[The hypothalamic-hypophyseal neurosecretory system of the Alosa fallax nilotica. A histological and ultrastructural study].
We studied the morphological, histochemical and ultrastructural aspects of the hypothalamic-pituitary system in the Alosa fallax nilotica. The secretory activity of the preoptic nucleus and of the lateral tuberal nucleus was also investigated with regard to the gonadal growth and development during the reproductive sexual cycle and the changing migrational environmental conditions (anadromous and catadromous phases). The hypothalamic-pituitary system is formed by: centers of neurosecretion synthesis (parvo and magnocellular preoptic nucleus and lateral tuberal nucleus), a conduit system (preoptic infundibular-neurohypophyseal tract) and a collecting center (neurohypophysis intermediate lobe). The neurosecretory cells show two distinct types of secretory granules with different ultrastructural features probably representing the morphological expression of two distinct hormones. These cells show also characterizations of cytoplasmic areas related to peculiar cyclic functional stages concerned with the reproductive sexual cycle. We observed significant quantitative and qualitative changes of the neurons both in the parvo- and magnocellular preoptic nucleus and in the lateral tuberal nucleus during anadromous migration and during spawning and fertilization. Almost insignificant changes of the neurosecretory material were observed in the preoptic-pituitary tract and in the intermediate-neurohypophyseal lobe. The results show that the hypothalamic-pituitary neurosecretory system play an important role in the osmoregulation (magnocellular preoptic nucleus) and on the reproductive cycle (lateral tuberal nucleus). The system probably also controls some other metabolic activities (utilization of the stored material) linked to peculiar environmental and feeding conditions.
Romita
G
G
Istituto di Anatomia Umana Normale Università degli Studi di Parma.
Bucci
G
G
Gatti
R
R
Orlandini
G
G
D000818:Animals; D003594:Cytoplasmic Granules / Q000648:ultrastructure; D005260:Female; D005399:Fishes / Q000033:anatomy & histology* / Q000502:physiology; D007030:Hypothalamo-Hypophyseal System / Q000033:anatomy & histology* / Q000648:ultrastructure; D008297:Male; D009489:Neurosecretion; D010904:Pituitary Gland, Posterior / Q000502:physiology / Q000648:ultrastructure; D012098:Reproduction; D014882:Water-Electrolyte Balance
Il sistema neurosecretorio ipotalamo-ipofisario dell'Alosa fallax nilotica. Studio istologico ed ultrastrutturale.