Summary

Crustaceans have been used extensively to study aggression from a variety of perspectives. Traits that make them good models for studies of aggression include the possession of prominent weapons and a ready willingness to fight, the ease with which they may be obtained and their ease of maintenance in the laboratory. Furthermore, hard exoskeletons mean that equipment such as heartbeat sensors can be easily attached directly to the animals and they are very amenable to physiological investigation. Therefore a feature of studies into the contest behaviour of crustaceans is a strong link between ultimate ‘functions’ and proximate ‘mechanisms’. Given the very wide range of studies on crustacean aggression any review of this group could potentially be extremely broad in focus. Rather than attempt such a broad review, I focus on studies that have combined ethological data with data on underlying mechanisms in order to address questions that have arisen from the body of evolutionary contest theory described in Chapter 2. This has meant that some areas of research on aggression in the Crustacea, such as the neuroendocrine control of aggression and studies of social aspects of aggression such as dominance hierarchies, are outlined only briefly. I consider evidence for information-gathering and decision-making in respect of resource holding potential and resource value, and describe how studies of the underlying motivation to fight can provide useful insights into what information fighting animals might use when making strategic decisions. I also consider studies of agonistic signals, which in crustaceans include visual, tactile and chemical modalities, with a particular consideration of the extent to which ‘dishonesty’ might play a role in crustacean agonistic dealings. I then review physiological aspects of fighting in crustaceans, including studies based on post-fight assays of metabolites and by-products, studies based on ‘real-time’ non-invasive techniques and studies based on a functional morphology approach of investigating whole organism performance capacities. Finally, I suggest ways in which studies on crustacean contests could inform new theoretical models of contest behaviour and discuss the potential for applying approaches used to study crustaceans to the study of contests in other taxa.