Urine insect pheromones

Our recent NSF-funded collaboration with Bets has yielded, for example, the first statistically significant evidence that male African elephants can distinguish conspecific female urine collected at the time of ovulation from urine obtained at the mid-luteal time of the estrous cycle (Bagley, Goodwin, Rasmussen and Schulte 2006). Additionally, we have published the first report of insect pheromones in the urine of female African elephants (Goodwin, Eggert, House, Weddell, Schulte and Rasmussen 2006). These findings bode well for the eventual discovery of the first African elephant pheromones. 

Abstract A relatively small number of mammalian pheromones has been identified, in contrast to a plethora of known insect pheromones, but two remarkable Asian elephant/insect pheromonal linkages have been elucidated, namely, (Z)-7-dodecen-1-yl acetate and frontalin. In addition, behavioral bioassays have demonstrated the presence of a chemical signal in the urine of female African elephants around the time of ovulation. Our search for possible ovulatory pheromones in the headspace over female African elephant urine has revealed for the first time the presence of a number of known insect pheromones. This search has been facilitated by the use of a powerful new analytical technique, automated solid phase dynamic extraction (SPDE)/GC-MS, as well as by novel macros for enhanced and rapid comparison of multiple mass spectral data files from Agilent ChemStation . This chapter will focus on our methodologies and results, as well as on a comparison of SPDE and the more established techniques of solid phase microextraction (SPME) and stir bar sorptive extraction (SBSE). 

Fig. 2.1 Compounds identified in female African elephant urine headspace that are known insect pheromones...

Use of automated headspace SPDE/GC-MS not only enabled the identification in female African elephant urine of a number of known insect pheromones (compounds 2-6, Fig. 2.1), but also revealed the presence of the beetle biochemical precursors to frontalin (2), exo-brevicomin (3) and ent/o-brevicomin (4), thus suggesting a common biosynthetic pathway (Goodwin et al. 2006). Extensive behavioral bioassays must be performed to determine whether any of these compounds is functioning as a pheromone among African elephants. 

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. 

Typical applications of thermal desorption are related to determination of volatiles and semivolatiles in air samples [55-58]. This technique has been applied for investigation of insect pheromones [59] and drugs in urine [60]. The same principles can be applied for solids or semisolids (soil, sediment, pharmaceutical raw materials, cream, ointments, polymers, etc.)... 

In rabbits, the as yet unidentified maternal signal during lactation has analogous properties in guiding the reliable orientation of suckling, mainly via MOS input (Hudson and Distel, 1986 Schaal et al., unpubl.). Minor fractions may still function as flag contributors, exemplified by the attractiveness of proestrous elephant urine. Male responses show that intact urine is conspicuously more attractive in comparison with the pure insect mammal pheromone (9.) presented in water (Rasmussen et al., 1996). 

Most compounds in vertebrates and insects contain polar functional groups (wheeler, 1977). An intriguing question is whether marking pheromones are less polar than water-soluble ones, such as those in urine. The polarity of non-pheromonal compounds in a mixture greatly affects pheromone release into the environment (Regnier and Goodwin, 1977). 

Pheromones are also important in mammals, although many fewer have been identified. As one example, (Z)-7-dodecen-l-yl acetate has recently been identified in the urine of female elephants when they are in heat. This ester elicits a specific sexual response in male elephants. Interestingly, this same ester is part of the pheromone mixture that many insects, especially moths, use as a sexual attractant. 

Pheromones are a group of natural substances involved in animal reproductive behavior and ecology. They are mainly excreted by skin and urine. For example, the 12-18 carbon chains of aldehydes excreted by insects can be detected well by BL concentrations of lO M pheromone can be measured in the air, which is very useful in agriculture pest control [41]. 

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