Gas bubble disease in the upside-down jellyfish Cassiopea sp.: Experimental induction and histopathological characterization

OBJECTIVE: Jellyfish are known to be difficult species to breed, yet little is known about the diseases that affect them. This study investigated the behavioral and histopathological changes caused by gas bubble disease (GBD) in upside-down jellyfish Cassiopea sp. METHODS: Upside-down jellyfish were assigned to control and microbubble-exposed tanks (n = 7 each; 36 L size). Microbubbles were supplied to the experimental group tank by inducing an insufficient water level in the sump tank, which allowed air to be entrained into the return pump. RESULT: All upside-down jellyfish maintained in the microbubble-exposed tank exhibited signs of GBD. Gas bubbles were observed both grossly and histologically, along with chronic lesions, which progressed to bell ulceration. Behavioral changes, including loss of equilibrium and abnormal pulsation, were observed. These results demonstrate that excessive microbubbles induce GBD. CONCLUSION: This study demonstrates that excessive microbubble exposure can experimentally induce GBD in upside-down jellyfish and highlights the need to monitor gas supersaturation during jellyfish rearing.