Proliferation zones in the adult brain of a sequential hermaphrodite teleost species (Sparus aurata)

Teleost sex change is an important model to understand general principles o f sexual differentiation and plasticity in the adult brain. The present stu dy is the first to examine the proliferation zones in the adult brain of ma les, females and sex-changing individuals of a protandrous teleost species (Sparus aurata), by means of 5-bromo-2-deoxyuridine immunocytochemistry. Po stnatal neurogenesis in the marine teleost brain was found in ventricular a nd subventricular areas of the brain that in most cases coincided with the embryonic proliferation zones. The molecular layer of corpus and valvula ce rebelli exhibited the highest mitotic activity in the adult brain. High mit otic activity was observed in the hypothalamic, thalamic and telencephalic ventricular areas, as well as the dorsal and ventral rim of the optic tectu m. Most of the labeled cells were elongated, indicating the initiation of m igratory activity. There were no qualitative differences in the distributio n of proliferation zones between the sex phases studied with the exception of the ventricular region of the dorsal hypothalamic area. Volume fraction analysis of the area occupied by the labeled cells suggested that this regi on included higher densities of newborn cells in the female animals. The pr oliferation pattern in the adult gilthead sea bream brain is in agreement w ith the hypothesis of the continuous generation of new cells in the teleost brain. Moreover, our data propose that cell proliferation differences poss ibly existing in the ventricular region of the dorsal hypothalamus between sexual phases, might be involved in central mechanisms of sexual plasticity in protandrous hermaphrodite teleosts. Copyright (C) 2001 S. Karger AG, Ba sel.