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

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) s...

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Bibliographic Details
Published in:	The International journal of developmental biology Vol. 49; no. 8; pp. 969 - 976
Main Authors:	Berking, Stefan, Czech, Nicole, Gerharz, Melanie, Herrmann, Klaus, Hoffmann, Uwe, Raifer, Hartmann, Sekul, Guy, Siefker, Barbara, Sommerei, Andrea, Vedder, Fritz
Format:	Journal Article
Language:	English
Published:	Spain 2005
Subjects:	Animals Aurelia Aurelia aurita Body Patterning - drug effects Body Patterning - genetics Cnidaria Iodine - metabolism Iodine - pharmacology Iodine Compounds - metabolism Marine Medusae Melanins - biosynthesis Oxidants - metabolism Oxidants - physiology Reactive Oxygen Species - metabolism Reactive Oxygen Species - pharmacology Scyphozoa Scyphozoa - embryology Scyphozoa - metabolism Temperature Tyrosine - pharmacology
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Summary:	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.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0214-6282
DOI:	10.1387/ijdb.052024sb