Experimental evidence that workers recognize reproductives through cuticular hydrocarbons in the ant Odontomachus brunneus
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Eusociality is characterized by a reproductive division of labor, wherein workers respond to the presence of reproductive individuals by refraining from reproduction themselves and restricting the reproductive efforts of others. Our understanding of how eusociality is maintained therefore depends on characterizing the mechanism by which workers detect the presence of a reproductive. Variations in cuticular hydrocarbons correspond to changes in reproductive ability in ants, and experimental studies are beginning to reveal the function of hydrocarbons as signals. In this study, we compare the cuticular hydrocarbon profiles of dominant and reproductive workers and queens of the ant Odontomachus brunneus with profiles of non-reproductive workers. Using split/reunification tests we document the existence of worker policing in both queenless and queenright colonies; supernumerary reproductives were treated aggressively by nestmates. Finally, we induce aggression and replicate queen-like submissive nestmate responses by supplementing the hydrocarbon profile of workers with (Z)-9-nonacosene, a compound that was significantly more abundant on the cuticles of reproductives. In three bioassays, we compare this manipulation to various control manipulations of the hydrocarbon profile and demonstrate that workers gauge the reproductive activity of nestmates through changes in their cuticular hydrocarbon profiles.
KeywordsCuticular hydrocarbon Fertility signal Pheromone Policing Dominance
We thank Walter R. Tschinkel for collection assistance and Fred Larabee for supplying additional colonies.
Aggression of nestmate ants of the species Odontomachus brunneus to a newly established reproductive and dominant worker upon reintroduction to her original queenless colony. The ant with a red paint mark on her abdomen is the reintroduced reproductive. The lid of the colony was removed for clarity. Several bouts of rapid antennation can be seen as well as aggression elevating to multiple workers biting, holding, and pulling on the reintroduced worker (WMV 12,575 kb)
Response of nestmate ants of the species Odontomachus brunneus to workers treated with Z9:C29 (with yellow paint mark on thorax). Response by rapid antennation and submissive reactions can be seen multiple times (WMV 4,630 kb)
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