Institute for Integrative Genome Biology

How Ants Identify Colony Members from Intruders

Reporting today in the journal Cell Reports, IIGB researchers led by neuroscientist Anandasankar Ray note that ants, which have evolved some of the largest families of olfactory receptor genes in insects, use their powerful sense of smell to sense hydrocarbon chemicals present on the cuticle (outer shell) of individuals to precisely identify different members of their society.

Ray explained that social insects like ants have remarkable ability to organize into large colonies with multiple castes participating for the colony to succeed, and like any large society this coordination requires effective communication between individuals. His lab applied a powerful electrophysiology method, to systematically test hydrocarbons present on the worker and queen cuticles that have previously been suspected to act as pheromone cues.

The researchers’ findings confirm the following unique aspects amongst social insects:

  • Recognition of individuals at very close proximity in a large crowd in a colony is facilitated by use of low volatility cuticular hydrocarbons. A more volatile cue would be confusing to associate with an individual, and could overwhelm the olfactory system in the colony by constantly activating it.
  • Ultimately each ant cuticle has a blend of several cuticular hydrocarbons. The precise composition of the blend could be a useful solution for coding information on several castes both inside a colony and intruders from outside a colony. In a way, each of these individual hydrocarbons act together in a “chemical barcode” which other individuals in a colony use for recognition of an ant’s caste or nest.
  • These two tasks are feasible not only because ants have a sophisticated olfactory receptor system with the largest odorant receptor gene family (more than 400 genes) known in insects, but also because they have remarkable abilities to learn and behaviorally discriminate closely related hydrocarbons.

Ray, who is the director of the Center for Disease Vector Research at UC Riverside, was joined in the study by Kavita R. Sharma (first author) at UCR; Brittany L. Enzmann, Dani Moore and Jürgen Liebig at Arizona State University, Tempe; Yvonne Schmidt and Berhard Breit at Albert-Ludwigs-Universität Freiburg, Germany; Graeme R. Jones and Jane Parker at Keele University, the United Kingdom; Shelly L. Berger at the University of Pennsylvania; Danny Reinberg at the New York University School of Medicine; and Laurence J. Zwiebel at Vanderbilt University, Tenn.

The research was funded by the Howard Hughes Medical Institute (HHMI) as a HMMI Collaborative Innovation Award to Reinberg and five co-PIs including Ray.

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