Synchrotron X-ray absorption spectroscopy of melanosomes in vertebrates and cephalopods: implications for the affinity of Tullimonstrum

Screening pigments are essential for vision in animals. Vertebrates use melanins bound in melanosomes as screening pigments, whereas cephalopods are assumed to use ommochromes. Preserved eye melanosomes in the controversial fossil (Mazon Creek, IL, USA) are partitioned by size and/or shape into dist...

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Bibliographic Details
Published in:Proceedings of the Royal Society. B, Biological sciences Biological sciences, 2019-10, Vol.286 (1913), p.20191649
Main Authors: Rogers, Christopher S, Astrop, Timothy I, Webb, Samuel M, Ito, Shosuke, Wakamatsu, Kazumasa, McNamara, Maria E
Format: Article
Language:English
Subjects:
Animals
BASIC BIOLOGICAL SCIENCES
Biological Evolution
Cephalopoda
fossil soft tissues
Fossils
Konservat-Lagerstätten
Melanins
Melanosomes
Palaeobiology
Phylogeny
Pigmentation
Synchrotrons
trace metals
Vertebrates
X-Ray Absorption Spectroscopy
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Summary:Screening pigments are essential for vision in animals. Vertebrates use melanins bound in melanosomes as screening pigments, whereas cephalopods are assumed to use ommochromes. Preserved eye melanosomes in the controversial fossil (Mazon Creek, IL, USA) are partitioned by size and/or shape into distinct layers. These layers resemble tissue-specific melanosome populations considered unique to the vertebrate eye. Here, we show that extant cephalopod eyes also show tissue-specific size- and/or shape-specific partitioning of melanosomes; these differ from vertebrate melanosomes in the relative abundance of trace metals and in the binding environment of copper. Chemical signatures of melanosomes in the eyes of more closely resemble those of modern cephalopods than those of vertebrates, suggesting that an invertebrate affinity for is plausible. Melanosome chemistry may thus provide insights into the phylogenetic affinities of enigmatic fossils where melanosome size and/or shape are equivocal.
ISSN:0962-8452
1471-2954
DOI:10.1098/rspb.2019.1649