Histopathology of oxygen intoxication in the juvenile red abalone, Haliotis rufescens Swainson

Abstract. Juvenile abalone were exposed to supersaturated oxygen conditions (about 150–200% of saturation) in order to reproduce similar conditions encountered in intensive husbandry systems and to then study the resultant lesions. Depigmentation, lethargy and swelling of tissues were observed clinically. Histopathology showed that the cytoplasmic vacuoles of large haemocytes were enlarged. Oxygen emboli were observed throughout the muscular tissue and connective tissue but separation of fibrous neural sheath from nerve cell bodies and surrounding tissue was the predominant lesion. Chromatin of the nuclei of nerve cells became marginated. Gaseous emboli were observed at various other locations in the vascular system. At termination of the experiment all animals sampled bacteriologically showed systemic infection with Vibrio alginolyticus . The clinical signs appeared to result from mechanical interference caused by the accumulation of oxygen and from dysfunction of neural structures. The predominant histopathological changes occurred after only 3 h or less exposure time. Normal histology of the haemocytes and nerve structures is described.