Squid Ink Has Not Changed in 160 Million Years

Posted on May 24, 2012

Researchers have found that squid ink from the Jurassic is identical to modern squid ink. Researchers studied two ink sacs from 160-million-year-old giant cephalopod fossils discovered two years ago in England. They were found to contain the pigment melanin. The pigment is essentially identical to the melanin found in the ink sac of a modern-day cuttlefish. The study suggests that the ink-screen escape mechanism of cephalopods - cuttlefish, squid and octopuses - has not evolved since the Jurassic period.

John Simon, one of the study authors, a chemistry professor and the executive vice president and provost at U.Va., says, "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."

One of the ink sacs studied is the only intact ink sac ever discovered. Phillip Wilby of the British Geological Survey found it in Christian Malford, Wiltshire, England, west of London near Bristol. He sent samples to Simon and Japanese chemist Shoskue Ito, both experts on melanin, who then engaged research colleagues in the United States, the United Kingdom, Japan and India to investigate the samples using a combination of direct, high-resolution chemical techniques to determine whether or not the melanin had been preserved. It had been preserved.

The investigators then compared the chemical composition of the fossil melanin to the melanin in the ink of the modern cuttlefish, Sepia officinalis, common to the Mediterranean, North and Baltic seas. They found a nearly identical match.

Simon says, "It's close enough that I would argue that the pigmentation in this class of animals has not evolved in 160 million years. 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, made up mostly of protein, typically degrades quickly. Over the course of millions of years all that is likely to be found from an animal is skeletal remains or an impression of the shape of the animal in surrounding rock. Scientists can learn a great deal about an animal by its bones and impressions, but without organic matter they are left with many unanswered questions. Melanin is an exception. Though organic, it is highly resilient to degradation over the course of vast amounts of time.

Simon says, "Out of all of the organic pigments in living systems, melanin has the highest odds of being found in the fossil record. 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 study is published online in the May 21 edition of the journal Proceedings of the National Academy of Sciences.

The ink escape method used by some cephalopods remains effective today. Here is a video of an octopus squirting ink at a diver. Take a look:

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