What are pheromones?
Pheromones, as defined by John W. Kimball, are chemicals released by an organism into its environment enabling it to communicate with other members of its own species. The term Pheromones (originates from two Greek words, pherein meaning transfer and hormone meaning to excite or stimulate), as proposed by Karlson and Luscher(1959) was used to describe a chemical secreted by an animal to release a specific reaction that triggers members of its own species. Pheromones are subclass of semiochemicals, a broader term for chemicals involved in animal communication within same species. And the action of pheromones between individuals is contrasted with the function of hormones as internal signals within an individual organism. 1.1 TYPES OF PHEROMONES
Pheromones are specific chemical signals produced by an organism to signal its presence to other member of its own species. Different organisms secrets different types of pheromones which helps them to identify each other for specific purposes ranging from insects to mammals. Pheromones in mammals is divided into Releaser pheromone and Primera pheromone , as proposed by Wilson and Bossert in 1963. The releaser is the pheromone which induce and mediate behavioural changes, and the primera is the pheromone which initiates changes in development such as sexual maturation. Furthermore, the insect pheromones are divided into; sex pheromone, aggregation pheromone, alarm and trail pheromones. Table 1. shows the different types of pheromones.
TYPES OF PHEROMONES| FUNCTION|
Insects Pheromones| |
1.Alarm pheromones| It signals alert when there is intrusion from predator| 2.Trail Pheromones| It attracts and guides other ants to the food| 3.Sex Pheromones| It is release by the female to attract the male for mating| 4.Aggregation Pheromones| It signals the formation of animal group of same species, it attracts conspecifics of both sexes| | |
Pheromones in Mammals| |
1.Releaser Pheromones| It signals alarm in their territory and its detected by a special cluster of cells(primary cilia) located at the tip of the nose | 2.Primera Pheromones| It elicit behaviour needed for mating and its detected by the olfactory epithelium and vemeronasal organ in most mammals.|
2. DISCOVERY OF PHEROMONES
The first pheromones was discovered from a powerful sex attractant for silkworm moth by a team of German researchers in 1956 who worked 20years to isolate it. After 20 years of research with 500,000 female moths, they extracted a peculiar compound from certain a glands located on the tip of the abdomen of these female moths. However, the male moths tends to beat their wings madly in a “flutter dance” when a minute amount of the compound is exposed to them. This discovery indicated by the reaction of the male moths enabled the scientists to extract and purify the extraneous matter and obtain a chemically pure pheromones. Contrarily, in dealing with mammals compared to insects whose behaviour is stereotyped and highly predictable, mammals are independent, ornery, complex structure with varying behaviour. In discovering the pheromones of mammals, Singer and Foteos Macrides of the Worcester Foundation for Experimental Biology in Massachusette, did found an assay that worked with hamster (lower mammals). From the experiment carried out it was observed that the male hamster gets triggered on perceiving the vaginal secretion of the female hamster through their vemeronasal organ (a patch of receptor tissue in the nasal cavity distinct from the olfactory organ). The receptors are G. Protein-coupled transmembrane proteins similar to those that mediate olfaction but encoded by different genes.
2.1 IDENTIFICATION OF PHEROMONES
How are Pheromones identified?
The chemical method used to identify pheromones depends on the properties of the compound...