title: A newly discovered oxidant defence system and its involvement in the development of Aurelia aurita (Scyphozoa, Cnidaria): reactive oxygen species and elemental iodine control medusa formation.
abstract: In Aurelia aurita, applied iodine induces medusa formation (strobilation). This process also occurs when the temperature is lowered. This was found to increase oxidative stress resulting in an increased production of iodine from iodide. One polyp produces several medusae (initially termed ephyrae) starting at the polyp's oral end. The spreading of strobilation down the body column is controlled by a feedback loop: ephyra anlagen decrease the tyrosine content in adjacent polyp tissue by producing melanin from tyrosine. Endogenous tyrosine is able to remove iodine by forming iodiferous tyrosine compounds. The reduced level of tyrosine causes the ephyra-polyp-border to move towards the basal end of the former polyp. We argue that an oxidant defence system may exist which makes use of iodide and tyrosine. Like other marine invertebrates, polyps of Aurelia contain iodide ions. Inevitably produced peroxides oxidise iodide into iodine. The danger to be harmed by iodine is strongly decreased by endogenous tyrosine which reacts with iodine to form iodiferous tyrosine compounds including thyroxin. Both substances together, iodide and tyrosine, form an efficient oxidant defence system which shields the tissue against damage by reactive oxygen species. In the course of evolution (from a species at the basis of the animal kingdom like Aurelia to a highly evolved species like man) the waste product thyroxin (indicating a high metabolic rate) has developed into a hormone which controls the metabolic rate.
authors.affiliation: Zoological Institute, University of Cologne, Köln, Germany. s.berking@uni-koeln.de
authors.forename: Stefan
authors.initials: S
authors.lastname: Berking
authors.forename: Nicole
authors.initials: N
authors.lastname: Czech
authors.forename: Melanie
authors.initials: M
authors.lastname: Gerharz
authors.forename: Klaus
authors.initials: K
authors.lastname: Herrmann
authors.forename: Uwe
authors.initials: U
authors.lastname: Hoffmann
authors.forename: Hartmann
authors.initials: H
authors.lastname: Raifer
authors.forename: Guy
authors.initials: G
authors.lastname: Sekul
authors.forename: Barbara
authors.initials: B
authors.lastname: Siefker
authors.forename: Andrea
authors.initials: A
authors.lastname: Sommerei
authors.forename: Fritz
authors.initials: F
authors.lastname: Vedder
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000187:drug effects / Q000235:genetics*; D007455:Iodine / Q000378:metabolism* / Q000494:pharmacology; D017613:Iodine Compounds / Q000378:metabolism; D008543:Melanins / Q000096:biosynthesis; D016877:Oxidants / Q000378:metabolism / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism* / Q000494:pharmacology; D037401:Scyphozoa / Q000196:embryology* / Q000378:metabolism*; D013696:Temperature; D014443:Tyrosine / Q000494:pharmacology
chemical_list: D017613:Iodine Compounds; D008543:Melanins; D016877:Oxidants; D017382:Reactive Oxygen Species; D014443:Tyrosine; D007455:Iodine