Rhizostomins are

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

s that are part of a

pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compo ...

family only found in

jellyfish Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella- ...

in the order Rhizostomeae. These proteins are composed of a Kringle domain inserted within a cysteine-rich Frizzled domain, first identified in 2004 as the blue pigment in the barrel jellyfish ''

Rhizostoma pulmo ''Rhizostoma pulmo'', commonly known as the barrel jellyfish, the dustbin-lid jellyfish or the frilly-mouthed jellyfish, is a scyphomedusa in the family Rhizostomatidae. It is found in the northeast Atlantic, and in the Adriatic, Mediterranean Se ...

''. It also appears in rhizostome jellyfish that do not appear blue, such as in '' Nemopilema nomurai'', which typically presents red-brown coloration. It has been hypothesized that pigments in this family act as a sunscreen, protecting from harmful

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...

radiation. Natural blue pigments, such as some of the rhizostomins, are rare and there is a growing need for industrial purposes.

References

{{reflist Protein domains Biological pigments Cnidarians