Henneguya zschokkei
Henneguya zschokkei.jpg
Henneguya zschokkei in salmon
Scientific classification edit
Kingdom: Animalia
Phylum: Cnidaria
Class: Myxosporea
Order: Bivalvulida
Family: Myxobolidae
Genus: Henneguya
H. zschokkei
Binomial name
Henneguya zschokkei
(Gurley, 1894)
  • Henneguya salminicola Ward, 1919

Henneguya zschokkei or Henneguya salminicola is a species of a myxosporean parasite of certain species of salmon of genus Oncorhynchus.[2][3] It causes milky flesh or tapioca disease.[1]

Henneguya salminicola is the first and thus far only known multicellular animal that completely lacks a mitochondrial genome and typical mitochondria, meaning it does not use aerobic respiration to produce energy, but some other, yet unknown, way;[4] it as such does not breathe oxygen.[5]

While eukaryotes are known for their aerobic respiration, a few unicellular lineages that develop in hypoxic environments have lost this capacity. These organisms' mitochondria have lost all or portions of their genomes in the absence of oxygen and developed into mitochondria-related organelles (MROs). The existence of MROs in animals has been a point of contention.[6]


Henneguya salminicola is found in fish as an ovoid spore with two anterior polar capsules and two long caudal appendages.[7] Individuals are very small (about 10 micrometers in diameter),[8] but are found aggregated into cysts 3–6 mm in diameter and can be found at any place in the muscle mass. The parasite is a cnidarian and as such a distant relative of jellyfish.[5]


Known hosts of Henneguya zschokkei include:[9]

Lack of mitochondrial genome

The anaerobic nature of Henneguya zschokkei was accidentally discovered by scientists at Tel Aviv University, who published their results in February 2020.[4] Professor Dorothee Huchon and colleagues noticed that this animal was missing a mitochondrial genome.[10]

See also



  1. ^ a b "Henneguya salminicola". fishpathogens.net. Oregon State University. Oregon Department of Fish and Wildlife. Retrieved 2020-02-28.
  2. ^ Ward, Henry B. (1919). "Notes on North American Myxosporidia". The Journal of Parasitology. 6 (2): 49–64. doi:10.2307/3270895. JSTOR 3270895. S2CID 88435361.
  3. ^ Greenwood, Veronique (28 February 2020). "This Parasite Doesn't Need Oxygen to Survive - But that's not the weirdest thing about this jellyfish cousin that turns up in the muscles of salmon". The New York Times. Retrieved 5 March 2020.
  4. ^ a b Yahalomi, Dayana; Atkinson, Stephen D.; Neuhof, Moran; Chang, E. Sally; Philippe, Hervé; Cartwright, Paulyn; Bartholomew, Jerri L.; Huchon, Dorothée (19 February 2020). "A cnidarian parasite of salmon (Myxozoa: Henneguya) lacks a mitochondrial genome". Proceedings of the National Academy of Sciences. 117 (10): 5358–5363. doi:10.1073/pnas.1909907117. PMC 7071853. PMID 32094163.; Lay summary: "Unique non-oxygen breathing animal discovered: The tiny relative of the jellyfish is parasitic and dwells in salmon tissue". ScienceDaily.
  5. ^ a b Brandon Specktor (24 February 2020). "Scientists discover first known animal that doesn't breathe". Live Science.
  6. ^ Yahalomi, Dayana; Atkinson, Stephen; Neuhof, Moran; Chang, E. Sally; Phillipe, Hervé; Cartwright, Paulyn; Bartholomew, Jerri; Hutchon, Dorothée (2020). "A cnidarian parasite of salmon (Myxozoa: Henneguya) lacks a mitochondrial genome". Proceedings of the National Academy of Sciences. 117 (10): 5358–5363. doi:10.1073/pnas.1909907117. PMC 7071853. PMID 32094163.
  7. ^ Meyers, T. R.; Burton, T.; Bentz, C.; Starkey, N. (July 2008). Common diseases of wild and cultured fishes in Alaska (PDF). Fish Pathology Laboratories. Alaska Department of Fish and Game. Yukon River Drainage Fisheries Association.((cite book)): CS1 maint: uses authors parameter (link)
  8. ^ "Spores of H. salminicola from a human stool specimen" – via ResearchGate.
  9. ^ Buchtová, H.; Dyková, I.; Vršková, D.; Krkoška, L. (2004). "Záchyt lososa masivně infikovaného myxosporidií Henneguya zschokkei" [Myxosporidia Henneguya zschokkei massive infection in a salmon]. Veterinářství (in Czech). 54: 47–48.
  10. ^ Andrew, Scottie (26 February 2020). "Scientists discovered the first animal that doesn't need oxygen to live. It's changing the definition of what an animal can be". CNN. Retrieved 2020-02-28.

Further reading