Introduction: Gas-bubble disease (GBD) can occur in aquatic organisms, mainly due to excess oxygen or nitrogen gas; it occurs at dissolved oxygen levels >200% or nitrogen gas levels >120%. Among amphibians, it was reported only in African clawed frogs.
Subject and methods: GBD in two giant salamanders (GSs) was studied through macroscopic examination and histopathology to clarify the features of GBD in GS.
History: On day 1 of the case, bubbles occurred on the body surface of fish and GSs inhabiting a common tank, and over 55 fish died. On day 2, approximately 75 fish died, and adult GSs showed cutaneous flushing. Both GSs and some of the remaining fish were dead on the morning of day 3. Dissolved oxygen was measured on days 1 and 2 (and dissolved nitrogen was inferred), which was 75.5% (90.6%) and 86.9% (103.1%), respectively.
Results: The GSs showed similar lesions. Macroscopic findings included cutaneous flushing, ocular protrusion, and congestive dilation and gas present in major the veins of the body cavity. Histolopathologically, congestion, non-congestive dilation (no hemocytes in vessels or dilation even though little hemocytes) and gas embolism-like dilation were observed in small and capillary vessels. These lesions were observed in the heart, spleen, lung, digestive tract, liver, kidney, pancreas, skin, and ocular region and the surrounding interstitial tissue.
Conclusion: The GSs were diagnosed with nitrogen GBD, which is a common fish disease. Circulatory disturbance due to intravascular gas retention and severe vasodilation was considered as the cause of death.
