title: Predators inhibit brain cell proliferation in natural populations of electric fish, Brachyhypopomus occidentalis.
abstract: Compared with laboratory environments, complex natural environments promote brain cell proliferation and neurogenesis. Predators are one important feature of many natural environments, but, in the laboratory, predatory stimuli tend to inhibit brain cell proliferation. Often, laboratory predatory stimuli also elevate plasma glucocorticoids, which can then reduce brain cell proliferation. However, it is unknown how natural predators affect cell proliferation or whether glucocorticoids mediate the neurogenic response to natural predators. We examined brain cell proliferation in six populations of the electric fish, Brachyhypopomus occidentalis, exposed to three forms of predator stimuli: (i) natural variation in the density of predatory catfish; (ii) tail injury, presumably from predation attempts; and (iii) the acute stress of capture. Populations with higher predation pressure had lower density of proliferating (PCNA+) cells, and fish with injured tails had lower proliferating cell density than those with intact tails. However, plasma cortisol did not vary at the population level according to predation pressure or at the individual level according to tail injury. Capture stress significantly increased cortisol, but only marginally decreased cell proliferation. Thus, it appears that the presence of natural predators inhibits brain cell proliferation, but not via mechanisms that depend on changes in basal cortisol levels. This study is the first demonstration of predator-induced alteration of brain cell proliferation in a free-living vertebrate.
authors: Department of Biology, Trinity College, Hartford, CT 06106, USA kent.dunlap@trincoll.edu.
authors: Kent D
authors: http://orcid.org/0000-0002-1153-7001
authors: KD
authors: Dunlap
authors: Department of Biology, McGill University, Montreal, Quebec, Canada H3A 1B1.
authors: Alex
authors: A
authors: Tran
authors: Department of Biology, Trinity College, Hartford, CT 06106, USA.
authors: Michael A
authors: MA
authors: Ragazzi
authors: Department of Biology, McGill University, Montreal, Quebec, Canada H3A 1B1.
authors: Rüdiger
authors: R
authors: Krahe
authors: Department of Biology, Cape Breton University, Sydney, Nova Scotia, Canada B1P 6L2.
authors: Vielka L
authors: VL
authors: Salazar
mesh_terms: D000818:Animals; D001921:Brain / Q000502:physiology*; D002397:Catfishes / Q000502:physiology*; D049109:Cell Proliferation; D004555:Electric Fish / Q000502:physiology*; D020387:Food Chain; D023702:Gymnotiformes / Q000293:injuries / Q000502:physiology*; D011235:Predatory Behavior; D013312:Stress, Physiological
keywords: brain cell proliferation; cortisol; fish; neurogenesis; predators