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To signal or not to signal? Chemical communication by urine-borne signals mirrors sexual conflict in crayfish

Berry, Fiona C.; Breithaupt, Thomas


Fiona C. Berry


Background: Sexual selection theory predicts that females, being the limiting sex, invest less in courtship signals than males. However, when chemical signals are involved it is often the female that initiates mating by producing stimuli that inform about sex and/or receptivity. This apparent contradiction has been discussed in the literature as 'the female pheromone fallacy'. Because the release of chemical stimuli may not have evolved to elicit the male's courtship response, whether these female stimuli represent signals remains an open question. Using techniques to visualise and block release of urine, we studied the role of urine signals during fighting and mating interactions of crayfish (Pacifastacus leniusculus). Test individuals were blindfolded to exclude visual disturbance from dye release and artificial urine introduction. Results: Staged female-male pairings during the reproductive season often resulted in male mating attempts. Blocking female urine release in such pairings prevented any male courtship behaviour. Artificial introduction of female urine re-established male mating attempts. Urine visualisation showed that female urine release coincides with aggressive behaviours but not with female submissive behaviour in reproductive interactions as well as in intersexual and intrasexual fights. In reproductive interactions, females predominately released urine during precopulatory aggression; males subsequently released significantly less urine during mating than in fights. Conclusions: Urine-blocking experiments demonstrate that female urine contains sex-specific components that elicit male mating behaviour. The coincidence of chemical signalling and aggressive behaviour in both females and males suggests that urine release has evolved as an aggressive signal in both sexes of crayfish. By limiting urine release to aggressive behaviours in reproductive interactions females challenge their potential mating partners at the same time as they trigger a sexual response. These double messages should favour stronger males that are able to overcome the resistance of the female. We conclude that the difference between the sexes in disclosing urine-borne information reflects their conflicting interests in reproduction. Males discontinue aggressive urine signalling in order to increase their chances of mating. Females resume urine signalling in connection with aggressive behaviour, potentially repelling low quality or sexually inactive males while favouring reproduction with high quality males.

Journal Article Type Article
Publication Date Mar 30, 2010
Journal BMC Biology
Electronic ISSN 1741-7007
Publisher Springer Verlag
Peer Reviewed Peer Reviewed
Volume 8
Article Number 25
Institution Citation Berry, F. C., & Breithaupt, T. (2010). To signal or not to signal? Chemical communication by urine-borne signals mirrors sexual conflict in crayfish. BMC biology, 8,
Keywords Biotechnology; Plant Science; General Biochemistry, Genetics and Molecular Biology; Developmental Biology; Cell Biology; Physiology; Ecology, Evolution, Behavior and Systematics; Structural Biology; General Agricultural and Biological Sciences
Publisher URL
Additional Information Copy of article first published in: BMC Biology, 2010, v.8, issue 25.


Berry & Breithaupt 2010.pdf (1 Mb)

Copyright Statement
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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