Steps toward a satisfactory historical narrative on the chemical senses

Natural products play a key role in the process of chemosensory signaling, either after being transported via fluid media (air or water), or after coming in direct contact with molecular sensors (receptors). In spite of this, the current definitions of olfaction (the sense of smell) and gustation (the sense of taste) are mainly based on the spatial range of action of the two chemical senses. Accordingly, olfaction is traditionally regarded as a "distance sense", while gustation is considered a "contact sense". This view has led to the belief that "odors" for aquatic animals are molecules in solution, just because in aquatic environments solubility, rather than volatility, is required for the long-distance transport of biomolecules. However, novel perspectives recognize a major source of bias in the above traditional differentiation between taste and smell (1,2), developing the insight that odorant compounds can also be detected by means of "tactile" forms of olfaction in aquatic environments. This thesis has been proved by exploring the defensive role of terpenes isolated from aquatic invertebrates, which act both as defensive toxic weapons and as olfactory signals (3). The obtained results will be discussed here to undermine some of the major obstacles for an effective debate on the evolutionary history of chemical communication. References 1.Mollo, E.; Fontana, A.; Roussis, V.; Polese G.; Amodeo, P.; Ghiselin, M. T. Front. Chem. 2014, 2, 92. 2.Mollo, E.; Garson, M. J.; Polese, G.; Amodeo, P.; Ghiselin, M. T. Nat. Prod. Rep. 2017, 34, 496-513. 3.Giordano, G.; Carbone, M.; Ciavatta, M. L.; Silvano, E.; Gavagnin, M.; Garson, M. J.; Cheney, K. L.; Mudianta, I. W.; Russo, G. F.; Villani, G.; Magliozzi, L.; Polese, G.; Zidorn, C.; Cutignano, A.; Fontana, A.; Ghiselin, M. T.; Mollo, E. Proc. Natl. Acad. Sci. USA 2017, 114, 3451-3456.