Social regulation of neurogenesis in teleosts

Salmonid fishes such as the rainbow trout (Oncorhynchus mykiss) are frequently used to study behavioral and neuroendocrine effects of socially induced stress. A predictable aggressive response to territorial intrusion, a well described neuroanatomy, and many essential similarities in the stress response in fishes and other vertebrates are among the advantages of this comparative model. One conspicuous difference when compared to mammals, however, is that in teleost fish and other non-mammalian vertebrates, neurogenesis persists into adulthood to a much higher degree. Very little is known about the functional significance of individual differences in the rate of brain cell proliferation in fish, or whether structural changes in the fish brain are influenced by the social environment. In this paper we discuss the observation that brain cell proliferation is reduced in subordinate fish, focusing in particular on whether such individual variation reflects a difference in coping style or is indeed a response to social interactions.