Study finds brilliant green-blue colours in 13,000-year old fossil insects
Vivid colours produced by photonic diamonds
University College Cork (UCC) scientists have discovered 13,000-year-old fossil insects with brilliant green-blue colours produced by microscopic photonic ‘diamonds’.
These tiny structures produce the brightest and purest colours in nature and are used by insects today to produce striking visual signals. The evolution of photonic diamonds, however, is poorly understood.
Remarkably, the fossil insects preserve ancient photonic diamonds within scales on their outer surface. Unlike many of today’s insects, which are thought to use photonic diamonds for mating displays or displays of fitness, the green hues of the fossil weevils probably functioned as camouflage.
The fossil insects examined were from ancient lake sediments from Lobsigensee in Switzerland. The study was led by UCC palaeobiologists Drs Luke McDonald and Maria McNamara in collaboration with applied physicist Dr Vinod Saranathan, an expert in biological photonic systems, from YaleNUS College in Singapore.
Study leader Dr McDonald said, “This is only the second time that 3D photonic crystals have been reported from the fossil record. We identified the microscopic structures in the fossil scales using powerful electron microscopes. The photonic ‘diamonds’ in the fossils interact with wavelengths of light to produce vivid colours.”
Senior author Dr McNamara said, “The fossil record is potentially a treasure trove of information on the evolution of these structures, but it’s largely an untapped resource. More work on fossils will help us understand how these incredibly complex tissue structures evolved and how their functions may have changed through deep time.”
Dr Saranathan, who structural and optical analyses using particle accelerator X-rays and modelling, added, “It is very interesting to discover that insects first seem to evolve complex 3D nanoscale architectures in order to escape predators by blending in with their background (usually brown or green). Only later do these colours diverge for other uses such as signalling potential mates or as a warning to predators that the insect is not worth eating.”
The study is published today in the journal Biology Letters.
McDonald, L.T., Narayanan, S., Sandy, A., Saranathan, V., McNamara, M.E., 2020. Brilliant angle-independent structural colours preserved in weevil scales from the Swiss Pleistocene. Biology Letters, 16, 20200063. DOI: https://doi.org/10.1098/rsbl.2020.0063.
To arrrange interviews contact Maria McNamara directly: 021 7434738 (home) / firstname.lastname@example.org
See below for news items on the study:
Maria spoke to Dr Naomi Lavelle at the Irish Examiner about gender balance in STEM – see article below!
It was Daniel’s first IGRM, held in Athlone last week. He gave a talk about the skeletal taphonomy of fossil anurans from the Geiseltal Collection (Germany) which won a Highly Commended award! The 63rd IGRM was a great meeting of not-only Irish scientists spanning all fields of geosciences.
Slater, T., Ashbrook, K., Kriwet, J., 2020. Evolutionary relationships among bullhead sharks (Chondrichthyes, Heterodontiformes). Papers in Palaeontology, available via Early View: https://doi.org/10.1002/spp2.1299.
Review of the PalAss 2019 Annual Meeting including a special mention for Maria’s Annual Address:
UCC palaeontologists have discovered new evidence on what type of animal is the bizarre 300 million year old fossil known as the “Tully Monster”. The new findings show that the Tully Monster may not be a backboned animal as previously thought.
This new twist in the tale of the Tully Monster is based on cutting-edge analyses of melanin granules – melanosomes – in Tully’s weird stalked eyes. Chemical tests show that Tully’s eye melanosomes resemble those in animals without backbones.
The study, published today in the journal Proceedings of the Royal Society B: Biological Sciences, was led by UCC’s Drs Chris Rogers and Maria McNamara with an international team of scientists from the UK, USA and Japan.
The team used cutting-edge techniques to analyse the structure and chemistry of the eyes of the Tully Monster fossil, along with various other fossils and modern animals.
The eyes of Tully contain layers of melanosomes, a feature thought to exist only in the eyes of animals with backbones. Surprisingly, however, the new study shows that these layers are also found in the eyes of animals without backbones, such as octopus and squid. ‘I was amazed’ said Dr Rogers. ‘for decades scientists have failed to identify the pigments in the eyes of animals like the octopus, but our chemical tests show it’s definitely melanin.’ Powerful X-ray analyses show that the eye melanosomes of animals with and without backbones contain different metals. Controversially, the metals in the Tully Monster’s eyes are like those of animals without backbones. ‘This means that invertebrates are still contenders for the Tully animal,’ says senior author Dr McNamara. ‘The riddle of what kind of fossil creature this is continues, but future X-ray work will probably play an important part in figuring out the identity of Tully Monster and other enigmatic fossils.’
Rogers, C.S., Astrop, T.I.A., McNamara, M.E., Webb, S., Ito, S., Wakamatsu, K. Synchrotron-X-ray absorption spectroscopy of melanosomes in vertebrates and cephalopods: implications for the affinity of Tullimonstrum. Proceedings B, 286, 20191649. DOI: https://doi.org/10.1098/rspb.2019.1649.
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Congratulations to UCC student Tiffany for her paper published last week, and adding fuel to the fossil feather preservation debate!
Slater, T.S., McNamara, M.E., Orr, P.J., Foley, T.B., Ito, S., Wakamatsu, K., 2019. Taphonomic experiments resolve controls on the preservation of melanosomes and keratinous tissues in feathers. Palaeontology, xx. DOI: 10.1111/pala.12445.
It is open-access and can be viewed at the following link: