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Pigmented anatomy in Carboniferous cyclostomes and the evolution of the vertebrate eye

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posted on 2016-10-05, 15:35 authored by Sarah E. Gabbott, Philip C. J. Donoghue, Robert S. Sansom, Jakob Vinther, Andrei Dolocan, Mark A. Purnell
The success of vertebrates is linked to the evolution of a camera-style eye and sophisticated visual system. In the absence of useful data from fossils, scenarios for evolutionary assembly of the vertebrate eye have been based necessarily on evidence from development, molecular genetics and comparative anatomy in living vertebrates. Unfortunately, steps in the transition from a light-sensitive 'eye spot' in invertebrate chordates to an image-forming camera-style eye in jawed vertebrates are constrained only by hagfish and lampreys (cyclostomes), which are interpreted to reflect either an intermediate or degenerate condition. Here, we report-based on evidence of size, shape, preservation mode and localized occurrence-the presence of melanosomes (pigment-bearing organelles) in fossil cyclostome eyes. Time of flight secondary ion mass spectrometry analyses reveal secondary ions with a relative intensity characteristic of melanin as revealed through principal components analyses. Our data support the hypotheses that extant hagfish eyes are degenerate, not rudimentary, that cyclostomes are monophyletic, and that the ancestral vertebrate had a functional visual system. We also demonstrate integument pigmentation in fossil lampreys, opening up the exciting possibility of investigating colour patterning in Palaeozoic vertebrates. The examples we report add to the record of melanosome preservation in Carboniferous fossils and attest to surprising durability of melanosomes and biomolecular melanin.

History

Citation

Proceedings of the Royal Society B: Biological Sciences, 2016, 283 (1836)

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Geology

Version

  • VoR (Version of Record)

Published in

Proceedings of the Royal Society B: Biological Sciences

Publisher

The Royal Society

issn

0962-8452

eissn

1471-2954

Acceptance date

2016-07-18

Copyright date

2016

Available date

2016-10-05

Publisher version

http://rspb.royalsocietypublishing.org/content/283/1836/20161151

Language

en

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