Pheromone
Chemical signals that trigger social responses within a species.
A pheromone is a chemical that an organism secretes or excretes to trigger a social response in others of the same species. These chemical messengers can influence behavior or physiology, and they are employed by a vast range of life, from simple unicellular prokaryotes to complex multicellular eukaryotes, with insect communication being especially well-documented. The term itself is a portmanteau coined in 1959 by Peter Karlson and Martin Lüscher, drawing from Greek roots. Earlier researchers, including Jean-Henri Fabre, Joseph A. Lintner, Adolf Butenandt, and Karl von Frisch, had studied these signals under names like "alarm substances." The modern term was proposed shortly after Butenandt characterized the first chemically well-defined pheromone, bombykol, a substance released by female silkworms to attract mates. Pheromones are sometimes classified as ecto-hormones, as they are transported outside the body. They affect the recipient’s neurocircuits, including the autonomic nervous system, and can trigger hormonal or cytokine-mediated physiological changes, inflammatory signaling, immune system alterations, or behavioral shifts. Pheromones serve diverse functions. Aggregation pheromones aid in mate choice, mass attacks to overcome host resistance, and predator defense, often attracting both sexes to a location. Alarm pheromones, released when an organism is attacked, can trigger flight in aphids or aggression in social insects like ants, bees, termites, and wasps; some plants also emit alarm pheromones when grazed, prompting tannin production in neighbors. An alarm pheromone has been documented in a mammal: the pronghorn releases a buttered-popcorn-scented compound from glands near its white rump hair. Epideictic pheromones signal to other females that a site is already used for egg-laying. Territorial pheromones, deposited in the environment through urine or preen gland secretions, mark boundaries and identity. Trail pheromones, common in social insects like ants, consist of volatile hydrocarbons that guide nestmates to food; when a food source dwindles, the trail is no longer renewed, and some ants even mark depleted trails with a repellent pheromone.
- coined_by
- Peter Karlson and Martin Lüscher
- etymology
- Greek φέρω (phérō, 'to bear') and hormone
- first_characterized_chemical
- bombykol
- first_characterized_by
- Adolf Butenandt
- field
- Chemical ecology
Lore & Background
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, such as '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. The term was proposed 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.
Reader's Guide
Pheromones are fundamental to communication across a vast range of organisms, from bacteria to mammals. Their ecological functions and evolution are a major topic of research in chemical ecology. Aggregation pheromones, for example, function in mate choice, overcoming host resistance by mass attack, and defense against predators, and have proven useful in the management of many pests, such as the boll weevil and stored product weevils, as they are non-toxic and effective at very low concentrations. Alarm pheromones trigger flight or aggression in species like aphids, ants, bees, termites, and wasps, and have even been documented in a mammalian species, the pronghorn. Trail pheromones are commonly used by social insects like ants to mark paths to food sources, and sex pheromones indicate the availability of females for breeding in animals, with some lepidopterans able to detect a potential mate from as far away as 10 km. The study of pheromones has also revealed that certain viruses can alter pheromone production, as seen in female Helicoverpa zea moths infected with Hz-2V virus, which produced five to seven times more pheromone and attracted twice as many males. These chemical signals thus play a critical role in behavior, reproduction, and survival across the biological world.
Did You Know?
- The first chemically characterized pheromone was bombykol, released by the female silkworm to attract mates.
- Alarm pheromones have been documented in a mammalian species, the pronghorn (Antilocapra americana), whose scent has been observed by humans 20 to 30 meters downwind.
- Pharaoh ants (Monomorium pharaonis) mark trails that no longer lead to food with a repellent pheromone, causing avoidance behavior.
- Some lepidopterans can detect a potential mate from as far away as 10 km (6.2 mi) using sex pheromones.
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