Ch11 Pheromones

• Pheromones were discussed on 11th December 2023 by Dr Amy Courtney from the MRC Laboratory of Molecular Biology, Cambridge, UK.
• Pheromones are substances secreted by an animal that cause a specific reaction in another animal, and more correctly, in another individual of the same species.
• Semiochemicals are chemicals involved in the chemical interaction between organisms, derived from the Greek words pherein, to transfer, and hormōn, to excite.
• Bolas spiders synthesize moth pheromones to lure moths to them.
• Pheromone signals can be eavesdropped by a predator.
• Sea anemones and clownfish use pheromone signals.
• Releaser pheromones provoke an immediate behavioural response.
• Primer pheromones need some time to induce changes.
• Signaller pheromones provide information.
• Modifier pheromones change mood or emotional status.
• Pheromones can range from small molecules such as the amino acids to larger molecules such as polypeptides and proteins.
• The molecule discovered in the first pheromone was from the silk moth, Bombyx mori, and is known as Bombykol.
• The surface of the antennae of the male moth are covered with 17,000 hairs, each with 3000 pores.
• Adolf Butenandt and his team discovered the first pheromone in 1959, which elicited a male wing flutter behavioural response.
• Jean Henri Fabre observed that male moths flock to female moths, but were not attracted to females in a clear sealed jar, indicating that the attraction was not visual.
• A 'pheromone binding protein’ has a pocket which fits bombykol and transports it to the receptor on the sensory neuron.
• The discovery of the first pheromone involved two decades of work, with over 500,000 female silk moths used for 6mg of material.
• Bombykol is hydrophobic, so it requires help to reach the receptor site.
• After the bombykol molecule gets through one of these pores, it must pass through a watery solution, called the sensillar lymph.
• The discovery of the first pheromone involved extracting, identifying and synthesizing the molecule.
• Pheromones are odours but not all odours are pheromones, most are sensed by smell and on rare occasions by taste.
• Human experiments involve spraying photos of men and women with androstanol and observing if they rate them more positively.
• The existence of a human vomeronasal organ is controversial.
• Castrated males do not elicit this response in females.
• Samples collected later in the cycle, at ovulation, had the opposite effect.
• Axillary glands are unique to humans and great apes.
• Women who live together and interact over several months can, under some circumstances, develop synchronised menstrual cycles.
• Donor samples secreted during the late follicular phase shortened their menstrual cycles.
• Stern & McClintock (1998) collected armpit samples from nine healthy donor women at different phases of the menstrual cycle.
• In mice, tears contain a chemosignal or pheromone.
• Intact male and castrated male are different in terms of their pheromone production.
• Female tears reduce sex arousal in men.
• Armpit hair grows and gland activity increases around puberty.
• The smells (when strong) from axillae can be detected from a distance.
• The smell of male goats stimulates female hormones.
• Axillae (armpits) are the source of human pheromones.
• Male and female axillae differ in their odours.
• The Honey Bee Society consists of a Queen, Workers, and Drones.
• Two alternative hypotheses to explain worker sterility: queen pheromones actively inhibit ovarian development in workers (arms race) or queen pheromones simply signal queen’s presence and workers behave in a way to maximize their inclusive fitness.
• Queen pheromones affecting behaviour and suppressing ovary development in workers.