Ultrastructure of the cell types and of the neurosecretory innervation in the pituitary of Mugil cephalus L. from freshwater, the sea, and a hypersaline lagoon III. the neuro-intermediate lobe

Abraham, M.

General and Comparative Endocrinology 29(4): 511-521


ISSN/ISBN: 0016-6480
PMID: 60270
DOI: 10.1016/0016-6480(76)90035-6
Accession: 068518947

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The neuro-intermediate lobe of the pituitary was studied in specimens of Mugil cephalus taken from biotopes of varying salinities. The neurohypophysis in hypersaline lagoon fish was larger than in those caught in freshwater or the sea. The distal neurohypophysis of lagoon adapted specimens was characterized by a large number of pale neurosecretory granules, an increase of microtubules in the subterminal region of the axons and an abundance of fibrillar pituicytes. These signs could indicate that the neurohypophysis has a specific role in the adaptation of M. cephalus to high salinities. Pars intermedia tissue consisted of periodic acid-Schiff staining cells on the islet borders and of melanophore expending hormone (MSH) cells inside the islets. The endoplasmic reticulum of the MSH cells was hypertrophied in freshwater specimens. Pars intermedia tissue contained neurosecretory axons of both the A- and B-types: A-type axons were particularly profuse, some of them making synaptoid contact with MSH cells.