27 Adult Neurogenesis in Teleost Fish

Abstract

In contrast to mammals, adult neurogenesis is extremely pronounced in teleost fish. As shown in this chapter, this includes an unsurpassed potential to replace neurons lost to injury by newly generated ones, leading to both structural and functional recovery after CNS trauma. These features make it particularly interesting to study the generation of new neurons in adult fish—not only to explore a fascinating biological phenomenon, but also to gain a better understanding of the evolutionary constraints that limit adult neurogenesis in the mammalian brain.

RATE OF CELL PROLIFERATION IN THE ADULT BRAIN
Quantitative analysis has suggested that the rate of cell proliferation is at least one, if not two, orders of magnitude higher in the adult fish brain than in the adult mammalian brain. In the most intensively studied model system, the brown ghost knifefish (Apteronotus leptorhynchus), approximately 100,000 cells are generated in the whole brain within any 2-hour period (Zupanc and Horschke 1995). In zebrafish, approximately 6000 cells are born within any 30-minute period (Hinsch and Zupanc 2007). These cell numbers correspond to approximately 0.2% and 0.06% of the total population of brain cells in each of the two species, respectively. Thus, the number of cells that enter the S phase of mitosis per time unit, relative to the total number of cells in the adult brain, appears to be similar in A. leptorhynchus and zebrafish.

In contrast, in the subventricular zone (SVZ) of adult mice, approximately 30,000 cells are formed every day (Lois and Alvarez-Buylla 1994), corresponding...