|PENICK, CLINT - Arizona State University|
|TROBAUGH, BETH - Arizona State University|
|LIEBIG, JUERGEN - Arizona State University|
Submitted to: Chemoecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2016
Publication Date: 8/6/2016
Citation: Brent, C.S., Penick, C.A., Trobaugh, B., Liebig, J. 2016. Induction of a reproductive-specific cuticular hydrocarbon profile by a juvenile hormone analog in the termite zootermopsis nevadensis. Chemoecology. 26(5):195-203.
Interpretive Summary: Social insect colonies are typically characterized by one or a few individuals that can reproduce, which are supported by the remaining population which is essentially sterile and performs most non-reproductive tasks. Maintaining this reproductive division of labor requires clear communications between nestmates. Reproductive members must signal their status to prevent other individuals from becoming reproductively active. Recent findings in some termites indicate that odorous waxes on their outer surface may reliably indicate reproductive state, but there is little evidence to show a direct link between an individual’s fertility and the signals it produces. Here, we report that in the termite Zootermopsis angusticollis the putative signaling mechanism is influenced by juvenile hormone (JH), a key driver of reproductive activity. Applying a mimic of this hormone to reproductively inactive adults caused a significant increase in the expression of surface waxes that are only found on active reproductives. In contrast, the hormone did not enhance development of the reproductive organs. The results suggest that JH drives the expression of reproductive-specific odors, but that an individual’s odor profile is not directly linked to its reproductive state. Rather than directly driving signal expression, the reproductive organs may act indirectly by influencing hormone levels which then regulate signal production.
Technical Abstract: The reproductive division of labor within social insect colonies relies on clear communication between nestmates. Fertile members must convey their status to prevent others from becoming reproductively active. Recent findings in some basal termites indicate that cuticular hydrocarbon profiles may reliably indicate reproductive state, but there is little evidence to show a direct linkage that would be a prerequisite for producing an “honest” fertility signal. Here, we report that the putative signaling mechanism is influenced by juvenile hormone (JH), a primary regulator of gonadal development and activity. Topical application of a JH analog, pyriproxifen, to reproductively inactive alates of the basal dampwood termite Zootermopsis nevadensis induced both females and males to express significantly more of a reproductive-specific hydrocarbon when examined weeks later. The compound also enhanced male gonadal development, but had no discernable effect on female ovarian state beyond what is normally observed in maturing alates. The results suggest a strong underlying linkage between reproductive state and hydrocarbon expression, supporting the argument that the cuticular profile can serve as reliable fertility marker usable in maintaining colony organization.