title: Multimodal signals: ultraviolet reflectance and chemical cues in stomatopod agonistic encounters.
abstract: Complex signals are commonly used during intraspecific contests over resources to assess an opponent's fighting ability and/or aggressive state. Stomatopod crustaceans may use complex signals when competing aggressively for refuges. Before physical attacks, stomatopods assess their opponents using chemical cues and perform threat displays showing a coloured patch, the meral spot. In some species, this spot reflects UV. However, despite their complex visual system with up to 20 photoreceptor classes, we do not know if stomatopods use chromatic or achromatic signals in contests. In a field study, we found thatNeogonodactylus oerstediimeral spot luminance varies with sex, habitat and, more weakly, body length. Next, we conducted an experimental manipulation which demonstrated that both chemical cues and chromatic signals are used during contests. In the absence of chemical cues, stomatopods approached an occupied refuge more quickly and performed offensive behaviours at a lower rate. When UV reflectance was absent, stomatopods performed offensive behaviours more frequently and contest duration trended towards shorter fights. These results provide new evidence that UV reflectance and/or visible spectrum luminance is used to amplify threat displays. Our results are the first to demonstrate that chemical and chromatic cues comprise a multimodal signal in stomatopod contests.
authors.affiliation: Department of Biology , Tufts University , Medford, MA 02155 , USA.
authors.forename: Amanda M
authors.identifier: 0000-0002-8650-8344
authors.initials: AM
authors.lastname: Franklin
authors.affiliation: Sensory Neurobiology Group, Queensland Brain Institute , University of Queensland , Brisbane, Queensland 4072 , Australia.
authors.forename: N Justin
authors.initials: NJ
authors.lastname: Marshall
authors.affiliation: Department of Biology , Tufts University , Medford, MA 02155 , USA.
authors.forename: Sara M
authors.initials: SM
authors.lastname: Lewis
keywords: agonistic; communication; complex signal; crustacean; multimodal signal; stomatopod