Proliferation Zones in the Adult Brain of a Sequential Hermaphrodite Teleost Species <i>(Sparus aurata)</i>

Abstract

Teleost sex change is an important model to understand general principles of sexual differentiation and plasticity in the adult brain. The present study is the first to examine the proliferation zones in the adult brain of males, females and sex-changing individuals of a protandrous teleost species (Sparus aurata), by means of 5-bromo-2-deoxyuridine immunocytochemistry. Postnatal neurogenesis in the marine teleost brain was found in ventricular and subventricular areas of the brain that in most cases coincided with the embryonic proliferation zones. The molecular layer of corpus and valvula cerebelli exhibited the highest mitotic activity in the adult brain. High mitotic activity was observed in the hypothalamic, thalamic and telencephalic ventricular areas, as well as the dorsal and ventral rim of the optic tectum. Most of the labeled cells were elongated, indicating the initiation of migratory activity. There were no qualitative differences in the distribution 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 region included higher densities of newborn cells in the female animals. The proliferation pattern in the adult gilthead sea bream brain is in agreement with the hypothesis of the continuous generation of new cells in the teleost brain. Moreover, our data propose that cell proliferation differences possibly 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.

Adult Neurogenesis and Neuronal Regeneration in the Central Nervous System of Teleost Fish

“…The concentration of these cells appears to be similarly high as seen in Apteronotus leptorhynchus [Zupanc and Horschke, 1995]. Kranz and Richter [1970a] and Zikopoulos et al [2000] also noted a close association of the sites where new cells are generated with the ventricular and paraventricular system, particularly in the diencephalon. This is also observed in Apteronotus leptorhynchus, thus suggesting that the generation of new cells at sites close to ventricular lumina is a conserved feature among teleosts.…”

“…Other zones of high mitotic activity were found in the preoptic region, in an area ventrally to the habenula, in the hypothalamus, caudal rhombencephalon ('lobus viscerosensibilis'), and both corpus and valvula cerebelli. Subsequent studies employing [ 3 H]thymidine autoradiography and BrdU immunohistochemistry have confirmed the existence of such proliferation zones in the zebrafish (Danio rerio) [Rahmann, 1968], guppy [Kranz and Richter, 1970a, b;Richter and Kranz, 1970a, b], goldfish (Carassius auratus) [Meyer, 1978], gilthead (Sparus auratus) [Zikopoulos et al, 2000], and three-spined stickleback (Gasterosteus aculeatus) [Ekström et al, 2001]. In both the guppy and the three-spined stickleback, a large number of mitotically dividing cells have been described in the preoptic region Ekström et al, 2001].…”

“…As in Apteronotus leptorhynchus, the cerebella of the guppy , the gilthead [Zikopoulos et al, 2000], and the three-spined stickleback [Ekström et al, 2001] display the highest rate of mitosis relative to the remaining areas of the adult brain. Most new cells of both the corpus cerebelli and the valvula cerebelli of .…”

Age‐dependent differential expression of genes involved in steroid signalling pathway in the brain of protandrous black porgy, Acanthopagrus schlegeli

“…Neuroestrogens in teleosts have been proposed to contribute to their continual neurogenesis throughout life (Menuet et al, 2003;Pellegrini et al, 2005). q-PCR analysis of pcna transcripts in black porgy brain showed normal proliferation throughout development, which can be correlated to the plasticity characterizing teleost brain (Zikopoulos et al, 2000;Ekström et al, 2001). Studies with AI have provided evidence for the importance of aromatase in sex differentiation of teleosts (Guiguen et al, 1999).…”

Adult and Reparative Neurogenesis in Fish Brain

“…In contrast to the mammalian brain, numerous proliferative regions have been found in adult fish. The presence of such regions was described in Apteronotus leptorhynchus [4], Sparus aurata [5], Gasterosteus aculeatus [6], Danio sp. [7,8], and Austrolebias sp.…”