Pheromone

A fanning honeybee exposes its Nasonov gland (located at the tip of the abdomen), releasing a pheromone to entice the swarm into an empty hive.

A pheromone is an endogenous (?) chemical secreted by an organism that triggers an innate behavioral response in another member of the same species. The use of pheromones among insects has been particularly well documented, although many vertebrates and plants also communicate using pheromones. (unknown in birds, also crustaceans, used by some fungi, slime molds, and algae in reproduction; role/presence in humans difficult to ascertain)

Often a communication that works by chemoreceptors (mostly smell and taste)

The term "pheromone" was introduced by Peter Karlson and Martin Lüscher in 1959, based on the Greek pherein (to carry or transfer) and hormon (to excite or stimulate). They proposed the term to describe chemical signals from conspecifics which elicit innate behaviors (maybe include exact definition?).

May be secreted by special glands (eg?) or incorporated into other substances like urine

Example of some functions: There are alarm pheromones, food trail pheromones, sex pheromones, and many others that affect behavior or physiology.

Will also want to compare to hormones early in the definition (internal signals within an individual organism)

Shared sex pheromone of elephants and moths: illustrates ubiquity of pheromones; not precise enough for moths (for whom pheromones are multi-component) and released in amounts to small for male elephants to detect (4-5)

Pheromones are a subclass of semiochemicals (chemicals involved in animal communication) used for communication within the species

The chemical composition of pheromones

text on chemical composition?

Production and action of hormones

In mammals and reptiles, pheromones may be detected by the vomeronasal organ, or Jacobson's organ, which lies between the nose and mouth, although some are detected by regular olfactory membranes.

Section on mechanism (165 plus)

Types of pheromones

Pheromones may be divided into two broad categories:

• Releaser pheromones, which typically have immediate effects on the behavior of the receiver and are quickly degraded.
• Primer pheromones, which trigger long-term physiological effects. Primer pheromones have a slower onset but longer duration than releaser pheromones.

These divisions are not strict, however, as many pheromones can play both roles. (example?)

Pheromones are typically classified by function. The divisions below represent only a sampling of the diverse activities coordinated by pheromones:

Sex pheromones

Paired male silkworm (above) and female (below).

In animals, sex pheromones indicate the availability of the female for breeding. One of the best known examples (and the first pheromone to be characterized) is a polyalcohol known as bombykol, which is released by the female silkworm (bombyx mori) to attract mates. The male's antennae are so sensitive to bymbykol that a female has simply to emit a small quantity of the substance and sit tight to secure a reproductive partner. The male needs a mere 200 molecules to strike his antennae within a second for him to be able to orient himself toward the waiting female and home in on her.

The use of sex pheromones is not limited to invertebrates. Farmers may use pheromones to detect oestrus in sows. Boar pheromones are sprayed into the sty, and those sows that exhibit sexual arousal are known to be currently available for breeding.

mate choice, also sexual competition: musth example; tobacco moth: preference for large males, which produc emore than twice as much wing-glang pheromone as smaller ones

may offer chemical mate guarding

gamete release (external fertilization) animals such as marine worms and sea urchins, to precisely synchronize release of gametes (egg and sperm)

avoiding inbreeding with kin (mice example)

Male animals also emit pheromones that convey information about what species they are, and their genotype. The purpose of pheromones giving information about genotype is a mechanism to avoid inbreeding. Females are attracted to males with the least similar genotype, which means they are attracted to males who are the least likely to be related to them. An exception to this is when the female is pregnant. Then they are most drawn to individuals with the most similar pheromones (and therefore genotype) because they want to keep family close by to aid with the raising of their young and to take advantage of protection.^{[citation needed]}

Alarm pheromones

After sex pheromones, alarm pheromones are the most commonly produced class of chemical signals in social insects ( a group that includes ants, bees, and some species of wasp and termite), and alarm hormones have evolved independently within all major taxa. This altruistic signaling probably developed as a means of warning kin of danger, but the benefits may extend to unrelated members of the species.

Black-tailed deer at Alum Rock Park in northern California.

Some species release a volatile substance when attacked by a predator that can trigger a flight response (in aphids, for example) or aggressive behavior (in bees) in members of the same species. When alarmed or pursued, black-tailed deer release a strong garlic-like odor as part of a larger system of signaling danger, which also includes visual and aural cues. The European minnow (phoxinus phoxinus) releases an alarm pheromone stored in specialized cells on its skin only when the skin is damaged, warning other fish of a predatory attack.

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.

Aggregation pheromones

In contrast to sex hormones, aggregation pheromones attract individuals of both sexes. These hormones lead to the formation of animal groups near the pheromone source, and can be used as cues for settlement or as a signal to cluster together for defense. An example of the former: thousands of bark beetles can be attracted to a suitable tree within the hour upon the release of pheromones by pioneer beetles at the site.

Recruitment signals

Recruitment pheromones are common in social insects, which use them for a variety of tasks related to coordinating the activities of the group.

For example, the Nasonov (alternatively, Nasanov) pheromone is released by worker bees to orient returning forager bees back to the colony as well as to recruit other workers outside the hive. To broadcast this scent, bees raise their abdomens, which contain the Nasonov glands, and fan their wings vigorously.

Foragers, such as ants, mark their paths with trail pheromones, which are non-volatile hydrocarbons. Certain ants lay down an initial trail of pheromones as they return to the nest with food. This trail attracts other ants and serves as a guide. (ref, year) As long as the food source remains, the pheromone trail will be continually renewed. The pheromone must be continually renewed because it degrades quickly. When the supply begins to dwindle, the trailmaking ceases. In at least one species of ant, trails that no longer lead to food are also marked with a repellent pheromone (ref, year).

Recognition mechanisms

honey-bee; pheromones and social organization; eusocial (116)

Honeybees have one of the most complex pheromonal communication systems found in nature, possessing 15 known glands that produce an array of compounds. Pheromones are produced as a liquid and transmitted by direct contact as a liquid or as a vapor. Pheromones may be volatile or non-volatile.

The pheromones are chemical messengers secreted by a queen, drone, worker bee or laying worker bee that elicit a response in other bees. The chemical messages are received by the bee's antenna and other body parts.

saddleback (102) recognition of kin/mother-infant recognition

Eusociality is the phenomenon of reproductive specialization found in some animals. It generally involves the production of sterile members of the species, which carry out specialized tasks, effectively caring for the reproductive members. It most commonly manifests in the appearance of individuals within a group whose behavior (and sometimes anatomy) is modified for group defense, including self-sacrifice ("altruism").

Eusociality with biologically sterile individuals represents the most extreme form of kin altruism. The analysis of eusociality played a key role in the development of theories in sociobiology.

The most familiar examples are insects such as ants, bees, and wasps (the order Hymenoptera), as well as termites (order Isoptera), all with reproductive queens and more or less sterile workers and/or soldiers. The only mammalian example is the naked mole rat.

The most commonly accepted defining features of eusociality are:

1. reproductive division of labor (with or without sterile castes)
2. overlap of generations
3. cooperative care of young (including protection)

Scent-marking and territorial pheromones

Scent-marking pheromones pheromones mark the boundaries of an organism's territory; they are particularly important in the territorial behavior of mammals and other terrestrial vertebrates. In dogs, a well-known-example example, these pheromones are present in the urine, which they deposit on landmarks serving to mark the perimeter of the claimed territory.

Host-marking pheromones

Many species of parastic insects leave a pheromone mark on or inside of the host, such as a small fruit or a caterpillar after laying an egg inside the host. Other females of the species usually avoid laying in these marked hosts, which are of limited size and can only successfully support the development of a limited number of larvae.

Other types?

• Nasonov pheromones (worker bees)
• Royal pheromones (bees)
• Calming (appeasement) pheromones (mammals)

section on illicit communication

Sesiidae on a pheromone trap.

signals intercepted or replicated by other species (229)

include pesticides (though not exactly the same): Insect pheromones of pest species, such as the Japanese beetle and the gypsy moth, can be used to trap them for monitoring purposes or for control by creating confusion, disrupting mating and preventing them from laying eggs.

The case for human pheromones

No defined pheromonal substance has ever been demonstrated to directly influence (split infinitive) human behavior in a peer reviewed, published study. A few well-controlled scientific studies have been published suggesting the possibility of pheromones in humans, however.

• The best-studied case involves the synchronization of menstrual cycles among women based on unconscious odor cues (the so called McClintock effect, named after the primary investigator). This study proposes that there are two types of pheromone involved: "One, produced prior to ovulation, shortens the ovarian cycle; and the second, produced just at ovulation, lengthens the cycle". This is analogous to the Whitten effect, a male pheromone mediated modulation of estrus observed in mice.
• Other studies have suggested that people might be using odor cues associated with the immune system to select mates who are not closely related to themselves. (See Disassortative sexual selection) Using a brain imaging technique, Swedish researchers have shown that homosexual and heterosexual males' brains respond differently to two odours that may be involved in sexual arousal, and that the homosexual men respond in the same way as heterosexual women. According to the researchers, this research suggests a possible role for human pheromones in the biological basis of sexual orientation .
• Another study demonstrated that the smell of androstadienone, a chemical component of male sweat, maintains higher levels of cortisol in females. The scientists suggest that the ability of this compound to influence the endocrine balance of the opposite sex makes it a human pheromonal chemosignal.
• In 2006 it was shown that a second mouse receptor sub-class is found in the olfactory epithelium. Called the trace amine-associated receptors (TAAR), some are activated by volatile compounds found in mouse urine, including one putative pheromone. Orthologous receptors exist in humans providing, the authors propose, evidence for a mechanism of human pheromone detection.

References

ISBN links support NWE through referral fees

• Barnard, C. 2004. ‘’Animal Behaviour: Mechanism, Development, Function and Evolution’’. Harlow, England: Pearson/Prentice Hall.
• Karlson, P. and M. Lüscher. 1959. Pheromones: a new term for a class of biologically active substances. Nature 183:55-6.
• Wyatt, T.D. 2003. ‘’Pheromones and Animal Behavior.’’ Cambridge, England: Cambridge University Press. ISBN 0-521-48526-6.
• Excited ants follow pheromone trail of same chemical they will use to paralyze their prey. Retrieved 2006-03-14.
• Study: Ants Use Scents Like Road Signs. Retrieved 2006-03-14.

Further reading

• Kohl, JV., Atzmueller, M., Fink, B. & Grammer, K. (2001). Human Pheromones: Integrating Neuroendocrinology and Ethology. Neuroendocrinology Letters, 22(5), 319-331. Full text

• Liberles, S.D., Buck, L.B. (2006). A second class of chemosensory receptors in the olfactory epithelium. Nature, 442, 645-50.

• McClintock, M.K. (1984). Estrous synchrony: modulation of ovarian cycle length by female pheromones. Physiological Behavior, 32, 701-705.

• Wilson, E. O., Bossert, W. H. (1963). Chemical communication among animals. Recent Progress in Hormone Research, 19, 673-716.

External links

• Pherobase, the database of insect pheromones
• SFSU study shows that synthetic pheromones in women's perfume increase intimate contact with men
• Male Axillary Extracts Contain Pheromones that Affect Pulsatile Secretion of Luteinizing Hormone and Mood in Women Recipients
• Sexual Orientation, in the Brain
• Review of published debate about HOW insects detect pheromones over large distances, even when the wind seems unfavourable
• Male sweat boosts women's hormone levels — from UC Berkeley, February 2007
• The Effect of Male Sweat on Women's Hormone Levels — from Science Daily, February 2007
• For women, nothing's like the smell of men's sweat — from Reuters (February 2007)
• Pheromones In Male Perspiration Reduce Women's Tension, Alter Hormone Response — from Science Daily (March 2003)

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