THORACIC NEUROSECRETORY STRUCTURES IN BRACHYURA. I. GROSS ANATOMY

Abstract

Three peripheral neurohaemal structures occur in the crab thorax: pericardial organs in the pericardium, anterior ramifications in the ventral sinuses near the scaphognathite muscles, and post-commissure organs in anterior sinuses ventral and lateral to the stomach. The pericardial organs and anterior ramifications apparently belong to 1 neurosecretory system, and receive secretory terminals from neurons located in the ventral thoracic ganglia. Weights of pericardial organs from 7 semitropical species were compared. In active forms such as Ocypode and Callinectes one organ comprises 0.0009-0.001% of total body weight; in Panopeus, the mud crab, it comprises 0.0004%. This is a significant difference, and suggests that pericardial organ size may be correlated with some aspect of physiological activity.