Amyloodinium ocellatum

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Figure 1. Image credit: Amyloodiniumocellatum.

Classification

Eukaryota; Myzozoa; Dinophyceae; Blastodiniales; Oodiniaceae

Species

NCBI: [1]

Oodinium ocellatum

Description and Significance

Amyloodinium ocellatum (also commonly known as marine velvet) is a dinoflagellate. It's an obligate parasite of many marine fish. Amyloodinium ocellatum creates a powdery and/or velvety appearance on species. The parasite is typically found in saltwater and brackish environments but can withstand a wide variety of water temperatures and salinities. This parasite is a major issue because it can cause lots of economic problems, especially in fish farming sites where the filtration and water quality are poor because this organism can quickly spread and cause high death in several hours. Pereira et al. (2010) reported that among the most important ectoparasitic protozoa is Amyloodinium ocellatum, a dinoflagellate that causes one of the most serious diseases of marine aquaculture.

Genome Structure

It's mean size has been reported as 61 x 50 m, which is about 7 to 8 times larger than a red blood cell. The parasite is oval/pear-shaped. Its appears circular and dark brown under a microscope. In it's cytoplasm in contains digestive vaculoes and starch granules.

Cell Structure, Metabolism and Life Cycle

Amyloodinium ocellatum attaches to hosts using a rhizoid root structure. It's an obligate parasite, so it needs the host to survive to complete it's life cycle. It is transmitted through contaminated water sources.

Its life cycle is very complex. It occurs in both the water column and in sediments. The tomont phase is the reproductive phase that takes place in sediments and each tomont divides into as many as 256 dinospores. Next, the dinospore phase occurs and that is the infective period. After that, is the trophont phase or the parasitic phase in the fish. Lastly, the mature trophont detaches and falls to the seafloor where it becomes encysted and prepares for the tomont phase again.

Ecology and Pathogenesis

Amyloodinium ocellatum is present in marine and brackish water environments, it infects animal (fish) hosts. It can infect a variety of fish in two ways, one is by attaching to the gills and the other is by attaching to the skin of the fish. Infected hosts display a variety of symptoms including scratching on objects, swimming irregularly and losing balance. It causes inflammation, hemorrhages, hyperplasia, anoxia, suffocation, and gill necrosis. Typically host death occurs within 12-48 hours of being infected and the mortality rate is roughly 100%.

References

Noga, E. J. (2011). amyloodinium ocellatum . Fish Parasites: Pathobiology and Protection, 19–29. https://doi.org/10.1079/9781845938062.0019

Plumb, J. A. (1997). Infectious diseases of striped bass. Striped Bass and Other Morone Culture, 271–313. https://doi.org/10.1016/s0167-9309(97)80013-0

U.S. National Library of Medicine. (n.d.). Amyloodinium+ocellatum. National Center for Biotechnology Information. Retrieved December 12, 2022, from https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?name=Amyloodinium%2Bocellatum

Worms - world register of marine species - oodinium ocellatum e.brown. (n.d.). Retrieved December 12, 2022, from https://www.marinespecies.org/aphia.php?p=taxdetails&id=563625

Author

Page authored by __Trey Thigpen___, student of Prof. Bradley Tolar at UNC Wilmington.