ABSTRACT
This chapter provides an examination of the parasite taxa that regularly infect threespined sticklebacks in natural environments and their impacts on host biology, with the aim of developing an understanding of their role as agents of natural and sexual selection in host populations. The taxonomic and life cycle diversity of stickleback parasites is introduced, and patterns of infection in stickleback populations are examined. The various behavioural mechanisms that sticklebacks can use to avoid parasites or otherwise reduce their own risk of infection or that of their offspring are reviewed. The biology of infected fish is discussed, and sections are included that address the impact of infection on host morphology, physiology, growth, and sexual development. Many stickleback parasites also affect the behaviour of their hosts, and behavioural changes resulting from parasite infections can have potentially significant consequences for the ecology of host individuals and the evolution of populations. In some cases, parasites may actually benefit from the changes in behaviour they induce in their hosts. The impact of parasites on the behaviour of host sticklebacks has been extensively tested, and the various changes that have been recorded and their likely physiological basis and consequences for host ecology are discussed in detail.
