Haemorrhagic Septicaemia in the Lamprey Geotria australis Gray

The early upstream migrants of the lamprey, Geotria australis , were occasionally found dead in the field and suffered a very heavy mortality when held in the laboratory. The clinical signs exhibited by dying animals included the production of massive amounts of mucus, petechial haemorrhage of the skin and fins, and both haemorrhage and oedema around the eyes. Necropsy also revealed haemorrhage and oedema in various internal structures and in one case thrombosis and degeneration of blood vessels in the gill. The disease was attributed to infection with Aeromonas hydrophila and Pseudomonas fluorescens which were cultured from the organs of diseased animals. No signs of this disease occurred when the aquaria water was treated with chlortetracycline immediately after the introduction of each new batch of animals.