Insect pheromones

Insect pheromones are neurotransmitters that serve the chemical communication between individuals of an insect species. They thus differ from kairomones, in other words, neurotransmitters that transmit information to non-species organisms. Insects produce pheromones in special glands and release them into the environment. In the pheromone receptors of the sensory cells of the recipient, they produce a nerve stimulus even in very low concentrations, which ultimately leads to a behavioral response. Intraspecific communication of insects via these substances takes place in a variety of ways and serves, among other things, to find sexual partner, to maintain harmony in a colony of socially living insects, to mark territories or to find nest sites and food sources. In 1959, the German biochemist and Nobel Prize winner Adolf Butenandt identified and synthesized the unsaturated fatty alcohol bombycol, the sex pheromone of the domestic silk moth (Bombyx mori), as the first known insect pheromone. The sex pheromones of female butterflies are mostly mono- or bis-olefinic fatty acids or their esters, fatty alcohols, their esters or the corresponding aldehydes. Male butterflies use a wide range of chemicals as sex pheromones, for example pyrrolizidine alkaloids, terpenes and aromatic compounds such as benzaldehyde. Research into the chemical communication of insects is expanding our understanding of how they locate their food sources or places to lay eggs. For example, beekeepers use an artificially produced Nasanov pheromone containing terpenes such as geraniol and citral to attract bees to an unused hive. The agriculture and forestry industries use insect pheromones commercially in pest control using insect traps to prevent egg laying and in practicing the mating disruption. It is expected that insect pheromones can also contribute in this way to the control of insect-borne infectious diseases such as malaria, dengue fever or African trypanosomiasis.

Etymology and classification Adolf Butenandt and Peter Karlson proposed the term pheromones in 1959 for substances that serve intraspecific communication. The definition of the term pheromone was given in the same year by Karlson and the Swiss zoologist Martin Lüscher. According to this, pheromones are"Substances released externally by one individual that elicit specific responses in another individual of the same species." – Peter Karlson, Martin Lüscher, 1959.The word pheromone consists of the ancient Greek parts of speech φέρειν phérein, überbringen, melden, and ὁρμᾶν hormān, antreiben, erregen. According to Karlson and Lüscher, the goal was to coin an internationally understandable scientific term for a class of substances based on a clear definition. It was to be a short word that could be spoken in many languages. The ending mone served as a suffix, as it occurs in the words hormone, kairomone, and allomone thus emphasizing their relationship. The term pheromone replaced the term ectohormone or homoiohormone, which Albrecht Bethe had already proposed in 1932 with the same definition. Bethe's term was not accepted because, according to Butenandt, the terms ecto and hormone were mutually exclusive. The mechanism of action of a pheromone also does not correspond to that of a hormone absorbed into the circulatory system by another individual and was therefore considered misleading. The classification of intraspecific pheromones in the group of semiochemicals, in other words, neurotransmitters that serve communication between organisms, is shown in the following diagram:

Karlson further divided them into the sense of smell and the oral-acting insect pheromones according to the mode of reception. In 1963, Edward O. Wilson, who had discovered ant trace pheromones the year before, and William H. Bossert introduced the concepts of releaser and primer pheromones. Releaser pheromones, which are usually perceived olfactorily, cause an instantaneously observable behavioral reaction, whereas primer pheromones, which are often oral, trigger physiological changes in the recipient. Primerpheromones, for example, suppress the formation of ovaries in worker bees. Often, pheromones are defined according to their behavior-triggering function. In addition to the well-known sex attractants, they act, among other things, as aggregation pheromones, dispersion pheromones, alarm pheromones, tracking pheromones, marker pheromones, brood recognition pheromones, egg-laying pheromones, recruitment pheromones, or as caste recognition agents. Vincent Dethier divided insect pheromones into six categories according to their general behavior-triggering effects. These include prisoners, which are normally only perceptible at short distances and cause an insect in motion to stop, and locomotor stimulants, which increase the insect's speed or decrease the number of directional changes. Lockstoffe are attractants that trigger an oriented movement toward the odor source, whereas repellents trigger an escape movement away from it. Feeding and oviposition stimulants, respectively, trigger feeding or oviposition. Deterrents, on the other hand, inhibit feeding or oviposition. Functionally defined insect pheromones often contain mixtures of different components in precisely defined proportions. These so-called pheromone cocktails often contain substances of different categories with near and far orientation functions. For example, the aggregation pheromone cocktail of the German cockroach Blattella germanica contains both substances that act as attractants and substances that act as arrestants. In part, insect pheromones are named after the site of their biological production. Males of various moth species, such as the banana butterfly, possess so-called androconial organs in the abdomen that release pheromones. These insect pheromones are appropriately called androconial pheromones. The queen bee of the Western honey bee produce the queen bee pheromone in mandibular glands. In English, they are therefore often referred to as queen mandibular gland pheromones.

History

First discoveries

… excerpt ends here. Continue reading the full article.