title: Post-hatching brain morphogenesis and cell proliferation in the pulse-type mormyrid Mormyrus rume proboscirostris.
abstract: The anatomical organization of African Mormyrids' brain is a clear example of departure from the average brain morphotype in teleosts, probably related to functional specialization associated to electrosensory processing and sensory-motor coordination. The brain of Mormyrids is characterized by a well-developed rhombencephalic electrosensory lobe interconnected with relatively large mesencephalic torus semicircularis and optic tectum, and a huge and complex cerebellum. This unique morphology might imply cell addition from extraventricular proliferation zones up to late developmental stages. Here we studied the ontogeny of these brain regions in Mormyrus rume proboscirostris from embryonic to adult stages by classical histological techniques and 3D reconstruction, and analyzed the spatial-temporal distribution of proliferating cells, using pulse type BrdU labeling. Brain morphogenesis and maturation progressed in rostral-caudal direction, from 4day old free embryos, through larvae, to juveniles whose brain almost attained adult morphological complexity. The change in the relative size of the telencephalon, and mesencephalic and rhombencephalic brain regions suggest a developmental shift in the relative importance of visual and electrosensory modalities. In free embryos, proliferating cells densely populated the lining of the ventricular system. During development, ventricular proliferating cells decreased in density and extension of distribution, constituting ventricular proliferation zones. The first recognizable one was found at the optic tectum of free embryos. Several extraventricular proliferation zones were found in the cerebellar divisions of larvae, persisting along life. Adult M. rume proboscirostris showed scarce ventricular but profuse cerebellar proliferation zones, particularly at the subpial layer of the valvula cerebelli, similar to lagomorphs. This might indicate that adult cerebellar proliferation is a conserved vertebrate feature.
authors.affiliation: Departamento de Histología y Embriología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay; Unidad Asociada "Histología de Sistemas Sensoriales", Facultad de Medicina-Instituto de Investigaciones Biológicas Clemente Estable, Uruguay. Electronic address: milka@fmed.edu.uy.
authors.forename: Milka
authors.initials: M
authors.lastname: Radmilovich
authors.affiliation: Unidad Asociada "Histología de Sistemas Sensoriales", Facultad de Medicina-Instituto de Investigaciones Biológicas Clemente Estable, Uruguay; Desarrollo y Evolución Neural, Departamento de Neurociencias Integrativas y Computacionales, Instituto de Investigaciones Biológicas Clemente Estable, Ministerio de Educación y Cultura, Montevideo, Uruguay. Electronic address: isabelpepis@gmail.com.
authors.forename: Isabel
authors.initials: I
authors.lastname: Barreiro
authors.affiliation: Desarrollo y Evolución Neural, Departamento de Neurociencias Integrativas y Computacionales, Instituto de Investigaciones Biológicas Clemente Estable, Ministerio de Educación y Cultura, Montevideo, Uruguay. Electronic address: irilet@gmail.com.
authors.forename: Leticia
authors.initials: L
authors.lastname: Iribarne
authors.affiliation: Unit of Neuroscience Information and Complexity, CNRS FRE, 3693 Gif-sur-Yvette, France. Electronic address: kirsty.grant.unic@gmail.com.
authors.forename: Kirsty
authors.initials: K
authors.lastname: Grant
authors.affiliation: Unit Biology and Ecology of Fishes, Faculty of Life Sciences, Humboldt University of Berlin, Berlin, Germany. Electronic address: frank.kirschbaum@staff.hu-berlin.de.
authors.forename: Frank
authors.initials: F
authors.lastname: Kirschbaum
authors.affiliation: Unidad Asociada "Histología de Sistemas Sensoriales", Facultad de Medicina-Instituto de Investigaciones Biológicas Clemente Estable, Uruguay; Desarrollo y Evolución Neural, Departamento de Neurociencias Integrativas y Computacionales, Instituto de Investigaciones Biológicas Clemente Estable, Ministerio de Educación y Cultura, Montevideo, Uruguay. Electronic address: mcastello@iibce.edu.uy.
authors.forename: María E
authors.initials: ME
authors.lastname: Castelló
mesh_terms: D000818:Animals; D001921:Brain / Q000166:cytology* / Q000254:growth & development*; D049109:Cell Proliferation; D004555:Electric Fish / Q000196:embryology* / Q000502:physiology; D009024:Morphogenesis / Q000502:physiology
keywords: 3-D reconstruction; 5-Bromo-2′-deoxyuridine; Brain ontogeny; Cerebellum; Electrosensory; Plasticity