A Neurohypophyseal Principle in the Elasmobranch Pituitary

Abstract

THE elasmobranch pituitary gland consists of three distinct and largely separate regions (Fig. 1). Two of these, the rostral and ventral lobes, appear to represent the pars anterior of higher vertebrates, while the third, the so-called neurointermediate lobe, consists of intimately interdigitated neural and intermediate tissue¹. Scharrer² has described a pre-optico-hypophyseal system in Scyliorhinus stettare, and our own unpublished histological studies on this system in S. caniculus have demonstrated the presence of material which is Gomori-positive, aldehyde-fuchsin-positive and stains by the performic acid-alcian blue technique of Adams and Sloper³. However, in spite of the undoubted existence of a neurohypophyseal system in elasmobranchs, evidence for the existence of the oxytocic and vasopressor principles characteristically present in the mammalian neurohypophysis is conflicting^4–8. The investigation reported here attempts to resolve the discrepancy between the morphological and physiological findings.