A Neurosecretory Tissue in Octopus

Abstract

IN view of the amount of information available about the structure of the nervous system in cephalopod molluscs, there is surprisingly little known about their neurosecretory systems. The epistellar body, associated with the stellar ganglion, was thought to be a neurosecretory organ¹, but it is now known to have the structure of a photoreceptor². Several other structures of unknown function have also been described that may have a neurosecretory function^3,4. The only organ that has been shown to have an endocrine function in cephalopods is the optic gland of Octopus; behavioural studies show that it controls maturation of the gonads and hence sexual maturity⁵. A preliminary report on the fine structure of this organ gave little information of any granular content of the cells⁶. A group of possible neurosecretory tissues that have a similar histological structure have recently been, described—the vena caval tissue, associated with the vena cava in Eledone cirrosa, Octopus vulgaris and Sepia officinalis^7,8, and the juxta-ganglionic tissue, associated with the inferior buccal ganglia and buccal sinus in Octopus vulgaris^9,10. The juxta-ganglionic tissue, first described by Bogoraze and Cazal⁹, consists of a group of small nerve cells lying outside, but associated with, the inferior buccal ganglia (see ref. 10 for diagram of its position). These cells give rise to axons that pass down to the buccal sinus and end on its surface as a tangled mass of interweaving fibres¹⁰.