups in U. manicatus pedipalps, substantially more than previously documented in scorpions. The cuticular microstructure – endo-, meso-, and exocuticle – of U. manicatus pedipalps is shown to be similar to other scorpions and that mesocuticle reinforces the chelae for predation and burrowing. Elemental mapping of the chelae teeth highlights enrichment incalcium, chlorine, nickel, phosphorus, potassium, sodium, vanadium, and zinc, with a marked lackof carbon. These elements reinforce the teeth, increasing robustness to better enable prey capture and incapacitation. Finally, the pinch force data demonstrate that U. manicatus can exert high pinch forces (4.1 N), further highlighting the application of chelae in subduing prey, asopposed to holding prey for envenomation. We demonstrate that U. manicatus has an array of adaptions for functioning

Reference:
Bicknell RD, Edgecombe GD, Goatley CH, Charlton G, Paterson JR. Pedipalp anatomy of the Australian black rock scorpion, Urodacus manicatus, with implications for functional morphology. Aust J Zool. 2024;72(2). [Open Access]

Two new species of Urodacus from Western Australia

 

Been awhile since I have seen any taxonomic news from "down under", but now I can report about a recent work by Bruno Buzatto and co-workers where two new species of the genus Urodacus Peters, 1861 (Scorpionidae*) are described from Western Australia.

Urodacus lunatus Buzatoo, Clark, Harvey & Volschenk, 2023

Urodacus uncinus Buzatoo, Clark, Harvey & Volschenk, 2023

The two new species are very similar and can only be separated based on the morphology of their hemispermatophores. I expect that a study of this genus with molecular technology may reveal more hidden species in Australia.

* The placement of the genus Urodacus is unlcear and the current authors have place it in the family Urodacidae, which currently is not used in The Scorpion Files.

Abstract:
Two new species of urodacid scorpion are described from the Pilbara region in Western Australia, where they are both patchily distributed along creek lines in the north-east of the region. Urodacus uncinus sp. nov. and Urodacus lunatus sp. nov. are indistinguishable based on external morphology: adults are medium-sized, yellow burrowing scorpions with remarkable sexual dimorphism in the, telson, in which males have a uniquely swollen vesicle and an aculeus that is more strongly curved than other known species of Urodacus. The species are superficially similar to Urodacus similis L.E. Koch, 1977 and Urodacus yaschenkoi Birula, 1903 in the morphology of the first four metasomal segments, which are extremely short and not much longer than high. The two new species canonly be discerned from each other based on the morphology of their hemispermatophores, which highlights the extremely conserved morphology of species in the genus and suggests that many new species await description with careful examination of their genitalia.

Reference:
Buzatto B, Clark H, Harvey M, Volschenk E. Two new species of burrowing scorpions Urodacus (Scorpiones: Urodacidae) from the Pilbara region of Western Australia with identical external morphology. Aust J Zool. [Open Access]

Family Scorpionidae

New study suggest that the widely distributed Aussi scorpion Urodacus yaschenkoi is a species complex

Australian scorpions have received less attention that scorpions from other continents. Karen Luna-Ramirez and co-workers have recently published a study of the widely distributed scorpion Urodacus yaschenko (Birula, 1903) (Scorpionidae). Both genetic and morphological data suggest that U. yaschenkoi is a species complex, consisting of three or more species. More specimens from different areas should be studied and a revision of the species should be made in the future before final conclusions can be made.

Abstract:
Background. Australian scorpions have received far less attention from researchers than their overseas counterparts. Here we provide the first insight into the molecular variation and evolutionary history of the endemic Australian scorpion Urodacus yaschenkoi. Also known as the inland robust scorpion, it is widely distributed throughout arid zones of the continent and is emerging as a model organism in biomedical research due to the chemical nature of its venom.

Methods. We employed Bayesian Inference (BI) methods for the phylogenetic reconstructions and divergence dating among lineages, using unique haplotype sequences from two mitochondrial loci (COXI, 16S) and one nuclear locus (28S). We also
implemented two DNA taxonomy approaches (GMYC and PTP/dPTP) to evaluate the presence of cryptic species. Linear Discriminant Analysis was used to test whether the linear combination of 21 variables (ratios of morphological measurements) can predict individual's membership to a putative species.

Results. Genetic and morphological data suggest that U. yaschenkoi is a species complex. High statistical support for the monophyly of several divergent lineages was found both at the mitochondrial loci and at a nuclear locus. The extent of mitochondrial divergence between these lineages exceeds estimates of interspecific divergence reported for other scorpion groups. The GMYC model and the PTP/bPTP approach identified major lineages and several sub-lineages as putative species. Ratios of several traits that approximate body shape had a strong predictive power (83 100%) in discriminating
two major molecular lineages. A time-calibrated phylogeny dates the early divergence at the onset of continental-wide aridification in late Miocene and Pliocene, with finer-scale phylogeographic patterns emerging during the Pleistocene. This structuring dynamics is congruent with the diversification history of other fauna of the Australian arid zones.

Discussion. Our results indicate that the taxonomic status of U. yaschenkoi requires revision, and we provide recommendations for such future efforts. A complex evolutionary history and extensive diversity highlights the importance of conserving U. yaschenkoi populations from different Australian arid zones in order to preserve patterns of endemism and evolutionary potential.

Reference:
Luna-Ramirez K, Miller AD, Rasic G. Genetic and morphological analyses indicate that the Australian endemic scorpion Urodacus yaschenkoi (Scorpiones: Urodacidae) is a species complex. PeerJ. 2017;5:e2759. [Open Access]

New Urodacus from Australia

Its holiday time, but I'm trying to post a message on the blog using a shaky internet connection from our cabin.

Erich Volschenk and co-workers have published a new Urodacus (Scorpionidae*) from western Australia.

Urodacus butleri Volschenk, Harvey & Prendini, 2012

*The status of the family Urodacidae is under discussion. Some authors have included the Urodacus in Scorpionidae and abolish the family, while others have retained Urodacidae as a valid family.

Abstract:
A new urodacid scorpion, Urodacus butleri, n. sp., is described from Barrow Island and the Pilbara bioregion of Western Australia. This species is unusually dark in color; it is compared and contrasted with three morphologically similar species, Urodacus manicatus (Thorell, 1876), Urodacus novaehollandiae Peters, 1861, and Urodacus planimanus Pocock, 1893.

Reference:
Volschenk, ES, Harvey, MS & Prendini, L. (2012). A new species of Urodacus ((Scorpiones: Urodacidae) from Western Australia. American Museum Novitates (3748):1-18. [Free full text]

Thanks to Gerald Dupre for sending me this paper!

Family Scorpionidae