The oldest pigment ever discovered has been found in 160-million-year-old fossilized giant squid ink sacs.
The pigment, melanin, has been found to be nearly identical to the melanin in modern-day cuttlefish.
It’s extremely rare to be able to identify an organic compound that is hundreds of millions of years old. These rare finds in the past have included blood from a T-Rex, 50-million-year-old reptile skin, and some bones and claws that still contained organic proteins.
The melanin found suggests that the ink-screen escape mechanisms used by cephalopods hasn’t changed much since the Jurassic period, and that there is the possibility of finding melanin intact in a range of different fossilized organisms.
“Though the other organic components of the cephalopod we studied are long gone, we’ve discovered through a variety of research methods that the melanin has remained in a condition that could be studied in exquisite detail,” said John Simon, one of the study authors, a chemistry professor and the executive vice president and provost at U.Va.
One of the ink sacs discovered is the only intact fossilized ink sac ever found.
It was found in Christian Malford, Wiltshire, England, by Philip Wilby of the British Geological Survey. He then sent the samples to John Simon and to a Japanese chemist Shoskue Ito, both of whom are experts on melanin. They then used their research colleagues spread throughout the US, UK, Japan, and India, to investigate whether or not there was any melanin remaining.
They found that there was, so they then compared the fossil melanin to the melanin of the modern cuttlefish, Sepia officinalis. It was a close match.
“It’s close enough that I would argue that the pigmentation in this class of animals has not evolved in 160 million years,” Simon said. “The whole machinery apparently has been locked in time and passed down through succeeding generations of cuttlefish. It’s a very optimized system for this animal and has been optimized for a long time.”
Animal tissue generally breaks down very quickly, after millions of years all that is likely to remain is skeletal remains, or an impression of the animal’s shape in the surrounding rocks.
Melanin, though, is apparently very resistant to degradation, even over these vast amounts of time.
“Out of all of the organic pigments in living systems, melanin has the highest odds of being found in the fossil record,” Simon said. “That attribute also makes it a challenge to study. We had to use innovative methods from chemistry, biology and physics to isolate the melanin from the inorganic material.”
The researchers cross-checked their findings using several separate complementary experiments, looking to confirm several molecular features unique to melanin. This in-depth, multi-disciplinary approach is not normally used to study fossils.
“I think the strength of this paper is that it is not tied to a single method,” Simon said. “Any one technique would have brought some insights, but potentially more questions than insights. It was really the more holistic approach that fully characterized it and allowed us to actually do a real comparison between what existed during the Jurassic period and what exists now.”
“It’s also given us a handle on ways of identifying organic components in fossils that might have been missed using standard methods.”
Source and Images: University of Virginia