ABSTRACT
Aquatic animals such as crayfi sh live in a soup of organic molecules, which mainly originate from other aquatic organisms. These chemicals are inevitable by-products of life’s processes including feeding, digestion, excretion, predation or decay. They contribute to the nutrient fl ow between organisms within an ecological network. In addition, the molecules may carry information and infl uence important decisions and behaviours of other organisms. Numerous studies have shown that most aquatic organisms respond to minute concentrations of chemical substances released by other organisms (Brönmark and Hansson 2012). Interactions between organisms based on such infochemicals (Dicke and Sabelis 1988)—also referred to as semiochemicals (Wyatt 2011)—are subject to the fi eld of chemical ecology, a very active and important subdiscipline of ecology. Based on the nature of interaction, diff erent types of infochemicals are recognized as (1) pheromones, they mediate interactions between organisms of the same species (e.g., sex pheromones or dominance pheromones) and the information transfer is benefi cial to both sender and receiver; (2) kairomones, they mediate interactions between individuals of diff erent species where the information transfer is benefi cial for the receiver but not the sender of the chemical (e.g., the detection of chemicals originating from a potential prey organisms or a predator is benefi cial to the receiver but may lead to death or missed feeding opportunity of the source organism); and (3) alarm substances (alarm cue, “Schreckstoff ”), they are chemicals released by an injured prey that evoke defensive or escape responses in conspecifi c receivers (see also Brönmark and Hansson 2012). The detection of infochemicals is crucial for the survival and reproductive success of crayfi sh. Chemicals released by potential prey organism can inform a crayfi sh about the presence and location of food (section ‘Foraging behaviour’). Excretory products of a predator or body fl uids set free during a predation event alarm the crayfi sh and may trigger fi ght or fl ight responses (section ‘Predator detection’). Pheromones originating from conspecifi cs carry
1 School of Biological, Biomedical and Environmental Sciences, University of Hull, Hull, HU6 7RX, United Kingdom. 2 Department of Biology, University of Florence, Via Romana 17, 50125 Florence (Italy). a Email: laura.aquiloni@unifi .it b Email: elena.tricarico@unifi .it * Corresponding author: t.breithaupt@hull.ac.uk # Francesca Gherardi had the initial idea for this chapter but sadly passed away on 14th February 2013 at the age of 57. She
was an unusually creative scientist, a dear colleague, mentor, teacher and friend, who has greatly infl uenced the research of crayfi sh ecology as well as many other areas of crustacean biology.
