The ultrastructure of the oval organ a mechanoreceptor in the second maxilla of decapod crustacea

Summary The oval organ is a mechanoreceptor in the second maxilla. It has a rich dendritic arborisation, suspended in the haemocoele of the appendage by a cone of connective tissue. The apex of the cone is firmly inserted onto a small apodeme at the base of the endites, from which strands of collagenous connective tissue fan out to end in an oval area of arthrodial membrane. Three large sensory units, whose cell bodies lie centrally in the suboesophageal ganglion, enter the connective tissue cone and use its strands as a supportive framework for the primary and secondary dendrites. Thin tertiary dendrites end in clusters of bulbous terminals embedded within the epidermis of the arthrodial membrane.