Pheromone production and release

Another aspect of the sex pheromone communication system concerns the endogenous signals that control pheromone production and release from the emitting insect. A number of hormones have been found to be involved in the control of pheromone production in various insect species (18). Juvenile hormone was found to induce vitellogenesis and sex pheromone production in some cockroach and beetle species. However, ecdysteroids were found to be involved in regulating reproductive processes, including vitellogenin synthesis, in dipteran species. 

Raina A. K., Wergin W. P., Murphy A. C. and Erbe E. F. (2000) Structural organization of the sex pheromone gland in Helicoverpa zea in relation to pheromone production and release. Arthropod Struct. Develop. 29, 343-353. 

Schal C., Ling D. and Blomquist G. J. (1997). Neural and endocrine control of pheromone production and release in cockroaches. In Insect Pheromone Research New Directions, eds R. T. Carde and A. K. Minks, pp. 3-20. Chapman and Hall, New York. 

Host plants may influence sex pheromone behaviour in insects both in pheromone production and release and in the responses obtained (Landolt and Phillips, 1997). Food odour synergists or other host-plant derived semiochemicals may be incorporated in pheromone trapping systems to improve their performance (Phillips, 1997). The combination of sex pheromone and food odour probably has... 

The role of the nervous system in pheromone biosynthesis in moths is not clearly understood. Christensen and co-workers [208-211] proposed that the neurotransmitter octopamine may be involved as an intermediate messenger during the stimulation of sex pheromone production in H. virescens. These workers suggested that octopamine was involved in the regulation of pheromone production and that PBAN s role lies in the stimulation of octopamine release at nerve endings. However, contradicting results concerning octopa-mine-stimulated pheromone production were reported in the same species as well as other moth species [163,172,212-214]. 

Neuronal signals that descend from the central nervous system (CNS) or ascend through the ventral nerve cord (VNC) can modulate sex pheromone production and/or its release. 

Mating in most species of moths is mediated through the production and release of species-specific sex pheromones by the females and, in a majority of the moths, reproductive activity is limited to the hours of darkness. To achieve this diurnal periodicity of mating, production of sex pheromone must also be synchronized (JL). In the corn earworm, Helicoverpa Heliothls) zea, and in many other species of moths, this synchronization is affected by a factor produced in the head of the female (2.). The factor was identified as a peptide hormone, produced in the suboesophageal ganglion (SOG) and most likely... 

Since spawning behavior and production and release of milt in male goldfish are influenced by the medial but not by the lateral olfactory tract, any terminal fields that are innervated by the medial tract, but not by the lateral tract, are likely candidates for mediating the effects of pheromones. Two such areas occur in the goldfish the medial terminal field of the ventromedial telencephalon and the anterior preoptic area (Ichikawa and Ueda, 1978 von Bartheld et al., 1984), both of which are implicated in the control of reproductive events. 

Production and release of pheromone attracts other conspecific beetles of both sexes and aggregation or mass attack is underway. In Ips, males attack first and additional males as well as females arrive. Males initiate new boring holes. Females locate established males, enter their boring holes and mate. In Den-droctonus, pheromone release is modified as a tree is colonized. The female arrives first and releases exo-brevicomin and myrene, which preferentially attract males. Male arrivals release frontalin near female entrance holes and the blend attracts both males and females in equal numbers. The release of ver-benone and trans-wQxbtnol then deters further arrivals (Wood, 1982). 

The studies on the synthesis of the terpene-derived pheromones have led to the hypothesis that these compounds are waste products from the detoxification of host terpenes that, as a consequence of the timing and conditions of their production and release, have secondarily been utilized as chemical messengers. The nature of these oxidations, the large quantities of products formed, and the formation of the same products by other insects such as house flies when exposed to the terpenes led to the suggestion that the mixed-function oxidase system in the insect may well be involved. ... 

The site of pheromone production in flies and cockroaches that utilize hydrocarbons is similar to that of the moths. Oenocyte cells produce the hydrocarbon pheromone which is transported by lipophorin in the hemolymph to epidermal cells throughout the body for release from the cuticular surface in general [20,21]. 

The queen is usually reproductively dominant within the colony and uses chemical cues as both primer and releaser pheromones to suppress the production or fecundity of other sexuals, inhibit reproduction by worker castes, modulate reproductive behaviors (e.g., inhibit swarming and orient swarms), attract males, regulate worker tasks and worker ontogeny, and produce host repellents in slave-making species. Considering the importance of queen semiochemicals in social hymenoptera, few queen pheromones have been chemically identified. The queens of most social hymenopteran colonies are attractive to workers, allowing them to be properly tended as well as to facilitate the dissemination of other pheromone cues. However, the retinue pheromone has been chemically identified in very few species. In the 1980s, queen pheromone components were identified in the fire ant, Solenopsis invicta [91,92], and in the Pharaoh s ant, Monomoriumpharaonis [93]. 

In moths, it was discovered in Helicoverpa zea that a peptide produced in the subesophageal ganglion portion of the brain complex regulates pheromone production in female moths (19). This factor has been purified and characterized in three species, Helicoverpa zea (20), Bombyx mori (21, 22), and Lymantria dispar (23). They are all a 33- or 34-amino acid peptide (named pheromone biosynthesis activating neuropeptide, PBAN) and have in common an amidated C-terminal 5-amino acid sequence (FXPRL-amide), which is the minimum peptide fragment required for pheromon-tropic activity. In the redbanded leafroller moth, it was shown that PBAN from the brain stimulates the release of a different peptide from the bursae copulatrix that is used to stimulate pheromone production in the pheromone gland found at the posterior tip of the abdomen (24). 

One may wonder why lobsters appear to use urine as a dispersal solvent for chemical signals, whereas terrestrial arthropods such as the well-studied insects use direct release of gland products into the air. Perhaps the answer is that small animals in air (such as insects) are always in danger of desiccation. By contrast, marine lobsters and crabs are relatively large and may experience only minor water loss problems due to osmosis. Thus, it may not be difficult for a 500-g lobster to store 10 ml of urine and release it during a dominance battle at a rate of up to 1 ml/min (27). The advantage of urine-carried pheromones is that the dispersal mechanism already exists urine is injected into the gill current, which in turn injects into ocean currents. 

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