ABSTRACT
Many organisms move through environments in a directed fashion to locate patchily distributed resources. To effectively orient or navigate, organisms need to acquire information about their environment using their sensory systems. This information can include the location of predators, food resources, potential mates, and habitats (e.g. Busdosh et al., 1982; Hargrave, 1985; Hessler et al., 1972; Ingram and Hessler, 1983; Peckarsky, 1980; Petranka et al., 1987; Sainte-Marie, 1986; Wilson and Smith, 1984). For a number of organisms, this information is obtained from chemical signals. For example, chemical signals are important for tracking scents (Hamner and Hamner, 1977), aggregating microorganisms (Bell and Mitchell, 1972), and migration in Daphnia (Dodson et al., 1997). In addition, algal exudates (e.g. Maier and Müller, 1986), pheromones (e.g. Atema and Engstrom, 1971; Gleeson et al., 1987), sperm attractants (e.g. Miller, 1979), and predatory chemicals (Peckarsky, 1980; Petranka et al., 1987) play crucial roles in the feeding, aggregation, and spawning of widely dispersed organisms. These signals serve as guideposts in orientation behaviour. In all of these instances, it has been shown that the chemical signals play an important role in the behaviour of animals.
