A ruthless fish killer: Treating and diagnosing Amyloodinium

There are a variety of parasites that effect marine fish, but often aquarists are stricken with one of the two most common. Cryptocaryon irritans (marine ich) and Amyloodinium ocellatum (marine velvet) are both parasites that uncommonly kill wild marine fish, but can wreak havoc on captive systems. I would like to address the latter parasite, as it often causes quick mortality of fish and is tough to diagnose. When it appears on the skin of marine fish it can easily be misidentified, appearing similar to marine ich. Treatment for this parasite presents an unwelcome challenge for marine aquarists, first because it often strikes with no outward signs of infection and second because it’s seemingly impervious to hypo-salinity.    What is Amyloodinium: Amyloodinium is an extracellular parasite that has a free swimming life phase. It uses a root like structure called rhizoids to attach itself to the gill and skin tissue of marine fish. Amyloodinium is a dinoflagellate of the family Blastodiniphyceae. Most dinoflagellates are free swimming, often photosynthetic microbes within planktonic food webs, serving as important food sources for various fish species. Only Amyloodinium is reported to cause disease in marine fish. Life cycle and survivability:Various studies have been conducted on Amyloodinium, mainly for the culture of food fish, specifically red drum and striped bass. The life cycle of the parasite is very similar to that of marine ich, meaning that it requires a fish host to survive and procreate. Once the parasite has embedded onto fish tissue, protected by the fish’s natural slime coat, it begins feeding off bodily fluids, dropping off within 7-10 days, falling into the substrate and reproducing up to 256 copies of itself. Like marine ich, encysted parasites are immune to any medication, with the only treatable part of the parasite’s life cycle being the free swimming stage. Amyloodinium is impervious to hypo-salinity and has been recorded in salinities down to 3 ppt, much lower than most marine fish can tolerate. Its fast life cycle leads to massive infestation of fish in the marine aquarium, once the life cycle has begun. It’s not uncommon for aquarists to start seeing loss of fish life within 12 hours of the parasite’s first symptoms. This parasite is perhaps both the deadliest and hardiest parasite that marine aquarists will encounter. Diagnosing and treating: Instead of re-iterate information second hand, I want to provide an outline for diagnosing and treating this parasite, based off personal experience.… More:

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