Insects (2018) 9 (4 - 151)

Tomas Vendl, Vaclav Stejskal and Radek Aulicky (2018)
First case of dual size asymmetry in an identical arthropod organ: Different asymmetries of the combative (sexual) and cutting (non-sexual) parts of mandibles in the horned stored-product beetle Gnatocerus cornutus (Fabricius, 1798)
Insects 9 (4 - 151)
Abstract: Although it is known that separate insect body structures may be asymmetrical within one species, the different functional asymmetries within a single organ as a result of differential selective regimes have not been described. Based on microscopic measurements and SEM photography, we examined the size, shape and asymmetry of the mandibular structures of males and females of the sexually dimorphic broad-horned flour beetle, Gnatocerus cornutus (Tenebrionidae, Coleoptera). It was found that sexual dimorphism only manifests in certain outgrowth parts (horns) of male mandibles, while the remaining cutting parts of the mandibles hold identical morphologies for both sexes. A more interesting finding—since this is the first published case of dual functionally selected asymmetry in an identical arthropod organ—was that the cutting part of the male mandible exhibited directional asymmetry, whereas the outgrowth horn part of the mandible showed a high degree of symmetry. Moreover, there was no relationship between the size and asymmetry of horns. The results indicate different regulatory mechanisms of sexually selected combative horns and the food-functional, more conservative (constrained by hard food and adult long life) cutting parts of mandibles.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
(original language: English)
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Database assignments for author(s): Vaclav Stejskal

Research topic(s) for pests/diseases/weeds:
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Gnatocerus cornutus		Japan