Abstract
Social insects exhibit sophisticated communication by means of pheromones, one example of which is the use of alarm pheromones to alert nestmates for colony defense. We review recent advances in the understanding of the processing of alarm pheromone information in the ant brain. We found that information about formic acid and n-undecane, alarm pheromone components, is processed in a set of specific glomeruli in the antennal lobe of the ant Camponotus obscuripes. Alarm pheromone information is then transmitted, via projection neurons (PNs), to the lateral horn and the calyces of the mushroom body of the protocerebrum. In the lateral horn, we found a specific area where terminal boutons of alarm pheromone-sensitive PNs are more densely distributed than in the rest of the lateral horn. Some neurons in the protocerebrum responded specifically to formic acid or n-undecane and they may participate in the control of behavioral responses to each pheromone component. Other neurons, especially those originating from the mushroom body lobe, responded also to non-pheromonal odors and may play roles in integration of pheromonal and non-pheromonal signals. We found that a class of neurons receive inputs in the lateral horn and the mushroom body lobe and terminate in a variety of premotor areas. These neurons may participate in the control of aggressive behavior, which is sensitized by alarm pheromones and is triggered by non-pheromonal sensory stimuli associated with a potential enemy. We propose that the alarm pheromone processing system has evolved by differentiation of a part of general odor processing system.
Highlights
Pheromones are potent signaling molecules that are fundamental for organizing a wide range of social behaviors in many vertebrates and invertebrates
Mechanisms by which sex pheromones are processed in the olfactory system have been extensively studied (Boeckh and Ernst, 1987; Kanzaki et al, 1994; Hildebrand and Shepherd, 1997), but little is known about how non-sexual, social pheromones are processed
Unusual sophistication of pheromone communication in eusocial insects is evidenced by the fact that they possess a diverse array of exocrine glands devoted to social communication, 39 such glands existing in formicine ants and 21 existing in honey bees (Billen, 1994)
Summary
Reviewed by: Wulfila Gronenberg, University of Arizona, USA Manfred Schmidt, Georgia State University, USA. Some neurons in the protocerebrum responded to formic acid or n-undecane and they may participate in the control of behavioral responses to each pheromone component. Other neurons, especially those originating from the mushroom body lobe, responded to non-pheromonal odors and may play roles in integration of pheromonal and non-pheromonal signals. We found that a class of neurons receive inputs in the lateral horn and the mushroom body lobe and terminate in a variety of premotor areas These neurons may participate in the control of aggressive behavior, which is sensitized by alarm pheromones and is triggered by non-pheromonal sensory stimuli associated with a potential enemy.
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