Ant Pheromone May Aid Alzheimer'...( rinate every few yards along their morn...)

rinate every few yards along their morning walk; they, too, are leaving a chemical calling card to mark a territory. Kin-recognition pheromones tell insects who's family and who's not, even within the same species, and non-kin trying to enter a nest without the appropriate pheromone are fought off or killed. Recruitment pheromones, such as those produced by the "Aphaenogaster rudis" ants, rally nest mates to follow a pheromone-scented trail to a source of food; by the time the ants reach the prey item, they are excited enough to attack with venom that contains the pheromone they were following.

-- ZIGZAG PATH: The pheromone trail left by an ant, such as the "A. rudis", is not the shortest distance between two points to begin with, and ants following the trail appear to zigzag along the way. That is because the pheromone receptors in the tips of their two antennae orient them to the source of the pheromone and direct them to turn left or right. When they veer off the trail to the right, the right-hand antennae -- receiving a weaker signal -- tell them to turn left. And if they overcompensate and zag too far to the left, the left-hand antennae make them steer to the right. An ant with only one antenna will only zig (or zag). And if ants' antennae become crossed, they are hopelessly disoriented.

-- EVOLUTION OF THE CHARISMA CHEMICAL: Not every ant species can draw a crowd with chemically sophisticated recruitment pheromones. The Myrmicine ants studied by Cornell researchers sometimes recruited seven or eight helpers. But army ants, generally regarded as being more advanced in an evolutionary sense, can summon thousands of compatriots with a single chemical signal. And more primitive ants, lacking a recruitment pheromone, leave no detectable trail. Setting off on a mission, a primitive ant practices tandem running -- that is, if it can persuade one other ant to come along.

-- SENSITIVE SENSORS: Pheromone receptors and the biological signali
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Contact: Roger Segelken
hrs2@cornell.edu
607-255-9736
Cornell University News Service
2-Feb-1998

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