Abstract
Many terrestrial and aquatic animals learn associations between environmental features and chemical cues of mortality risk (e.g. conspecific alarm pheromones or predator-derived cues), but the chemical nature of the cues that mediate this type of learning are rarely considered. Fatty acid necromones (particularly oleic and linoleic acids) are well established as cues associated with dead or injured conspecifics. Necromones elicit risk aversive behavior across diverse arthropod phylogenies, yet they have not been linked to associative learning. Here, we provide evidence that necromones can mediate associative olfactory learning in an insect by acting as an aversive reinforcement. When house crickets (Achetadomesticus) were forced to inhabit an environment containing an initially attractive odor along with a necromone cue, they subsequently avoided the previously attractive odor and displayed tolerance for an initially unattractive odor. This occurred when crickets were conditioned with linoleic acid but not when they were conditioned with oleic acid. Similar aversive learning occurred when crickets were conditioned with ethanol body extracts composed of male and female corpses combined, as well as extracts composed of female corpses alone. Conditioning with male body extract did not elicit learned aversion in either sex, even though we detected no notable differences in fatty acid composition between male and female body extracts. We suggest that necromone-mediated learning responses might vary depending on synergistic or antagonistic interactions with sex or species-specific recognition cues.
Highlights
In both terrestrial and aquatic environments, animals utilize chemical cues to detect and avoid prevailing mortality risks (Dicke and Grostal 2001, Ferrari et al 2010)
When house crickets (Acheta domesticus) were forced to inhabit an environment containing an initially attractive odor along with a necromone cue, they subsequently avoided the previously attractive odor and displayed tolerance for an initially unattractive odor. This occurred when crickets were conditioned with linoleic acid but not when they were conditioned with oleic acid
Learning responses were not observed when crickets were conditioned with body extracts of male crickets (Fig. 1) even though male and female body extracts did not appear to differ in fatty acid composition (Table 1)
Summary
In both terrestrial and aquatic environments, animals utilize chemical cues to detect and avoid prevailing mortality risks (Dicke and Grostal 2001, Ferrari et al 2010). Learned risk avoidance via association with chemical cues has been experimentally demonstrated in a wide range of animal taxa, including insects (Wisenden et al 1997, Dukas 1998, Nomikou et al 2003, Yao et al 2009), molluscs (Dalesman et al 2006), crustaceans (Hazlett et al 2002, Yao et al 2009), fish (Magurran 1989, Chivers and Smith 1994), and amphibians (Polo-Cavia and Gomez-Mestre 2014) Protocols for assessing this type of learning usually consist of at least two phases. Despite the applicability of this learning protocol across diverse taxa (Ferrari et al 2010), the specific chemical nature of the cues that may mediate learned responses has rarely been considered
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
