Semiochemicals mammalian

Keywords Mammalian semiochemicals Mammalian pheromones Mammalian exocrine secretions Chemical communication Territorial marking... 

Burger, B.V. (2005) Mammalian Semiochemicals. In S. Schulz (Ed.), The Chemistry of Pheromones and Other Semiochemicals II (Topics in Current Chemistry 240). Springer-Verlag, Heidelberg, pp. 231-278. 

Abstract Progress that has been made in research on the chemical aspects of mammalian semiochemistry over the past decade is discussed on the basis of examples from the most topical problem areas. The chemical characterization of the volatile organic constituents of the urine, anal gland secretions and exocrine gland secretions of rodents, carnivores, proboscids, artiodactyls and primates, and their possible role in the semiochemical communication of these mammals are discussed, with particular emphasis on the advances made in the elaboration of the function of proteins as controlled release carrier materials for the semiochemicals of some of these animals. 

Only a few compounds or mixtures of compounds have been shown beyond doubt to be mammalian pheromones. This is the main reason why the subject matter of this chapter is not restricted to pheromones and why exocrine secretions and other mammalian excretions in general will be discussed as possible sources of pheromones, even though their role in the chemical communication of the species under discussion has not yet been established. Feeding deterrents are not discussed. In general defensive secretions are also not discussed, but the anal sac secretions of the mustelids are included, because it is possible that these secretions could also fulfill a semiochemical role, in addition to being used for defense. 

Techniques developed for the identification of insect semiochemicals and the determination of environmental contaminants have been used equally effectively in chemical work on mammals. Some of these methods will therefore be discussed only as far as their application is of particular significance in mammalian semiochemistry. Examples can be found in the literature of cases in which conclusions were drawn from results that were obtained by using inappropriate or, at least, doubtful analytical techniques. A few of the problem areas will be highlighted without giving the relevant literature references. 

GC-MS analysis has become standard practice in semiochemical research. There is, however, a real danger that information based exclusively on the results of computerized library searches without mass spectral and retention-time comparison with authentic synthetic material can be introduced into the literature. This could be problem especially in mammalian semiochemistry, because researchers often are faced with the problem of having to identify large numbers of compounds of which many may have very uninformative mass spectra. A critical reader of the original publication could still be aware of the unverified nature of some of the information, but this may not be pointed out in later references to the work. 

Tarsal, metatarsal, caudal, interdigital and preorbital glandular structures have been described in the black-tailed deer, Odocoileus hemionus columbianus. The tarsal organ received considerable attention from chemists and behavioral scientists during the early years of chemical research on mammalian semiochemicals. The major constituent of the complex mixture of volatile compounds associated with the tarsal hair tuft of this mule deer, (Z)-6-dodecen-4-olide [ 125], was subsequently found to be a mixture of the R and S enantiomers in a ratio of 89 11 respectively [ 126]. It was later found that this compound does not originate in the tarsal structure itself, but that it is extracted from the animal s urine by the tarsal hair tuft, which is specially adapted to extract lipids from urine [127]. 

Reading the literature on mammalian semiochemistry over the past decade, a chemist is impressed by the enormous volume of biological information that has been gathered in well planned and meticulously executed studies of the modulation of the behavior of mammals by the chemicals released by con-specifics. One cannot, however, escape the impression that the chemical basis of many of these studies is lacking. Some of the problem areas were pointed out in the foregoing sections. To a certain extent there seems to be lack of appreciation of the diffusion rates of compounds with different volatilities and of the extent to which these differences can influence the outcome of behavioral tests. It is difficult to make an estimate of the persistence of semiochemicals that are released into the laboratory atmosphere or that are left on objects or surfaces in arenas in which tests are conducted. From what is known about the evaporation rate of some heavy compounds that are considered to be semiochemicals, it could take several weeks or even months for these compounds to be depleted to levels that cannot be detected by currently available instrumentation levels at which meaningful information could still be available to experimental animals. This then leaves the question unanswered as to when it would be safe to conduct behavioral experiments in a laboratory or arena that had been occupied by conspecifics. 

The bulk of the applications of semiochemicals in vertebrates are aimed at mammals. However, it must be remembered that mammalian behavior is complex and management by chemical cues is more challenging than in insects, for example. 

Prior to delving into the details, this overview briefly summarizes the recent progress made as follows (1) progress in structure elucidation, (2) complexity of the multicomponent pheromone, (3) stereochemical aspects of chemical ecology, (4) dual roles of semiochemicals such as pheromones and kairomones, and (5) new trends in mammalian chemical ecology. 

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