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Pedipalp anatomy of the Australian black rock scorpion, Urodacus manicatus, with implications for functional morphology

Pedipalp anatomy of the Australian black rock scorpion, Urodacus manicatus, with implications for functional morphology
Pedipalp anatomy of the Australian black rock scorpion, Urodacus manicatus, with implications for functional morphology
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 in calcium, chlorine, nickel, phosphorus, potassium, sodium, vanadium, and zinc, with a marked lack of 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, as opposed to holding prey for envenomation. We demonstrate that U. manicatus has an array of adaptions for functioning as a sit-and-wait predator that primarily uses highly reinforced chelae to process prey.
Australia, energy dispersive X-ray spectroscopy, micro-computed tomography, microstructure, morphology, musculature, scanning electron microscopy, scorpions, Urodacus manicatus
0004-959X
Bicknell, Russell D.C.
104caf3d-a6aa-4728-b1d7-f6d93033bc83
Edgecombe, Gregory D.
7cc18fe0-1a14-4f17-b419-6729db682d32
Goatley, Christopher H.R.
b158dc1a-76f3-4ace-9d33-260d8c76ac93
Charlton, Glen
f45503b8-ae0c-4868-bf61-474ffeda0031
Paterson, John R.
8f8133aa-11b4-43a3-8b54-2050195650e5
et al.
Bicknell, Russell D.C.
104caf3d-a6aa-4728-b1d7-f6d93033bc83
Edgecombe, Gregory D.
7cc18fe0-1a14-4f17-b419-6729db682d32
Goatley, Christopher H.R.
b158dc1a-76f3-4ace-9d33-260d8c76ac93
Charlton, Glen
f45503b8-ae0c-4868-bf61-474ffeda0031
Paterson, John R.
8f8133aa-11b4-43a3-8b54-2050195650e5

Bicknell, Russell D.C., Edgecombe, Gregory D. and Goatley, Christopher H.R. , et al. (2024) Pedipalp anatomy of the Australian black rock scorpion, Urodacus manicatus, with implications for functional morphology. Australian Journal of Zoology, 72 (2), [ZO23044]. (doi:10.1071/ZO23044).

Record type: Article

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 in calcium, chlorine, nickel, phosphorus, potassium, sodium, vanadium, and zinc, with a marked lack of 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, as opposed to holding prey for envenomation. We demonstrate that U. manicatus has an array of adaptions for functioning as a sit-and-wait predator that primarily uses highly reinforced chelae to process prey.

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Submitted date: 26 October 2023
Accepted/In Press date: 5 April 2024
e-pub ahead of print date: 13 May 2024
Published date: 13 May 2024
Additional Information: Publisher Copyright: © 2022 The Author(s).
Keywords: Australia, energy dispersive X-ray spectroscopy, micro-computed tomography, microstructure, morphology, musculature, scanning electron microscopy, scorpions, Urodacus manicatus

Identifiers

Local EPrints ID: 490117
URI: http://eprints.soton.ac.uk/id/eprint/490117
ISSN: 0004-959X
PURE UUID: 5f5da256-5cdc-4769-a208-24774653c173
ORCID for Christopher H.R. Goatley: ORCID iD orcid.org/0000-0002-2930-5591

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Date deposited: 14 May 2024 17:04
Last modified: 05 Jun 2024 02:05

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Contributors

Author: Russell D.C. Bicknell
Author: Gregory D. Edgecombe
Author: Christopher H.R. Goatley ORCID iD
Author: Glen Charlton
Author: John R. Paterson
Corporate Author: et al.

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