Chemical communication by infochemicals

Abstract

Homo sapiens depends very much on visual and acoustic stimuli to get along in every day life whereas the role of odours is considered as of secondary importance. This is very different for most environmental organisms who live in an “odour world” and depend strongly on chemical stimuli to learn about their biotic and abiotic environments. These chemical cues are called infochemicals. The chemical environment plays a prevalent role for the fine tuning of articles that increase the survival of a species, such as searching food or shelter, reproducing, optimizing the survival conditions for the offspring or avoiding potential predators. Especially in aquatic systems, the dominance of the chemical sense has clear advantages as it allows to perceive stimuli at night as well as in turbid water, and visual obstacles are no hindrance for perception. The complexity and sophistication of the chemical communication systems are difficult to imagine from the human perspective (Burks and Lodge 2002; Bronmark and Hansson 2000; Dodson et al. 1994; Klaschka 2008a, b). Natural infochemicals are usually odorants. Therefore, the knowledge of the basic steps of the reaction cascade of the olfactory perception is needed to understand the chemical communication by infochemicals. A generalized scheme is depicted in Fig. 1. Infochemicals are released by a biotic or abiotic sender. They may find the olfactory epithelium of a receiver where they can bind to specific odorant-binding proteins leading to the formation of an electrical signal which is transduced to the central nervous system evoking the perception. The perception of an infochemical can lead to morphological, physiological or behavioral reactions of the receiver or even to changes on population levels. Internal factors (such as age, sex, activity state) and external factors (such as time of the day or the year, temperature) can influence the emission of infochemicals by the sender as well as the various steps of the reaction cascade in the receiver.