Pheromone

pheromone

Any chemical compound secreted by an organism in minute amounts to elicit a particular reaction from other organisms of the same species. Pheromones are widespread among insects and vertebrates (except birds) and are present in some fungi, slime molds, and algae. The chemicals may be secreted by special glands or incorporated into other substances (e.g., urine), shed freely, or deposited in selected locations. Pheromones are used to bring creatures together (e.g., in termite, bee, and ant colonies), lead them to food (e.g., in scent trails laid by ants), signal danger (e.g., when released by wounded fish to alert others), attract a mate and elicit sexual behaviour (numerous examples, possibly including humans), and influence sexual development (in many mammals and certain insects). Alarm pheromones often last a shorter time and travel a shorter distance than other types. In vertebrates, chemical stimuli often influence parent-young responses. Sex-attractant pheromones are used in certain products to lure and trap unwanted or harmful insects.

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Pheromone

A substance that acts as a molecular messenger, transmitting information from one member of a species to another member of the same species. A distinction is made between releaser pheromones, which elicit a rapid, behavioral response, and primer pheromones, which elicit a slower, developmental response and may pave the way for a future behavior.

Communication via pheromones is common throughout nature, including some eukaryotic microorganisms such as fungi that exchange vital chemical signals. The cellular slime molds form large aggregations of amebas which unite to form a sorocarp made up of a long, slender stalk that supports a spore-containing fruiting body. A pheromone is responsible for the aggregation. In several species of algae, relatively simple hydrocarbons act as sperm attractants.

By far the largest number of characterized pheromones come from insect species. In social insects, such as termites and ants, there may be as many as a dozen different types of messages that are used to coordinate the complex activities which must be carried out to maintain a healthy colony. These activities might require specialized pheromones such as trail pheromones (to lead to a food source), alarm pheromones (recruiting soldiers to the site of an enemy attack), or pheromones connected with reproductive behavior. Much less is known about mammalian pheromones because mammalian behavior is more difficult to study. There are, however, a small number of well-characterized mammalian pheromones from pigs, dogs, hamsters, mice, and marmosets.

There is great potential for controlling the behavior of a given species by manipulating its natural chemical signals. For example, pheromones have been used to disrupt the reproduction of certain insect pests. This approach can lead to reduced use of pesticides as well as advances in the control of both agricultural pests and disease vectors. See Chemical ecology, Chemoreception, Social insects