Functional significance of an unusual chela dimorphism in a marine decapod: specialisation as a weapon?

T. Claverie, I.P. Smith

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

The squat lobster Munida rugosa has an unusual chela dimorphism exhibited mainly by large males. Some individuals have ‘arched’ chelae in which there is a gap between the dactylus and the pollex when closed, and others have a ‘straight’ morphology in which the dactylus and pollex oppose along most of their length. Geometric morphometric analysis indicated that, compared with males, the arched morphology does not develop fully in females, so further investigation was confined to males. In males, the distal part of the chela was similar in both the forms and seemed to be adapted to hold and shred prey items. Both morphologies had a major cylindrical tooth on the inner proximal part of the dactylus, but the arched morphology had a higher and wider propodus, a greater major tooth–pollex distance and a greater force generation than the straight morphology. The findings suggest that the arched chela morphology in M. rugosa is a sexually selected trait adapted to inflict puncture wounds on opponents during agonistic interactions. The arched morphology, therefore, appears to have evolved in males by means of sexual selection because it enhanced the function of the chela as a weapon, while retaining functionality for feeding.
Original languageEnglish
Pages (from-to)3033-3038
Number of pages6
JournalProceedings of the Royal Society of London. B, Biological Sciences
Volume274
Issue number1628
DOIs
Publication statusPublished - 7 Dec 2007

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Decapoda (Crustacea)
Weapons
dimorphism
weapon
Decapoda
Cynodon
Punctures
sexual selection
Tooth
teeth
lobster
chelon
Chela
tooth
Wounds and Injuries

Cite this

Functional significance of an unusual chela dimorphism in a marine decapod : specialisation as a weapon? / Claverie, T.; Smith, I.P.

In: Proceedings of the Royal Society of London. B, Biological Sciences, Vol. 274, No. 1628, 07.12.2007, p. 3033-3038.

Research output: Contribution to journalArticle

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abstract = "The squat lobster Munida rugosa has an unusual chela dimorphism exhibited mainly by large males. Some individuals have ‘arched’ chelae in which there is a gap between the dactylus and the pollex when closed, and others have a ‘straight’ morphology in which the dactylus and pollex oppose along most of their length. Geometric morphometric analysis indicated that, compared with males, the arched morphology does not develop fully in females, so further investigation was confined to males. In males, the distal part of the chela was similar in both the forms and seemed to be adapted to hold and shred prey items. Both morphologies had a major cylindrical tooth on the inner proximal part of the dactylus, but the arched morphology had a higher and wider propodus, a greater major tooth–pollex distance and a greater force generation than the straight morphology. The findings suggest that the arched chela morphology in M. rugosa is a sexually selected trait adapted to inflict puncture wounds on opponents during agonistic interactions. The arched morphology, therefore, appears to have evolved in males by means of sexual selection because it enhanced the function of the chela as a weapon, while retaining functionality for feeding.",
author = "T. Claverie and I.P. Smith",
note = "No procedures were used that required licence, and nothing done infringed any ethical guidelines. This work was funded by the Sheina Marshall Bequest. We are grateful to Dr Douglas M. Neil and Prof. R. Jim A. Atkinson for their helpful advice, Howard McCrindle and Campbell McLachlan for their help with animal collection, Thomas D. I. Stevenson, Moira Cameron and Lorraine A. Fraser for their help with developing the force measurement apparatus, James Allen and Dr Peter R. O. Barnett for their help with development of the cheliped holding jig, Sebastian Valanko and Kenneth S. Cameron for their help with strength measurement and Anna Kerouanton for chelae drawings.",
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