Pheromone

A pheromone (from Ancient Greek φέρω phero 'to bear' and hormone) is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to impact the behavior of the receiving individuals. There are alarm pheromones, food trail pheromones, sex pheromones, and many others that affect behavior or physiology. Pheromones are used from basic unicellular prokaryotes to complex multicellular eukaryotes. Their use among insects has been particularly well documented. In addition, some vertebrates, plants and ciliates communicate by using pheromones. A pheromone (from Ancient Greek φέρω phero 'to bear' and hormone) is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to impact the behavior of the receiving individuals. There are alarm pheromones, food trail pheromones, sex pheromones, and many others that affect behavior or physiology. Pheromones are used from basic unicellular prokaryotes to complex multicellular eukaryotes. Their use among insects has been particularly well documented. In addition, some vertebrates, plants and ciliates communicate by using pheromones. The portmanteau word 'pheromone' was coined by Peter Karlson and Martin Lüscher in 1959, based on the Greek φερω pheroo ('I carry') and ὁρμων hormon ('stimulating'). Pheromones are also sometimes classified as ecto-hormones. They were researched earlier by various scientists, including Jean-Henri Fabre, Joseph A. Lintner, Adolf Butenandt, and ethologist Karl von Frisch who called them various names, like for instance 'alarm substances'. These chemical messengers are transported outside of the body and affect neurocircuits, including the autonomous nervous system with hormone or cytokine mediated physiological changes, inflammatory signaling, immune system changes and/or behavioral change in the recipient. They proposed the term to describe chemical signals from conspecifics that elicit innate behaviors soon after the German biochemist Adolf Butenandt had characterized the first such chemical, bombykol, a chemically well-characterized pheromone released by the female silkworm to attract mates. Aggregation pheromones function in mate selection, overcoming host resistance by mass attack, and defense against predators. A group of individuals at one location is referred to as an aggregation, whether consisting of one sex or both sexes. Male-produced sex attractants have been called aggregation pheromones, because they usually result in the arrival of both sexes at a calling site and increase the density of conspecifics surrounding the pheromone source. Most sex pheromones are produced by the females; only a small percentage of sex attractants are produced by males. Aggregation pheromones have been found in members of the Coleoptera, Diptera, Hemiptera, Dictyoptera, and Orthoptera. In recent decades, the importance of applying aggregation pheromones in the management of the boll weevil (Anthonomus grandis), stored product weevils (Sitophilus zeamais), Sitophilus granarius, Sitophilus oryzae, and pea and bean weevil (Sitona lineatus) has been demonstrated. Aggregation pheromones are among the most ecologically selective pest suppression methods. They are nontoxic and effective at very low concentrations. Some species release a volatile substance when attacked by a predator that can trigger flight (in aphids) or aggression (in ants, bees, termites) in members of the same species. For example, Vespula squamosa use alarm pheromones to alert others to a threat. In Polistes exclamans, alarm pheromones are also used as an alert to incoming predators. Pheromones also exist in plants: Certain plants emit alarm pheromones when grazed upon, resulting in tannin production in neighboring plants. These tannins make the plants less appetizing for the herbivore. Epideictic pheromones are different from territory pheromones, when it comes to insects. Fabre observed and noted how 'females who lay their eggs in these fruits deposit these mysterious substances in the vicinity of their clutch to signal to other females of the same species they should clutch elsewhere.' It may be helpful to note that the word epideictic, having to do with display or show (from the Greek 'deixis'), has a different but related meaning in rhetoric, the human art of persuasion by means of words. Releaser pheromones are pheromones that cause an alteration in the behavior of the recipient. For example, some organisms use powerful attractant molecules to attract mates from a distance of two miles or more. In general, this type of pheromone elicits a rapid response, but is quickly degraded. In contrast, a primer pheromone has a slower onset and a longer duration. For example, rabbit (mothers) release mammary pheromones that trigger immediate nursing behavior by their babies. Signal pheromones cause short-term changes, such as the neurotransmitter release that activates a response. For instance, GnRH molecule functions as a neurotransmitter in rats to elicit lordosis behavior.