Canada goose posterior lobe pituicytes: seasonal ultrastructural changes in relation to axonal release of neurosecretion.
Changes in ultrastructure of the posterior lobe pituicytes during six phases (Spring premigratory, Spring postmigratory, breeding, moulting, Fall premigratory and Fall postmigratory) of the annual life cycle of the migratory Canada goose, were studied. Pituicyte nuclear volume in females was significantly greater than that in males during the Spring premigratory and moulting phases. In the Fall postmigratory phase, nuclear volume in males was greater than that in females. During Spring premigratory phase, the axonal endings in males contained fewer neurosecretory granules (NSG) than those in the Fall postmigratory phase. In females, however, the number of NSG was relatively more than that in males in the Spring premigratory phase but fewer in the moulting phase. Nuclear volume is correlated with pituicyte function in releasing NSG containing arginine vasotocin (AVT) from axonal endings. The significance of AVT release is discussed in relation to initiation of reproductive and migratory behaviour, and to osmotic and metabolic regulation.
D000064:Acclimatization; D000818:Animals; D000835:Animals, Wild; D001369:Axons / Q000502:physiology*; D005777:Geese / Q000502:physiology*; D008854:Microscopy, Electron; D009489:Neurosecretion; D010904:Pituitary Gland, Posterior / Q000648:ultrastructure*; D012621:Seasons