Sexually dimorphic male horns and their use in agonistic behaviors in the horn-headed cricket Loxoblemmus doenitzi (Orthoptera: Gryllidae)

Sexual dimorphism, the difference between the sexes in secondary sexual characters, is in general driven by processes of sexual selection. The horn-headed cricket, Loxoblemmus doenitzi, exhibits sexual dimorphism in head shape. Males have flat heads and triangular horns on both sides of their heads,...

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Bibliographic Details
Published in:Journal of ethology 2011-09, Vol.29 (3), p.435-441
Main Authors: Kim, Hokyung, Jang, Yikweon, Choe, Jae C
Format: Article
Language:English
Subjects:
Animal Ecology
Animal ethology
Behavioral Sciences
Biological and medical sciences
Biomedical and Life Sciences
body size
Evolutionary Biology
females
Fundamental and applied biological sciences. Psychology
Gryllidae
head
horns
Insecta
Invertebrates
Life Sciences
males
Orthoptera
prediction
Psychology. Psychoanalysis. Psychiatry
regression analysis
sexual dimorphism
sexual selection
thorax
Zoology
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Summary:Sexual dimorphism, the difference between the sexes in secondary sexual characters, is in general driven by processes of sexual selection. The horn-headed cricket, Loxoblemmus doenitzi, exhibits sexual dimorphism in head shape. Males have flat heads and triangular horns on both sides of their heads, whereas females have rounded heads and no horns. We hypothesized that male horns have evolved due to intra-sexual selection, in which males use these horns as weapons in aggressive interactions. We tested two predictions of this hypothesis by conducting agonistic trials with field-caught males of L. doenitzi: (1) the horns should be used in agonistic interactions between males, and (2) the asymmetry in horn size or horn use may determine contest outcome. Horn length was significantly correlated with thorax length and hind femur length. During agonistic interactions, males aggressively used their horns by beating the opponent’s horns with their own or by poking the opponent’s body. However, logistic regression analysis revealed that neither horn length nor horn use were significant factors for contest outcome. Instead, body size was significant for determining contest outcome. We discuss possible scenarios for evolution of male horns in L. doenitzi.
ISSN:0289-0771
1439-5444
DOI:10.1007/s10164-011-0277-x