Aurich Lawson/T. Clements et al.
Sometimes science can be a negative endeavor – not to mention “disgusting and smelly.” That’s how the British researchers described their study of monitoring the dead bodies of the sea as they decomposed over the course of 70 days. In the process, they discovered fascinating insights into how (and why) organ tissue can be preserved throughout history, according to a new paper published in the journal Palaeontology.
Most fossils are bones, shells, teeth, and other types of “hard” material, but sometimes rare fossils are found that preserve soft tissues such as skin, muscles, organs, or the eye. This can tell scientists many aspects of the biology, ecology, and evolution of these ancient creatures that skeletons alone cannot explain. For example, earlier this year, researchers created the most detailed 3D model of a 365-million-year-old ammonite fossil from the Jurassic period by combining modeling techniques, revealing inner muscles that have not been noticed before.
“One of the best ways that the soft tissue can turn into stones is by changing it to a mineral called calcium phosphate (sometimes called apatite),” said author Thomas. Clements of the University of Birmingham. “Scientists have been studying calcium phosphate for years trying to understand how this process happens—but one question we don’t understand is why it seems to protect some internal organs better than others. “
In particular, muscles, stomach, and intestines tend to “phosphatize” more than other organs, such as the kidneys and gonads. There are two common theories to explain this. First, different organs decompose at different rates, and the pH of some organs will fall below the critical level of 6.4. As these organs decompose, they create a specific pH microenvironment that increases the likelihood of those organs being fertilized. Different minerals can form in different parts of the same body.
Reproduction / Examples of phosphatized rings in fossils: (a) a frog stomach with phosphatized voids; (b) micro-CT image of a Brazilian fish harboring organs in phosophate; (c) Colubrid snakes with phosphatized skin.
The second point is that the biochemistry of the body plays a big role. In particular, an environment of pH that occurs in the body and continues until the corpse breaks down.
According to Clement et al., no previous study has focused on recording the pH gradients associated with the decomposition of specific physical features such as a body that decomposes in real time; past experiments have focused on recording pH changes outside the cadaver. So the team decided to correct that gap and conducted tests on rotten fish, recording how the pH gradient changed over the course of two and a half months.
First, they bought adult European fish from a local fishmonger as soon as they died (no more than 24-36 hours). The fish were kept on ice to slow down the spoilage before freezing to avoid any spoilage. Next, they inserted pH tests in different places on each of the six bodies of the sea to target specific organs: stomach, liver, intestines, and epaxial muscles. A fifth probe was used to monitor the pH of the environment between 1 and 2 mm away from the carcass.
Proliferation / Best examples of phosphatized lungs in fossils: (d) Polychaete worms with striated musculature; (e) trilobite with phosphatized intestinal parts; and (f) vampyropod octopus under UV light showing phosphatized tissue.
