Presenter Information

Chelsey N. CaldwellFollow

Presentation Type

Poster

Faculty Mentor’s Full Name

Doug Emlen

Faculty Mentor’s Department

DBS

Abstract

The Asian Rhinoceros beetle, Trypoxylus dichotomus, is characterized by its large “pitchfork” horns on the heads of males. They use these horns to engage in male competition; battling each other for access to limited females. However, recent field studies suggest that females are choosy, selecting male mates based on traits other than horn size. In many insects, cuticular hydrocarbons are used by females to choose attractive, high quality males as mating partners. CHC’s are the molecules present in the waxy outer layer of the cuticle, functioning in waterproofing but also acting as pheromones. Individual CHC profiles can be indicative of physiological condition, as well as overall body size. In order to test whether CHC’s function this way in Rhino beetles, I conducted the first ever quantification of CHC profiles in this species. I collected CHC samples from both males and females and used Gas Chromatography-Mass Spectrometry (GC-MS) to test for correlations between CHC profiles, static condition (body size), and sex. I found that males and females have very different blends of cuticular hydrocarbons, that males are more variable from individual to individual than are females, and that some of this variation correlates with male body size. Thus, CHCs in rhinoceros beetles have all of the prerequisites of a reliable signal of sex and body size. Future studies will be needed to test whether CHC profiles also signal male physiological condition, and to explore whether females use these signals when they select mates.

Category

Life Sciences

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The smell of attraction: cuticular hydrocarbon (CHC) profiles in a horned beetle

The Asian Rhinoceros beetle, Trypoxylus dichotomus, is characterized by its large “pitchfork” horns on the heads of males. They use these horns to engage in male competition; battling each other for access to limited females. However, recent field studies suggest that females are choosy, selecting male mates based on traits other than horn size. In many insects, cuticular hydrocarbons are used by females to choose attractive, high quality males as mating partners. CHC’s are the molecules present in the waxy outer layer of the cuticle, functioning in waterproofing but also acting as pheromones. Individual CHC profiles can be indicative of physiological condition, as well as overall body size. In order to test whether CHC’s function this way in Rhino beetles, I conducted the first ever quantification of CHC profiles in this species. I collected CHC samples from both males and females and used Gas Chromatography-Mass Spectrometry (GC-MS) to test for correlations between CHC profiles, static condition (body size), and sex. I found that males and females have very different blends of cuticular hydrocarbons, that males are more variable from individual to individual than are females, and that some of this variation correlates with male body size. Thus, CHCs in rhinoceros beetles have all of the prerequisites of a reliable signal of sex and body size. Future studies will be needed to test whether CHC profiles also signal male physiological condition, and to explore whether females use these signals when they select mates.