Ultrastructure of the dogfish adenohypophysis.

Granular hormone-producing cells and agranular cells (stellate cells, including giant and pericavitary cells) were electron microscopically studied in the hypophysis of the small spotted dogfish (Scyllium canicula) up to several months after hatching. Comparisons of results obtained in embryos, newly-hatched fish and adults show an increase of the mean granule diameter in the four major endocrine cell types. Small granule cells which are present in all lobes are especially numerous in the ventral lobe. The structures observed in certain cavity boundary cells suggest a role in resorption and transport.