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Scientific classification
Domain: Eukaryota
(unranked): Excavata
Phylum: Metamonada
Order: Diplomonadida
Family: Hexamitidae
Genus: Spironucleus

Spironucleus barkhanus
Spironucleus meleagridis
Spironucleus muris
Spironucleus salmonicida
Spironucleus salmonis
Spironucleus torosa
Spironucleus vortens

Spironucleus is a genus of Diplomonad flagellates that inhabit the digestive tract of a variety of animal hosts. Some are pathogens and others are commensals. Spironucleus parasites are often found in fish, but can be found in mice and birds.[1]

Life Cycle of Spironucleus and Transmission First stage of Spironucleus is the trophozoite stage in which live inside the intestial tract of the host fish. Second stage, Spironucleus start to reproduce asexually by longitudinal binary fission and during this stage the Spironucleus turn more spherical (round). Stage three of Spironucleus starts to colonize the intestinal and later invade the intestinal mucosa which leads to systemic infection. Stage four once host fish has systemic infection the Spironucleus create lesions on the host fish and then Spironucleus encase themselves in cyst which are later are released into the water and is consumed by other fish to repeat the life cycle[2] [3].

Identification of Spironucleus The active Stage of Spironucleus (known as Trophozoites) can only be identified under a microscope. Sprionucleus are small and are approximately 12.5-20.5µm long and 5.0-11.2µm wide. Spironucleus tend to be ovoid to pear-shaped, but become more spherical (round) during reproduction[2].


  1. ^ Andersson, J. O., Sjogren, A. M., Horner, D. S., Murphy, C. A., Dyal, P. L., Svard, S. G., & Ragan, M. A. (2007, February 14). A genomic survey of the fish parasite Spironucleus salmonicida indicates genomic plasticity among diplomonads and significant lateral gene transfer in eukaryote genome evolution. BMC Genomics, 8(51). doi:10.1186/1471-2164-8-51
  2. ^ a b Yanong, Ruth Francis-Floyd and Roy P. E. (2016-01-13). "Spironucleus Infestations (Spironucleosis) in Freshwater Aquarium Fish". edis.ifas.ufl.edu. Retrieved 2018-11-09.
  3. ^ Williams, Catrin Ffion (2013). Life cycle, biochemistry and chemotherapy of Spironucleus vortens. Diss. Cardiff University.

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