Autolysis in axon terminals of a new neurohaemal organ in the cockroach Periplaneta americana.

An ultrastructural investigation showed that there was a neurohaemal organ in the wall of the ampulla of the antennal pulsatile organ. The neurosecretory axon terminals occurred singly or in small groups, rather than closely packed together as in other neurohaemal organs. All axons contained the same type of neurosecretory granule. The granules had varying electron density and a diameter in the range 1000-2500 A. Some terminals contained small, elliptical electron-transparent vesicles and the axolemma was apposed to the stroma. Other terminals were large and enveloped by glial tissue and the contents of the terminals exhibited varying degrees of autolytic degeneration. Autolysis was characterized by the occurrence of dense bodies and multilaminate bodies which enclosed mitochondria and neurosecretory granules. It was suggested that the neurosecretory material affects antennal function.